summaryrefslogtreecommitdiff
path: root/src/transport/gnunet-service-tng.c
blob: 6494a5dfd491af270b0b57dea60f5bb0c240d6fe (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
/*
 This file is part of GNUnet.
 Copyright (C) 2010-2016, 2018, 2019 GNUnet e.V.

 GNUnet is free software: you can redistribute it and/or modify it
 under the terms of the GNU Affero General Public License as published
 by the Free Software Foundation, either version 3 of the License,
 or (at your option) any later version.

 GNUnet is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */
/**
 * @file transport/gnunet-service-tng.c
 * @brief main for gnunet-service-tng
 * @author Christian Grothoff
 *
 * TODO:
 * - figure out how to transmit (selective) ACKs in case of uni-directional
 *   communicators (with/without core? DV-only?) When do we use ACKs?
 *   => communicators use selective ACKs for flow control
 *   => transport uses message-level ACKs for RTT, fragment confirmation
 *   => integrate DV into transport, use neither core nor communicators
 *      but rather give communicators transport-encapsulated messages
 *      (which could be core-data, background-channel traffic, or
 *       transport-to-transport traffic)
 *
 * Implement next:
 * - address validation: what is our plan here?
 *   #1 Peerstore only gets 'validated' addresses
 *   #2 transport needs another API to "trigger" validation!
 *      API may be used by core/application or communicators;
 *      => use yet another lib/MQ/connection?
 *   #3 transport should use validation to also establish
 *      effective flow control (for uni-directional transports!)
 *   #4 UDP broadcasting logic must be extended to use the new API
 *   #5 only validated addresses are selected for scheduling; that
 *      also ensures we know the RTT
 *   #6 to ensure flow control and RTT are OK, we always do the
 *      'validation', even if address comes from PEERSTORE
 *   #7
 * - ACK handling / retransmission
 * - address verification
 * - track RTT, distance, loss, etc.
 * - DV data structures:
 *   + learning
 *   + forgetting
 *   + using them!
 * - routing of messages (using DV data structures!)
 * - handling of DV-boxed messages that need to be forwarded
 * - backchannel message encryption & decryption
 * -
 *
 * Easy:
 * - figure out how to call XXX_suggestion_cb!
 *
 * Later:
 * - change transport-core API to provide proper flow control in both
 *   directions, allow multiple messages per peer simultaneously (tag
 *   confirmations with unique message ID), and replace quota-out with
 *   proper flow control;
 * - if messages are below MTU, consider adding ACKs and other stuff
 *   (requires planning at receiver, and additional MST-style demultiplex
 *    at receiver!)
 * - could avoid copying body of message into each fragment and keep
 *   fragments as just pointers into the original message and only
 *   fully build fragments just before transmission (optimization, should
 *   reduce CPU and memory use)
 *
 * Design realizations / discussion:
 * - communicators do flow control by calling MQ "notify sent"
 *   when 'ready'. They determine flow implicitly (i.e. TCP blocking)
 *   or explicitly via background channel FC ACKs.  As long as the
 *   channel is not full, they may 'notify sent' even if the other
 *   peer has not yet confirmed receipt. The other peer confirming
 *   is _only_ for FC, not for more reliable transmission; reliable
 *   transmission (i.e. of fragments) is left to _transport_.
 * - ACKs sent back in uni-directional communicators are done via
 *   the background channel API; here transport _may_ initially
 *   broadcast (with bounded # hops) if no path is known;
 * - transport should _integrate_ DV-routing and build a view of
 *   the network; then background channel traffic can be
 *   routed via DV as well as explicit "DV" traffic.
 * - background channel is also used for ACKs and NAT traversal support
 * - transport service is responsible for AEAD'ing the background
 *   channel, timestamps and monotonic time are used against replay
 *   of old messages -> peerstore needs to be supplied with
 *   "latest timestamps seen" data
 * - if transport implements DV, we likely need a 3rd peermap
 *   in addition to ephemerals and (direct) neighbours
 *   ==> check if stuff needs to be moved out of "Neighbour"
 * - transport should encapsualte core-level messages and do its
 *   own ACKing for RTT/goodput/loss measurements _and_ fragment
 *   for retransmission
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_statistics_service.h"
#include "gnunet_transport_monitor_service.h"
#include "gnunet_peerstore_service.h"
#include "gnunet_hello_lib.h"
#include "gnunet_signatures.h"
#include "transport.h"


/**
 * What is the size we assume for a read operation in the
 * absence of an MTU for the purpose of flow control?
 */
#define IN_PACKET_SIZE_WITHOUT_MTU 128

/**
 * If a queue delays the next message by more than this number
 * of seconds we log a warning. Note: this is for testing,
 * the value chosen here might be too aggressively low!
 */
#define DELAY_WARN_THRESHOLD GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 5)

/**
 * How long are ephemeral keys valid?
 */
#define EPHEMERAL_VALIDITY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_HOURS, 4)

/**
 * How long do we keep partially reassembled messages around before giving up?
 */
#define REASSEMBLY_EXPIRATION GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 4)

/**
 * How many messages can we have pending for a given communicator
 * process before we start to throttle that communicator?
 *
 * Used if a communicator might be CPU-bound and cannot handle the traffic.
 */
#define COMMUNICATOR_TOTAL_QUEUE_LIMIT 512

/**
 * How many messages can we have pending for a given queue (queue to
 * a particular peer via a communicator) process before we start to
 * throttle that queue?
 */
#define QUEUE_LENGTH_LIMIT 32


GNUNET_NETWORK_STRUCT_BEGIN

/**
 * Outer layer of an encapsulated backchannel message.
 */
struct TransportBackchannelEncapsulationMessage
{
  /**
   * Type is #GNUNET_MESSAGE_TYPE_TRANSPORT_BACKCHANNEL_ENCAPSULATION.
   */
  struct GNUNET_MessageHeader header;

  /**
   * Distance the backchannel message has traveled, to be updated at
   * each hop.  Used to bound the number of hops in case a backchannel
   * message is broadcast and thus travels without routing
   * information (during initial backchannel discovery).
   */
  uint32_t distance;

  /**
   * Target's peer identity (as backchannels may be transmitted
   * indirectly, or even be broadcast).
   */
  struct GNUNET_PeerIdentity target;

  /**
   * Ephemeral key setup by the sender for @e target, used
   * to encrypt the payload.
   */
  struct GNUNET_CRYPTO_EcdhePublicKey ephemeral_key;

  // FIXME: probably should add random IV here as well,
  // especially if we re-use ephemeral keys!

  /**
   * HMAC over the ciphertext of the encrypted, variable-size
   * body that follows.  Verified via DH of @e target and
   * @e ephemeral_key
   */
  struct GNUNET_HashCode hmac;

  /* Followed by encrypted, variable-size payload */
};


/**
 * Body by which a peer confirms that it is using an ephemeral key.
 */
struct EphemeralConfirmation
{

  /**
   * Purpose is #GNUNET_SIGNATURE_PURPOSE_TRANSPORT_EPHEMERAL
   */
  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;

  /**
   * How long is this signature over the ephemeral key valid?
   * Note that the receiver MUST IGNORE the absolute time, and
   * only interpret the value as a mononic time and reject
   * "older" values than the last one observed.  Even with this,
   * there is no real guarantee against replay achieved here,
   * as the latest timestamp is not persisted.  This is
   * necessary as we do not want to require synchronized
   * clocks and may not have a bidirectional communication
   * channel.  Communicators must protect against replay
   * attacks when using backchannel communication!
   */
  struct GNUNET_TIME_AbsoluteNBO ephemeral_validity;

  /**
   * Target's peer identity.
   */
  struct GNUNET_PeerIdentity target;

  /**
   * Ephemeral key setup by the sender for @e target, used
   * to encrypt the payload.
   */
  struct GNUNET_CRYPTO_EcdhePublicKey ephemeral_key;

};


/**
 * Plaintext of the variable-size payload that is encrypted
 * within a `struct TransportBackchannelEncapsulationMessage`
 */
struct TransportBackchannelRequestPayload
{

  /**
   * Sender's peer identity.
   */
  struct GNUNET_PeerIdentity sender;

  /**
   * Signature of the sender over an
   * #GNUNET_SIGNATURE_PURPOSE_TRANSPORT_EPHEMERAL.
   */
  struct GNUNET_CRYPTO_EddsaSignature sender_sig;

  /**
   * How long is this signature over the ephemeral key
   * valid?
   */
  struct GNUNET_TIME_AbsoluteNBO ephemeral_validity;

  /**
   * Current monotonic time of the sending transport service.  Used to
   * detect replayed messages.  Note that the receiver should remember
   * a list of the recently seen timestamps and only reject messages
   * if the timestamp is in the list, or the list is "full" and the
   * timestamp is smaller than the lowest in the list.  This list of
   * timestamps per peer should be persisted to guard against replays
   * after restarts.
   */
  struct GNUNET_TIME_AbsoluteNBO monotonic_time;

  /* Followed by a `struct GNUNET_MessageHeader` with a message
     for a communicator */

  /* Followed by a 0-termianted string specifying the name of
     the communicator which is to receive the message */

};


/**
 * Outer layer of an encapsulated unfragmented application message sent
 * over an unreliable channel.
 */
struct TransportReliabilityBox
{
  /**
   * Type is #GNUNET_MESSAGE_TYPE_TRANSPORT_RELIABILITY_BOX
   */
  struct GNUNET_MessageHeader header;

  /**
   * Number of messages still to be sent before a commulative
   * ACK is requested.  Zero if an ACK is requested immediately.
   * In NBO.  Note that the receiver may send the ACK faster
   * if it believes that is reasonable.
   */
  uint32_t ack_countdown GNUNET_PACKED;

  /**
   * Unique ID of the message used for signalling receipt of
   * messages sent over possibly unreliable channels.  Should
   * be a random.
   */
  struct GNUNET_ShortHashCode msg_uuid;
};


/**
 * Confirmation that the receiver got a
 * #GNUNET_MESSAGE_TYPE_TRANSPORT_RELIABILITY_BOX. Note that the
 * confirmation may be transmitted over a completely different queue,
 * so ACKs are identified by a combination of PID of sender and
 * message UUID, without the queue playing any role!
 */
struct TransportReliabilityAckMessage
{
  /**
   * Type is #GNUNET_MESSAGE_TYPE_TRANSPORT_RELIABILITY_ACK
   */
  struct GNUNET_MessageHeader header;

  /**
   * Reserved. Zero.
   */
  uint32_t reserved GNUNET_PACKED;

  /**
   * How long was the ACK delayed relative to the average time of
   * receipt of the messages being acknowledged?  Used to calculate
   * the average RTT by taking the receipt time of the ack minus the
   * average transmission time of the sender minus this value.
   */
  struct GNUNET_TIME_RelativeNBO avg_ack_delay;

  /* followed by any number of `struct GNUNET_ShortHashCode`
     messages providing ACKs */
};


/**
 * Outer layer of an encapsulated fragmented application message.
 */
struct TransportFragmentBox
{
  /**
   * Type is #GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT
   */
  struct GNUNET_MessageHeader header;

  /**
   * Unique ID of this fragment (and fragment transmission!). Will
   * change even if a fragement is retransmitted to make each
   * transmission attempt unique! Should be incremented by one for
   * each fragment transmission. If a client receives a duplicate
   * fragment (same @e frag_off), it must send
   * #GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT_ACK immediately.
   */
  uint32_t frag_uuid GNUNET_PACKED;

  /**
   * Original message ID for of the message that all the1
   * fragments belong to.  Must be the same for all fragments.
   */
  struct GNUNET_ShortHashCode msg_uuid;

  /**
   * Offset of this fragment in the overall message.
   */
  uint16_t frag_off GNUNET_PACKED;

  /**
   * Total size of the message that is being fragmented.
   */
  uint16_t msg_size GNUNET_PACKED;

};


/**
 * Outer layer of an fragmented application message sent over a queue
 * with finite MTU.  When a #GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT is
 * received, the receiver has two RTTs or 64 further fragments with
 * the same basic message time to send an acknowledgement, possibly
 * acknowledging up to 65 fragments in one ACK.  ACKs must also be
 * sent immediately once all fragments were sent.
 */
struct TransportFragmentAckMessage
{
  /**
   * Type is #GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT_ACK
   */
  struct GNUNET_MessageHeader header;

  /**
   * Unique ID of the lowest fragment UUID being acknowledged.
   */
  uint32_t frag_uuid GNUNET_PACKED;

  /**
   * Bitfield of up to 64 additional fragments following the
   * @e msg_uuid being acknowledged by this message.
   */
  uint64_t extra_acks GNUNET_PACKED;

  /**
   * Original message ID for of the message that all the
   * fragments belong to.
   */
  struct GNUNET_ShortHashCode msg_uuid;

  /**
   * How long was the ACK delayed relative to the average time of
   * receipt of the fragments being acknowledged?  Used to calculate
   * the average RTT by taking the receipt time of the ack minus the
   * average transmission time of the sender minus this value.
   */
  struct GNUNET_TIME_RelativeNBO avg_ack_delay;

  /**
   * How long until the receiver will stop trying reassembly
   * of this message?
   */
  struct GNUNET_TIME_RelativeNBO reassembly_timeout;
};


/**
 * Internal message used by transport for distance vector learning.
 * If @e num_hops does not exceed the threshold, peers should append
 * themselves to the peer list and flood the message (possibly only
 * to a subset of their neighbours to limit discoverability of the
 * network topology).  To the extend that the @e bidirectional bits
 * are set, peers may learn the inverse paths even if they did not
 * initiate.
 *
 * Unless received on a bidirectional queue and @e num_hops just
 * zero, peers that can forward to the initator should always try to
 * forward to the initiator.
 */
struct TransportDVLearn
{
  /**
   * Type is #GNUNET_MESSAGE_TYPE_TRANSPORT_DV_LEARN
   */
  struct GNUNET_MessageHeader header;

  /**
   * Number of hops this messages has travelled, in NBO. Zero if
   * sent by initiator.
   */
  uint16_t num_hops GNUNET_PACKED;

  /**
   * Bitmask of the last 16 hops indicating whether they are confirmed
   * available (without DV) in both directions or not, in NBO.  Used
   * to possibly instantly learn a path in both directions.  Each peer
   * should shift this value by one to the left, and then set the
   * lowest bit IF the current sender can be reached from it (without
   * DV routing).
   */
  uint16_t bidirectional GNUNET_PACKED;

  /**
   * Peers receiving this message and delaying forwarding to other
   * peers for any reason should increment this value such as to
   * enable the origin to determine the actual network-only delay
   * in addition to the real-time delay (assuming the message loops
   * back to the origin).
   */
  struct GNUNET_TIME_Relative cummulative_non_network_delay;

  /**
   * Identity of the peer that started this learning activity.
   */
  struct GNUNET_PeerIdentity initiator;

  /* Followed by @e num_hops `struct GNUNET_PeerIdentity` values,
     excluding the initiator of the DV trace; the last entry is the
     current sender; the current peer must not be included. */

};


/**
 * Outer layer of an encapsulated message send over multiple hops.
 * The path given only includes the identities of the subsequent
 * peers, i.e. it will be empty if we are the receiver. Each
 * forwarding peer should scan the list from the end, and if it can,
 * forward to the respective peer. The list should then be shortened
 * by all the entries up to and including that peer.  Each hop should
 * also increment @e total_hops to allow the receiver to get a precise
 * estimate on the number of hops the message travelled.  Senders must
 * provide a learned path that thus should work, but intermediaries
 * know of a shortcut, they are allowed to send the message via that
 * shortcut.
 *
 * If a peer finds itself still on the list, it must drop the message.
 */
struct TransportDVBox
{
  /**
   * Type is #GNUNET_MESSAGE_TYPE_TRANSPORT_DV_BOX
   */
  struct GNUNET_MessageHeader header;

  /**
   * Number of total hops this messages travelled. In NBO.
   * @e origin sets this to zero, to be incremented at
   * each hop.
   */
  uint16_t total_hops GNUNET_PACKED;

  /**
   * Number of hops this messages includes. In NBO.
   */
  uint16_t num_hops GNUNET_PACKED;

  /**
   * Identity of the peer that originated the message.
   */
  struct GNUNET_PeerIdentity origin;

  /* Followed by @e num_hops `struct GNUNET_PeerIdentity` values;
     excluding the @e origin and the current peer, the last must be
     the ultimate target; if @e num_hops is zero, the receiver of this
     message is the ultimate target. */

  /* Followed by the actual message, which itself may be
     another box, but not a DV_LEARN or DV_BOX message! */
};


GNUNET_NETWORK_STRUCT_END


/**
 * What type of client is the `struct TransportClient` about?
 */
enum ClientType
{
  /**
   * We do not know yet (client is fresh).
   */
  CT_NONE = 0,

  /**
   * Is the CORE service, we need to forward traffic to it.
   */
  CT_CORE = 1,

  /**
   * It is a monitor, forward monitor data.
   */
  CT_MONITOR = 2,

  /**
   * It is a communicator, use for communication.
   */
  CT_COMMUNICATOR = 3,

  /**
   * "Application" telling us where to connect (i.e. TOPOLOGY, DHT or CADET).
   */
  CT_APPLICATION = 4
};


/**
 * Entry in our cache of ephemeral keys we currently use.
 * This way, we only sign an ephemeral once per @e target,
 * and then can re-use it over multiple
 * #GNUNET_MESSAGE_TYPE_TRANSPORT_BACKCHANNEL_ENCAPSULATION
 * messages (as signing is expensive).
 */
struct EphemeralCacheEntry
{

  /**
   * Target's peer identity (we don't re-use ephemerals
   * to limit linkability of messages).
   */
  struct GNUNET_PeerIdentity target;

