/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ /*** This file is part of systemd. Copyright 2014 Lennart Poettering 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 "missing.h" #include "strv.h" #include "socket-util.h" #include "af-list.h" #include "random-util.h" #include "hostname-util.h" #include "dns-domain.h" #include "resolved-llmnr.h" #include "resolved-dns-scope.h" #define MULTICAST_RATELIMIT_INTERVAL_USEC (1*USEC_PER_SEC) #define MULTICAST_RATELIMIT_BURST 1000 /* After how much time to repeat LLMNR requests, see RFC 4795 Section 7 */ #define MULTICAST_RESEND_TIMEOUT_MIN_USEC (100 * USEC_PER_MSEC) #define MULTICAST_RESEND_TIMEOUT_MAX_USEC (1 * USEC_PER_SEC) int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int family) { DnsScope *s; assert(m); assert(ret); s = new0(DnsScope, 1); if (!s) return -ENOMEM; s->manager = m; s->link = l; s->protocol = protocol; s->family = family; s->resend_timeout = MULTICAST_RESEND_TIMEOUT_MIN_USEC; LIST_PREPEND(scopes, m->dns_scopes, s); dns_scope_llmnr_membership(s, true); log_debug("New scope on link %s, protocol %s, family %s", l ? l->name : "*", dns_protocol_to_string(protocol), family == AF_UNSPEC ? "*" : af_to_name(family)); /* Enforce ratelimiting for the multicast protocols */ RATELIMIT_INIT(s->ratelimit, MULTICAST_RATELIMIT_INTERVAL_USEC, MULTICAST_RATELIMIT_BURST); *ret = s; return 0; } DnsScope* dns_scope_free(DnsScope *s) { DnsTransaction *t; DnsResourceRecord *rr; if (!s) return NULL; log_debug("Removing scope on link %s, protocol %s, family %s", s->link ? s->link->name : "*", dns_protocol_to_string(s->protocol), s->family == AF_UNSPEC ? "*" : af_to_name(s->family)); dns_scope_llmnr_membership(s, false); while ((t = hashmap_steal_first(s->transactions))) { /* Abort the transaction, but make sure it is not * freed while we still look at it */ t->block_gc++; dns_transaction_complete(t, DNS_TRANSACTION_ABORTED); t->block_gc--; dns_transaction_free(t); } hashmap_free(s->transactions); while ((rr = ordered_hashmap_steal_first(s->conflict_queue))) dns_resource_record_unref(rr); ordered_hashmap_free(s->conflict_queue); sd_event_source_unref(s->conflict_event_source); dns_cache_flush(&s->cache); dns_zone_flush(&s->zone); LIST_REMOVE(scopes, s->manager->dns_scopes, s); strv_free(s->domains); free(s); return NULL; } DnsServer *dns_scope_get_dns_server(DnsScope *s) { assert(s); if (s->protocol != DNS_PROTOCOL_DNS) return NULL; if (s->link) return link_get_dns_server(s->link); else return manager_get_dns_server(s->manager); } void dns_scope_next_dns_server(DnsScope *s) { assert(s); if (s->protocol != DNS_PROTOCOL_DNS) return; if (s->link) link_next_dns_server(s->link); else manager_next_dns_server(s->manager); } void dns_scope_packet_received(DnsScope *s, usec_t rtt) { assert(s); if (rtt > s->max_rtt) { s->max_rtt = rtt; s->resend_timeout = MIN(MAX(MULTICAST_RESEND_TIMEOUT_MIN_USEC, s->max_rtt * 2), MULTICAST_RESEND_TIMEOUT_MAX_USEC); } } void dns_scope_packet_lost(DnsScope *s, usec_t usec) { assert(s); if (s->resend_timeout <= usec) s->resend_timeout = MIN(s->resend_timeout * 2, MULTICAST_RESEND_TIMEOUT_MAX_USEC); } int dns_scope_emit(DnsScope *s, int fd, DnsPacket *p) { union in_addr_union addr; int ifindex = 0, r; int family; uint16_t port; uint32_t mtu; assert(s); assert(p); assert(p->protocol == s->protocol); assert((s->protocol == DNS_PROTOCOL_DNS) != (fd < 0)); if (s->link) { mtu = s->link->mtu; ifindex = s->link->ifindex; } else mtu = manager_find_mtu(s->manager); switch (s->protocol) { case DNS_PROTOCOL_DNS: if (DNS_PACKET_QDCOUNT(p) > 1) return -EOPNOTSUPP; if (p->size > DNS_PACKET_UNICAST_SIZE_MAX) return -EMSGSIZE; if (p->size + UDP_PACKET_HEADER_SIZE > mtu) return -EMSGSIZE; r = manager_write(s->manager, fd, p); if (r < 0) return r; break; case DNS_PROTOCOL_LLMNR: if (DNS_PACKET_QDCOUNT(p) > 1) return -EOPNOTSUPP; if (!ratelimit_test(&s->ratelimit)) return -EBUSY; family = s->family; port = LLMNR_PORT; if (family == AF_INET) { addr.in = LLMNR_MULTICAST_IPV4_ADDRESS; fd = manager_llmnr_ipv4_udp_fd(s->manager); } else if (family == AF_INET6) { addr.in6 = LLMNR_MULTICAST_IPV6_ADDRESS; fd = manager_llmnr_ipv6_udp_fd(s->manager); } else return -EAFNOSUPPORT; if (fd < 0) return fd; r = manager_send(s->manager, fd, ifindex, family, &addr, port, p); if (r < 0) return r; break; default: return -EAFNOSUPPORT; } return 1; } static int dns_scope_socket(DnsScope *s, int type, int family, const union in_addr_union *address, uint16_t port, DnsServer **server) { DnsServer *srv = NULL; _cleanup_close_ int fd = -1; union sockaddr_union sa = {}; socklen_t salen; static const int one = 1; int ret, r; assert(s); assert((family == AF_UNSPEC) == !address); if (family == AF_UNSPEC) { srv = dns_scope_get_dns_server(s); if (!srv) return -ESRCH; sa.sa.sa_family = srv->family; if (srv->family == AF_INET) { sa.in.sin_port = htobe16(port); sa.in.sin_addr = srv->address.in; salen = sizeof(sa.in); } else if (srv->family == AF_INET6) { sa.in6.sin6_port = htobe16(port); sa.in6.sin6_addr = srv->address.in6; sa.in6.sin6_scope_id = s->link ? s->link->ifindex : 0; salen = sizeof(sa.in6); } else return -EAFNOSUPPORT; } else { sa.sa.sa_family = family; if (family == AF_INET) { sa.in.sin_port = htobe16(port); sa.in.sin_addr = address->in; salen = sizeof(sa.in); } else if (family == AF_INET6) { sa.in6.sin6_port = htobe16(port); sa.in6.sin6_addr = address->in6; sa.in6.sin6_scope_id = s->link ? s->link->ifindex : 0; salen = sizeof(sa.in6); } else return -EAFNOSUPPORT; } fd = socket(sa.sa.sa_family, type|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); if (fd < 0) return -errno; if (type == SOCK_STREAM) { r = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one)); if (r < 0) return -errno; } if (s->link) { uint32_t ifindex = htobe32(s->link->ifindex); if (sa.sa.sa_family == AF_INET) { r = setsockopt(fd, IPPROTO_IP, IP_UNICAST_IF, &ifindex, sizeof(ifindex)); if (r < 0) return -errno; } else if (sa.sa.sa_family == AF_INET6) { r = setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_IF, &ifindex, sizeof(ifindex)); if (r < 0) return -errno; } } if (s->protocol == DNS_PROTOCOL_LLMNR) { /* RFC 4795, section 2.5 requires the TTL to be set to 1 */ if (sa.sa.sa_family == AF_INET) { r = setsockopt(fd, IPPROTO_IP, IP_TTL, &one, sizeof(one)); if (r < 0) return -errno; } else if (sa.sa.sa_family == AF_INET6) { r = setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &one, sizeof(one)); if (r < 0) return -errno; } } r = connect(fd, &sa.sa, salen); if (r < 0 && errno != EINPROGRESS) return -errno; if (server) *server = srv; ret = fd; fd = -1; return ret; } int dns_scope_udp_dns_socket(DnsScope *s, DnsServer **server) { return dns_scope_socket(s, SOCK_DGRAM, AF_UNSPEC, NULL, 53, server); } int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *address, uint16_t port, DnsServer **server) { return dns_scope_socket(s, SOCK_STREAM, family, address, port, server); } DnsScopeMatch dns_scope_good_domain(DnsScope *s, int ifindex, uint64_t flags, const char *domain) { char **i; assert(s); assert(domain); if (ifindex != 0 && (!s->link || s->link->ifindex != ifindex)) return DNS_SCOPE_NO; if ((SD_RESOLVED_FLAGS_MAKE(s->protocol, s->family) & flags) == 0) return DNS_SCOPE_NO; if (dns_name_root(domain) != 0) return DNS_SCOPE_NO; /* Never