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 #include "gnunet_container_lib.h"
  35
  36 struct dns_cls {
  37         struct GNUNET_SCHEDULER_Handle *sched;
  38
  39         struct GNUNET_NETWORK_Handle *dnsout;
  40
  41         unsigned short dnsoutport;
  42
  43         struct answer_packet_list *head;
  44         struct answer_packet_list *tail;
  45 };
  46 static struct dns_cls mycls;
  47
  48 struct dns_query_id_state {
  49         unsigned valid:1;
  50         struct GNUNET_SERVER_Client* client;
  51         unsigned local_ip:32;
  52         unsigned local_port:16;
  53 };
  54 static struct dns_query_id_state query_states[65536]; /* This is < 1MiB */
  55
  56 void hijack(unsigned short port) {
  57         char port_s[6];
  58
  59         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Hijacking, port is %d\n", port);
  60         snprintf(port_s, 6, "%d", port);
  61         GNUNET_OS_start_process(NULL, NULL, "gnunet-helper-hijack-dns", "gnunet-hijack-dns", port_s, NULL);
  62 }
  63
  64 void unhijack(unsigned short port) {
  65         char port_s[6];
  66
  67         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "unHijacking, port is %d\n", port);
  68         snprintf(port_s, 6, "%d", port);
  69         GNUNET_OS_start_process(NULL, NULL, "gnunet-helper-hijack-dns", "gnunet-hijack-dns", "-d", port_s, NULL);
  70 }
  71
  72 void receive_query(void *cls, struct GNUNET_SERVER_Client *client, const struct GNUNET_MessageHeader *message)
  73 {
  74         struct query_packet* pkt = (struct query_packet*)message;
  75         struct dns_pkt* dns = (struct dns_pkt*)pkt->data;
  76
  77         struct sockaddr_in dest;
  78         memset(&dest, 0, sizeof dest);
  79         dest.sin_port = htons(53);
  80         dest.sin_addr.s_addr = pkt->orig_to;
  81
  82         query_states[dns->id].valid = 1;
  83         query_states[dns->id].client = client;
  84         query_states[dns->id].local_ip = pkt->orig_from;
  85         query_states[dns->id].local_port = pkt->src_port;
  86
  87         /* int r = */ GNUNET_NETWORK_socket_sendto(mycls.dnsout, dns, ntohs(pkt->hdr.size) - sizeof(struct query_packet) + 1, (struct sockaddr*) &dest, sizeof dest);
  88
  89         GNUNET_SERVER_receive_done(client, GNUNET_OK);
  90 }
  91
  92 size_t send_answer(void* cls, size_t size, void* buf) {
  93         struct answer_packet_list* query = mycls.head;
  94         size_t len = ntohs(query->pkt.hdr.size);
  95
  96         GNUNET_assert(len <= size);
  97
  98         memcpy(buf, &query->pkt.hdr, len);
  99
 100         GNUNET_CONTAINER_DLL_remove (mycls.head, mycls.tail, query);
 101
 102         GNUNET_free(query);
 103
 104         if (mycls.head != NULL) {
 105                 GNUNET_SERVER_notify_transmit_ready(cls, ntohs(mycls.head->pkt.hdr.size), GNUNET_TIME_UNIT_FOREVER_REL, &send_answer, cls);
 106         }
 107
 108         return len;
 109 }
 110
 111 static void read_response (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc) {
 112         unsigned char buf[65536];
 113         struct dns_pkt* dns = (struct dns_pkt*)buf;
 114
 115         if (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN)
 116                 return;
 117
 118         struct sockaddr_in addr;
 119         memset(&addr, 0, sizeof addr);
 120         unsigned int addrlen = sizeof addr;
 121
 122         int r;
 123         r = GNUNET_NETWORK_socket_recvfrom(mycls.dnsout, buf, 65536, (struct sockaddr*)&addr, &addrlen);
 124
 125         /* if (r < 0) TODO */
 126
 127         if (query_states[dns->id].valid == 1) {
 128                 query_states[dns->id].valid = 0;
 129
 130                 size_t len = sizeof(struct answer_packet) + r - 1; /* 1 for the unsigned char data[1]; */
 131                 struct answer_packet_list* answer = GNUNET_malloc(len + 2*sizeof(struct answer_packet_list*));
 132                 answer->pkt.hdr.type = htons(GNUNET_MESSAGE_TYPE_LOCAL_RESPONSE_DNS);
 133                 answer->pkt.hdr.size = htons(len);
 134                 answer->pkt.from = addr.sin_addr.s_addr;
 135                 answer->pkt.to = query_states[dns->id].local_ip;
 136                 answer->pkt.dst_port = query_states[dns->id].local_port;
 137                 memcpy(answer->pkt.data, buf, r);
 138
 139                 GNUNET_CONTAINER_DLL_insert_after(mycls.head, mycls.tail, mycls.tail, answer);
 140
 141                 /* struct GNUNET_CONNECTION_TransmitHandle* th = */ GNUNET_SERVER_notify_transmit_ready(query_states[dns->id].client, len, GNUNET_TIME_UNIT_FOREVER_REL, &send_answer, query_states[dns->id].client);
 142         }
 143
 144         GNUNET_SCHEDULER_add_read_net(mycls.sched, GNUNET_TIME_UNIT_FOREVER_REL, mycls.dnsout, &read_response, NULL);
 145 }
 146
 147
 148 /**
 149  * Task run during shutdown.
