src/vpn/gnunet-service-dns.c

   1 /*
   2      This file is part of GNUnet.
   3      (C) 2009 Christian Grothoff (and other contributing authors)
   4
   5      GNUnet is free software; you can redistribute it and/or modify
   6      it under the terms of the GNU General Public License as published
   7      by the Free Software Foundation; either version 3, or (at your
   8      option) any later version.
   9
  10      GNUnet is distributed in the hope that it will be useful, but
  11      WITHOUT ANY WARRANTY; without even the implied warranty of
  12      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13      General Public License for more details.
  14
  15      You should have received a copy of the GNU General Public License
  16      along with GNUnet; see the file COPYING.  If not, write to the
  17      Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18      Boston, MA 02111-1307, USA.
  19 */
  20
  21 /**
  22  * @file vpn/gnunet-service-dns.c
  23  * @author Philipp Tölke
  24  */
  25 #include "platform.h"
  26 #include "gnunet_getopt_lib.h"
  27 #include "gnunet_service_lib.h"
  28 #include "gnunet_network_lib.h"
  29 #include "gnunet_os_lib.h"
  30 #include "gnunet-service-dns-p.h"
  31 #include "gnunet_protocols.h"
  32 #include "gnunet-vpn-packet.h"
  33 #include "gnunet-vpn-pretty-print.h"
  34
  35 struct dns_cls {
  36         struct GNUNET_SCHEDULER_Handle *sched;
  37
  38         struct GNUNET_NETWORK_Handle *dnsout;
  39
  40         unsigned short dnsoutport;
  41 };
  42 static struct dns_cls mycls;
  43
  44 struct dns_query_id_state {
  45         unsigned valid:1;
  46         struct GNUNET_SERVER_Client* client;
  47         unsigned local_ip:32;
  48         unsigned local_port:16;
  49 };
  50 static struct dns_query_id_state query_states[65536]; /* This is < 1MiB */
  51
  52 void hijack(unsigned short port) {
  53         char port_s[6];
  54
  55         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Hijacking, port is %d\n", port);
  56         snprintf(port_s, 6, "%d", port);
  57         GNUNET_OS_start_process(NULL, NULL, "gnunet-helper-hijack-dns", "gnunet-hijack-dns", port_s, NULL);
  58 }
  59
  60 void unhijack(unsigned short port) {
  61         char port_s[6];
  62
  63         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "unHijacking, port is %d\n", port);
  64         snprintf(port_s, 6, "%d", port);
  65         GNUNET_OS_start_process(NULL, NULL, "gnunet-helper-hijack-dns", "gnunet-hijack-dns", "-d", port_s, NULL);
  66 }
  67
  68 void receive_query(void *cls, struct GNUNET_SERVER_Client *client, const struct GNUNET_MessageHeader *message)
  69 {
  70         struct query_packet* pkt = (struct query_packet*)message;
  71         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Received query of length %d\n", ntohs(pkt->hdr.size));
  72         struct dns_pkt* dns = (struct dns_pkt*)pkt->data;
  73
  74         struct sockaddr_in dest;
  75         memset(&dest, 0, sizeof dest);
  76         dest.sin_port = htons(53);
  77         dest.sin_addr.s_addr = pkt->orig_to;
  78
  79         query_states[dns->id].valid = 1;
  80         query_states[dns->id].client = client;
  81         query_states[dns->id].local_ip = pkt->orig_from;
  82         query_states[dns->id].local_port = pkt->src_port;
  83
  84         int r = GNUNET_NETWORK_socket_sendto(mycls.dnsout, dns, ntohs(pkt->hdr.size) - sizeof(struct query_packet) + 1, (struct sockaddr*) &dest, sizeof dest);
  85         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "send %d bytes to socket\n", r);
  86
  87         GNUNET_SERVER_receive_done(client, GNUNET_OK);
  88 }
  89
  90 static void read_response (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc) {
  91         unsigned char buf[65536];
  92         struct dns_pkt* dns = (struct dns_pkt*)buf;
  93
  94         if (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN)
  95                 return;
  96
  97         int r;
  98         r = GNUNET_NETWORK_socket_recv(mycls.dnsout, buf, 65536);
  99
 100         if (query_states[dns->id].valid == 1) {
 101                 query_states[dns->id].valid = 0;
 102
 103                 GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Would send answer to Client %x, to IP %x:%d\n", query_states[dns->id].client, ntohl(query_states[dns->id].local_ip), ntohs(query_states[dns->id].local_port));
 104         }
 105
 106         GNUNET_SCHEDULER_add_read_net(mycls.sched, GNUNET_TIME_UNIT_FOREVER_REL, mycls.dnsout, &read_response, NULL);
 107 }
 108
 109
 110 /**
 111  * Task run during shutdown.