resolve any loopback hostname or IP address via DNS, * LLMNR or mDNS. Instead, always rely on synthesized RRs for * these. */ if (is_localhost(domain) || dns_name_endswith(domain, "127.in-addr.arpa") > 0 || dns_name_equal(domain, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0) return DNS_SCOPE_NO; STRV_FOREACH(i, s->domains) if (dns_name_endswith(domain, *i) > 0) return DNS_SCOPE_YES; switch (s->protocol) { case DNS_PROTOCOL_DNS: if (dns_name_endswith(domain, "254.169.in-addr.arpa") == 0 && dns_name_endswith(domain, "0.8.e.f.ip6.arpa") == 0 && dns_name_single_label(domain) == 0) return DNS_SCOPE_MAYBE; return DNS_SCOPE_NO; case DNS_PROTOCOL_MDNS: if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) || (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0) || (dns_name_endswith(domain, "local") > 0 && /* only resolve names ending in .local via mDNS */ dns_name_equal(domain, "local") == 0 && /* but not the single-label "local" name itself */ manager_is_own_hostname(s->manager, domain) <= 0)) /* never resolve the local hostname via mDNS */ return DNS_SCOPE_NO; case DNS_PROTOCOL_LLMNR: if ((s->family == AF_INET && dns_name_endswith(domain, "in-addr.arpa") > 0) || (s->family == AF_INET6 && dns_name_endswith(domain, "ip6.arpa") > 0) || (dns_name_single_label(domain) > 0 && /* only resolve single label names via LLMNR */ !is_gateway_hostname(domain) && /* don't resolve "gateway" with LLMNR, let nss-myhostname handle this */ manager_is_own_hostname(s->manager, domain) <= 0)) /* never resolve the local hostname via LLMNR */ return DNS_SCOPE_MAYBE; return DNS_SCOPE_NO; default: assert_not_reached("Unknown scope protocol"); } } int dns_scope_good_key(DnsScope *s, DnsResourceKey *key) { assert(s); assert(key); if (s->protocol == DNS_PROTOCOL_DNS) return true; /* On mDNS and LLMNR, send A and AAAA queries only on the * respective scopes */ if (s->family == AF_INET && key->class == DNS_CLASS_IN && key->type == DNS_TYPE_AAAA) return false; if (s->family == AF_INET6 && key->class == DNS_CLASS_IN && key->type == DNS_TYPE_A) return false; return true; } int dns_scope_llmnr_membership(DnsScope *s, bool b) { int fd; assert(s); if (s->protocol != DNS_PROTOCOL_LLMNR) return 0; assert(s->link); if (s->family == AF_INET) { struct ip_mreqn mreqn = { .imr_multiaddr = LLMNR_MULTICAST_IPV4_ADDRESS, .imr_ifindex = s->link->ifindex, }; fd = manager_llmnr_ipv4_udp_fd(s->manager); if (fd < 0) return fd; /* Always first try to drop membership before we add * one. This is necessary on some devices, such as * veth. */ if (b) (void) setsockopt(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn)); if (setsockopt(fd, IPPROTO_IP, b ? IP_ADD_MEMBERSHIP : IP_DROP_MEMBERSHIP, &mreqn, sizeof(mreqn)) < 0) return -errno; } else if (s->family == AF_INET6) { struct ipv6_mreq mreq = { .ipv6mr_multiaddr = LLMNR_MULTICAST_IPV6_ADDRESS, .ipv6mr_interface = s->link->ifindex, }; fd = manager_llmnr_ipv6_udp_fd(s->manager); if (fd < 0) return fd; if (b) (void) setsockopt(fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq)); if (setsockopt(fd, IPPROTO_IPV6, b ? IPV6_ADD_MEMBERSHIP : IPV6_DROP_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) return -errno; } else return -EAFNOSUPPORT; return 0; } static int dns_scope_make_reply_packet( DnsScope *s, uint16_t id, int rcode, DnsQuestion *q, DnsAnswer *answer, DnsAnswer *soa, bool tentative, DnsPacket **ret) { _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; unsigned i; int r; assert(s); assert(ret); if ((!q || q->n_keys <= 0) && (!answer || answer->n_rrs <= 0) && (!soa || soa->n_rrs <= 0)) return -EINVAL; r = dns_packet_new(&p, s->protocol, 