  /**
   * Signature affirming @e ephemeral_key of type
   * #GNUNET_SIGNATURE_PURPOSE_TRANSPORT_EPHEMERAL
   */
  struct GNUNET_CRYPTO_EddsaSignature sender_sig;

  /**
   * How long is @e sender_sig valid
   */
  struct GNUNET_TIME_Absolute ephemeral_validity;

  /**
   * Our ephemeral key.
   */
  struct GNUNET_CRYPTO_EcdhePublicKey ephemeral_key;

  /**
   * Our private ephemeral key.
   */
  struct GNUNET_CRYPTO_EcdhePrivateKey private_key;

  /**
   * Node in the ephemeral cache for this entry.
   * Used for expiration.
   */
  struct GNUNET_CONTAINER_HeapNode *hn;
};


/**
 * Client connected to the transport service.
 */
struct TransportClient;


/**
 * A neighbour that at least one communicator is connected to.
 */
struct Neighbour;


/**
 * Entry in our #dv_routes table, representing a (set of) distance
 * vector routes to a particular peer.
 */
struct DistanceVector;

/**
 * One possible hop towards a DV target.
 */
struct DistanceVectorHop
{

  /**
   * Kept in a MDLL, sorted by @e timeout.
   */
  struct DistanceVectorHop *next_dv;

  /**
   * Kept in a MDLL, sorted by @e timeout.
   */
  struct DistanceVectorHop *prev_dv;

  /**
   * Kept in a MDLL.
   */
  struct DistanceVectorHop *next_neighbour;

  /**
   * Kept in a MDLL.
   */
  struct DistanceVectorHop *prev_neighbour;

  /**
   * What would be the next hop to @e target?
   */
  struct Neighbour *next_hop;

  /**
   * Distance vector entry this hop belongs with.
   */
  struct DistanceVector *dv;

  /**
   * Array of @e distance hops to the target, excluding @e next_hop.
   * NULL if the entire path is us to @e next_hop to `target`. Allocated
   * at the end of this struct.
   */
  const struct GNUNET_PeerIdentity *path;

  /**
   * At what time do we forget about this path unless we see it again
   * while learning?
   */
  struct GNUNET_TIME_Absolute timeout;

  /**
   * How many hops in total to the `target` (excluding @e next_hop and `target` itself),
   * thus 0 still means a distance of 2 hops (to @e next_hop and then to `target`)?
   */
  unsigned int distance;
};


/**
 * Entry in our #dv_routes table, representing a (set of) distance
 * vector routes to a particular peer.
 */
struct DistanceVector
{

  /**
   * To which peer is this a route?
   */
  struct GNUNET_PeerIdentity target;

  /**
   * Known paths to @e target.
   */
  struct DistanceVectorHop *dv_head;

  /**
   * Known paths to @e target.
   */
  struct DistanceVectorHop *dv_tail;

  /**
   * Task scheduled to purge expired paths from @e dv_head MDLL.
   */
  struct GNUNET_SCHEDULER_Task *timeout_task;
};


/**
 * A queue is a message queue provided by a communicator
 * via which we can reach a particular neighbour.
 */
struct Queue;


/**
 * Entry identifying transmission in one of our `struct
 * Queue` which still awaits an ACK.  This is used to
 * ensure we do not overwhelm a communicator and limit the number of
 * messages outstanding per communicator (say in case communicator is
 * CPU bound) and per queue (in case bandwidth allocation exceeds
 * what the communicator can actually provide towards a particular
 * peer/target).
 */
struct QueueEntry
{

  /**
   * Kept as a DLL.
   */
  struct QueueEntry *next;

  /**
   * Kept as a DLL.
   */
  struct QueueEntry *prev;

  /**
   * Queue this entry is queued with.
   */
  struct Queue *queue;

  /**
   * Message ID used for this message with the queue used for transmission.
   */
  uint64_t mid;
};


/**
 * A queue is a message queue provided by a communicator
 * via which we can reach a particular neighbour.
 */
struct Queue
{
  /**
   * Kept in a MDLL.
   */
  struct Queue *next_neighbour;

  /**
   * Kept in a MDLL.
   */
  struct Queue *prev_neighbour;

  /**
   * Kept in a MDLL.
   */
  struct Queue *prev_client;

  /**
   * Kept in a MDLL.
   */
  struct Queue *next_client;

  /**
   * Head of DLL of unacked transmission requests.
   */
  struct QueueEntry *queue_head;

  /**
   * End of DLL of unacked transmission requests.
   */
  struct QueueEntry *queue_tail;

  /**
   * Which neighbour is this queue for?
   */
  struct Neighbour *neighbour;

  /**
   * Which communicator offers this queue?
   */
  struct TransportClient *tc;

  /**
   * Address served by the queue.
   */
  const char *address;

  /**
   * Task scheduled for the time when this queue can (likely) transmit the
   * next message. Still needs to check with the @e tracker_out to be sure.
   */
  struct GNUNET_SCHEDULER_Task *transmit_task;

  /**
   * Our current RTT estimate for this queue.
   */
  struct GNUNET_TIME_Relative rtt;

  /**
   * Message ID generator for transmissions on this queue.
   */
  uint64_t mid_gen;

  /**
   * Unique identifier of this queue with the communicator.
   */
  uint32_t qid;

  /**
   * Maximum transmission unit supported by this queue.
   */
  uint32_t mtu;

  /**
   * Distance to the target of this queue.
   */
  uint32_t distance;

  /**
   * Messages pending.
   */
  uint32_t num_msg_pending;

  /**
   * Bytes pending.
   */
  uint32_t num_bytes_pending;

  /**
   * Length of the DLL starting at @e queue_head.
   */
  unsigned int queue_length;

  /**
   * Network type offered by this queue.
   */
  enum GNUNET_NetworkType nt;

  /**
   * Connection status for this queue.
   */
  enum GNUNET_TRANSPORT_ConnectionStatus cs;

  /**
   * How much outbound bandwidth do we have available for this queue?
   */
  struct GNUNET_BANDWIDTH_Tracker tracker_out;

  /**
   * How much inbound bandwidth do we have available for this queue?
   */
  struct GNUNET_BANDWIDTH_Tracker tracker_in;
};


/**
 * Information we keep for a message that we are reassembling.
 */
struct ReassemblyContext
{

  /**
   * Original message ID for of the message that all the
   * fragments belong to.
   */
  struct GNUNET_ShortHashCode msg_uuid;

  /**
   * Which neighbour is this context for?
   */
  struct Neighbour *neighbour;

  /**
   * Entry in the reassembly heap (sorted by expiration).
   */
  struct GNUNET_CONTAINER_HeapNode *hn;

  /**
   * Bitfield with @e msg_size bits representing the positions
   * where we have received fragments.  When we receive a fragment,
   * we check the bits in @e bitfield before incrementing @e msg_missing.
   *
   * Allocated after the reassembled message.
   */
  uint8_t *bitfield;

  /**
   * Task for sending ACK. We may send ACKs either because of hitting
   * the @e extra_acks limit, or based on time and @e num_acks.  This
   * task is for the latter case.
   */
  struct GNUNET_SCHEDULER_Task *ack_task;

  /**
   * At what time will we give up reassembly of this message?
   */
  struct GNUNET_TIME_Absolute reassembly_timeout;

  /**
   * Average delay of all acks in @e extra_acks and @e frag_uuid.
   * Should be reset to zero when @e num_acks is set to 0.
   */
  struct GNUNET_TIME_Relative avg_ack_delay;

  /**
   * Time we received the last fragment.  @e avg_ack_delay must be
   * incremented by now - @e last_frag multiplied by @e num_acks.
   */
  struct GNUNET_TIME_Absolute last_frag;

  /**
   * Bitfield of up to 64 additional fragments following @e frag_uuid
   * to be acknowledged in the next cummulative ACK.
   */
  uint64_t extra_acks;

  /**
   * Unique ID of the lowest fragment UUID to be acknowledged in the
   * next cummulative ACK.  Only valid if @e num_acks > 0.
   */
  uint32_t frag_uuid;

  /**
   * Number of ACKs we have accumulated so far.  Reset to 0
   * whenever we send a #GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT_ACK.
   */
  unsigned int num_acks;

  /**
   * How big is the message we are reassembling in total?
   */
  uint16_t msg_size;

  /**
   * How many bytes of the message are still missing?  Defragmentation
   * is complete when @e msg_missing == 0.
   */
  uint16_t msg_missing;

  /* Followed by @e msg_size bytes of the (partially) defragmented original message */

  /* Followed by @e bitfield data */
};


/**
 * A neighbour that at least one communicator is connected to.
 */
struct Neighbour
{

  /**
   * Which peer is this about?
   */
  struct GNUNET_PeerIdentity pid;

  /**
   * Map with `struct ReassemblyContext` structs for fragments under
   * reassembly. May be NULL if we currently have no fragments from
   * this @e pid (lazy initialization).
   */
  struct GNUNET_CONTAINER_MultiShortmap *reassembly_map;

  /**
   * Heap with `struct ReassemblyContext` structs for fragments under
   * reassembly. May be NULL if we currently have no fragments from
   * this @e pid (lazy initialization).
   */
  struct GNUNET_CONTAINER_Heap *reassembly_heap;

  /**
   * Task to free old entries from the @e reassembly_heap and @e reassembly_map.
   */
  struct GNUNET_SCHEDULER_Task *reassembly_timeout_task;

  /**
   * Head of list of messages pending for this neighbour.
   */
  struct PendingMessage *pending_msg_head;

  /**
   * Tail of list of messages pending for this neighbour.
   */
  struct PendingMessage *pending_msg_tail;

  /**
   * Head of MDLL of DV hops that have this neighbour as next hop. Must be
   * purged if this neighbour goes down.
   */
  struct DistanceVectorHop *dv_head;

  /**
   * Tail of MDLL of DV hops that have this neighbour as next hop. Must be
   * purged if this neighbour goes down.
   */
  struct DistanceVectorHop *dv_tail;

  /**
   * Head of DLL of queues to this peer.
   */
  struct Queue *queue_head;

  /**
   * Tail of DLL of queues to this peer.
   */
  struct Queue *queue_tail;

  /**
   * Task run to cleanup pending messages that have exceeded their timeout.
   */
  struct GNUNET_SCHEDULER_Task *timeout_task;

  /**
   * Quota at which CORE is allowed to transmit to this peer.
   *
   * FIXME: not yet used, tricky to get right given multiple queues!
   *        (=> Idea: measure???)
   * FIXME: how do we set this value initially when we tell CORE?
   *    Options: start at a minimum value or at literally zero?
   *         (=> Current thought: clean would be zero!)
   */
  struct GNUNET_BANDWIDTH_Value32NBO quota_out;

  /**
   * What is the earliest timeout of any message in @e pending_msg_tail?
   */
  struct GNUNET_TIME_Absolute earliest_timeout;

};


/**
 * A peer that an application (client) would like us to talk to directly.
 */
struct PeerRequest
{

  /**
   * Which peer is this about?
   */
  struct GNUNET_PeerIdentity pid;

  /**
   * Client responsible for the request.
   */
  struct TransportClient *tc;

  /**
   * Handle for watching the peerstore for HELLOs for this peer.
   */
  struct GNUNET_PEERSTORE_WatchContext *wc;

  /**
   * What kind of performance preference does this @e tc have?
   */
  enum GNUNET_MQ_PreferenceKind pk;

  /**
   * How much bandwidth would this @e tc like to see?
   */
  struct GNUNET_BANDWIDTH_Value32NBO bw;

};


/**
 * Types of different pending messages.
 */
enum PendingMessageType
{

  /**
   * Ordinary message received from the CORE service.
   */
  PMT_CORE = 0,

  /**
   * Fragment box.
   */
  PMT_FRAGMENT_BOX = 1,

  /**
   * Reliability box.
   */
  PMT_RELIABILITY_BOX = 2,

  /**
   * Any type of acknowledgement.
   */
  PMT_ACKNOWLEDGEMENT = 3


};


/**
 * Transmission request that is awaiting delivery.  The original
 * transmission requests from CORE may be too big for some queues.
 * In this case, a *tree* of fragments is created.  At each
 * level of the tree, fragments are kept in a DLL ordered by which
 * fragment should be sent next (at the head).  The tree is searched
 * top-down, with the original message at the root.
 *
 * To select a node for transmission, first it is checked if the
 * current node's message fits with the MTU.  If it does not, we
 * either calculate the next fragment (based on @e frag_off) from the
 * current node, or, if all fragments have already been created,
 * descend to the @e head_frag.  Even though the node was already
 * fragmented, the fragment may be too big if the fragment was
 * generated for a queue with a larger MTU. In this case, the node
 * may be fragmented again, thus creating a tree.
 *
 * When acknowledgements for fragments are received, the tree
 * must be pruned, removing those parts that were already
 * acknowledged.  When fragments are sent over a reliable
 * channel, they can be immediately removed.
 *
 * If a message is ever fragmented, then the original "full" message
 * is never again transmitted (even if it fits below the MTU), and
 * only (remaining) fragments are sent.
 */
struct PendingMessage
{
  /**
   * Kept in a MDLL of messages for this @a target.
   */
  struct PendingMessage *next_neighbour;

  /**
   * Kept in a MDLL of messages for this @a target.
   */
  struct PendingMessage *prev_neighbour;

  /**
   * Kept in a MDLL of messages from this @a client (if @e pmt is #PMT_CORE)
   */
  struct PendingMessage *next_client;

  /**
   * Kept in a MDLL of messages from this @a client  (if @e pmt is #PMT_CORE)
   */
  struct PendingMessage *prev_client;

  /**
   * Kept in a MDLL of messages from this @a cpm (if @e pmt is #PMT_FRAGMENT_BOx)
   */
  struct PendingMessage *next_frag;

  /**
   * Kept in a MDLL of messages from this @a cpm  (if @e pmt is #PMT_FRAGMENT_BOX)
   */
  struct PendingMessage *prev_frag;

  /**
   * This message, reliability boxed. Only possibly available if @e pmt is #PMT_CORE.
   */
  struct PendingMessage *bpm;

  /**
   * Target of the request.
   */
  struct Neighbour *target;

  /**
   * Client that issued the transmission request, if @e pmt is #PMT_CORE.
   */
  struct TransportClient *client;

  /**
   * Head of a MDLL of fragments created for this core message.
   */
  struct PendingMessage *head_frag;

  /**
   * Tail of a MDLL of fragments created for this core message.
   */
  struct PendingMessage *tail_frag;

  /**
   * Our parent in the fragmentation tree.
   */
  struct PendingMessage *frag_parent;

  /**
   * At what time should we give up on the transmission (and no longer retry)?
   */
  struct GNUNET_TIME_Absolute timeout;

  /**
   * What is the earliest time for us to retry transmission of this message?
   */
  struct GNUNET_TIME_Absolute next_attempt;

  /**
   * UUID to use for this message (used for reassembly of fragments, only
   * initialized if @e msg_uuid_set is #GNUNET_YES).
   */
  struct GNUNET_ShortHashCode msg_uuid;

  /**
   * Counter incremented per generated fragment.
   */
  uint32_t frag_uuidgen;

  /**
   * Type of the pending message.
   */
  enum PendingMessageType pmt;

  /**
   * Size of the original message.
   */
  uint16_t bytes_msg;

  /**
   * Offset at which we should generate the next fragment.
   */
  uint16_t frag_off;

  /**
   * #GNUNET_YES once @e msg_uuid was initialized
   */
  int16_t msg_uuid_set;

  /* Followed by @e bytes_msg to transmit */
};


/**
 * One of the addresses of this peer.
 */
struct AddressListEntry
{

  /**
   * Kept in a DLL.
   */
  struct AddressListEntry *next;

  /**
   * Kept in a DLL.
   */
  struct AddressListEntry *prev;

  /**
   * Which communicator provides this address?
   */
  struct TransportClient *tc;

  /**
   * The actual address.
   */
  const char *address;

  /**
   * Current context for storing this address in the peerstore.
   */
  struct GNUNET_PEERSTORE_StoreContext *sc;

  /**
   * Task to periodically do @e st operation.
   */
  struct GNUNET_SCHEDULER_Task *st;

  /**
   * What is a typical lifetime the communicator expects this
   * address to have? (Always from now.)
   */
  struct GNUNET_TIME_Relative expiration;

  /**
   * Address identifier used by the communicator.
   */
  uint32_t aid;

  /**
   * Network type offered by this address.
   */
  enum GNUNET_NetworkType nt;

};


/**
 * Client connected to the transport service.
 */
struct TransportClient
{

  /**
   * Kept in a DLL.
   */
  struct TransportClient *next;

  /**
   * Kept in a DLL.
   */
  struct TransportClient *prev;

  /**
   * Handle to the client.
   */
  struct GNUNET_SERVICE_Client *client;

  /**
   * Message queue to the client.
   */
  struct GNUNET_MQ_Handle *mq;

  /**
   * What type of client is this?
   */
  enum ClientType type;

  union
  {

    /**
     * Information for @e type #CT_CORE.
     */
    struct {

      /**
       * Head of list of messages pending for this client, sorted by
       * transmission time ("next_attempt" + possibly internal prioritization).
       */
      struct PendingMessage *pending_msg_head;

      /**
       * Tail of list of messages pending for this client.
       */
      struct PendingMessage *pending_msg_tail;

    } core;

    /**
     * Information for @e type #CT_MONITOR.
     */
    struct {

      /**
       * Peer identity to monitor the addresses of.
       * Zero to monitor all neighbours.  Valid if
       * @e type is #CT_MONITOR.
       */
      struct GNUNET_PeerIdentity peer;

      /**
       * Is this a one-shot monitor?
       */
      int one_shot;

    } monitor;


