From bc7702b098b63031767174206f5df14a8ccb45cf Mon Sep 17 00:00:00 2001 From: Daniel Mack Date: Fri, 10 Jul 2015 15:48:13 -0400 Subject: resolved: add infrastructure for mDNS related sockets Just hook up mDNS listeners with an empty packet dispather function, introduce a config directive, man page updates etc. --- src/resolve/resolved-mdns.c | 231 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 231 insertions(+) create mode 100644 src/resolve/resolved-mdns.c (limited to 'src/resolve/resolved-mdns.c') diff --git a/src/resolve/resolved-mdns.c b/src/resolve/resolved-mdns.c new file mode 100644 index 0000000000..6767706f6e --- /dev/null +++ b/src/resolve/resolved-mdns.c @@ -0,0 +1,231 @@ +/*-*- 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 . + ***/ + +#include +#include +#include + +#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) { + /* TODO */ + 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) { + r = -errno; + goto fail; + } + + return m->mdns_ipv6_fd; + +fail: + m->mdns_ipv6_fd = safe_close(m->mdns_ipv6_fd); + return r; +} -- cgit v1.2.3-54-g00ecf From 124602aea81a27dda02e898798a18f95bf03734e Mon Sep 17 00:00:00 2001 From: Daniel Mack Date: Fri, 10 Jul 2015 20:44:59 -0400 Subject: resolved: add mDNS packet dispatcher Add the packet dispatching routine for mDNS. It differs to what LLMNR and DNS dispatchers do in the way it matches incoming packets. In mDNS, we actually handle all incoming packets, regardless whether we asked for them earlier or not. --- src/resolve/resolved-mdns.c | 59 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 58 insertions(+), 1 deletion(-) (limited to 'src/resolve/resolved-mdns.c') diff --git a/src/resolve/resolved-mdns.c b/src/resolve/resolved-mdns.c index 6767706f6e..096a4b1fe5 100644 --- a/src/resolve/resolved-mdns.c +++ b/src/resolve/resolved-mdns.c @@ -70,7 +70,64 @@ eaddrinuse: } static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) { - /* TODO */ + _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) { + unsigned i; + + 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); + + for (i = 0; i < p->answer->n_rrs; i++) { + DnsResourceRecord *rr; + DnsTransaction *t; + + rr = p->answer->items[i].rr; + + 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; } -- cgit v1.2.3-54-g00ecf