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 #include "gnunet-dns-parser.h"
  36
  37 struct dns_cls {
  38         struct GNUNET_SCHEDULER_Handle *sched;
  39
  40         struct GNUNET_NETWORK_Handle *dnsout;
  41
  42         unsigned short dnsoutport;
  43
  44         struct answer_packet_list *head;
  45         struct answer_packet_list *tail;
  46 };
  47 static struct dns_cls mycls;
  48
  49 struct dns_query_id_state {
  50         unsigned valid:1;
  51         struct GNUNET_SERVER_Client* client;
  52         unsigned local_ip:32;
  53         unsigned local_port:16;
  54 };
  55 static struct dns_query_id_state query_states[65536]; /* This is < 1MiB */
  56
  57 void hijack(unsigned short port) {
  58         char port_s[6];
  59
  60         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Hijacking, port is %d\n", port);
  61         snprintf(port_s, 6, "%d", port);
  62         GNUNET_OS_start_process(NULL, NULL, "gnunet-helper-hijack-dns", "gnunet-hijack-dns", port_s, NULL);
  63 }
  64
  65 void unhijack(unsigned short port) {
  66         char port_s[6];
  67
  68         GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "unHijacking, port is %d\n", port);
  69         snprintf(port_s, 6, "%d", port);
  70         GNUNET_OS_start_process(NULL, NULL, "gnunet-helper-hijack-dns", "gnunet-hijack-dns", "-d", port_s, NULL);
  71 }
  72
  73 /**
  74  * This receives the dns-payload from the daemon-vpn and sends it on over the udp-socket
  75  */
  76 void receive_query(void *cls, struct GNUNET_SERVER_Client *client, const struct GNUNET_MessageHeader *message)
  77 {
  78         struct query_packet* pkt = (struct query_packet*)message;
  79         struct dns_pkt* dns = (struct dns_pkt*)pkt->data;
  80         struct dns_pkt_parsed* pdns = parse_dns_packet(dns);
  81
  82         if (pdns->queries[0]->namelen > 9 &&
  83             0 == strncmp(pdns->queries[0]->name+(pdns->queries[0]->namelen - 9), ".gnunet.", 9)) {
  84             GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Query for .gnunet!\n");
  85         }
  86
  87         GNUNET_free(pdns);
  88
  89         struct sockaddr_in dest;
  90         memset(&dest, 0, sizeof dest);
  91         dest.sin_port = htons(53);
  92         dest.sin_addr.s_addr = pkt->orig_to;
  93
  94         query_states[dns->s.id].valid = 1;
  95         query_states[dns->s.id].client = client;
  96         query_states[dns->s.id].local_ip = pkt->orig_from;
  97         query_states[dns->s.id].local_port = pkt->src_port;
  98
  99         /* int r = */ GNUNET_NETWORK_socket_sendto(mycls.dnsout, dns, ntohs(pkt->hdr.size) - sizeof(struct query_packet) + 1, (struct sockaddr*) &dest, sizeof dest);
 100
 101         GNUNET_SERVER_receive_done(client, GNUNET_OK);
 102 }
 103
 104 size_t send_answer(void* cls, size_t size, void* buf) {
 105         struct answer_packet_list* query = mycls.head;
 106         size_t len = ntohs(query->pkt.hdr.size);
 107
 108         GNUNET_assert(len <= size);
 109
 110         memcpy(buf, &query->pkt.hdr, len);
 111
 112         GNUNET_CONTAINER_DLL_remove (mycls.head, mycls.tail, query);
 113
 114         GNUNET_free(query);
 115
 116         if (mycls.head != NULL) {
 117                 GNUNET_SERVER_notify_transmit_ready(cls, ntohs(mycls.head->pkt.hdr.size), GNUNET_TIME_UNIT_FOREVER_REL, &send_answer, cls);
 118         }
 119
 120         return len;
 121 }
 122
 123 static void read_response (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc) {
 124         unsigned char buf[65536];
 125         struct dns_pkt* dns = (struct dns_pkt*)buf;
 126
 127         if (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN)
 128                 return;
 129
 130         struct sockaddr_in addr;
 131         memset(&addr, 0, sizeof addr);
 132         unsigned int addrlen = sizeof addr;
 133
 134         int r;
 135         r = GNUNET_NETWORK_socket_recvfrom(mycls.dnsout, buf, 65536, (struct sockaddr*)&addr, &addrlen);
 136
 137         /* if (r < 0) TODO */
 138
 139         if (query_states[dns->s.id].valid == 1) {
 140                 query_states[dns->s.id].valid = 0;
 141
 142                 size_t len = sizeof(struct answer_packet) + r - 1; /* 1 for the unsigned char data[1]; */
 143                 struct answer_packet_list* answer = GNUNET_malloc(len + 2*sizeof(struct answer_packet_list*));
 144                 answer->pkt.hdr.type = htons(GNUNET_MESSAGE_TYPE_LOCAL_RESPONSE_DNS);
 145                 answer->pkt.hdr.size = htons(len);
 146                 answer->pkt.from = addr.sin_addr.s_addr;
 147                 answer->pkt.to = query_states[dns->s.id].local_ip;
 148                 answer->pkt.dst_port = query_states[dns->s.id].local_port;
 149                 memcpy(answer->pkt.data, buf, r);
 150
 151                 GNUNET_CONTAINER_DLL_insert_after(mycls.head, mycls.tail, mycls.tail, answer);
 152
 153                 /* struct GNUNET_CONNECTION_TransmitHandle* th = */ GNUNET_SERVER_notify_transmit_ready(query_states[dns->s.id].client, len, GNUNET_TIME_UNIT_FOREVER_REL, &send_answer, query_states[dns->s.id].client);
 154         }
 155
 156         GNUNET_SCHEDULER_add_read_net(mycls.sched, GNUNET_TIME_UNIT_FOREVER_REL, mycls.dnsout, &read_response, NULL);
 157 }
 158
 159
 160 /**
 161  * Task run during shutdown.
