src/resolve/resolved-mdns.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2015 Daniel Mack
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20  ***/
  21
  22 #include <resolv.h>
  23 #include <netinet/in.h>
  24 #include <arpa/inet.h>
  25
  26 #include "fd-util.h"
  27 #include "resolved-manager.h"
  28 #include "resolved-mdns.h"
  29
  30 void manager_mdns_stop(Manager *m) {
  31         assert(m);
  32
  33         m->mdns_ipv4_event_source = sd_event_source_unref(m->mdns_ipv4_event_source);
  34         m->mdns_ipv4_fd = safe_close(m->mdns_ipv4_fd);
  35
  36         m->mdns_ipv6_event_source = sd_event_source_unref(m->mdns_ipv6_event_source);
  37         m->mdns_ipv6_fd = safe_close(m->mdns_ipv6_fd);
  38 }
  39
  40 int manager_mdns_start(Manager *m) {
  41         int r;
  42
  43         assert(m);
  44
  45         if (m->mdns_support == SUPPORT_NO)
  46                 return 0;
  47
  48         r = manager_mdns_ipv4_fd(m);
  49         if (r == -EADDRINUSE)
  50                 goto eaddrinuse;
  51         if (r < 0)
  52                 return r;
  53
  54         if (socket_ipv6_is_supported()) {
  55                 r = manager_mdns_ipv6_fd(m);
  56                 if (r == -EADDRINUSE)
  57                         goto eaddrinuse;
  58                 if (r < 0)
  59                         return r;
  60         }
  61
  62         return 0;
  63
  64 eaddrinuse:
  65         log_warning("There appears to be another mDNS responder running. Turning off mDNS support.");
  66         m->mdns_support = SUPPORT_NO;
  67         manager_mdns_stop(m);
  68
  69         return 0;
  70 }
  71
  72 static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
  73         /* TODO */
  74         return 0;
  75 }
  76
  77 int manager_mdns_ipv4_fd(Manager *m) {
  78         union sockaddr_union sa = {
  79                 .in.sin_family = AF_INET,
  80                 .in.sin_port = htobe16(MDNS_PORT),
  81         };
  82         static const int one = 1, pmtu = IP_PMTUDISC_DONT, ttl = 255;
  83         int r;
  84
  85         assert(m);
  86
  87         if (m->mdns_ipv4_fd >= 0)
  88                 return m->mdns_ipv4_fd;
  89
  90         m->mdns_ipv4_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
  91         if (m->mdns_ipv4_fd < 0)
  92                 return -errno;
  93
  94         r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
  95         if (r < 0) {
  96                 r = -errno;
  97                 goto fail;
  98         }
  99
 100         r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
 101         if (r < 0) {
 102                 r = -errno;
 103                 goto fail;
 104         }
 105
 106         r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one, sizeof(one));
 107         if (r < 0) {
 108                 r = -errno;
 109                 goto fail;
 110         }
 111
 112         r = setsockopt(m->mdns_ipv4_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
 113         if (r < 0) {
 114                 r = -errno;
 115                 goto fail;
 116         }
 117
 118         r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_PKTINFO, &one, sizeof(one));
 119         if (r < 0) {
 120                 r = -errno;
 121                 goto fail;
 122         }
 123
 124         r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_RECVTTL, &one, sizeof(one));
 125         if (r < 0) {
 126                 r = -errno;
 127                 goto fail;
 128         }
 129
 130         /* Disable Don't-Fragment bit in the IP header */
 131         r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MTU_DISCOVER, &pmtu, sizeof(pmtu));
 132         if (r < 0) {
 133                 r = -errno;
 134                 goto fail;
 135         }
 136
 137         r = bind(m->mdns_ipv4_fd, &sa.sa, sizeof(sa.in));
 138         if (r < 0) {
 139                 r = -errno;
 140                 goto fail;
 141         }
 142
 143         r = sd_event_add_io(m->event, &m->mdns_ipv4_event_source, m->mdns_ipv4_fd, EPOLLIN, on_mdns_packet, m);
 144         if (r < 0)
 145                 goto fail;
 146
 147         return m->mdns_ipv4_fd;
 148
 149 fail:
 150         m->mdns_ipv4_fd = safe_close(m->mdns_ipv4_fd);
 151         return r;
 152 }
 153
 154 int manager_mdns_ipv6_fd(Manager *m) {
 155         union sockaddr_union sa = {
 156                 .in6.sin6_family = AF_INET6,
 157                 .in6.sin6_port = htobe16(MDNS_PORT),
 158         };
 159         static const int one = 1, ttl = 255;
 160         int r;
 161
 162         assert(m);
 163
 164         if (m->mdns_ipv6_fd >= 0)
 165                 return m->mdns_ipv6_fd;
 166
 167         m->mdns_ipv6_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
 168         if (m->mdns_ipv6_fd < 0)
 169                 return -errno;
 170
 171         r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof(ttl));
 172         if (r < 0) {
 173                 r = -errno;
 174                 goto fail;
 175         }
 176
 177         /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
 178         r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl));
 179         if (r < 0) {
 180                 r = -errno;
 181                 goto fail;
 182         }
 183
 184         r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &one, sizeof(one));
 185         if (r < 0) {
 186                 r = -errno;
 187                 goto fail;
 188         }
 189
 190         r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
 191         if (r < 0) {
 192                 r = -errno;
 193                 goto fail;
 194         }
 195
 196         r = setsockopt(m->mdns_ipv6_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
 197         if (r < 0) {
 198                 r = -errno;
 199                 goto fail;
 200         }
 201
 202         r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
 203         if (r < 0) {
 204                 r = -errno;
 205                 goto fail;
 206         }
 207
 208         r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &one, sizeof(one));
 209         if (r < 0) {
 210                 r = -errno;
 211                 goto fail;
 212         }
 213
 214         r = bind(m->mdns_ipv6_fd, &sa.sa, sizeof(sa.in6));
 215         if (r < 0) {
 216                 r = -errno;
 217                 goto fail;
 218         }
 219
 220         r = sd_event_add_io(m->event, &m->mdns_ipv6_event_source, m->mdns_ipv6_fd, EPOLLIN, on_mdns_packet, m);
 221         if (r < 0)  {
 222                 r = -errno;
 223                 goto fail;
 224         }
 225
 226         return m->mdns_ipv6_fd;
 227
 228 fail:
 229         m->mdns_ipv6_fd = safe_close(m->mdns_ipv6_fd);
 230         return r;
 231 }