]>
git.ipfire.org Git - thirdparty/systemd.git/blob - src/resolve/resolved-mdns.c
2 This file is part of systemd.
4 Copyright 2015 Daniel Mack
6 systemd is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Lesser General Public License as published by
8 the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version.
11 systemd is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public License
17 along with systemd; If not, see <http://www.gnu.org/licenses/>.
21 #include <netinet/in.h>
22 #include <arpa/inet.h>
25 #include "resolved-manager.h"
26 #include "resolved-mdns.h"
28 void manager_mdns_stop(Manager
*m
) {
31 m
->mdns_ipv4_event_source
= sd_event_source_unref(m
->mdns_ipv4_event_source
);
32 m
->mdns_ipv4_fd
= safe_close(m
->mdns_ipv4_fd
);
34 m
->mdns_ipv6_event_source
= sd_event_source_unref(m
->mdns_ipv6_event_source
);
35 m
->mdns_ipv6_fd
= safe_close(m
->mdns_ipv6_fd
);
38 int manager_mdns_start(Manager
*m
) {
43 if (m
->mdns_support
== RESOLVE_SUPPORT_NO
)
46 r
= manager_mdns_ipv4_fd(m
);
52 if (socket_ipv6_is_supported()) {
53 r
= manager_mdns_ipv6_fd(m
);
63 log_warning("There appears to be another mDNS responder running. Turning off mDNS support.");
64 m
->mdns_support
= RESOLVE_SUPPORT_NO
;
70 static int on_mdns_packet(sd_event_source
*s
, int fd
, uint32_t revents
, void *userdata
) {
71 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
72 Manager
*m
= userdata
;
76 r
= manager_recv(m
, fd
, DNS_PROTOCOL_MDNS
, &p
);
80 scope
= manager_find_scope(m
, p
);
82 log_warning("Got mDNS UDP packet on unknown scope. Ignoring.");
86 if (dns_packet_validate_reply(p
) > 0) {
87 DnsResourceRecord
*rr
;
89 log_debug("Got mDNS reply packet");
92 * mDNS is different from regular DNS and LLMNR with regard to handling responses.
93 * While on other protocols, we can ignore every answer that doesn't match a question
94 * we broadcast earlier, RFC6762, section 18.1 recommends looking at and caching all
95 * incoming information, regardless of the DNS packet ID.
97 * Hence, extract the packet here, and try to find a transaction for answer the we got
98 * and complete it. Also store the new information in scope's cache.
100 r
= dns_packet_extract(p
);
102 log_debug("mDNS packet extraction failed.");
106 dns_scope_check_conflicts(scope
, p
);
108 DNS_ANSWER_FOREACH(rr
, p
->answer
) {
109 const char *name
= DNS_RESOURCE_KEY_NAME(rr
->key
);
112 /* If the received reply packet contains ANY record that is not .local or .in-addr.arpa,
113 * we assume someone's playing tricks on us and discard the packet completely. */
114 if (!(dns_name_endswith(name
, "in-addr.arpa") > 0 ||
115 dns_name_endswith(name
, "local") > 0))
118 t
= dns_scope_find_transaction(scope
, rr
->key
, false);
120 dns_transaction_process_reply(t
, p
);
123 dns_cache_put(&scope
->cache
, NULL
, DNS_PACKET_RCODE(p
), p
->answer
, false, (uint32_t) -1, 0, p
->family
, &p
->sender