    /**
     * Information for @e type #CT_COMMUNICATOR.
     */
    struct {
      /**
       * If @e type is #CT_COMMUNICATOR, this communicator
       * supports communicating using these addresses.
       */
      char *address_prefix;

      /**
       * Head of DLL of queues offered by this communicator.
       */
      struct Queue *queue_head;

      /**
       * Tail of DLL of queues offered by this communicator.
       */
      struct Queue *queue_tail;

      /**
       * Head of list of the addresses of this peer offered by this communicator.
       */
      struct AddressListEntry *addr_head;

      /**
       * Tail of list of the addresses of this peer offered by this communicator.
       */
      struct AddressListEntry *addr_tail;

      /**
       * Number of queue entries in all queues to this communicator. Used
       * throttle sending to a communicator if we see that the communicator
       * is globally unable to keep up.
       */
      unsigned int total_queue_length;

      /**
       * Characteristics of this communicator.
       */
      enum GNUNET_TRANSPORT_CommunicatorCharacteristics cc;

    } communicator;

    /**
     * Information for @e type #CT_APPLICATION
     */
    struct {

      /**
       * Map of requests for peers the given client application would like to
       * see connections for.  Maps from PIDs to `struct PeerRequest`.
       */
      struct GNUNET_CONTAINER_MultiPeerMap *requests;

    } application;

  } details;

};


/**
 * Head of linked list of all clients to this service.
 */
static struct TransportClient *clients_head;

/**
 * Tail of linked list of all clients to this service.
 */
static struct TransportClient *clients_tail;

/**
 * Statistics handle.
 */
static struct GNUNET_STATISTICS_Handle *GST_stats;

/**
 * Configuration handle.
 */
static const struct GNUNET_CONFIGURATION_Handle *GST_cfg;

/**
 * Our public key.
 */
static struct GNUNET_PeerIdentity GST_my_identity;

/**
 * Our private key.
 */
static struct GNUNET_CRYPTO_EddsaPrivateKey *GST_my_private_key;

/**
 * Map from PIDs to `struct Neighbour` entries.  A peer is
 * a neighbour if we have an MQ to it from some communicator.
 */
static struct GNUNET_CONTAINER_MultiPeerMap *neighbours;

/**
 * Map from PIDs to `struct DistanceVector` entries describing
 * known paths to the peer.
 */
static struct GNUNET_CONTAINER_MultiPeerMap *dv_routes;

/**
 * Database for peer's HELLOs.
 */
static struct GNUNET_PEERSTORE_Handle *peerstore;

/**
 * Heap sorting `struct EphemeralCacheEntry` by their
 * key/signature validity.
 */
static struct GNUNET_CONTAINER_Heap *ephemeral_heap;

/**
 * Hash map for looking up `struct EphemeralCacheEntry`s
 * by peer identity. (We may have ephemerals in our
 * cache for which we do not have a neighbour entry,
 * and similar many neighbours may not need ephemerals,
 * so we use a second map.)
 */
static struct GNUNET_CONTAINER_MultiPeerMap *ephemeral_map;

/**
 * Task to free expired ephemerals.
 */
static struct GNUNET_SCHEDULER_Task *ephemeral_task;


/**
 * Free cached ephemeral key.
 *
 * @param ece cached signature to free
 */
static void
free_ephemeral (struct EphemeralCacheEntry *ece)
{
  GNUNET_CONTAINER_multipeermap_remove (ephemeral_map,
                                        &ece->target,
                                        ece);
  GNUNET_CONTAINER_heap_remove_node (ece->hn);
  GNUNET_free (ece);
}


/**
 * Lookup neighbour record for peer @a pid.
 *
 * @param pid neighbour to look for
 * @return NULL if we do not have this peer as a neighbour
 */
static struct Neighbour *
lookup_neighbour (const struct GNUNET_PeerIdentity *pid)
{
  return GNUNET_CONTAINER_multipeermap_get (neighbours,
                                            pid);
}


/**
 * Details about what to notify monitors about.
 */
struct MonitorEvent
{
  /**
   * @deprecated To be discussed if we keep these...
   */
  struct GNUNET_TIME_Absolute last_validation;
  struct GNUNET_TIME_Absolute valid_until;
  struct GNUNET_TIME_Absolute next_validation;

  /**
   * Current round-trip time estimate.
   */
  struct GNUNET_TIME_Relative rtt;

  /**
   * Connection status.
   */
  enum GNUNET_TRANSPORT_ConnectionStatus cs;

  /**
   * Messages pending.
   */
  uint32_t num_msg_pending;

  /**
   * Bytes pending.
   */
  uint32_t num_bytes_pending;


};


/**
 * Free a @dvh, and if it is the last path to the `target`,also
 * free the associated DV entry in #dv_routes.
 *
 * @param dvh hop to free
 */
static void
free_distance_vector_hop (struct DistanceVectorHop *dvh)
{
  struct Neighbour *n = dvh->next_hop;
  struct DistanceVector *dv = dvh->dv;

  GNUNET_CONTAINER_MDLL_remove (neighbour,
				n->dv_head,
				n->dv_tail,
				dvh);
  GNUNET_CONTAINER_MDLL_remove (dv,
				dv->dv_head,
				dv->dv_tail,
				dvh);
  GNUNET_free (dvh);
  if (NULL == dv->dv_head)
  {
    GNUNET_assert (GNUNET_YES ==
                   GNUNET_CONTAINER_multipeermap_remove (dv_routes,
                                                         &dv->target,
                                                         dv));
    if (NULL != dv->timeout_task)
      GNUNET_SCHEDULER_cancel (dv->timeout_task);
    GNUNET_free (dv);
  }
}


/**
 * Free entry in #dv_routes.  First frees all hops to the target, and
 * the last target will implicitly free @a dv as well.
 *
 * @param dv route to free
 */
static void
free_dv_route (struct DistanceVector *dv)
{
  struct DistanceVectorHop *dvh;

  while (NULL != (dvh = dv->dv_head))
    free_distance_vector_hop (dvh);
}


/**
 * Notify monitor @a tc about an event.  That @a tc
 * cares about the event has already been checked.
 *
 * Send @a tc information in @a me about a @a peer's status with
 * respect to some @a address to all monitors that care.
 *
 * @param tc monitor to inform
 * @param peer peer the information is about
 * @param address address the information is about
 * @param nt network type associated with @a address
 * @param me detailed information to transmit
 */
static void
notify_monitor (struct TransportClient *tc,
                const struct GNUNET_PeerIdentity *peer,
                const char *address,
                enum GNUNET_NetworkType nt,
                const struct MonitorEvent *me)
{
  struct GNUNET_MQ_Envelope *env;
  struct GNUNET_TRANSPORT_MonitorData *md;
  size_t addr_len = strlen (address) + 1;

  env = GNUNET_MQ_msg_extra (md,
                             addr_len,
                             GNUNET_MESSAGE_TYPE_TRANSPORT_MONITOR_DATA);
  md->nt = htonl ((uint32_t) nt);
  md->peer = *peer;
  md->last_validation = GNUNET_TIME_absolute_hton (me->last_validation);
  md->valid_until = GNUNET_TIME_absolute_hton (me->valid_until);
  md->next_validation = GNUNET_TIME_absolute_hton (me->next_validation);
  md->rtt = GNUNET_TIME_relative_hton (me->rtt);
  md->cs = htonl ((uint32_t) me->cs);
  md->num_msg_pending = htonl (me->num_msg_pending);
  md->num_bytes_pending = htonl (me->num_bytes_pending);
  memcpy (&md[1],
          address,
          addr_len);
  GNUNET_MQ_send (tc->mq,
                  env);
}


/**
 * Send information in @a me about a @a peer's status with respect
 * to some @a address to all monitors that care.
 *
 * @param peer peer the information is about
 * @param address address the information is about
 * @param nt network type associated with @a address
 * @param me detailed information to transmit
 */
static void
notify_monitors (const struct GNUNET_PeerIdentity *peer,
                 const char *address,
                 enum GNUNET_NetworkType nt,
                 const struct MonitorEvent *me)
{
  static struct GNUNET_PeerIdentity zero;

  for (struct TransportClient *tc = clients_head;
       NULL != tc;
       tc = tc->next)
  {
    if (CT_MONITOR != tc->type)
      continue;
    if (tc->details.monitor.one_shot)
      continue;
    if ( (0 != memcmp (&tc->details.monitor.peer,
                       &zero,
                       sizeof (zero))) &&
         (0 != memcmp (&tc->details.monitor.peer,
                       peer,
                       sizeof (*peer))) )
      continue;
    notify_monitor (tc,
                    peer,
                    address,
                    nt,
                    me);
  }
}


/**
 * Called whenever a client connects.  Allocates our
 * data structures associated with that client.
 *
 * @param cls closure, NULL
 * @param client identification of the client
 * @param mq message queue for the client
 * @return our `struct TransportClient`
 */
static void *
client_connect_cb (void *cls,
                   struct GNUNET_SERVICE_Client *client,
                   struct GNUNET_MQ_Handle *mq)
{
  struct TransportClient *tc;

  tc = GNUNET_new (struct TransportClient);
  tc->client = client;
  tc->mq = mq;
  GNUNET_CONTAINER_DLL_insert (clients_head,
                               clients_tail,
                               tc);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client %p connected\n",
              tc);
  return tc;
}


/**
 * Free @a rc
 *
 * @param rc data structure to free
 */
static void
free_reassembly_context (struct ReassemblyContext *rc)
{
  struct Neighbour *n = rc->neighbour;

  GNUNET_assert (rc ==
                 GNUNET_CONTAINER_heap_remove_node (rc->hn));
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CONTAINER_multishortmap_remove (n->reassembly_map,
                                                        &rc->msg_uuid,
                                                        rc));
  GNUNET_free (rc);
}


/**
 * Task run to clean up reassembly context of a neighbour that have expired.
 *
 * @param cls a `struct Neighbour`
 */
static void
reassembly_cleanup_task (void *cls)
{
  struct Neighbour *n = cls;
  struct ReassemblyContext *rc;

  n->reassembly_timeout_task = NULL;
  while (NULL != (rc = GNUNET_CONTAINER_heap_peek (n->reassembly_heap)))
  {
    if (0 == GNUNET_TIME_absolute_get_remaining (rc->reassembly_timeout).rel_value_us)
    {
      free_reassembly_context (rc);
      continue;
    }
    GNUNET_assert (NULL == n->reassembly_timeout_task);
    n->reassembly_timeout_task = GNUNET_SCHEDULER_add_at (rc->reassembly_timeout,
                                                          &reassembly_cleanup_task,
                                                          n);
    return;
  }
}


/**
 * function called to #free_reassembly_context().
 *
 * @param cls NULL
 * @param key unused
 * @param value a `struct ReassemblyContext` to free
 * @return #GNUNET_OK (continue iteration)
 */
static int
free_reassembly_cb (void *cls,
		    const struct GNUNET_ShortHashCode *key,
		    void *value)
{
  struct ReassemblyContext *rc = value;
  (void) cls;
  (void) key;

  free_reassembly_context (rc);
  return GNUNET_OK;
}


/**
 * Release memory used by @a neighbour.
 *
 * @param neighbour neighbour entry to free
 */
static void
free_neighbour (struct Neighbour *neighbour)
{
  struct DistanceVectorHop *dvh;

  GNUNET_assert (NULL == neighbour->queue_head);
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CONTAINER_multipeermap_remove (neighbours,
                                                       &neighbour->pid,
                                                       neighbour));
  if (NULL != neighbour->timeout_task)
    GNUNET_SCHEDULER_cancel (neighbour->timeout_task);
  if (NULL != neighbour->reassembly_map)
  {
    GNUNET_CONTAINER_multishortmap_iterate (neighbour->reassembly_map,
                                            &free_reassembly_cb,
                                            NULL);
    GNUNET_CONTAINER_multishortmap_destroy (neighbour->reassembly_map);
    neighbour->reassembly_map = NULL;
    GNUNET_CONTAINER_heap_destroy (neighbour->reassembly_heap);
    neighbour->reassembly_heap = NULL;
  }
  while (NULL != (dvh = neighbour->dv_head))
    free_distance_vector_hop (dvh);
  if (NULL != neighbour->reassembly_timeout_task)
    GNUNET_SCHEDULER_cancel (neighbour->reassembly_timeout_task);
  GNUNET_free (neighbour);
}


/**
 * Send message to CORE clients that we lost a connection.
 *
 * @param tc client to inform (must be CORE client)
 * @param pid peer the connection is for
 * @param quota_out current quota for the peer
 */
static void
core_send_connect_info (struct TransportClient *tc,
                        const struct GNUNET_PeerIdentity *pid,
                        struct GNUNET_BANDWIDTH_Value32NBO quota_out)
{
  struct GNUNET_MQ_Envelope *env;
  struct ConnectInfoMessage *cim;

  GNUNET_assert (CT_CORE == tc->type);
  env = GNUNET_MQ_msg (cim,
                       GNUNET_MESSAGE_TYPE_TRANSPORT_CONNECT);
  cim->quota_out = quota_out;
  cim->id = *pid;
  GNUNET_MQ_send (tc->mq,
		  env);
}


/**
 * Send message to CORE clients that we gained a connection
 *
 * @param pid peer the queue was for
 * @param quota_out current quota for the peer
 */
static void
cores_send_connect_info (const struct GNUNET_PeerIdentity *pid,
                         struct GNUNET_BANDWIDTH_Value32NBO quota_out)
{
  for (struct TransportClient *tc = clients_head;
       NULL != tc;
       tc = tc->next)
  {
    if (CT_CORE != tc->type)
      continue;
    core_send_connect_info (tc,
                            pid,
                            quota_out);
  }
}


/**
 * Send message to CORE clients that we lost a connection.
 *
 * @param pid peer the connection was for
 */
static void
cores_send_disconnect_info (const struct GNUNET_PeerIdentity *pid)
{
  for (struct TransportClient *tc = clients_head;
       NULL != tc;
       tc = tc->next)
  {
    struct GNUNET_MQ_Envelope *env;
    struct DisconnectInfoMessage *dim;

    if (CT_CORE != tc->type)
      continue;
    env = GNUNET_MQ_msg (dim,
                         GNUNET_MESSAGE_TYPE_TRANSPORT_DISCONNECT);
    dim->peer = *pid;
    GNUNET_MQ_send (tc->mq,
                    env);
  }
}


/**
 * We believe we are ready to transmit a message on a queue. Double-checks
 * with the queue's "tracker_out" and then gives the message to the
 * communicator for transmission (updating the tracker, and re-scheduling
 * itself if applicable).
 *
 * @param cls the `struct Queue` to process transmissions for
 */
static void
transmit_on_queue (void *cls);


/**
 * Schedule next run of #transmit_on_queue().  Does NOTHING if
 * we should run immediately or if the message queue is empty.
 * Test for no task being added AND queue not being empty to
 * transmit immediately afterwards!  This function must only
 * be called if the message queue is non-empty!
 *
 * @param queue the queue to do scheduling for
 */
static void
schedule_transmit_on_queue (struct Queue *queue)
{
  struct Neighbour *n = queue->neighbour;
  struct PendingMessage *pm = n->pending_msg_head;
  struct GNUNET_TIME_Relative out_delay;
  unsigned int wsize;

  GNUNET_assert (NULL != pm);
  if (queue->tc->details.communicator.total_queue_length >=
      COMMUNICATOR_TOTAL_QUEUE_LIMIT)
  {
    GNUNET_STATISTICS_update (GST_stats,
                              "# Transmission throttled due to communicator queue limit",
                              1,
                              GNUNET_NO);
    return;
  }
  if (queue->queue_length >= QUEUE_LENGTH_LIMIT)
  {
    GNUNET_STATISTICS_update (GST_stats,
                              "# Transmission throttled due to queue queue limit",
                              1,
                              GNUNET_NO);
    return;
  }

  wsize = (0 == queue->mtu)
    ? pm->bytes_msg /* FIXME: add overheads? */
    : queue->mtu;
  out_delay = GNUNET_BANDWIDTH_tracker_get_delay (&queue->tracker_out,
                                                  wsize);
  out_delay = GNUNET_TIME_relative_max (GNUNET_TIME_absolute_get_remaining (pm->next_attempt),
                                        out_delay);
  if (0 == out_delay.rel_value_us)
    return; /* we should run immediately! */
  /* queue has changed since we were scheduled, reschedule again */
  queue->transmit_task
    = GNUNET_SCHEDULER_add_delayed (out_delay,
                                    &transmit_on_queue,
                                    queue);
  if (out_delay.rel_value_us > DELAY_WARN_THRESHOLD.rel_value_us)
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Next transmission on queue `%s' in %s (high delay)\n",
                queue->address,
                GNUNET_STRINGS_relative_time_to_string (out_delay,
                                                        GNUNET_YES));
  else
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Next transmission on queue `%s' in %s\n",
                queue->address,
                GNUNET_STRINGS_relative_time_to_string (out_delay,
                                                        GNUNET_YES));
}


