diff options
Diffstat (limited to 'src/resolve/resolved-mdns.c')
| -rw-r--r-- | src/resolve/resolved-mdns.c | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/src/resolve/resolved-mdns.c b/src/resolve/resolved-mdns.c new file mode 100644 index 0000000000..d6973a6999 --- /dev/null +++ b/src/resolve/resolved-mdns.c @@ -0,0 +1,290 @@ +/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ + +/*** + This file is part of systemd. + + Copyright 2015 Daniel Mack + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. + ***/ + +#include <resolv.h> +#include <netinet/in.h> +#include <arpa/inet.h> + +#include "fd-util.h" +#include "resolved-manager.h" +#include "resolved-mdns.h" + +void manager_mdns_stop(Manager *m) { + assert(m); + + m->mdns_ipv4_event_source = sd_event_source_unref(m->mdns_ipv4_event_source); + m->mdns_ipv4_fd = safe_close(m->mdns_ipv4_fd); + + m->mdns_ipv6_event_source = sd_event_source_unref(m->mdns_ipv6_event_source); + m->mdns_ipv6_fd = safe_close(m->mdns_ipv6_fd); +} + +int manager_mdns_start(Manager *m) { + int r; + + assert(m); + + if (m->mdns_support == SUPPORT_NO) + return 0; + + r = manager_mdns_ipv4_fd(m); + if (r == -EADDRINUSE) + goto eaddrinuse; + if (r < 0) + return r; + + if (socket_ipv6_is_supported()) { + r = manager_mdns_ipv6_fd(m); + if (r == -EADDRINUSE) + goto eaddrinuse; + if (r < 0) + return r; + } + + return 0; + +eaddrinuse: + log_warning("There appears to be another mDNS responder running. Turning off mDNS support."); + m->mdns_support = SUPPORT_NO; + manager_mdns_stop(m); + + return 0; +} + +static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) { + _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; + Manager *m = userdata; + DnsScope *scope; + int r; + + r = manager_recv(m, fd, DNS_PROTOCOL_MDNS, &p); + if (r <= 0) + return r; + + scope = manager_find_scope(m, p); + if (!scope) { + log_warning("Got mDNS UDP packet on unknown scope. Ignoring."); + return 0; + } + + if (dns_packet_validate_reply(p) > 0) { + DnsResourceRecord *rr; + + log_debug("Got mDNS reply packet"); + + /* + * mDNS is different from regular DNS and LLMNR with regard to handling responses. + * While on other protocols, we can ignore every answer that doesn't match a question + * we broadcast earlier, RFC6762, section 18.1 recommends looking at and caching all + * incoming information, regardless of the DNS packet ID. + * + * Hence, extract the packet here, and try to find a transaction for answer the we got + * and complete it. Also store the new information in scope's cache. + */ + r = dns_packet_extract(p); + if (r < 0) { + log_debug("mDNS packet extraction failed."); + return 0; + } + + dns_scope_check_conflicts(scope, p); + + DNS_ANSWER_FOREACH(rr, p->answer) { + const char *name = DNS_RESOURCE_KEY_NAME(rr->key); + DnsTransaction *t; + + /* If the received reply packet contains ANY record that is not .local or .in-addr.arpa, + * we assume someone's playing tricks on us and discard the packet completely. */ + if (!(dns_name_endswith(name, "in-addr.arpa") > 0 || + dns_name_endswith(name, "local") > 0)) + return 0; + + t = dns_scope_find_transaction(scope, rr->key, false); + if (t) + dns_transaction_process_reply(t, p); + } + + dns_cache_put(&scope->cache, NULL, DNS_PACKET_RCODE(p), p->answer, + p->answer->n_rrs, false, 0, p->family, &p->sender); + + } else if (dns_packet_validate_query(p) > 0) { + log_debug("Got mDNS query packet for id %u", DNS_PACKET_ID(p)); + + dns_scope_process_query(scope, NULL, p); + } else + log_debug("Invalid mDNS UDP packet."); + + return 0; +} + +int manager_mdns_ipv4_fd(Manager *m) { + union sockaddr_union sa = { + .in.sin_family = AF_INET, + .in.sin_port = htobe16(MDNS_PORT), + }; + static const int one = 1, pmtu = IP_PMTUDISC_DONT, ttl = 255; + int r; + + assert(m); + + if (m->mdns_ipv4_fd >= 0) + return m->mdns_ipv4_fd; + + m->mdns_ipv4_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); + if (m->mdns_ipv4_fd < 0) + return -errno; + + r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv4_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_PKTINFO, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_RECVTTL, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + /* Disable Don't-Fragment bit in the IP header */ + r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MTU_DISCOVER, &pmtu, sizeof(pmtu)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = bind(m->mdns_ipv4_fd, &sa.sa, sizeof(sa.in)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = sd_event_add_io(m->event, &m->mdns_ipv4_event_source, m->mdns_ipv4_fd, EPOLLIN, on_mdns_packet, m); + if (r < 0) + goto fail; + + return m->mdns_ipv4_fd; + +fail: + m->mdns_ipv4_fd = safe_close(m->mdns_ipv4_fd); + return r; +} + +int manager_mdns_ipv6_fd(Manager *m) { + union sockaddr_union sa = { + .in6.sin6_family = AF_INET6, + .in6.sin6_port = htobe16(MDNS_PORT), + }; + static const int one = 1, ttl = 255; + int r; + + assert(m); + + if (m->mdns_ipv6_fd >= 0) + return m->mdns_ipv6_fd; + + m->mdns_ipv6_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); + if (m->mdns_ipv6_fd < 0) + return -errno; + + r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof(ttl)); + if (r < 0) { + r = -errno; + goto fail; + } + + /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */ + r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv6_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &one, sizeof(one)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = bind(m->mdns_ipv6_fd, &sa.sa, sizeof(sa.in6)); + if (r < 0) { + r = -errno; + goto fail; + } + + r = sd_event_add_io(m->event, &m->mdns_ipv6_event_source, m->mdns_ipv6_fd, EPOLLIN, on_mdns_packet, m); + if (r < 0) + goto fail; + + return m->mdns_ipv6_fd; + +fail: + m->mdns_ipv6_fd = safe_close(m->mdns_ipv6_fd); + return r; +} |