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