/**
 * Free @a queue.
 *
 * @param queue the queue to free
 */
static void
free_queue (struct Queue *queue)
{
  struct Neighbour *neighbour = queue->neighbour;
  struct TransportClient *tc = queue->tc;
  struct MonitorEvent me = {
    .cs = GNUNET_TRANSPORT_CS_DOWN,
    .rtt = GNUNET_TIME_UNIT_FOREVER_REL
  };
  struct QueueEntry *qe;
  int maxxed;

  if (NULL != queue->transmit_task)
  {
    GNUNET_SCHEDULER_cancel (queue->transmit_task);
    queue->transmit_task = NULL;
  }
  GNUNET_CONTAINER_MDLL_remove (neighbour,
                                neighbour->queue_head,
                                neighbour->queue_tail,
                                queue);
  GNUNET_CONTAINER_MDLL_remove (client,
                                tc->details.communicator.queue_head,
                                tc->details.communicator.queue_tail,
                                queue);
  maxxed = (COMMUNICATOR_TOTAL_QUEUE_LIMIT >= tc->details.communicator.total_queue_length);
  while (NULL != (qe = queue->queue_head))
  {
    GNUNET_CONTAINER_DLL_remove (queue->queue_head,
                                 queue->queue_tail,
                                 qe);
    queue->queue_length--;
    tc->details.communicator.total_queue_length--;
    GNUNET_free (qe);
  }
  GNUNET_assert (0 == queue->queue_length);
  if ( (maxxed) &&
       (COMMUNICATOR_TOTAL_QUEUE_LIMIT < tc->details.communicator.total_queue_length) )
  {
    /* Communicator dropped below threshold, resume all queues */
    GNUNET_STATISTICS_update (GST_stats,
                              "# Transmission throttled due to communicator queue limit",
                              -1,
                              GNUNET_NO);
    for (struct Queue *s = tc->details.communicator.queue_head;
         NULL != s;
         s = s->next_client)
      schedule_transmit_on_queue (s);
  }
  notify_monitors (&neighbour->pid,
                   queue->address,
                   queue->nt,
                   &me);
  GNUNET_BANDWIDTH_tracker_notification_stop (&queue->tracker_in);
  GNUNET_BANDWIDTH_tracker_notification_stop (&queue->tracker_out);
  GNUNET_free (queue);
  if (NULL == neighbour->queue_head)
  {
    cores_send_disconnect_info (&neighbour->pid);
    free_neighbour (neighbour);
  }
}


/**
 * Free @a ale
 *
 * @param ale address list entry to free
 */
static void
free_address_list_entry (struct AddressListEntry *ale)
{
  struct TransportClient *tc = ale->tc;

  GNUNET_CONTAINER_DLL_remove (tc->details.communicator.addr_head,
                               tc->details.communicator.addr_tail,
                               ale);
  if (NULL != ale->sc)
  {
    GNUNET_PEERSTORE_store_cancel (ale->sc);
    ale->sc = NULL;
  }
  if (NULL != ale->st)
  {
    GNUNET_SCHEDULER_cancel (ale->st);
    ale->st = NULL;
  }
  GNUNET_free (ale);
}


/**
 * Stop the peer request in @a value.
 *
 * @param cls a `struct TransportClient` that no longer makes the request
 * @param pid the peer's identity
 * @param value a `struct PeerRequest`
 * @return #GNUNET_YES (always)
 */
static int
stop_peer_request (void *cls,
                   const struct GNUNET_PeerIdentity *pid,
                   void *value)
{
  struct TransportClient *tc = cls;
  struct PeerRequest *pr = value;

  GNUNET_PEERSTORE_watch_cancel (pr->wc);
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CONTAINER_multipeermap_remove (tc->details.application.requests,
                                                       pid,
                                                       pr));
  GNUNET_free (pr);

  return GNUNET_OK;
}


/**
 * Called whenever a client is disconnected.  Frees our
 * resources associated with that client.
 *
 * @param cls closure, NULL
 * @param client identification of the client
 * @param app_ctx our `struct TransportClient`
 */
static void
client_disconnect_cb (void *cls,
                      struct GNUNET_SERVICE_Client *client,
                      void *app_ctx)
{
  struct TransportClient *tc = app_ctx;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client %p disconnected, cleaning up.\n",
              tc);
  GNUNET_CONTAINER_DLL_remove (clients_head,
                               clients_tail,
                               tc);
  switch (tc->type)
  {
  case CT_NONE:
    break;
  case CT_CORE:
    {
      struct PendingMessage *pm;

      while (NULL != (pm = tc->details.core.pending_msg_head))
      {
        GNUNET_CONTAINER_MDLL_remove (client,
                                      tc->details.core.pending_msg_head,
                                      tc->details.core.pending_msg_tail,
                                      pm);
        pm->client = NULL;
      }
    }
    break;
  case CT_MONITOR:
    break;
  case CT_COMMUNICATOR:
    {
      struct Queue *q;
      struct AddressListEntry *ale;

      while (NULL != (q = tc->details.communicator.queue_head))
        free_queue (q);
      while (NULL != (ale = tc->details.communicator.addr_head))
        free_address_list_entry (ale);
      GNUNET_free (tc->details.communicator.address_prefix);
    }
    break;
  case CT_APPLICATION:
    GNUNET_CONTAINER_multipeermap_iterate (tc->details.application.requests,
                                           &stop_peer_request,
                                           tc);
    GNUNET_CONTAINER_multipeermap_destroy (tc->details.application.requests);
    break;
  }
  GNUNET_free (tc);
}


/**
 * Iterator telling new CORE client about all existing
 * connections to peers.
 *
 * @param cls the new `struct TransportClient`
 * @param pid a connected peer
 * @param value the `struct Neighbour` with more information
 * @return #GNUNET_OK (continue to iterate)
 */
static int
notify_client_connect_info (void *cls,
                            const struct GNUNET_PeerIdentity *pid,
                            void *value)
{
  struct TransportClient *tc = cls;
  struct Neighbour *neighbour = value;

  core_send_connect_info (tc,
                          pid,
                          neighbour->quota_out);
  return GNUNET_OK;
}


/**
 * Initialize a "CORE" client.  We got a start message from this
 * client, so add it to the list of clients for broadcasting of
 * inbound messages.
 *
 * @param cls the client
 * @param start the start message that was sent
 */
static void
handle_client_start (void *cls,
                     const struct StartMessage *start)
{
  struct TransportClient *tc = cls;
  uint32_t options;

  options = ntohl (start->options);
  if ( (0 != (1 & options)) &&
       (0 !=
        memcmp (&start->self,
                &GST_my_identity,
                sizeof (struct GNUNET_PeerIdentity)) ) )
  {
    /* client thinks this is a different peer, reject */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  if (CT_NONE != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  tc->type = CT_CORE;
  GNUNET_CONTAINER_multipeermap_iterate (neighbours,
                                         &notify_client_connect_info,
                                         tc);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Client asked for transmission to a peer.  Process the request.
 *
 * @param cls the client
 * @param obm the send message that was sent
 */
static int
check_client_send (void *cls,
                   const struct OutboundMessage *obm)
{
  struct TransportClient *tc = cls;
  uint16_t size;
  const struct GNUNET_MessageHeader *obmm;

  if (CT_CORE != tc->type)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  size = ntohs (obm->header.size) - sizeof (struct OutboundMessage);
  if (size < sizeof (struct GNUNET_MessageHeader))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  obmm = (const struct GNUNET_MessageHeader *) &obm[1];
  if (size != ntohs (obmm->size))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Free fragment tree below @e root, excluding @e root itself.
 *
 * @param root root of the tree to free
 */
static void
free_fragment_tree (struct PendingMessage *root)
{
  struct PendingMessage *frag;

  while (NULL != (frag = root->head_frag))
  {
    free_fragment_tree (frag);
    GNUNET_CONTAINER_MDLL_remove (frag,
				  root->head_frag,
				  root->tail_frag,
				  frag);
    GNUNET_free (frag);
  }
}


/**
 * Release memory associated with @a pm and remove @a pm from associated
 * data structures.  @a pm must be a top-level pending message and not
 * a fragment in the tree.  The entire tree is freed (if applicable).
 *
 * @param pm the pending message to free
 */
static void
free_pending_message (struct PendingMessage *pm)
{
  struct TransportClient *tc = pm->client;
  struct Neighbour *target = pm->target;

  if (NULL != tc)
  {
    GNUNET_CONTAINER_MDLL_remove (client,
                                  tc->details.core.pending_msg_head,
                                  tc->details.core.pending_msg_tail,
                                  pm);
  }
  GNUNET_CONTAINER_MDLL_remove (neighbour,
                                target->pending_msg_head,
                                target->pending_msg_tail,
                                pm);
  free_fragment_tree (pm);
  GNUNET_free_non_null (pm->bpm);
  GNUNET_free (pm);
}


/**
 * Send a response to the @a pm that we have processed a
 * "send" request with status @a success. We
 * transmitted @a bytes_physical on the actual wire.
 * Sends a confirmation to the "core" client responsible
 * for the original request and free's @a pm.
 *
 * @param pm handle to the original pending message
 * @param success status code, #GNUNET_OK on success, #GNUNET_SYSERR
 *          for transmission failure
 * @param bytes_physical amount of bandwidth consumed
 */
static void
client_send_response (struct PendingMessage *pm,
                      int success,
                      uint32_t bytes_physical)
{
  struct TransportClient *tc = pm->client;
  struct Neighbour *target = pm->target;
  struct GNUNET_MQ_Envelope *env;
  struct SendOkMessage *som;

  if (NULL != tc)
  {
    env = GNUNET_MQ_msg (som,
                         GNUNET_MESSAGE_TYPE_TRANSPORT_SEND_OK);
    som->success = htonl ((uint32_t) success);
    som->bytes_msg = htons (pm->bytes_msg);
    som->bytes_physical = htonl (bytes_physical);
    som->peer = target->pid;
    GNUNET_MQ_send (tc->mq,
		    env);
  }
  free_pending_message (pm);
}


/**
 * Checks the message queue for a neighbour for messages that have timed
 * out and purges them.
 *
 * @param cls a `struct Neighbour`
 */
static void
check_queue_timeouts (void *cls)
{
  struct Neighbour *n = cls;
  struct PendingMessage *pm;
  struct GNUNET_TIME_Absolute now;
  struct GNUNET_TIME_Absolute earliest_timeout;

  n->timeout_task = NULL;
  earliest_timeout = GNUNET_TIME_UNIT_FOREVER_ABS;
  now = GNUNET_TIME_absolute_get ();
  for (struct PendingMessage *pos = n->pending_msg_head;
       NULL != pos;
       pos = pm)
  {
    pm = pos->next_neighbour;
    if (pos->timeout.abs_value_us <= now.abs_value_us)
    {
      GNUNET_STATISTICS_update (GST_stats,
                                "# messages dropped (timeout before confirmation)",
                                1,
                                GNUNET_NO);
      client_send_response (pm,
			    GNUNET_NO,
			    0);
      continue;
    }
    earliest_timeout = GNUNET_TIME_absolute_min (earliest_timeout,
                                                 pos->timeout);
  }
  n->earliest_timeout = earliest_timeout;
  if (NULL != n->pending_msg_head)
    n->timeout_task = GNUNET_SCHEDULER_add_at (earliest_timeout,
                                               &check_queue_timeouts,
                                               n);
}


/**
 * Client asked for transmission to a peer.  Process the request.
 *
 * @param cls the client
 * @param obm the send message that was sent
 */
static void
handle_client_send (void *cls,
                    const struct OutboundMessage *obm)
{
  struct TransportClient *tc = cls;
  struct PendingMessage *pm;
  const struct GNUNET_MessageHeader *obmm;
  struct Neighbour *target;
  uint32_t bytes_msg;
  int was_empty;

  GNUNET_assert (CT_CORE == tc->type);
  obmm = (const struct GNUNET_MessageHeader *) &obm[1];
  bytes_msg = ntohs (obmm->size);
  target = lookup_neighbour (&obm->peer);
  if (NULL == target)
  {
    /* Failure: don't have this peer as a neighbour (anymore).
       Might have gone down asynchronously, so this is NOT
       a protocol violation by CORE. Still count the event,
       as this should be rare. */
    struct GNUNET_MQ_Envelope *env;
    struct SendOkMessage *som;

    env = GNUNET_MQ_msg (som,
                         GNUNET_MESSAGE_TYPE_TRANSPORT_SEND_OK);
    som->success = htonl (GNUNET_SYSERR);
    som->bytes_msg = htonl (bytes_msg);
    som->bytes_physical = htonl (0);
    som->peer = obm->peer;
    GNUNET_MQ_send (tc->mq,
                    env);
    GNUNET_SERVICE_client_continue (tc->client);
    GNUNET_STATISTICS_update (GST_stats,
                              "# messages dropped (neighbour unknown)",
                              1,
                              GNUNET_NO);
    return;
  }
  was_empty = (NULL == target->pending_msg_head);
  pm = GNUNET_malloc (sizeof (struct PendingMessage) + bytes_msg);
  pm->client = tc;
  pm->target = target;
  pm->bytes_msg = bytes_msg;
  pm->timeout = GNUNET_TIME_relative_to_absolute (GNUNET_TIME_relative_ntoh (obm->timeout));
  memcpy (&pm[1],
          &obm[1],
          bytes_msg);
  GNUNET_CONTAINER_MDLL_insert (neighbour,
                                target->pending_msg_head,
                                target->pending_msg_tail,
                                pm);
  GNUNET_CONTAINER_MDLL_insert (client,
                                tc->details.core.pending_msg_head,
                                tc->details.core.pending_msg_tail,
                                pm);
  if (target->earliest_timeout.abs_value_us > pm->timeout.abs_value_us)
  {
    target->earliest_timeout.abs_value_us = pm->timeout.abs_value_us;
    if (NULL != target->timeout_task)
      GNUNET_SCHEDULER_cancel (target->timeout_task);
    target->timeout_task
      = GNUNET_SCHEDULER_add_at (target->earliest_timeout,
                                 &check_queue_timeouts,
                                 target);
  }
  if (! was_empty)
    return; /* all queues must already be busy */
  for (struct Queue *queue = target->queue_head;
       NULL != queue;
       queue = queue->next_neighbour)
  {
    /* try transmission on any queue that is idle */
    if (NULL == queue->transmit_task)
      queue->transmit_task = GNUNET_SCHEDULER_add_now (&transmit_on_queue,
                                                       queue);
  }
}


/**
 * Communicator started.  Test message is well-formed.
 *
 * @param cls the client
 * @param cam the send message that was sent
 */
static int
check_communicator_available (void *cls,
                              const struct GNUNET_TRANSPORT_CommunicatorAvailableMessage *cam)
{
  struct TransportClient *tc = cls;
  uint16_t size;

  if (CT_NONE != tc->type)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  tc->type = CT_COMMUNICATOR;
  size = ntohs (cam->header.size) - sizeof (*cam);
  if (0 == size)
    return GNUNET_OK; /* receive-only communicator */
  GNUNET_MQ_check_zero_termination (cam);
  return GNUNET_OK;
}


/**
 * Communicator started.  Process the request.
 *
 * @param cls the client
 * @param cam the send message that was sent
 */
static void
handle_communicator_available (void *cls,
                               const struct GNUNET_TRANSPORT_CommunicatorAvailableMessage *cam)
{
  struct TransportClient *tc = cls;
  uint16_t size;

  size = ntohs (cam->header.size) - sizeof (*cam);
  if (0 == size)
    return; /* receive-only communicator */
  tc->details.communicator.address_prefix
    = GNUNET_strdup ((const char *) &cam[1]);
  tc->details.communicator.cc
    = (enum GNUNET_TRANSPORT_CommunicatorCharacteristics) ntohl (cam->cc);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Communicator requests backchannel transmission.  Check the request.
 *
 * @param cls the client
 * @param cb the send message that was sent
 * @return #GNUNET_OK if message is well-formed
 */
static int
check_communicator_backchannel (void *cls,
                                const struct GNUNET_TRANSPORT_CommunicatorBackchannel *cb)
{
  const struct GNUNET_MessageHeader *inbox;
  const char *is;
  uint16_t msize;
  uint16_t isize;

  msize = ntohs (cb->header.size) - sizeof (*cb);
  if (UINT16_MAX - msize >
      sizeof (struct TransportBackchannelEncapsulationMessage) +
      sizeof (struct TransportBackchannelRequestPayload) )
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  inbox = (const struct GNUNET_MessageHeader *) &cb[1];
  isize = ntohs (inbox->size);
  if (isize >= msize)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  is = (const char *) inbox;
  is += isize;
  msize -= isize;
  GNUNET_assert (msize > 0);
  if ('\0' != is[msize-1])
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Remove memory used by expired ephemeral keys.
 *
 * @param cls NULL
 */
static void
expire_ephemerals (void *cls)
{
  struct EphemeralCacheEntry *ece;

  (void) cls;
  ephemeral_task = NULL;
  while (NULL != (ece = GNUNET_CONTAINER_heap_peek (ephemeral_heap)))
  {
    if (0 == GNUNET_TIME_absolute_get_remaining (ece->ephemeral_validity).rel_value_us)
    {
      free_ephemeral (ece);
      continue;
    }
    ephemeral_task = GNUNET_SCHEDULER_add_at (ece->ephemeral_validity,
					      &expire_ephemerals,
					      NULL);
    return;
  }
}


