-adding tool to test dnsparser.c

1 files changed, 207 insertions, 0 deletions

diff --git a/src/dns/gnunet-dns-redirector.c b/src/dns/gnunet-dns-redirector.c
new file mode 100644
index 000000000..bde869816
--- /dev/null
+++ b/src/dns/gnunet-dns-redirector.c
@@ -0,0 +1,207 @@
+/*
+     This file is part of GNUnet.
+     (C) 2011 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, 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
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file src/dns/gnunet-dns-redirector.c
+ * @brief Tool to change DNS replies (for testing)
+ * @author Christian Grothoff
+ */
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+#include "gnunet_dns_service-new.h"
+#include "gnunet_dnsparser_lib.h"
+
+/**
+ * Handle to transport service.
+ */
+static struct GNUNET_DNS_Handle *handle;
+
+/**
+ * New target for A records.
+ */
+static char *n4;
+
+/**
+ * New target for AAAA records.
+ */
+static char *n6;
+
+/**
+ * Global return value (0 success).
+ */
+static int ret;
+
+/**
+ * Selected level of verbosity.
+ */
+static int verbosity;
+
+
+/**
+ * Output the given DNS query to stdout.
+ *
+ * @param query query to display.
+ */
+static void
+modify_record (const struct GNUNET_DNSPARSER_Record *record)
+{
+  switch (record->type)
+  {
+  case GNUNET_DNSPARSER_TYPE_A:    
+    if (record->data.raw.data_len != sizeof (struct in_addr))
+      return;
+    if (NULL != n4)
+      inet_pton (AF_INET, n4, record->data.raw.data);
+    break;
+  case GNUNET_DNSPARSER_TYPE_AAAA:
+    if (record->data.raw.data_len != sizeof (struct in6_addr))
+      return;
+    if (NULL != n6)
+      inet_pton (AF_INET6, n6, record->data.raw.data);
+    break;
+  case GNUNET_DNSPARSER_TYPE_NS:
+  case GNUNET_DNSPARSER_TYPE_CNAME:
+  case GNUNET_DNSPARSER_TYPE_PTR:
+  case GNUNET_DNSPARSER_TYPE_SOA:
+  case GNUNET_DNSPARSER_TYPE_MX:
+  case GNUNET_DNSPARSER_TYPE_TXT:
+    break;
+  default:
+    break;
+  }
+}
+
+
+/**
+ * Signature of a function that is called whenever the DNS service
+ * encounters a DNS request and needs to do something with it.  The
+ * function has then the chance to generate or modify the response by
+ * calling one of the three "GNUNET_DNS_request_*" continuations.
+ *
+ * When a request is intercepted, this function is called first to
+ * give the client a chance to do the complete address resolution;
+ * "rdata" will be NULL for this first call for a DNS request, unless
+ * some other client has already filled in a response.
+ *
+ * If multiple clients exist, all of them are called before the global
+ * DNS.  The global DNS is only called if all of the clients'
+ * functions call GNUNET_DNS_request_forward.  Functions that call
+ * GNUNET_DNS_request_forward will be called again before a final
+ * response is returned to the application.  If any of the clients'
+ * functions call GNUNET_DNS_request_drop, the response is dropped.
+ *
+ * @param cls closure
+ * @param rh request handle to user for reply
+ * @param request_length number of bytes in request
+ * @param request udp payload of the DNS request
+ */
+static void 
+modify_request (void *cls,
+                struct GNUNET_DNS_RequestHandle *rh,
+                size_t request_length,
+                const char *request)
+{
+  struct GNUNET_DNSPARSER_Packet *p;
+  unsigned int i;
+  char *buf;
+  size_t len;
+  int ret;
+
+  p = GNUNET_DNSPARSER_parse (request, request_length);
+  if (NULL == p)
+  {
+    fprintf (stderr, "Received malformed DNS packet!\n");
+    // FIXME: drop instead?
+    GNUNET_DNS_request_forward (rh);
+    return;
+  }
+  for (i=0;i<p->num_answers;i++)
+    modify_record (&p->answers[i]);
+  buf = NULL;
+  ret = GNUNET_DNSPARSER_pack (p, 1024, &buf, &len);
+  GNUNET_DNSPARSER_free_packet (p);
+  fprintf (stderr, "PACK: %d\n", ret);
+  if (GNUNET_OK != ret)
+    GNUNET_DNS_request_forward (rh);
+  else
+    GNUNET_DNS_request_answer (rh, len, buf);
+  GNUNET_free_non_null (buf);      
+}
+
+
+/**
+ * Shutdown.
+ */
+static void
+do_disconnect (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  if (NULL != handle)
+  {
+    GNUNET_DNS_disconnect (handle);
+    handle = NULL;
+  }
+}
+
+
+/**
+ * Main function that will be run by the scheduler.
+ *
+ * @param cls closure
+ * @param args remaining command-line arguments
+ * @param cfgfile name of the configuration file used (for saving, can be NULL!)
+ * @param cfg configuration
+ */
+static void
+run (void *cls, char *const *args, const char *cfgfile,
+     const struct GNUNET_CONFIGURATION_Handle *cfg)
+{
+  handle =
+    GNUNET_DNS_connect (cfg, 
+                        GNUNET_DNS_FLAG_POST_RESOLUTION,
+                        &modify_request,
+                        NULL);
+  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL,
+                                &do_disconnect, NULL);
+}
+
+
+int
+main (int argc, char *const *argv)
+{
+  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
+    {'4', "ipv4", "IPV4",
+     gettext_noop ("set A records"),
+     1, &GNUNET_GETOPT_set_string, &n4},
+    {'6', "ipv4", "IPV6",
+     gettext_noop ("set AAAA records"),
+     1, &GNUNET_GETOPT_set_string, &n6},
+    GNUNET_GETOPT_OPTION_VERBOSE (&verbosity),
+    GNUNET_GETOPT_OPTION_END
+  };
+  return (GNUNET_OK ==
+          GNUNET_PROGRAM_run (argc, argv, "gnunet-dns-redirector",
+                              gettext_noop
+                              ("Change DNS replies to point elsewhere."), options,
+                              &run, NULL)) ? ret : 1;
+}
+
+
+/* end of gnunet-dns-redirector.c */