 162  *
 163  * @param cls unused
 164  * @param tc unused
 165  */
 166 static void
 167 cleanup_task (void *cls,
 168               const struct GNUNET_SCHEDULER_TaskContext *tc)
 169 {
 170         unhijack(mycls.dnsoutport);
 171 }
 172
 173 /**
 174  * @param cls closure
 175  * @param sched scheduler to use
 176  * @param server the initialized server
 177  * @param cfg configuration to use
 178  */
 179 static void
 180 run (void *cls,
 181      struct GNUNET_SCHEDULER_Handle *sched,
 182      struct GNUNET_SERVER_Handle *server,
 183      const struct GNUNET_CONFIGURATION_Handle *cfg)
 184 {
 185   static const struct GNUNET_SERVER_MessageHandler handlers[] = {
 186           /* callback, cls, type, size */
 187     {&receive_query, NULL, GNUNET_MESSAGE_TYPE_LOCAL_QUERY_DNS, 0},
 188     {NULL, NULL, 0, 0}
 189   };
 190
 191   {
 192   int i;
 193   for (i = 0; i < 65536; i++) {
 194     query_states[i].valid = 0;
 195   }
 196   }
 197
 198   struct sockaddr_in addr;
 199
 200   mycls.sched = sched;
 201   mycls.dnsout = GNUNET_NETWORK_socket_create (AF_INET, SOCK_DGRAM, 0);
 202   if (mycls.dnsout == NULL)
 203     return;
 204   memset(&addr, 0, sizeof(struct sockaddr_in));
 205
 206   int err = GNUNET_NETWORK_socket_bind (mycls.dnsout,
 207                                         (struct sockaddr*)&addr,
 208                                         sizeof(struct sockaddr_in));
 209
 210   if (err != GNUNET_YES) {
 211         GNUNET_log(GNUNET_ERROR_TYPE_ERROR, "Could not bind a port, exiting\n");
 212         return;
 213   }
 214   socklen_t addrlen = sizeof(struct sockaddr_in);
 215   err = getsockname(GNUNET_NETWORK_get_fd(mycls.dnsout),
 216                     (struct sockaddr*) &addr,
 217                     &addrlen);
 218
 219   mycls.dnsoutport = htons(addr.sin_port);
 220
 221   hijack(htons(addr.sin_port));
 222
 223         GNUNET_SCHEDULER_add_read_net(sched, GNUNET_TIME_UNIT_FOREVER_REL, mycls.dnsout, &read_response, NULL);
 224
 225   GNUNET_SERVER_add_handlers (server, handlers);
 226   GNUNET_SCHEDULER_add_delayed (sched,
 227                   GNUNET_TIME_UNIT_FOREVER_REL,
 228                   &cleanup_task,
 229                   cls);
 230 }
 231
 232 /**
 233  * The main function for the dns service.
 234  *
 235  * @param argc number of arguments from the command line
 236  * @param argv command line arguments
 237  * @return 0 ok, 1 on error
 238  */
 239 int
 240 main (int argc, char *const *argv)
 241 {
 242   return (GNUNET_OK ==
 243           GNUNET_SERVICE_run (argc,
 244                               argv,
 245                               "dns",
 246                               GNUNET_SERVICE_OPTION_NONE,
 247                               &run, NULL)) ? 0 : 1;
 248 }