/**
 * Lookup ephemeral key in our #ephemeral_map. If no valid one exists, generate
 * one, cache it and return it.
 *
 * @param pid peer to look up ephemeral for
 * @param private_key[out] set to the private key
 * @param ephemeral_key[out] set to the key
 * @param ephemeral_sender_sig[out] set to the signature
 * @param ephemeral_validity[out] set to the validity expiration time
 */
static void
lookup_ephemeral (const struct GNUNET_PeerIdentity *pid,
                  struct GNUNET_CRYPTO_EcdhePrivateKey *private_key,
                  struct GNUNET_CRYPTO_EcdhePublicKey *ephemeral_key,
                  struct GNUNET_CRYPTO_EddsaSignature *ephemeral_sender_sig,
                  struct GNUNET_TIME_Absolute *ephemeral_validity)
{
  struct EphemeralCacheEntry *ece;
  struct EphemeralConfirmation ec;

  ece = GNUNET_CONTAINER_multipeermap_get (ephemeral_map,
					   pid);
  if ( (NULL != ece) &&
       (0 == GNUNET_TIME_absolute_get_remaining (ece->ephemeral_validity).rel_value_us) )
  {
    free_ephemeral (ece);
    ece = NULL;
  }
  if (NULL == ece)
  {
    ece = GNUNET_new (struct EphemeralCacheEntry);
    ece->target = *pid;
    ece->ephemeral_validity = GNUNET_TIME_absolute_add (GNUNET_TIME_absolute_get_monotonic (GST_cfg),
							EPHEMERAL_VALIDITY);
    GNUNET_assert (GNUNET_OK ==
		   GNUNET_CRYPTO_ecdhe_key_create2 (&ece->private_key));
    GNUNET_CRYPTO_ecdhe_key_get_public (&ece->private_key,
					&ece->ephemeral_key);
    ec.purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_TRANSPORT_EPHEMERAL);
    ec.purpose.size = htonl (sizeof (ec));
    ec.target = *pid;
    ec.ephemeral_key = ece->ephemeral_key;
    GNUNET_assert (GNUNET_OK ==
		   GNUNET_CRYPTO_eddsa_sign (GST_my_private_key,
					     &ec.purpose,
					     &ece->sender_sig));
    ece->hn = GNUNET_CONTAINER_heap_insert (ephemeral_heap,
					    ece,
					    ece->ephemeral_validity.abs_value_us);
    GNUNET_assert (GNUNET_OK ==
		   GNUNET_CONTAINER_multipeermap_put (ephemeral_map,
						      &ece->target,
						      ece,
						      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
    if (NULL == ephemeral_task)
      ephemeral_task = GNUNET_SCHEDULER_add_at (ece->ephemeral_validity,
						&expire_ephemerals,
						NULL);
  }
  *private_key = ece->private_key;
  *ephemeral_key = ece->ephemeral_key;
  *ephemeral_sender_sig = ece->sender_sig;
  *ephemeral_validity = ece->ephemeral_validity;
}


/**
 * We need to transmit @a hdr to @a target.  If necessary, this may
 * involve DV routing or even broadcasting and fragmentation.
 *
 * @param target peer to receive @a hdr
 * @param hdr header of the message to route
 */
static void
route_message (const struct GNUNET_PeerIdentity *target,
	       struct GNUNET_MessageHeader *hdr)
{
  // FIXME: send hdr to target, free hdr (possibly using DV, possibly broadcasting)
  GNUNET_free (hdr);
}


/**
 * Communicator requests backchannel transmission.  Process the request.
 *
 * @param cls the client
 * @param cb the send message that was sent
 */
static void
handle_communicator_backchannel (void *cls,
                                 const struct GNUNET_TRANSPORT_CommunicatorBackchannel *cb)
{
  struct TransportClient *tc = cls;
  struct GNUNET_CRYPTO_EcdhePrivateKey private_key;
  struct GNUNET_TIME_Absolute ephemeral_validity;
  struct TransportBackchannelEncapsulationMessage *enc;
  struct TransportBackchannelRequestPayload ppay;
  char *mpos;
  uint16_t msize;

  /* encapsulate and encrypt message */
  msize = ntohs (cb->header.size) - sizeof (*cb) + sizeof (struct TransportBackchannelRequestPayload);
  enc = GNUNET_malloc (sizeof (*enc) + msize);
  enc->header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_BACKCHANNEL_ENCAPSULATION);
  enc->header.size = htons (sizeof (*enc) + msize);
  enc->target = cb->pid;
  lookup_ephemeral (&cb->pid,
		    &private_key,
		    &enc->ephemeral_key,
		    &ppay.sender_sig,
		    &ephemeral_validity);
  // FIXME: setup 'iv'
#if FIXME
  dh_key_derive (&private_key,
		 &cb->pid,
		 &enc->iv,
		 &key);
#endif
  ppay.ephemeral_validity = GNUNET_TIME_absolute_hton (ephemeral_validity);
  ppay.monotonic_time = GNUNET_TIME_absolute_hton (GNUNET_TIME_absolute_get_monotonic (GST_cfg));
  mpos = (char *) &enc[1];
#if FIXME
  encrypt (key,
	   &ppay,
	   &mpos,
	   sizeof (ppay));
  encrypt (key,
	   &cb[1],
	   &mpos,
	   ntohs (cb->header.size) - sizeof (*cb));
  hmac (key,
	&enc->hmac);
#endif
  route_message (&cb->pid,
		 &enc->header);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Address of our peer added.  Test message is well-formed.
 *
 * @param cls the client
 * @param aam the send message that was sent
 * @return #GNUNET_OK if message is well-formed
 */
static int
check_add_address (void *cls,
                   const struct GNUNET_TRANSPORT_AddAddressMessage *aam)
{
  struct TransportClient *tc = cls;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  GNUNET_MQ_check_zero_termination (aam);
  return GNUNET_OK;
}


/**
 * Ask peerstore to store our address.
 *
 * @param cls an `struct AddressListEntry *`
 */
static void
store_pi (void *cls);


/**
 * Function called when peerstore is done storing our address.
 */
static void
peerstore_store_cb (void *cls,
                    int success)
{
  struct AddressListEntry *ale = cls;

  ale->sc = NULL;
  if (GNUNET_YES != success)
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
		"Failed to store our own address `%s' in peerstore!\n",
		ale->address);
  /* refresh period is 1/4 of expiration time, that should be plenty
     without being excessive. */
  ale->st = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_divide (ale->expiration,
								       4ULL),
					  &store_pi,
					  ale);
}


/**
 * Ask peerstore to store our address.
 *
 * @param cls an `struct AddressListEntry *`
 */
static void
store_pi (void *cls)
{
  struct AddressListEntry *ale = cls;
  void *addr;
  size_t addr_len;
  struct GNUNET_TIME_Absolute expiration;

  ale->st = NULL;
  expiration = GNUNET_TIME_relative_to_absolute (ale->expiration);
  GNUNET_HELLO_sign_address (ale->address,
			     ale->nt,
			     expiration,
			     GST_my_private_key,
			     &addr,
			     &addr_len);
  ale->sc = GNUNET_PEERSTORE_store (peerstore,
				    "transport",
				    &GST_my_identity,
				    GNUNET_HELLO_PEERSTORE_KEY,
				    addr,
				    addr_len,
				    expiration,
				    GNUNET_PEERSTORE_STOREOPTION_MULTIPLE,
				    &peerstore_store_cb,
				    ale);
  GNUNET_free (addr);
  if (NULL == ale->sc)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
		"Failed to store our address `%s' with peerstore\n",
		ale->address);
    ale->st = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
					    &store_pi,
					    ale);
  }
}


/**
 * Address of our peer added.  Process the request.
 *
 * @param cls the client
 * @param aam the send message that was sent
 */
static void
handle_add_address (void *cls,
                    const struct GNUNET_TRANSPORT_AddAddressMessage *aam)
{
  struct TransportClient *tc = cls;
  struct AddressListEntry *ale;
  size_t slen;

  slen = ntohs (aam->header.size) - sizeof (*aam);
  ale = GNUNET_malloc (sizeof (struct AddressListEntry) + slen);
  ale->tc = tc;
  ale->address = (const char *) &ale[1];
  ale->expiration = GNUNET_TIME_relative_ntoh (aam->expiration);
  ale->aid = aam->aid;
  ale->nt = (enum GNUNET_NetworkType) ntohl (aam->nt);
  memcpy (&ale[1],
          &aam[1],
          slen);
  GNUNET_CONTAINER_DLL_insert (tc->details.communicator.addr_head,
                               tc->details.communicator.addr_tail,
                               ale);
  ale->st = GNUNET_SCHEDULER_add_now (&store_pi,
				      ale);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Address of our peer deleted.  Process the request.
 *
 * @param cls the client
 * @param dam the send message that was sent
 */
static void
handle_del_address (void *cls,
                    const struct GNUNET_TRANSPORT_DelAddressMessage *dam)
{
  struct TransportClient *tc = cls;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  for (struct AddressListEntry *ale = tc->details.communicator.addr_head;
       NULL != ale;
       ale = ale->next)
  {
    if (dam->aid != ale->aid)
      continue;
    GNUNET_assert (ale->tc == tc);
    free_address_list_entry (ale);
    GNUNET_SERVICE_client_continue (tc->client);
  }
  GNUNET_break (0);
  GNUNET_SERVICE_client_drop (tc->client);
}


/**
 * Context from #handle_incoming_msg().  Closure for many
 * message handlers below.
 */
struct CommunicatorMessageContext
{
  /**
   * Which communicator provided us with the message.
   */
  struct TransportClient *tc;

  /**
   * Additional information for flow control and about the sender.
   */
  struct GNUNET_TRANSPORT_IncomingMessage im;

  /**
   * Number of hops the message has travelled (if DV-routed).
   * FIXME: make use of this in ACK handling!
   */
  uint16_t total_hops;
};


/**
 * Given an inbound message @a msg from a communicator @a cmc,
 * demultiplex it based on the type calling the right handler.
 *
 * @param cmc context for demultiplexing
 * @param msg message to demultiplex
 */
static void
demultiplex_with_cmc (struct CommunicatorMessageContext *cmc,
		      const struct GNUNET_MessageHeader *msg);


/**
 * Send ACK to communicator (if requested) and free @a cmc.
 *
 * @param cmc context for which we are done handling the message
 */
static void
finish_cmc_handling (struct CommunicatorMessageContext *cmc)
{
  if (0 != ntohl (cmc->im.fc_on))
  {
    /* send ACK when done to communicator for flow control! */
    struct GNUNET_MQ_Envelope *env;
    struct GNUNET_TRANSPORT_IncomingMessageAck *ack;

    env = GNUNET_MQ_msg (ack,
			 GNUNET_MESSAGE_TYPE_TRANSPORT_INCOMING_MSG_ACK);
    ack->reserved = htonl (0);
    ack->fc_id = cmc->im.fc_id;
    ack->sender = cmc->im.sender;
    GNUNET_MQ_send (cmc->tc->mq,
		    env);
  }
  GNUNET_SERVICE_client_continue (cmc->tc->client);
  GNUNET_free (cmc);
}


/**
 * Communicator gave us an unencapsulated message to pass as-is to
 * CORE.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param mh the message that was received
 */
static void
handle_raw_message (void *cls,
		    const struct GNUNET_MessageHeader *mh)
{
  struct CommunicatorMessageContext *cmc = cls;
  uint16_t size = ntohs (mh->size);

  if ( (size > UINT16_MAX - sizeof (struct InboundMessage)) ||
       (size < sizeof (struct GNUNET_MessageHeader)) )
  {
    struct GNUNET_SERVICE_Client *client = cmc->tc->client;

    GNUNET_break (0);
    finish_cmc_handling (cmc);
    GNUNET_SERVICE_client_drop (client);
    return;
  }
  /* Forward to all CORE clients */
  for (struct TransportClient *tc = clients_head;
       NULL != tc;
       tc = tc->next)
  {
    struct GNUNET_MQ_Envelope *env;
    struct InboundMessage *im;

    if (CT_CORE != tc->type)
      continue;
    env = GNUNET_MQ_msg_extra (im,
			       size,
			       GNUNET_MESSAGE_TYPE_TRANSPORT_RECV);
    im->peer = cmc->im.sender;
    memcpy (&im[1],
	    mh,
	    size);
    GNUNET_MQ_send (tc->mq,
		    env);
  }
  /* FIXME: consider doing this _only_ once the message
     was drained from the CORE MQs to extend flow control to CORE!
     (basically, increment counter in cmc, decrement on MQ send continuation! */
  finish_cmc_handling (cmc);
}


/**
 * Communicator gave us a fragment box.  Check the message.
 *
 * @param cls a `struct CommunicatorMessageContext`
 * @param fb the send message that was sent
 * @return #GNUNET_YES if message is well-formed
 */
static int
check_fragment_box (void *cls,
		    const struct TransportFragmentBox *fb)
{
  uint16_t size = ntohs (fb->header.size);
  uint16_t bsize = size - sizeof (*fb);

  if (0 == bsize)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (bsize + ntohs (fb->frag_off) > ntohs (fb->msg_size))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (ntohs (fb->frag_off) >= ntohs (fb->msg_size))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_YES;
}


/**
 * Generate a fragment acknowledgement for an @a rc.
 *
 * @param rc context to generate ACK for, @a rc ACK state is reset
 */
static void
send_fragment_ack (struct ReassemblyContext *rc)
{
  struct TransportFragmentAckMessage *ack;

  ack = GNUNET_new (struct TransportFragmentAckMessage);
  ack->header.size = htons (sizeof (struct TransportFragmentAckMessage));
  ack->header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT_ACK);
  ack->frag_uuid = htonl (rc->frag_uuid);
  ack->extra_acks = GNUNET_htonll (rc->extra_acks);
  ack->msg_uuid = rc->msg_uuid;
  ack->avg_ack_delay = GNUNET_TIME_relative_hton (rc->avg_ack_delay);
  if (0 == rc->msg_missing)
    ack->reassembly_timeout
      = GNUNET_TIME_relative_hton (GNUNET_TIME_UNIT_FOREVER_REL); /* signal completion */
  else
    ack->reassembly_timeout
      = GNUNET_TIME_relative_hton (GNUNET_TIME_absolute_get_remaining (rc->reassembly_timeout));
  route_message (&rc->neighbour->pid,
		 &ack->header);
  rc->avg_ack_delay = GNUNET_TIME_UNIT_ZERO;
  rc->num_acks = 0;
  rc->extra_acks = 0LLU;
}


/**
 * Communicator gave us a fragment.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param fb the message that was received
 */
static void
handle_fragment_box (void *cls,
		     const struct TransportFragmentBox *fb)
{
  struct CommunicatorMessageContext *cmc = cls;
  struct Neighbour *n;
  struct ReassemblyContext *rc;
  const struct GNUNET_MessageHeader *msg;
  uint16_t msize;
  uint16_t fsize;
  uint16_t frag_off;
  uint32_t frag_uuid;
  char *target;
  struct GNUNET_TIME_Relative cdelay;
  int ack_now;

  n = GNUNET_CONTAINER_multipeermap_get (neighbours,
					 &cmc->im.sender);
  if (NULL == n)
  {
    struct GNUNET_SERVICE_Client *client = cmc->tc->client;

    GNUNET_break (0);
    finish_cmc_handling (cmc);
    GNUNET_SERVICE_client_drop (client);
    return;
  }
  if (NULL == n->reassembly_map)
  {
    n->reassembly_map = GNUNET_CONTAINER_multishortmap_create (8,
							       GNUNET_YES);
    n->reassembly_heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
    n->reassembly_timeout_task = GNUNET_SCHEDULER_add_delayed (REASSEMBLY_EXPIRATION,
							       &reassembly_cleanup_task,
							       n);
  }
  msize = ntohs (fb->msg_size);
  rc = GNUNET_CONTAINER_multishortmap_get (n->reassembly_map,
					   &fb->msg_uuid);
  if (NULL == rc)
  {
    rc = GNUNET_malloc (sizeof (*rc) +
			msize + /* reassembly payload buffer */
			(msize + 7) / 8 * sizeof (uint8_t) /* bitfield */);
    rc->msg_uuid = fb->msg_uuid;
    rc->neighbour = n;
    rc->msg_size = msize;
    rc->reassembly_timeout = GNUNET_TIME_relative_to_absolute (REASSEMBLY_EXPIRATION);
    rc->last_frag = GNUNET_TIME_absolute_get ();
    rc->hn = GNUNET_CONTAINER_heap_insert (n->reassembly_heap,
					   rc,
					   rc->reassembly_timeout.abs_value_us);
    GNUNET_assert (GNUNET_OK ==
		   GNUNET_CONTAINER_multishortmap_put (n->reassembly_map,
						       &rc->msg_uuid,
						       rc,
						       GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
    target = (char *) &rc[1];
    rc->bitfield = (uint8_t *) (target + rc->msg_size);
    rc->msg_missing = rc->msg_size;
  }
  else
  {
    target = (char *) &rc[1];
  }
  if (msize != rc->msg_size)
  {
    GNUNET_break (0);
    finish_cmc_handling (cmc);
    return;
  }

  /* reassemble */
  fsize = ntohs (fb->header.size) - sizeof (*fb);
  frag_off = ntohs (fb->frag_off);
  memcpy (&target[frag_off],
	  &fb[1],
	  fsize);
  /* update bitfield and msg_missing */
  for (unsigned int i=frag_off;i<frag_off+fsize;i++)
  {
    if (0 == (rc->bitfield[i / 8] & (1 << (i % 8))))
    {
      rc->bitfield[i / 8] |= (1 << (i % 8));
      rc->msg_missing--;
    }
  }

  /* Compute cummulative ACK */
  frag_uuid = ntohl (fb->frag_uuid);
  cdelay = GNUNET_TIME_absolute_get_duration (rc->last_frag);
  cdelay = GNUNET_TIME_relative_multiply (cdelay,
					  rc->num_acks);
  rc->last_frag = GNUNET_TIME_absolute_get ();
  rc->avg_ack_delay = GNUNET_TIME_relative_add (rc->avg_ack_delay,
						cdelay);
  ack_now = GNUNET_NO;
  if (0 == rc->num_acks)
  {
    /* case one: first ack */
    rc->frag_uuid = frag_uuid;
    rc->extra_acks = 0LLU;
    rc->num_acks = 1;
  }
  else if ( (frag_uuid >= rc->frag_uuid) &&
	    (frag_uuid <= rc->frag_uuid + 64) )
  {
    /* case two: ack fits after existing min UUID */
    if ( (frag_uuid == rc->frag_uuid) ||
	 (0 != (rc->extra_acks & (1LLU << (frag_uuid - rc->frag_uuid - 1)))) )
    {
      /* duplicate fragment, ack now! */
      ack_now = GNUNET_YES;
    }
    else
    {
      rc->extra_acks |= (1LLU << (frag_uuid - rc->frag_uuid - 1));
      rc->num_acks++;
    }
  }
  else if ( (rc->frag_uuid > frag_uuid) &&
	    ( ( (rc->frag_uuid == frag_uuid + 64) &&
		(0 == rc->extra_acks) ) ||
	      ( (rc->frag_uuid < frag_uuid + 64) &&
		(rc->extra_acks == (rc->extra_acks & ~ ((1LLU << (64 - (rc->frag_uuid - frag_uuid))) - 1LLU))) ) ) )
  {
    /* can fit ack by shifting extra acks and starting at
       frag_uid, test above esured that the bits we will
       shift 'extra_acks' by are all zero. */
    rc->extra_acks <<= (rc->frag_uuid - frag_uuid);
    rc->extra_acks |= (1LLU << (rc->frag_uuid - frag_uuid - 1));
    rc->frag_uuid = frag_uuid;
    rc->num_acks++;
  }
  if (65 == rc->num_acks) /* FIXME: maybe use smaller threshold? This is very aggressive. */
    ack_now = GNUNET_YES; /* maximum acks received */
  // FIXME: possibly also ACK based on RTT (but for that we'd need to
  // determine the queue used for the ACK first!)