0); if (r < 0) return r; DNS_PACKET_HEADER(p)->id = id; DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS( 1 /* qr */, 0 /* opcode */, 0 /* c */, 0 /* tc */, tentative, 0 /* (ra) */, 0 /* (ad) */, 0 /* (cd) */, rcode)); if (q) { for (i = 0; i < q->n_keys; i++) { r = dns_packet_append_key(p, q->keys[i], NULL); if (r < 0) return r; } DNS_PACKET_HEADER(p)->qdcount = htobe16(q->n_keys); } if (answer) { for (i = 0; i < answer->n_rrs; i++) { r = dns_packet_append_rr(p, answer->items[i].rr, NULL); if (r < 0) return r; } DNS_PACKET_HEADER(p)->ancount = htobe16(answer->n_rrs); } if (soa) { for (i = 0; i < soa->n_rrs; i++) { r = dns_packet_append_rr(p, soa->items[i].rr, NULL); if (r < 0) return r; } DNS_PACKET_HEADER(p)->arcount = htobe16(soa->n_rrs); } *ret = p; p = NULL; return 0; } static void dns_scope_verify_conflicts(DnsScope *s, DnsPacket *p) { unsigned n; assert(s); assert(p); if (p->question) for (n = 0; n < p->question->n_keys; n++) dns_zone_verify_conflicts(&s->zone, p->question->keys[n]); if (p->answer) for (n = 0; n < p->answer->n_rrs; n++) dns_zone_verify_conflicts(&s->zone, p->answer->items[n].rr->key); } void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) { _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL; _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL, *soa = NULL; bool tentative = false; int r, fd; assert(s); assert(p); if (p->protocol != DNS_PROTOCOL_LLMNR) return; if (p->ipproto == IPPROTO_UDP) { /* Don't accept UDP queries directed to anything but * the LLMNR multicast addresses. See RFC 4795, * section 2.5. */ if (p->family == AF_INET && !in_addr_equal(AF_INET, &p->destination, (union in_addr_union*) &LLMNR_MULTICAST_IPV4_ADDRESS)) return; if (p->family == AF_INET6 && !in_addr_equal(AF_INET6, &p->destination, (union in_addr_union*) &LLMNR_MULTICAST_IPV6_ADDRESS)) return; } r = dns_packet_extract(p); if (r < 0) { log_debug_errno(r, "Failed to extract resources from incoming packet: %m"); return; } if (DNS_PACKET_LLMNR_C(p)) { /* Somebody notified us about a possible conflict */ dns_scope_verify_conflicts(s, p); return; } r = dns_zone_lookup(&s->zone, p->question, &answer, &soa, &tentative); if (r < 0) { log_debug_errno(r, "Failed to lookup key: %m"); return; } if (r == 0) return; if (answer) dns_answer_order_by_scope(answer, in_addr_is_link_local(p->family, &p->sender) > 0); r = dns_scope_make_reply_packet(s, DNS_PACKET_ID(p), DNS_RCODE_SUCCESS, p->question, answer, soa, tentative, &reply); if (r < 0) { log_debug_errno(r, "Failed to build reply packet: %m"); return; } if (stream) r = dns_stream_write_packet(stream, reply); else { if (!ratelimit_test(&s->ratelimit)) return; if (p->family == AF_INET) fd = manager_llmnr_ipv4_udp_fd(s->manager); else if (p->family == AF_INET6) fd = manager_llmnr_ipv6_udp_fd(s->manager); else { log_debug("Unknown protocol"); return; } if (fd < 0) { log_debug_errno(fd, "Failed to get reply socket: %m"); return; } /* Note that we always immediately reply to all LLMNR * requests, and do not wait any time, since we * verified uniqueness for all records. Also see RFC * 4795, Section 2.7 */ r = manager_send(s->manager, fd, p->ifindex, p->family, &p->sender, p->sender_port, reply); } if (r < 0) { log_debug_errno(r, "Failed to send reply packet: %m"); return; } } DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsResourceKey *key, bool cache_ok) { DnsTransaction *t; assert(scope); assert(key); /* Try to find an ongoing transaction that is a equal to the * specified question */ t = hashmap_get(scope->transactions, key); if (!t) return NULL; /* Refuse reusing transactions that completed based on cached * data instead