 150  *
 151  * @param cls unused
 152  * @param tc unused
 153  */
 154 static void
 155 cleanup_task (void *cls,
 156               const struct GNUNET_SCHEDULER_TaskContext *tc)
 157 {
 158         unhijack(mycls.dnsoutport);
 159 }
 160
 161 /**
 162  * @param cls closure
 163  * @param sched scheduler to use
 164  * @param server the initialized server
 165  * @param cfg configuration to use
 166  */
 167 static void
 168 run (void *cls,
 169      struct GNUNET_SCHEDULER_Handle *sched,
 170      struct GNUNET_SERVER_Handle *server,
 171      const struct GNUNET_CONFIGURATION_Handle *cfg)
 172 {
 173   static const struct GNUNET_SERVER_MessageHandler handlers[] = {
 174           /* callback, cls, type, size */
 175     {&receive_query, NULL, GNUNET_MESSAGE_TYPE_LOCAL_QUERY_DNS, 0},
 176     {NULL, NULL, 0, 0}
 177   };
 178
 179   {
 180   int i;
 181   for (i = 0; i < 65536; i++) {
 182     query_states[i].valid = 0;
 183   }
 184   }
 185
 186   struct sockaddr_in addr;
 187
 188   mycls.sched = sched;
 189   mycls.dnsout = GNUNET_NETWORK_socket_create (AF_INET, SOCK_DGRAM, 0);
 190   if (mycls.dnsout == NULL)
 191     return;
 192   memset(&addr, 0, sizeof(struct sockaddr_in));
 193
 194   int err = GNUNET_NETWORK_socket_bind (mycls.dnsout,
 195                                         (struct sockaddr*)&addr,
 196                                         sizeof(struct sockaddr_in));
 197
 198   if (err != GNUNET_YES) {
 199         GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "Could not bind a port, exiting\n");
 200         return;
 201   }
 202   socklen_t addrlen = sizeof(struct sockaddr_in);
 203   err = getsockname(GNUNET_NETWORK_get_fd(mycls.dnsout),
 204                     (struct sockaddr*) &addr,
 205                     &addrlen);
 206
 207   mycls.dnsoutport = htons(addr.sin_port);
 208
 209   hijack(htons(addr.sin_port));
 210
 211         GNUNET_SCHEDULER_add_read_net(sched, GNUNET_TIME_UNIT_FOREVER_REL, mycls.dnsout, &read_response, NULL);
 212
 213   GNUNET_SERVER_add_handlers (server, handlers);
 214   GNUNET_SCHEDULER_add_delayed (sched,
 215                   GNUNET_TIME_UNIT_FOREVER_REL,
 216                   &cleanup_task,
 217                   cls);
 218 }
 219
 220 /**
 221  * The main function for the dns service.
 222  *
 223  * @param argc number of arguments from the command line
 224  * @param argv command line arguments
 225  * @return 0 ok, 1 on error
 226  */
 227 int
 228 main (int argc, char *const *argv)
 229 {
 230   return (GNUNET_OK ==
 231           GNUNET_SERVICE_run (argc,
 232                               argv,
 233                               "dns",
 234                               GNUNET_SERVICE_OPTION_NONE,
 235                               &run, NULL)) ? 0 : 1;
 236 }