  /* is reassembly complete? */
  if (0 != rc->msg_missing)
  {
    if (ack_now)
      send_fragment_ack (rc);
    finish_cmc_handling (cmc);
    return;
  }
  /* reassembly is complete, verify result */
  msg = (const struct GNUNET_MessageHeader *) &rc[1];
  if (ntohs (msg->size) != rc->msg_size)
  {
    GNUNET_break (0);
    free_reassembly_context (rc);
    finish_cmc_handling (cmc);
    return;
  }
  /* successful reassembly */
  send_fragment_ack (rc);
  demultiplex_with_cmc (cmc,
			msg);
  /* FIXME: really free here? Might be bad if fragments are still
     en-route and we forget that we finished this reassembly immediately!
     -> keep around until timeout?
     -> shorten timeout based on ACK? */
  free_reassembly_context (rc);
}


/**
 * Communicator gave us a fragment acknowledgement.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param fa the message that was received
 */
static void
handle_fragment_ack (void *cls,
		     const struct TransportFragmentAckMessage *fa)
{
  struct CommunicatorMessageContext *cmc = cls;

  // FIXME: do work: identify original message; then identify fragments being acked;
  // remove those from the tree to prevent retransmission;
  // compute RTT
  // if entire message is ACKed, handle that as well.
  finish_cmc_handling (cmc);
}


/**
 * Communicator gave us a reliability box.  Check the message.
 *
 * @param cls a `struct CommunicatorMessageContext`
 * @param rb the send message that was sent
 * @return #GNUNET_YES if message is well-formed
 */
static int
check_reliability_box (void *cls,
		       const struct TransportReliabilityBox *rb)
{
  GNUNET_MQ_check_boxed_message (rb);
  return GNUNET_YES;
}


/**
 * Communicator gave us a reliability box.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param rb the message that was received
 */
static void
handle_reliability_box (void *cls,
			const struct TransportReliabilityBox *rb)
{
  struct CommunicatorMessageContext *cmc = cls;
  const struct GNUNET_MessageHeader *inbox = (const struct GNUNET_MessageHeader *) &rb[1];

  if (0 == ntohl (rb->ack_countdown))
  {
    struct TransportReliabilityAckMessage *ack;

    /* FIXME: implement cummulative ACKs and ack_countdown,
       then setting the avg_ack_delay field below: */
    ack = GNUNET_malloc (sizeof (*ack) +
			 sizeof (struct GNUNET_ShortHashCode));
    ack->header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_RELIABILITY_ACK);
    ack->header.size = htons (sizeof (*ack) +
			      sizeof (struct GNUNET_ShortHashCode));
    memcpy (&ack[1],
	    &rb->msg_uuid,
	    sizeof (struct GNUNET_ShortHashCode));
    route_message (&cmc->im.sender,
		   &ack->header);
  }
  /* continue with inner message */
  demultiplex_with_cmc (cmc,
			inbox);
}


/**
 * Communicator gave us a reliability ack.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param ra the message that was received
 */
static void
handle_reliability_ack (void *cls,
                        const struct TransportReliabilityAckMessage *ra)
{
  struct CommunicatorMessageContext *cmc = cls;

  // FIXME: do work: find message that was acknowledged, and
  // remove from transmission queue; update RTT.
  finish_cmc_handling (cmc);
}


/**
 * Communicator gave us a backchannel encapsulation.  Check the message.
 *
 * @param cls a `struct CommunicatorMessageContext`
 * @param be the send message that was sent
 * @return #GNUNET_YES if message is well-formed
 */
static int
check_backchannel_encapsulation (void *cls,
                                 const struct TransportBackchannelEncapsulationMessage *be)
{
  uint16_t size = ntohs (be->header.size);

  if (size - sizeof (*be) < sizeof (struct GNUNET_MessageHeader))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_YES;
}


/**
 * Communicator gave us a backchannel encapsulation.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param be the message that was received
 */
static void
handle_backchannel_encapsulation (void *cls,
                                  const struct TransportBackchannelEncapsulationMessage *be)
{
  struct CommunicatorMessageContext *cmc = cls;

  if (0 != memcmp (&be->target,
		   &GST_my_identity,
		   sizeof (struct GNUNET_PeerIdentity)))
  {
    /* not for me, try to route to target */
    route_message (&be->target,
		   GNUNET_copy_message (&be->header));
    finish_cmc_handling (cmc);
    return;
  }
  // FIXME: compute shared secret
  // FIXME: check HMAC
  // FIXME: decrypt payload
  // FIXME: forward to specified communicator!
  // (using GNUNET_MESSAGE_TYPE_TRANSPORT_COMMUNICATOR_BACKCHANNEL_INCOMING)
  finish_cmc_handling (cmc);
}


/**
 * Communicator gave us a DV learn message.  Check the message.
 *
 * @param cls a `struct CommunicatorMessageContext`
 * @param dvl the send message that was sent
 * @return #GNUNET_YES if message is well-formed
 */
static int
check_dv_learn (void *cls,
                const struct TransportDVLearn *dvl)
{
  uint16_t size = ntohs (dvl->header.size);
  uint16_t num_hops = ntohs (dvl->num_hops);
  const struct GNUNET_PeerIdentity *hops = (const struct GNUNET_PeerIdentity *) &dvl[1];

  if (size != sizeof (*dvl) + num_hops * sizeof (struct GNUNET_PeerIdentity))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  for (unsigned int i=0;i<num_hops;i++)
  {
    if (0 == memcmp (&dvl->initiator,
                     &hops[i],
                     sizeof (struct GNUNET_PeerIdentity)))
    {
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    if (0 == memcmp (&GST_my_identity,
                     &hops[i],
                     sizeof (struct GNUNET_PeerIdentity)))
    {
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
  }
  return GNUNET_YES;
}


/**
 * Communicator gave us a DV learn message.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param dvl the message that was received
 */
static void
handle_dv_learn (void *cls,
                 const struct TransportDVLearn *dvl)
{
  struct CommunicatorMessageContext *cmc = cls;

  // FIXME: learn path from DV message (if bi-directional flags are set)
  // FIXME: expand DV message, forward on (unless path is getting too long)
  finish_cmc_handling (cmc);
}


/**
 * Communicator gave us a DV box.  Check the message.
 *
 * @param cls a `struct CommunicatorMessageContext`
 * @param dvb the send message that was sent
 * @return #GNUNET_YES if message is well-formed
 */
static int
check_dv_box (void *cls,
              const struct TransportDVBox *dvb)
{
  uint16_t size = ntohs (dvb->header.size);
  uint16_t num_hops = ntohs (dvb->num_hops);
  const struct GNUNET_PeerIdentity *hops = (const struct GNUNET_PeerIdentity *) &dvb[1];
  const struct GNUNET_MessageHeader *inbox = (const struct GNUNET_MessageHeader *) &hops[num_hops];
  uint16_t isize;
  uint16_t itype;

  if (size < sizeof (*dvb) + num_hops * sizeof (struct GNUNET_PeerIdentity) + sizeof (struct GNUNET_MessageHeader))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  isize = ntohs (inbox->size);
  if (size != sizeof (*dvb) + num_hops * sizeof (struct GNUNET_PeerIdentity) + isize)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  itype = ntohs (inbox->type);
  if ( (GNUNET_MESSAGE_TYPE_TRANSPORT_DV_BOX == itype) ||
       (GNUNET_MESSAGE_TYPE_TRANSPORT_DV_LEARN == itype) )
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_YES;
}


/**
 * Communicator gave us a DV box.  Process the request.
 *
 * @param cls a `struct CommunicatorMessageContext` (must call #finish_cmc_handling() when done)
 * @param dvb the message that was received
 */
static void
handle_dv_box (void *cls,
	       const struct TransportDVBox *dvb)
{
  struct CommunicatorMessageContext *cmc = cls;
  uint16_t size = ntohs (dvb->header.size) - sizeof (*dvb);
  uint16_t num_hops = ntohs (dvb->num_hops);
  const struct GNUNET_PeerIdentity *hops = (const struct GNUNET_PeerIdentity *) &dvb[1];
  const struct GNUNET_MessageHeader *inbox = (const struct GNUNET_MessageHeader *) &hops[num_hops];

  if (num_hops > 0)
  {
    // FIXME: if we are not the target, shorten path and forward along.
    // Try from the _end_ of hops array if we know the given
    // neighbour (shortening the path!).
    // NOTE: increment total_hops!
    finish_cmc_handling (cmc);
    return;
  }
  /* We are the target. Unbox and handle message. */
  cmc->im.sender = dvb->origin;
  cmc->total_hops = ntohs (dvb->total_hops);
  demultiplex_with_cmc (cmc,
			inbox);
}


/**
 * Client notified us about transmission from a peer.  Process the request.
 *
 * @param cls a `struct TransportClient` which sent us the message
 * @param obm the send message that was sent
 * @return #GNUNET_YES if message is well-formed
 */
static int
check_incoming_msg (void *cls,
                    const struct GNUNET_TRANSPORT_IncomingMessage *im)
{
  struct TransportClient *tc = cls;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  GNUNET_MQ_check_boxed_message (im);
  return GNUNET_OK;
}


/**
 * Incoming meessage.  Process the request.
 *
 * @param im the send message that was received
 */
static void
handle_incoming_msg (void *cls,
                     const struct GNUNET_TRANSPORT_IncomingMessage *im)
{
  struct TransportClient *tc = cls;
  struct CommunicatorMessageContext *cmc = GNUNET_new (struct CommunicatorMessageContext);

  cmc->tc = tc;
  cmc->im = *im;
  demultiplex_with_cmc (cmc,
			(const struct GNUNET_MessageHeader *) &im[1]);
}


/**
 * Given an inbound message @a msg from a communicator @a cmc,
 * demultiplex it based on the type calling the right handler.
 *
 * @param cmc context for demultiplexing
 * @param msg message to demultiplex
 */
static void
demultiplex_with_cmc (struct CommunicatorMessageContext *cmc,
		      const struct GNUNET_MessageHeader *msg)
{
  struct GNUNET_MQ_MessageHandler handlers[] = {
    GNUNET_MQ_hd_var_size (fragment_box,
			   GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT,
			   struct TransportFragmentBox,
			   &cmc),
    GNUNET_MQ_hd_fixed_size (fragment_ack,
			     GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT_ACK,
			     struct TransportFragmentAckMessage,
			     &cmc),
    GNUNET_MQ_hd_var_size (reliability_box,
			   GNUNET_MESSAGE_TYPE_TRANSPORT_RELIABILITY_BOX,
			   struct TransportReliabilityBox,
			   &cmc),
    GNUNET_MQ_hd_fixed_size (reliability_ack,
			     GNUNET_MESSAGE_TYPE_TRANSPORT_RELIABILITY_ACK,
			     struct TransportReliabilityAckMessage,
			     &cmc),
    GNUNET_MQ_hd_var_size (backchannel_encapsulation,
			   GNUNET_MESSAGE_TYPE_TRANSPORT_BACKCHANNEL_ENCAPSULATION,
			   struct TransportBackchannelEncapsulationMessage,
			   &cmc),
    GNUNET_MQ_hd_var_size (dv_learn,
			   GNUNET_MESSAGE_TYPE_TRANSPORT_DV_LEARN,
			   struct TransportDVLearn,
			   &cmc),
    GNUNET_MQ_hd_var_size (dv_box,
			   GNUNET_MESSAGE_TYPE_TRANSPORT_DV_BOX,
			   struct TransportDVBox,
			   &cmc),
    GNUNET_MQ_handler_end()
  };
  int ret;

  ret = GNUNET_MQ_handle_message (handlers,
				  msg);
  if (GNUNET_SYSERR == ret)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (cmc->tc->client);
    GNUNET_free (cmc);
    return;
  }
  if (GNUNET_NO == ret)
  {
    /* unencapsulated 'raw' message */
    handle_raw_message (&cmc,
			msg);
  }
}


/**
 * New queue became available.  Check message.
 *
 * @param cls the client
 * @param aqm the send message that was sent
 */
static int
check_add_queue_message (void *cls,
                         const struct GNUNET_TRANSPORT_AddQueueMessage *aqm)
{
  struct TransportClient *tc = cls;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  GNUNET_MQ_check_zero_termination (aqm);
  return GNUNET_OK;
}


/**
 * Bandwidth tracker informs us that the delay until we should receive
 * more has changed.
 *
 * @param cls a `struct Queue` for which the delay changed
 */
static void
tracker_update_in_cb (void *cls)
{
  struct Queue *queue = cls;
  struct GNUNET_TIME_Relative in_delay;
  unsigned int rsize;

  rsize = (0 == queue->mtu) ? IN_PACKET_SIZE_WITHOUT_MTU : queue->mtu;
  in_delay = GNUNET_BANDWIDTH_tracker_get_delay (&queue->tracker_in,
						 rsize);
  // FIXME: how exactly do we do inbound flow control?
}


/**
 * If necessary, generates the UUID for a @a pm
 *
 * @param pm pending message to generate UUID for.
 */
static void
set_pending_message_uuid (struct PendingMessage *pm)
{
  if (pm->msg_uuid_set)
    return;
  GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_NONCE,
			      &pm->msg_uuid,
			      sizeof (pm->msg_uuid));
  pm->msg_uuid_set = GNUNET_YES;
}


/**
 * Fragment the given @a pm to the given @a mtu.  Adds
 * additional fragments to the neighbour as well. If the
 * @a mtu is too small, generates and error for the @a pm
 * and returns NULL.
 *
 * @param pm pending message to fragment for transmission
 * @param mtu MTU to apply
 * @return new message to transmit
 */
static struct PendingMessage *
fragment_message (struct PendingMessage *pm,
		  uint16_t mtu)
{
  struct PendingMessage *ff;

  set_pending_message_uuid (pm);

  /* This invariant is established in #handle_add_queue_message() */
  GNUNET_assert (mtu > sizeof (struct TransportFragmentBox));

  /* select fragment for transmission, descending the tree if it has
     been expanded until we are at a leaf or at a fragment that is small enough */
  ff = pm;
  while ( ( (ff->bytes_msg > mtu) ||
	    (pm == ff) ) &&
	  (ff->frag_off == ff->bytes_msg) &&
	  (NULL != ff->head_frag) )
  {
    ff = ff->head_frag; /* descent into fragmented fragments */
  }

  if ( ( (ff->bytes_msg > mtu) ||
	 (pm == ff) ) &&
       (pm->frag_off < pm->bytes_msg) )
  {
    /* Did not yet calculate all fragments, calculate next fragment */
    struct PendingMessage *frag;
    struct TransportFragmentBox tfb;
    const char *orig;
    char *msg;
    uint16_t fragmax;
    uint16_t fragsize;
    uint16_t msize;
    uint16_t xoff = 0;

    orig = (const char *) &ff[1];
    msize = ff->bytes_msg;
    if (pm != ff)
    {
      const struct TransportFragmentBox *tfbo;

      tfbo = (const struct TransportFragmentBox *) orig;
      orig += sizeof (struct TransportFragmentBox);
      msize -= sizeof (struct TransportFragmentBox);
      xoff = ntohs (tfbo->frag_off);
    }
    fragmax = mtu - sizeof (struct TransportFragmentBox);
    fragsize = GNUNET_MIN (msize - ff->frag_off,
			   fragmax);
    frag = GNUNET_malloc (sizeof (struct PendingMessage) +
			  sizeof (struct TransportFragmentBox) +
			  fragsize);
    frag->target = pm->target;
    frag->frag_parent = ff;
    frag->timeout = pm->timeout;
    frag->bytes_msg = sizeof (struct TransportFragmentBox) + fragsize;
    frag->pmt = PMT_FRAGMENT_BOX;
    msg = (char *) &frag[1];
    tfb.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_FRAGMENT);
    tfb.header.size = htons (sizeof (struct TransportFragmentBox) +
			     fragsize);
    tfb.frag_uuid = htonl (pm->frag_uuidgen++);
    tfb.msg_uuid = pm->msg_uuid;
    tfb.frag_off = htons (ff->frag_off + xoff);
    tfb.msg_size = htons (pm->bytes_msg);
    memcpy (msg,
	    &tfb,
	    sizeof (tfb));
    memcpy (&msg[sizeof (tfb)],
	    &orig[ff->frag_off],
	    fragsize);
    GNUNET_CONTAINER_MDLL_insert (frag,
				  ff->head_frag,
				  ff->tail_frag,
				  frag);
    ff->frag_off += fragsize;
    ff = frag;
  }