);
125 } else if (dns_packet_validate_query(p
) > 0) {
126 log_debug("Got mDNS query packet for id %u", DNS_PACKET_ID(p
));
128 dns_scope_process_query(scope
, NULL
, p
);
130 log_debug("Invalid mDNS UDP packet.");
135 int manager_mdns_ipv4_fd(Manager
*m
) {
136 union sockaddr_union sa
= {
137 .in
.sin_family
= AF_INET
,
138 .in
.sin_port
= htobe16(MDNS_PORT
),
140 static const int one
= 1, pmtu
= IP_PMTUDISC_DONT
, ttl
= 255;
145 if (m
->mdns_ipv4_fd
>= 0)
146 return m
->mdns_ipv4_fd
;
148 m
->mdns_ipv4_fd
= socket(AF_INET
, SOCK_DGRAM
|SOCK_CLOEXEC
|SOCK_NONBLOCK
, 0);
149 if (m
->mdns_ipv4_fd
< 0)
152 r
= setsockopt(m
->mdns_ipv4_fd
, IPPROTO_IP
, IP_TTL
, &ttl
, sizeof(ttl
));
158 r
= setsockopt(m
->mdns_ipv4_fd
, IPPROTO_IP
, IP_MULTICAST_TTL
, &ttl
, sizeof(ttl
));
164 r
= setsockopt(m
->mdns_ipv4_fd
, IPPROTO_IP
, IP_MULTICAST_LOOP
, &one
, sizeof(one
));
170 r
= setsockopt(m
->mdns_ipv4_fd
, SOL_SOCKET
, SO_REUSEADDR
, &one
, sizeof(one
));
176 r
= setsockopt(m
->mdns_ipv4_fd
, IPPROTO_IP
, IP_PKTINFO
, &one
, sizeof(one
));
182 r
= setsockopt(m
->mdns_ipv4_fd
, IPPROTO_IP
, IP_RECVTTL
, &one
, sizeof(one
));
188 /* Disable Don't-Fragment bit in the IP header */
189 r
= setsockopt(m
->mdns_ipv4_fd
, IPPROTO_IP
, IP_MTU_DISCOVER
, &pmtu
, sizeof(pmtu
));
195 r
= bind(m
->mdns_ipv4_fd
, &sa
.sa
, sizeof(sa
.in
));
201 r
= sd_event_add_io(m
->event
, &m
->mdns_ipv4_event_source
, m
->mdns_ipv4_fd
, EPOLLIN
, on_mdns_packet
, m
);
205 return m
->mdns_ipv4_fd
;
208 m
->mdns_ipv4_fd
= safe_close(m
->mdns_ipv4_fd
);
212 int manager_mdns_ipv6_fd(Manager
*m
) {
213 union sockaddr_union sa
= {
214 .in6
.sin6_family
= AF_INET6
,
215 .in6
.sin6_port
= htobe16(MDNS_PORT
),
217 static const int one
= 1, ttl
= 255;
222 if (m
->mdns_ipv6_fd
>= 0)
223 return m
->mdns_ipv6_fd
;
225 m
->mdns_ipv6_fd
= socket(AF_INET6
, SOCK_DGRAM
|SOCK_CLOEXEC
|SOCK_NONBLOCK
, 0);
226 if (m
->mdns_ipv6_fd
< 0)
229 r
= setsockopt(m
->mdns_ipv6_fd
, IPPROTO_IPV6
, IPV6_UNICAST_HOPS
, &ttl
, sizeof(ttl
));
235 /* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
236 r
= setsockopt(m
->mdns_ipv6_fd
, IPPROTO_IPV6
, IPV6_MULTICAST_HOPS
, &ttl
, sizeof(ttl
));
242 r
= setsockopt(m
->mdns_ipv6_fd
, IPPROTO_IPV6
, IPV6_MULTICAST_LOOP
, &one
, sizeof(one
));
248 r
= setsockopt(m
->mdns_ipv6_fd
, IPPROTO_IPV6
, IPV6_V6ONLY
, &one
, sizeof(one
));
254 r
= setsockopt(m
->mdns_ipv6_fd
, SOL_SOCKET
, SO_REUSEADDR
, &one
, sizeof(one
));
260 r
= setsockopt(m
->mdns_ipv6_fd
, IPPROTO_IPV6
, IPV6_RECVPKTINFO
, &one
, sizeof(one
));
266 r
= setsockopt(m
->mdns_ipv6_fd
, IPPROTO_IPV6
, IPV6_RECVHOPLIMIT
, &one
, sizeof(one
));
272 r
= bind(m
->mdns_ipv6_fd
, &sa
.sa
, sizeof(sa
.in6
));
278 r
= sd_event_add_io(m
->event
, &m
->mdns_ipv6_event_source
, m
->mdns_ipv6_fd
, EPOLLIN
, on_mdns_packet
, m
);
282 return m
->mdns_ipv6_fd
;
285 m
->mdns_ipv6_fd
= safe_close(m
->mdns_ipv6_fd
);