 112  *
 113  * @param cls unused
 114  * @param tc unused
 115  */
 116 static void
 117 cleanup_task (void *cls,
 118               const struct GNUNET_SCHEDULER_TaskContext *tc)
 119 {
 120         unhijack(mycls.dnsoutport);
 121 }
 122
 123 /**
 124  * @param cls closure
 125  * @param sched scheduler to use
 126  * @param server the initialized server
 127  * @param cfg configuration to use
 128  */
 129 static void
 130 run (void *cls,
 131      struct GNUNET_SCHEDULER_Handle *sched,
 132      struct GNUNET_SERVER_Handle *server,
 133      const struct GNUNET_CONFIGURATION_Handle *cfg)
 134 {
 135   static const struct GNUNET_SERVER_MessageHandler handlers[] = {
 136           /* callback, cls, type, size */
 137     {&receive_query, NULL, GNUNET_MESSAGE_TYPE_LOCAL_QUERY_DNS, 0},
 138     {NULL, NULL, 0, 0}
 139   };
 140
 141   {
 142   int i;
 143   for (i = 0; i < 65536; i++) {
 144     query_states[i].valid = 0;
 145   }
 146   }
 147
 148   struct sockaddr_in addr;
 149
 150   mycls.sched = sched;
 151   mycls.dnsout = GNUNET_NETWORK_socket_create (AF_INET, SOCK_DGRAM, 0);
 152   if (mycls.dnsout == NULL)
 153     return;
 154   memset(&addr, 0, sizeof(struct sockaddr_in));
 155
 156   int err = GNUNET_NETWORK_socket_bind (mycls.dnsout,
 157                                         (struct sockaddr*)&addr,
 158                                         sizeof(struct sockaddr_in));
 159
 160   if (err != GNUNET_YES) {
 161         GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "Could not bind a port, exiting\n");
 162         return;
 163   }
 164   socklen_t addrlen = sizeof(struct sockaddr_in);
 165   err = getsockname(GNUNET_NETWORK_get_fd(mycls.dnsout),
 166                     (struct sockaddr*) &addr,
 167                     &addrlen);
 168
 169   mycls.dnsoutport = htons(addr.sin_port);
 170
 171   hijack(htons(addr.sin_port));
 172
 173         GNUNET_SCHEDULER_add_read_net(sched, GNUNET_TIME_UNIT_FOREVER_REL, mycls.dnsout, &read_response, NULL);
 174
 175   GNUNET_SERVER_add_handlers (server, handlers);
 176   GNUNET_SCHEDULER_add_delayed (sched,
 177                   GNUNET_TIME_UNIT_FOREVER_REL,
 178                   &cleanup_task,
 179                   cls);
 180 }
 181
 182 /**
 183  * The main function for the dns service.
 184  *
 185  * @param argc number of arguments from the command line
 186  * @param argv command line arguments
 187  * @return 0 ok, 1 on error
 188  */
 189 int
 190 main (int argc, char *const *argv)
 191 {
 192   return (GNUNET_OK ==
 193           GNUNET_SERVICE_run (argc,
 194                               argv,
 195                               "dns",
 196                               GNUNET_SERVICE_OPTION_NONE,
 197                               &run, NULL)) ? 0 : 1;
 198 }