  /* Move head to the tail and return it */
  GNUNET_CONTAINER_MDLL_remove (frag,
				ff->frag_parent->head_frag,
				ff->frag_parent->tail_frag,
				ff);
  GNUNET_CONTAINER_MDLL_insert_tail (frag,
				     ff->frag_parent->head_frag,
				     ff->frag_parent->tail_frag,
				     ff);
  return ff;
}


/**
 * Reliability-box the given @a pm. On error (can there be any), NULL
 * may be returned, otherwise the "replacement" for @a pm (which
 * should then be added to the respective neighbour's queue instead of
 * @a pm).  If the @a pm is already fragmented or reliability boxed,
 * or itself an ACK, this function simply returns @a pm.
 *
 * @param pm pending message to box for transmission over unreliabile queue
 * @return new message to transmit
 */
static struct PendingMessage *
reliability_box_message (struct PendingMessage *pm)
{
  struct TransportReliabilityBox rbox;
  struct PendingMessage *bpm;
  char *msg;

  if (PMT_CORE != pm->pmt)
    return pm;  /* already fragmented or reliability boxed, or control message: do nothing */
  if (NULL != pm->bpm)
    return pm->bpm; /* already computed earlier: do nothing */
  GNUNET_assert (NULL == pm->head_frag);
  if (pm->bytes_msg + sizeof (rbox) > UINT16_MAX)
  {
    /* failed hard */
    GNUNET_break (0);
    client_send_response (pm,
			  GNUNET_NO,
			  0);
    return NULL;
  }
  bpm = GNUNET_malloc (sizeof (struct PendingMessage) +
		       sizeof (rbox) +
		       pm->bytes_msg);
  bpm->target = pm->target;
  bpm->frag_parent = pm;
  GNUNET_CONTAINER_MDLL_insert (frag,
				pm->head_frag,
				pm->tail_frag,
				bpm);
  bpm->timeout = pm->timeout;
  bpm->pmt = PMT_RELIABILITY_BOX;
  bpm->bytes_msg = pm->bytes_msg + sizeof (rbox);
  set_pending_message_uuid (bpm);
  rbox.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_RELIABILITY_BOX);
  rbox.header.size = htons (sizeof (rbox) + pm->bytes_msg);
  rbox.ack_countdown = htonl (0); // FIXME: implement ACK countdown support
  rbox.msg_uuid = pm->msg_uuid;
  msg = (char *) &bpm[1];
  memcpy (msg,
	  &rbox,
	  sizeof (rbox));
  memcpy (&msg[sizeof (rbox)],
	  &pm[1],
	  pm->bytes_msg);
  pm->bpm = bpm;
  return bpm;
}


/**
 * We believe we are ready to transmit a message on a queue. Double-checks
 * with the queue's "tracker_out" and then gives the message to the
 * communicator for transmission (updating the tracker, and re-scheduling
 * itself if applicable).
 *
 * @param cls the `struct Queue` to process transmissions for
 */
static void
transmit_on_queue (void *cls)
{
  struct Queue *queue = cls;
  struct Neighbour *n = queue->neighbour;
  struct QueueEntry *qe;
  struct PendingMessage *pm;
  struct PendingMessage *s;
  uint32_t overhead;
  struct GNUNET_TRANSPORT_SendMessageTo *smt;
  struct GNUNET_MQ_Envelope *env;

  queue->transmit_task = NULL;
  if (NULL == (pm = n->pending_msg_head))
  {
    /* no message pending, nothing to do here! */
    return;
  }
  schedule_transmit_on_queue (queue);
  if (NULL != queue->transmit_task)
    return; /* do it later */
  overhead = 0;
  if (GNUNET_TRANSPORT_CC_RELIABLE != queue->tc->details.communicator.cc)
    overhead += sizeof (struct TransportReliabilityBox);
  s = pm;
  if ( ( (0 != queue->mtu) &&
	 (pm->bytes_msg + overhead > queue->mtu) ) ||
       (pm->bytes_msg > UINT16_MAX - sizeof (struct GNUNET_TRANSPORT_SendMessageTo)) ||
       (NULL != pm->head_frag /* fragments already exist, should
				 respect that even if MTU is 0 for
				 this queue */) )
    s = fragment_message (s,
                          (0 == queue->mtu)
                          ? UINT16_MAX - sizeof (struct GNUNET_TRANSPORT_SendMessageTo)
                          : queue->mtu);
  if (NULL == s)
  {
    /* Fragmentation failed, try next message... */
    schedule_transmit_on_queue (queue);
    return;
  }
  if (GNUNET_TRANSPORT_CC_RELIABLE != queue->tc->details.communicator.cc)
    s = reliability_box_message (s);
  if (NULL == s)
  {
    /* Reliability boxing failed, try next message... */
    schedule_transmit_on_queue (queue);
    return;
  }

  /* Pass 's' for transission to the communicator */
  qe = GNUNET_new (struct QueueEntry);
  qe->mid = queue->mid_gen++;
  qe->queue = queue;
  // qe->pm = s; // FIXME: not so easy, reference management on 'free(s)'!
  GNUNET_CONTAINER_DLL_insert (queue->queue_head,
			       queue->queue_tail,
			       qe);
  env = GNUNET_MQ_msg_extra (smt,
			     s->bytes_msg,
			     GNUNET_MESSAGE_TYPE_TRANSPORT_SEND_MSG);
  smt->qid = queue->qid;
  smt->mid = qe->mid;
  smt->receiver = n->pid;
  memcpy (&smt[1],
          &s[1],
          s->bytes_msg);
  GNUNET_assert (CT_COMMUNICATOR == queue->tc->type);
  queue->queue_length++;
  queue->tc->details.communicator.total_queue_length++;
  GNUNET_MQ_send (queue->tc->mq,
                  env);

  // FIXME: do something similar to the logic below
  // in defragmentation / reliability ACK handling!

  /* Check if this transmission somehow conclusively finished handing 'pm'
     even without any explicit ACKs */
  if ( (PMT_CORE == s->pmt) &&
       (GNUNET_TRANSPORT_CC_RELIABLE == queue->tc->details.communicator.cc) )
  {
    /* Full message sent, and over reliabile channel */
    client_send_response (pm,
                          GNUNET_YES,
                          pm->bytes_msg);
  }
  else if ( (GNUNET_TRANSPORT_CC_RELIABLE == queue->tc->details.communicator.cc) &&
	    (PMT_FRAGMENT_BOX == s->pmt) )
  {
    struct PendingMessage *pos;

    /* Fragment sent over reliabile channel */
    free_fragment_tree (s);
    pos = s->frag_parent;
    GNUNET_CONTAINER_MDLL_remove (frag,
                                  pos->head_frag,
                                  pos->tail_frag,
                                  s);
    GNUNET_free (s);
    /* check if subtree is done */
    while ( (NULL == pos->head_frag) &&
	    (pos->frag_off == pos->bytes_msg) &&
	    (pos != pm) )
    {
      s = pos;
      pos = s->frag_parent;
      GNUNET_CONTAINER_MDLL_remove (frag,
                                    pos->head_frag,
                                    pos->tail_frag,
                                    s);
      GNUNET_free (s);
    }

    /* Was this the last applicable fragmment? */
    if ( (NULL == pm->head_frag) &&
	 (pm->frag_off == pm->bytes_msg) )
      client_send_response (pm,
                            GNUNET_YES,
                            pm->bytes_msg /* FIXME: calculate and add overheads! */);
  }
  else if (PMT_CORE != pm->pmt)
  {
    /* This was an acknowledgement of some type, always free */
    free_pending_message (pm);
  }
  else
  {
    /* message not finished, waiting for acknowledgement */
    struct Neighbour *neighbour = pm->target;
    /* Update time by which we might retransmit 's' based on queue
       characteristics (i.e. RTT); it takes one RTT for the message to
       arrive and the ACK to come back in the best case; but the other
       side is allowed to delay ACKs by 2 RTTs, so we use 4 RTT before
       retransmitting.  Note that in the future this heuristic should
       likely be improved further (measure RTT stability, consider
       message urgency and size when delaying ACKs, etc.) */
    s->next_attempt = GNUNET_TIME_relative_to_absolute
      (GNUNET_TIME_relative_multiply (queue->rtt,
                                      4));
    if (s == pm)
    {
      struct PendingMessage *pos;

      /* re-insert sort in neighbour list */
      GNUNET_CONTAINER_MDLL_remove (neighbour,
                                    neighbour->pending_msg_head,
                                    neighbour->pending_msg_tail,
                                    pm);
      pos = neighbour->pending_msg_tail;
      while ( (NULL != pos) &&
	      (pm->next_attempt.abs_value_us > pos->next_attempt.abs_value_us) )
        pos = pos->prev_neighbour;
      GNUNET_CONTAINER_MDLL_insert_after (neighbour,
                                          neighbour->pending_msg_head,
                                          neighbour->pending_msg_tail,
                                          pos,
                                          pm);
    }
    else
    {
      /* re-insert sort in fragment list */
      struct PendingMessage *fp = s->frag_parent;
      struct PendingMessage *pos;

      GNUNET_CONTAINER_MDLL_remove (frag,
                                    fp->head_frag,
                                    fp->tail_frag,
                                    s);
      pos = fp->tail_frag;
      while ( (NULL != pos) &&
	      (s->next_attempt.abs_value_us > pos->next_attempt.abs_value_us) )
        pos = pos->prev_frag;
      GNUNET_CONTAINER_MDLL_insert_after (frag,
                                          fp->head_frag,
                                          fp->tail_frag,
                                          pos,
                                          s);
    }
  }

  /* finally, re-schedule queue transmission task itself */
  schedule_transmit_on_queue (queue);
}


/**
 * Bandwidth tracker informs us that the delay until we
 * can transmit again changed.
 *
 * @param cls a `struct Queue` for which the delay changed
 */
static void
tracker_update_out_cb (void *cls)
{
  struct Queue *queue = cls;
  struct Neighbour *n = queue->neighbour;

  if (NULL == n->pending_msg_head)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
		"Bandwidth allocation updated for empty transmission queue `%s'\n",
		queue->address);
    return; /* no message pending, nothing to do here! */
  }
  GNUNET_SCHEDULER_cancel (queue->transmit_task);
  queue->transmit_task = NULL;
  schedule_transmit_on_queue (queue);
}


/**
 * Bandwidth tracker informs us that excessive outbound bandwidth was
 * allocated which is not being used.
 *
 * @param cls a `struct Queue` for which the excess was noted
 */
static void
tracker_excess_out_cb (void *cls)
{
  /* FIXME: trigger excess bandwidth report to core? Right now,
     this is done internally within transport_api2_core already,
     but we probably want to change the logic and trigger it
     from here via a message instead! */
  /* TODO: maybe inform someone at this point? */
  GNUNET_STATISTICS_update (GST_stats,
                            "# Excess outbound bandwidth reported",
                            1,
                            GNUNET_NO);
}



/**
 * Bandwidth tracker informs us that excessive inbound bandwidth was allocated
 * which is not being used.
 *
 * @param cls a `struct Queue` for which the excess was noted
 */
static void
tracker_excess_in_cb (void *cls)
{
  /* TODO: maybe inform somone at this point? */
  GNUNET_STATISTICS_update (GST_stats,
                            "# Excess inbound bandwidth reported",
                            1,
                            GNUNET_NO);
}


/**
 * New queue became available.  Process the request.
 *
 * @param cls the client
 * @param aqm the send message that was sent
 */
static void
handle_add_queue_message (void *cls,
                          const struct GNUNET_TRANSPORT_AddQueueMessage *aqm)
{
  struct TransportClient *tc = cls;
  struct Queue *queue;
  struct Neighbour *neighbour;
  const char *addr;
  uint16_t addr_len;

  if (ntohl (aqm->mtu) <= sizeof (struct TransportFragmentBox))
  {
    /* MTU so small as to be useless for transmissions,
       required for #fragment_message()! */
    GNUNET_break_op (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  neighbour = lookup_neighbour (&aqm->receiver);
  if (NULL == neighbour)
  {
    neighbour = GNUNET_new (struct Neighbour);
    neighbour->earliest_timeout = GNUNET_TIME_UNIT_FOREVER_ABS;
    neighbour->pid = aqm->receiver;
    GNUNET_assert (GNUNET_OK ==
                   GNUNET_CONTAINER_multipeermap_put (neighbours,
                                                      &neighbour->pid,
                                                      neighbour,
                                                      GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
    cores_send_connect_info (&neighbour->pid,
                             GNUNET_BANDWIDTH_ZERO);
  }
  addr_len = ntohs (aqm->header.size) - sizeof (*aqm);
  addr = (const char *) &aqm[1];

  queue = GNUNET_malloc (sizeof (struct Queue) + addr_len);
  queue->tc = tc;
  queue->address = (const char *) &queue[1];
  queue->rtt = GNUNET_TIME_UNIT_FOREVER_REL;
  queue->qid = aqm->qid;
  queue->mtu = ntohl (aqm->mtu);
  queue->nt = (enum GNUNET_NetworkType) ntohl (aqm->nt);
  queue->cs = (enum GNUNET_TRANSPORT_ConnectionStatus) ntohl (aqm->cs);
  queue->neighbour = neighbour;
  GNUNET_BANDWIDTH_tracker_init2 (&queue->tracker_in,
                                  &tracker_update_in_cb,
                                  queue,
                                  GNUNET_BANDWIDTH_ZERO,
                                  GNUNET_CONSTANTS_MAX_BANDWIDTH_CARRY_S,
                                  &tracker_excess_in_cb,
                                  queue);
  GNUNET_BANDWIDTH_tracker_init2 (&queue->tracker_out,
                                  &tracker_update_out_cb,
                                  queue,
                                  GNUNET_BANDWIDTH_ZERO,
                                  GNUNET_CONSTANTS_MAX_BANDWIDTH_CARRY_S,
                                  &tracker_excess_out_cb,
                                  queue);
  memcpy (&queue[1],
          addr,
          addr_len);
  /* notify monitors about new queue */
  {
    struct MonitorEvent me = {
      .rtt = queue->rtt,
      .cs = queue->cs
    };

    notify_monitors (&neighbour->pid,
                     queue->address,
                     queue->nt,
                     &me);
  }
  GNUNET_CONTAINER_MDLL_insert (neighbour,
                                neighbour->queue_head,
                                neighbour->queue_tail,
                                queue);
  GNUNET_CONTAINER_MDLL_insert (client,
                                tc->details.communicator.queue_head,
                                tc->details.communicator.queue_tail,
                                queue);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Queue to a peer went down.  Process the request.
 *
 * @param cls the client
 * @param dqm the send message that was sent
 */
static void
handle_del_queue_message (void *cls,
                          const struct GNUNET_TRANSPORT_DelQueueMessage *dqm)
{
  struct TransportClient *tc = cls;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  for (struct Queue *queue = tc->details.communicator.queue_head;
       NULL != queue;
       queue = queue->next_client)
  {
    struct Neighbour *neighbour = queue->neighbour;

    if ( (dqm->qid != queue->qid) ||
	 (0 != memcmp (&dqm->receiver,
		       &neighbour->pid,
		       sizeof (struct GNUNET_PeerIdentity))) )
      continue;
    free_queue (queue);
    GNUNET_SERVICE_client_continue (tc->client);
    return;
  }
  GNUNET_break (0);
  GNUNET_SERVICE_client_drop (tc->client);
}


/**
 * Message was transmitted.  Process the request.
 *
 * @param cls the client
 * @param sma the send message that was sent
 */
static void
handle_send_message_ack (void *cls,
                         const struct GNUNET_TRANSPORT_SendMessageToAck *sma)
{
  struct TransportClient *tc = cls;
  struct QueueEntry *qe;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }

  /* find our queue entry matching the ACK */
  qe = NULL;
  for (struct Queue *queue = tc->details.communicator.queue_head;
       NULL != queue;
       queue = queue->next_client)
  {
    if (0 != memcmp (&queue->neighbour->pid,
		     &sma->receiver,
		     sizeof (struct GNUNET_PeerIdentity)))
      continue;
    for (struct QueueEntry *qep = queue->queue_head;
         NULL != qep;
         qep = qep->next)
    {
      if (qep->mid != sma->mid)
        continue;
      qe = qep;
      break;
    }
    break;
  }
  if (NULL == qe)
  {
    /* this should never happen */
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  GNUNET_CONTAINER_DLL_remove (qe->queue->queue_head,
                               qe->queue->queue_tail,
                               qe);
  qe->queue->queue_length--;
  tc->details.communicator.total_queue_length--;
  GNUNET_SERVICE_client_continue (tc->client);

  /* if applicable, resume transmissions that waited on ACK */
  if (COMMUNICATOR_TOTAL_QUEUE_LIMIT - 1 == tc->details.communicator.total_queue_length)
  {
    /* Communicator dropped below threshold, resume all queues */
    GNUNET_STATISTICS_update (GST_stats,
                              "# Transmission throttled due to communicator queue limit",
                              -1,
                              GNUNET_NO);
    for (struct Queue *queue = tc->details.communicator.queue_head;
         NULL != queue;
         queue = queue->next_client)
      schedule_transmit_on_queue (queue);
  }
  else if (QUEUE_LENGTH_LIMIT - 1 == qe->queue->queue_length)
  {
    /* queue dropped below threshold; only resume this one queue */
    GNUNET_STATISTICS_update (GST_stats,
                              "# Transmission throttled due to queue queue limit",
                              -1,
                              GNUNET_NO);
    schedule_transmit_on_queue (qe->queue);
  }

  /* TODO: we also should react on the status! */
  // FIXME: this probably requires queue->pm = s assignment!
  // FIXME: react to communicator status about transmission request. We got:
  sma->status; // OK success, SYSERR failure

