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/*-*- 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 == RESOLVE_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 = RESOLVE_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, false, (uint32_t) -1, 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;
}
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