of a real packet, if that's requested. */ if (!cache_ok && IN_SET(t->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_FAILURE) && !t->received) return NULL; return t; } static int dns_scope_make_conflict_packet( DnsScope *s, DnsResourceRecord *rr, DnsPacket **ret) { _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; int r; assert(s); assert(rr); assert(ret); r = dns_packet_new(&p, s->protocol, 0); if (r < 0) return r; DNS_PACKET_HEADER(p)->flags = htobe16(DNS_PACKET_MAKE_FLAGS( 0 /* qr */, 0 /* opcode */, 1 /* conflict */, 0 /* tc */, 0 /* t */, 0 /* (ra) */, 0 /* (ad) */, 0 /* (cd) */, 0)); random_bytes(&DNS_PACKET_HEADER(p)->id, sizeof(uint16_t)); DNS_PACKET_HEADER(p)->qdcount = htobe16(1); DNS_PACKET_HEADER(p)->arcount = htobe16(1); r = dns_packet_append_key(p, rr->key, NULL); if (r < 0) return r; r = dns_packet_append_rr(p, rr, NULL); if (r < 0) return r; *ret = p; p = NULL; return 0; } static int on_conflict_dispatch(sd_event_source *es, usec_t usec, void *userdata) { DnsScope *scope = userdata; int r; assert(es); assert(scope); scope->conflict_event_source = sd_event_source_unref(scope->conflict_event_source); for (;;) { _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; rr = ordered_hashmap_steal_first(scope->conflict_queue); if (!rr) break; r = dns_scope_make_conflict_packet(scope, rr, &p); if (r < 0) { log_error_errno(r, "Failed to make conflict packet: %m"); return 0; } r = dns_scope_emit(scope, -1, p); if (r < 0) log_debug_errno(r, "Failed to send conflict packet: %m"); } return 0; } int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) { usec_t jitter; int r; assert(scope); assert(rr); /* We don't send these queries immediately. Instead, we queue * them, and send them after some jitter delay. */ r = ordered_hashmap_ensure_allocated(&scope->conflict_queue, &dns_resource_key_hash_ops); if (r < 0) { log_oom(); return r; } /* We only place one RR per key in the conflict * messages, not all of them. That should be enough to * indicate where there might be a conflict */ r = ordered_hashmap_put(scope->conflict_queue, rr->key, rr); if (r == -EEXIST || r == 0) return 0; if (r < 0) return log_debug_errno(r, "Failed to queue conflicting RR: %m"); dns_resource_record_ref(rr); if (scope->conflict_event_source) return 0; random_bytes(&jitter, sizeof(jitter)); jitter %= LLMNR_JITTER_INTERVAL_USEC; r = sd_event_add_time(scope->manager->event, &scope->conflict_event_source, clock_boottime_or_monotonic(), now(clock_boottime_or_monotonic()) + jitter, LLMNR_JITTER_INTERVAL_USEC, on_conflict_dispatch, scope); if (r < 0) return log_debug_errno(r, "Failed to add conflict dispatch event: %m"); return 0; } void dns_scope_check_conflicts(DnsScope *scope, DnsPacket *p) { unsigned i; int r; assert(scope); assert(p); if (p->protocol != DNS_PROTOCOL_LLMNR) return; if (DNS_PACKET_RRCOUNT(p) <= 0) return; if (DNS_PACKET_LLMNR_C(p) != 0) return; if (DNS_PACKET_LLMNR_T(p) != 0) return; if (manager_our_packet(scope->manager, p)) return; r = dns_packet_extract(p); if (r < 0) { log_debug_errno(r, "Failed to extract packet: %m"); return; } log_debug("Checking for conflicts..."); for (i = 0; i < p->answer->n_rrs; i++) { /* Check for conflicts against the local zone. If we * found one, we won't check any further */ r = dns_zone_check_conflicts(&scope->zone, p->answer->items[i].rr); if (r != 0) continue; /* Check for conflicts against the local cache. If so, * send out an advisory query, to inform everybody */ r = dns_cache_check_conflicts(&scope->cache, p->answer->items[i].rr, p->family, &p->sender); if (r <= 0) continue; dns_scope_notify_conflict(scope, p->answer->items[i].rr); } }