  GNUNET_free (qe);
}


/**
 * Iterator telling new MONITOR client about all existing
 * queues to peers.
 *
 * @param cls the new `struct TransportClient`
 * @param pid a connected peer
 * @param value the `struct Neighbour` with more information
 * @return #GNUNET_OK (continue to iterate)
 */
static int
notify_client_queues (void *cls,
                      const struct GNUNET_PeerIdentity *pid,
                      void *value)
{
  struct TransportClient *tc = cls;
  struct Neighbour *neighbour = value;

  GNUNET_assert (CT_MONITOR == tc->type);
  for (struct Queue *q = neighbour->queue_head;
       NULL != q;
       q = q->next_neighbour)
  {
    struct MonitorEvent me = {
      .rtt = q->rtt,
      .cs = q->cs,
      .num_msg_pending = q->num_msg_pending,
      .num_bytes_pending = q->num_bytes_pending
    };

    notify_monitor (tc,
                    pid,
                    q->address,
                    q->nt,
                    &me);
  }
  return GNUNET_OK;
}


/**
 * Initialize a monitor client.
 *
 * @param cls the client
 * @param start the start message that was sent
 */
static void
handle_monitor_start (void *cls,
		      const struct GNUNET_TRANSPORT_MonitorStart *start)
{
  struct TransportClient *tc = cls;

  if (CT_NONE != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  tc->type = CT_MONITOR;
  tc->details.monitor.peer = start->peer;
  tc->details.monitor.one_shot = ntohl (start->one_shot);
  GNUNET_CONTAINER_multipeermap_iterate (neighbours,
                                         &notify_client_queues,
                                         tc);
  GNUNET_SERVICE_client_mark_monitor (tc->client);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Find transport client providing communication service
 * for the protocol @a prefix.
 *
 * @param prefix communicator name
 * @return NULL if no such transport client is available
 */
static struct TransportClient *
lookup_communicator (const char *prefix)
{
  for (struct TransportClient *tc = clients_head;
       NULL != tc;
       tc = tc->next)
  {
    if (CT_COMMUNICATOR != tc->type)
      continue;
    if (0 == strcmp (prefix,
		     tc->details.communicator.address_prefix))
      return tc;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
              "Somone suggested use of communicator for `%s', but we do not have such a communicator!\n",
              prefix);
  return NULL;
}


/**
 * Signature of a function called with a communicator @a address of a peer
 * @a pid that an application wants us to connect to.
 *
 * @param pid target peer
 * @param address the address to try
 */
static void
suggest_to_connect (const struct GNUNET_PeerIdentity *pid,
                    const char *address)
{
  static uint32_t idgen;
  struct TransportClient *tc;
  char *prefix;
  struct GNUNET_TRANSPORT_CreateQueue *cqm;
  struct GNUNET_MQ_Envelope *env;
  size_t alen;

  prefix = GNUNET_HELLO_address_to_prefix (address);
  if (NULL == prefix)
  {
    GNUNET_break (0); /* We got an invalid address!? */
    return;
  }
  tc = lookup_communicator (prefix);
  if (NULL == tc)
  {
    GNUNET_STATISTICS_update (GST_stats,
                              "# Suggestions ignored due to missing communicator",
                              1,
                              GNUNET_NO);
    return;
  }
  /* forward suggestion for queue creation to communicator */
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Request #%u for `%s' communicator to create queue to `%s'\n",
              (unsigned int) idgen,
              prefix,
              address);
  alen = strlen (address) + 1;
  env = GNUNET_MQ_msg_extra (cqm,
                             alen,
                             GNUNET_MESSAGE_TYPE_TRANSPORT_QUEUE_CREATE);
  cqm->request_id = htonl (idgen++);
  cqm->receiver = *pid;
  memcpy (&cqm[1],
	  address,
	  alen);
  GNUNET_MQ_send (tc->mq,
		  env);
}


/**
 * Communicator tells us that our request to create a queue "worked", that
 * is setting up the queue is now in process.
 *
 * @param cls the `struct TransportClient`
 * @param cqr confirmation message
 */
static void
handle_queue_create_ok (void *cls,
                        const struct GNUNET_TRANSPORT_CreateQueueResponse *cqr)
{
  struct TransportClient *tc = cls;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  GNUNET_STATISTICS_update (GST_stats,
                            "# Suggestions succeeded at communicator",
                            1,
                            GNUNET_NO);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Request #%u for communicator to create queue succeeded\n",
              (unsigned int) ntohs (cqr->request_id));
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Communicator tells us that our request to create a queue failed. This usually
 * indicates that the provided address is simply invalid or that the communicator's
 * resources are exhausted.
 *
 * @param cls the `struct TransportClient`
 * @param cqr failure message
 */
static void
handle_queue_create_fail (void *cls,
                          const struct GNUNET_TRANSPORT_CreateQueueResponse *cqr)
{
  struct TransportClient *tc = cls;

  if (CT_COMMUNICATOR != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Request #%u for communicator to create queue failed\n",
              (unsigned int) ntohs (cqr->request_id));
  GNUNET_STATISTICS_update (GST_stats,
                            "# Suggestions failed in queue creation at communicator",
                            1,
                            GNUNET_NO);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Function called by PEERSTORE for each matching record.
 *
 * @param cls closure
 * @param record peerstore record information
 * @param emsg error message, or NULL if no errors
 */
static void
handle_hello (void *cls,
              const struct GNUNET_PEERSTORE_Record *record,
              const char *emsg)
{
  struct PeerRequest *pr = cls;
  const char *val;

  if (NULL != emsg)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Got failure from PEERSTORE: %s\n",
                emsg);
    return;
  }
  val = record->value;
  if ( (0 == record->value_size) ||
       ('\0' != val[record->value_size - 1]) )
  {
    GNUNET_break (0);
    return;
  }
  suggest_to_connect (&pr->pid,
                      (const char *) record->value);
}


/**
 * We have received a `struct ExpressPreferenceMessage` from an application client.
 *
 * @param cls handle to the client
 * @param msg the start message
 */
static void
handle_suggest (void *cls,
                const struct ExpressPreferenceMessage *msg)
{
  struct TransportClient *tc = cls;
  struct PeerRequest *pr;

  if (CT_NONE == tc->type)
  {
    tc->type = CT_APPLICATION;
    tc->details.application.requests
      = GNUNET_CONTAINER_multipeermap_create (16,
                                              GNUNET_YES);
  }
  if (CT_APPLICATION != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client suggested we talk to %s with preference %d at rate %u\n",
              GNUNET_i2s (&msg->peer),
              (int) ntohl (msg->pk),
              (int) ntohl (msg->bw.value__));
  pr = GNUNET_new (struct PeerRequest);
  pr->tc = tc;
  pr->pid = msg->peer;
  pr->bw = msg->bw;
  pr->pk = (enum GNUNET_MQ_PreferenceKind) ntohl (msg->pk);
  if (GNUNET_YES !=
      GNUNET_CONTAINER_multipeermap_put (tc->details.application.requests,
                                         &pr->pid,
                                         pr,
                                         GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
  {
    GNUNET_break (0);
    GNUNET_free (pr);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  pr->wc = GNUNET_PEERSTORE_watch (peerstore,
                                   "transport",
                                   &pr->pid,
                                   "hello",
                                   &handle_hello,
                                   pr);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * We have received a `struct ExpressPreferenceMessage` from an application client.
 *
 * @param cls handle to the client
 * @param msg the start message
 */
static void
handle_suggest_cancel (void *cls,
                       const struct ExpressPreferenceMessage *msg)
{
  struct TransportClient *tc = cls;
  struct PeerRequest *pr;

  if (CT_APPLICATION != tc->type)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  pr = GNUNET_CONTAINER_multipeermap_get (tc->details.application.requests,
                                          &msg->peer);
  if (NULL == pr)
  {
    GNUNET_break (0);
    GNUNET_SERVICE_client_drop (tc->client);
    return;
  }
  (void) stop_peer_request (tc,
                            &pr->pid,
                            pr);
  GNUNET_SERVICE_client_continue (tc->client);
}


/**
 * Check #GNUNET_MESSAGE_TYPE_TRANSPORT_ADDRESS_CONSIDER_VERIFY
 * messages. We do nothing here, real verification is done later.
 *
 * @param cls a `struct TransportClient *`
 * @param msg message to verify
 * @return #GNUNET_OK
 */
static int
check_address_consider_verify (void *cls,
                               const struct GNUNET_TRANSPORT_AddressToVerify *hdr)
{
  (void) cls;
  (void) hdr;
  return GNUNET_OK;
}


/**
 * Given another peers address, consider checking it for validity
 * and then adding it to the Peerstore.
 *
 * @param cls a `struct TransportClient`
 * @param hdr message containing the raw address data and
 *        signature in the body, see #GNUNET_HELLO_extract_address()
 */
static void
handle_address_consider_verify (void *cls,
                                const struct GNUNET_TRANSPORT_AddressToVerify *hdr)
{
  char *address;
  enum GNUNET_NetworkType nt;
  struct GNUNET_TIME_Absolute expiration;

  (void) cls;
  // FIXME: pre-check: do we know this address already?
  // FIXME: pre-check: rate-limit signature verification / validation!
  address = GNUNET_HELLO_extract_address (&hdr[1],
                                          ntohs (hdr->header.size) - sizeof (*hdr),
                                          &hdr->peer,
                                          &nt,
                                          &expiration);
  if (NULL == address)
  {
    GNUNET_break_op (0);
    return;
  }
  if (0 == GNUNET_TIME_absolute_get_remaining (expiration).rel_value_us)
    return; /* expired */
  // FIXME: do begin actual verification here!
  GNUNET_free (address);
}


/**
 * Free neighbour entry.
 *
 * @param cls NULL
 * @param pid unused
 * @param value a `struct Neighbour`
 * @return #GNUNET_OK (always)
 */
static int
free_neighbour_cb (void *cls,
                   const struct GNUNET_PeerIdentity *pid,
                   void *value)
{
  struct Neighbour *neighbour = value;

  (void) cls;
  (void) pid;
  GNUNET_break (0); // should this ever happen?
  free_neighbour (neighbour);

  return GNUNET_OK;
}


/**
 * Free DV route entry.
 *
 * @param cls NULL
 * @param pid unused
 * @param value a `struct DistanceVector`
 * @return #GNUNET_OK (always)
 */
static int
free_dv_routes_cb (void *cls,
                   const struct GNUNET_PeerIdentity *pid,
                   void *value)
{
  struct DistanceVector *dv = value;

  (void) cls;
  (void) pid;
  free_dv_route (dv);

  return GNUNET_OK;
}


/**
 * Free ephemeral entry.
 *
 * @param cls NULL
 * @param pid unused
 * @param value a `struct Neighbour`
 * @return #GNUNET_OK (always)
 */
static int
free_ephemeral_cb (void *cls,
                   const struct GNUNET_PeerIdentity *pid,
                   void *value)
{
  struct EphemeralCacheEntry *ece = value;

  (void) cls;
  (void) pid;
  free_ephemeral (ece);
  return GNUNET_OK;
}


/**
 * Function called when the service shuts down.  Unloads our plugins
 * and cancels pending validations.
 *
 * @param cls closure, unused
 */
static void
do_shutdown (void *cls)
{
  (void) cls;

  if (NULL != ephemeral_task)
  {
    GNUNET_SCHEDULER_cancel (ephemeral_task);
    ephemeral_task = NULL;
  }
  GNUNET_CONTAINER_multipeermap_iterate (neighbours,
                                         &free_neighbour_cb,
                                         NULL);
  if (NULL != peerstore)
  {
    GNUNET_PEERSTORE_disconnect (peerstore,
				 GNUNET_NO);
    peerstore = NULL;
  }
  if (NULL != GST_stats)
  {
    GNUNET_STATISTICS_destroy (GST_stats,
                               GNUNET_NO);
    GST_stats = NULL;
  }
  if (NULL != GST_my_private_key)
  {
    GNUNET_free (GST_my_private_key);
    GST_my_private_key = NULL;
  }
  GNUNET_CONTAINER_multipeermap_destroy (neighbours);
  neighbours = NULL;
  GNUNET_CONTAINER_multipeermap_iterate (dv_routes,
					 &free_dv_routes_cb,
					 NULL);
  GNUNET_CONTAINER_multipeermap_destroy (dv_routes);
  dv_routes = NULL;
  GNUNET_CONTAINER_multipeermap_iterate (ephemeral_map,
					 &free_ephemeral_cb,
					 NULL);
  GNUNET_CONTAINER_multipeermap_destroy (ephemeral_map);
  ephemeral_map = NULL;
  GNUNET_CONTAINER_heap_destroy (ephemeral_heap);
  ephemeral_heap = NULL;
}


/**
 * Initiate transport service.
 *
 * @param cls closure
 * @param c configuration to use
 * @param service the initialized service
 */
static void
run (void *cls,
     const struct GNUNET_CONFIGURATION_Handle *c,
     struct GNUNET_SERVICE_Handle *service)
{
  (void) cls;
  /* setup globals */
  GST_cfg = c;
  neighbours = GNUNET_CONTAINER_multipeermap_create (1024,
                                                     GNUNET_YES);
  dv_routes = GNUNET_CONTAINER_multipeermap_create (1024,
                                                    GNUNET_YES);
  ephemeral_map = GNUNET_CONTAINER_multipeermap_create (32,
                                                        GNUNET_YES);
  ephemeral_heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
  GST_my_private_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (GST_cfg);
  if (NULL == GST_my_private_key)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                _("Transport service is lacking key configuration settings. Exiting.\n"));
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  GNUNET_CRYPTO_eddsa_key_get_public (GST_my_private_key,
                                      &GST_my_identity.public_key);
  GNUNET_log(GNUNET_ERROR_TYPE_INFO,
             "My identity is `%s'\n",
             GNUNET_i2s_full (&GST_my_identity));
  GST_stats = GNUNET_STATISTICS_create ("transport",
                                        GST_cfg);
  GNUNET_SCHEDULER_add_shutdown (&do_shutdown,
				 NULL);
  peerstore = GNUNET_PEERSTORE_connect (GST_cfg);
  if (NULL == peerstore)
  {
    GNUNET_break (0);
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
}


/**
 * Define "main" method using service macro.
 */
GNUNET_SERVICE_MAIN
("transport",
 GNUNET_SERVICE_OPTION_SOFT_SHUTDOWN,
 &run,
 &client_connect_cb,
 &client_disconnect_cb,
 NULL,
 /* communication with applications */
 GNUNET_MQ_hd_fixed_size (suggest,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_SUGGEST,
                          struct ExpressPreferenceMessage,
                          NULL),
 GNUNET_MQ_hd_fixed_size (suggest_cancel,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_SUGGEST_CANCEL,
                          struct ExpressPreferenceMessage,
                          NULL),
 /* communication with core */
 GNUNET_MQ_hd_fixed_size (client_start,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_START,
                          struct StartMessage,
                          NULL),
 GNUNET_MQ_hd_var_size (client_send,
                        GNUNET_MESSAGE_TYPE_TRANSPORT_SEND,
                        struct OutboundMessage,
                        NULL),
 /* communication with communicators */
 GNUNET_MQ_hd_var_size (communicator_available,
                        GNUNET_MESSAGE_TYPE_TRANSPORT_NEW_COMMUNICATOR,
                        struct GNUNET_TRANSPORT_CommunicatorAvailableMessage,
                        NULL),
 GNUNET_MQ_hd_var_size (communicator_backchannel,
                        GNUNET_MESSAGE_TYPE_TRANSPORT_COMMUNICATOR_BACKCHANNEL,
                        struct GNUNET_TRANSPORT_CommunicatorBackchannel,
                        NULL),
 GNUNET_MQ_hd_var_size (add_address,
                        GNUNET_MESSAGE_TYPE_TRANSPORT_ADD_ADDRESS,
                        struct GNUNET_TRANSPORT_AddAddressMessage,
                        NULL),
 GNUNET_MQ_hd_fixed_size (del_address,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_DEL_ADDRESS,
                          struct GNUNET_TRANSPORT_DelAddressMessage,
                          NULL),
 GNUNET_MQ_hd_var_size (incoming_msg,
                        GNUNET_MESSAGE_TYPE_TRANSPORT_INCOMING_MSG,
                        struct GNUNET_TRANSPORT_IncomingMessage,
                        NULL),
 GNUNET_MQ_hd_fixed_size (queue_create_ok,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_QUEUE_CREATE_OK,
                          struct GNUNET_TRANSPORT_CreateQueueResponse,
                          NULL),
 GNUNET_MQ_hd_fixed_size (queue_create_fail,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_QUEUE_CREATE_FAIL,
                          struct GNUNET_TRANSPORT_CreateQueueResponse,
                          NULL),
 GNUNET_MQ_hd_var_size (add_queue_message,
                        GNUNET_MESSAGE_TYPE_TRANSPORT_QUEUE_SETUP,
                        struct GNUNET_TRANSPORT_AddQueueMessage,
                        NULL),
 GNUNET_MQ_hd_var_size (address_consider_verify,
                        GNUNET_MESSAGE_TYPE_TRANSPORT_ADDRESS_CONSIDER_VERIFY,
                        struct GNUNET_TRANSPORT_AddressToVerify,
                        NULL),
 GNUNET_MQ_hd_fixed_size (del_queue_message,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_QUEUE_TEARDOWN,
                          struct GNUNET_TRANSPORT_DelQueueMessage,
                          NULL),
 GNUNET_MQ_hd_fixed_size (send_message_ack,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_SEND_MSG_ACK,
                          struct GNUNET_TRANSPORT_SendMessageToAck,
                          NULL),
 /* communication with monitors */
 GNUNET_MQ_hd_fixed_size (monitor_start,
                          GNUNET_MESSAGE_TYPE_TRANSPORT_MONITOR_START,
                          struct GNUNET_TRANSPORT_MonitorStart,
                          NULL),
 GNUNET_MQ_handler_end ());


/* end of file gnunet-service-transport.c */