4 files changed, 55 insertions, 25 deletions

diff --git a/src/exit/gnunet-daemon-exit.c b/src/exit/gnunet-daemon-exit.c
index 664a86f23..482eaae7e 100644
--- a/src/exit/gnunet-daemon-exit.c
+++ b/src/exit/gnunet-daemon-exit.c
@@ -1091,6 +1091,7 @@ prepare_ipv4_packet (const void *payload, size_t payload_length,
       memcpy (&pkt4_tcp[1], payload, payload_length);
       pkt4_tcp->spt = htons (src_address->port);
       pkt4_tcp->dpt = htons (dst_address->port);
+      
       pkt4_tcp->crc = 0;
       uint32_t sum = 0;
       sum = GNUNET_CRYPTO_crc16_step (sum, 
@@ -1194,19 +1195,12 @@ prepare_ipv6_packet (const void *payload, size_t payload_length,
       struct GNUNET_TUN_TcpHeader *pkt6_tcp = (struct GNUNET_TUN_TcpHeader *) pkt6;
       
       memcpy (pkt6_tcp, payload, payload_length);
-      pkt6_tcp->crc = 0;
       pkt6_tcp->spt = htons (src_address->port);
       pkt6_tcp->dpt = htons (dst_address->port);
-
-      uint32_t sum = 0;
-      sum = GNUNET_CRYPTO_crc16_step (sum, &pkt6->source_address, 
-                                      sizeof (struct in6_addr) * 2);
-      uint32_t tmp = htonl (len);
-      sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
-      tmp = htonl (pkt6->next_header);
-      sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));      
-      sum = GNUNET_CRYPTO_crc16_step (sum,  pkt6_tcp, len);
-      pkt6_tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+      GNUNET_TUN_calculate_tcp6_checksum (pkt6,
+                                          pkt6_tcp,
+                                          payload,
+                                          payload_length);
     }
     break;
   default:
diff --git a/src/include/gnunet_tun_lib.h b/src/include/gnunet_tun_lib.h
index 89cfdd2b3..b30b2b03a 100644
--- a/src/include/gnunet_tun_lib.h
+++ b/src/include/gnunet_tun_lib.h
@@ -181,5 +181,19 @@ GNUNET_TUN_initialize_ipv6_header (struct GNUNET_TUN_IPv6Header *ip,
                                    const struct in6_addr *src,
                                    const struct in6_addr *dst);
 
+/**
+ * Calculate IPv6 TCP checksum.
+ *
+ * @param ipv6 header fully initialized
+ * @param tcp header (initialized except for CRC)
+ * @param payload the TCP payload
+ * @param payload_length number of bytes of TCP payload
+ */
+void
+GNUNET_TUN_calculate_tcp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
+                                    struct GNUNET_TUN_TcpHeader *tcp,
+                                    const void *payload,
+                                    uint16_t payload_length);
+
 
 #endif
diff --git a/src/tun/tun.c b/src/tun/tun.c
index 005c7013d..c30861cce 100644
--- a/src/tun/tun.c
+++ b/src/tun/tun.c
@@ -95,5 +95,37 @@ GNUNET_TUN_initialize_ipv6_header (struct GNUNET_TUN_IPv6Header *ip,
 }
 
 
+/**
+ * Calculate IPv6 TCP checksum.
+ *
+ * @param ipv6 header fully initialized
+ * @param tcp header (initialized except for CRC)
+ * @param payload the TCP payload
+ * @param payload_length number of bytes of TCP payload
+ */
+void
+GNUNET_TUN_calculate_tcp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
+                                    struct GNUNET_TUN_TcpHeader *tcp,
+                                    const void *payload,
+                                    uint16_t payload_length)
+{
+  uint32_t sum;
+  uint32_t tmp;
+
+  GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_IPv6Header) + sizeof (struct GNUNET_TUN_TcpHeader) ==
+                 ntohs (ip->payload_length));
+  tcp->crc = 0;
+  sum = GNUNET_CRYPTO_crc16_step (0, &ip->source_address, 2 * sizeof (struct in6_addr));
+  tmp = htonl (sizeof (struct GNUNET_TUN_TcpHeader) + payload_length);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+  tmp = htonl (IPPROTO_TCP);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
+  sum = GNUNET_CRYPTO_crc16_step (sum, tcp,
+                                  sizeof (struct GNUNET_TUN_TcpHeader));
+  sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+  tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
 
 /* end of tun.c */
diff --git a/src/vpn/gnunet-service-vpn.c b/src/vpn/gnunet-service-vpn.c
index b352e216b..0d236975e 100644
--- a/src/vpn/gnunet-service-vpn.c
+++ b/src/vpn/gnunet-service-vpn.c
@@ -1643,20 +1643,10 @@ receive_tcp_back (void *cls GNUNET_UNUSED, struct GNUNET_MESH_Tunnel *tunnel,
                                            &ts->source_ip.v6);
         tcp->spt = htons (ts->destination_port);
         tcp->dpt = htons (ts->source_port);
-        tcp->crc = 0;
-        {
-          uint32_t sum = 0;
-          uint32_t tmp;
-
-          sum = GNUNET_CRYPTO_crc16_step (sum, &ipv6->source_address, 2 * sizeof (struct in6_addr));
-          tmp = htonl (sizeof (struct GNUNET_TUN_TcpHeader) + mlen);
-          sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
-          tmp = htonl (IPPROTO_TCP);
-          sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t));
-          sum = GNUNET_CRYPTO_crc16_step (sum, tcp,
-                                          sizeof (struct GNUNET_TUN_TcpHeader) + mlen);
-          tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
-        }
+        GNUNET_TUN_calculate_tcp6_checksum (ipv6,
+                                            tcp,
+                                            &tcp[1],
+                                            mlen);
         (void) GNUNET_HELPER_send (helper_handle,
                                    msg,
                                    GNUNET_YES,