/*** 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 "af-list.h" #include "alloc-util.h" #include "dns-domain.h" #include "fd-util.h" #include "hostname-util.h" #include "missing.h" #include "random-util.h" #include "resolved-dns-scope.h" #include "resolved-llmnr.h" #include "resolved-mdns.h" #include "socket-util.h" #include "strv.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; if (protocol == DNS_PROTOCOL_DNS) { /* Copy DNSSEC mode from the link if it is set there, * otherwise take the manager's DNSSEC mode. Note that * we copy this only at scope creation time, and do * not update it from the on, even if the setting * changes. */ if (l) s->dnssec_mode = link_get_dnssec_mode(l); else s->dnssec_mode = manager_get_dnssec_mode(m); } else s->dnssec_mode = DNSSEC_NO; LIST_PREPEND(scopes, m->dns_scopes, s); dns_scope_llmnr_membership(s, true); dns_scope_mdns_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; } static void dns_scope_abort_transactions(DnsScope *s) { assert(s); while (s->transactions) { DnsTransaction *t = s->transactions; /* Abort the transaction, but make sure it is not * freed while we still look at it */ t->block_gc++; if (DNS_TRANSACTION_IS_LIVE(t->state)) dns_transaction_complete(t, DNS_TRANSACTION_ABORTED); t->block_gc--; dns_transaction_free(t); } } DnsScope* dns_scope_free(DnsScope *s) { 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); dns_scope_mdns_membership(s, false); dns_scope_abort_transactions(s); while (s->query_candidates) dns_query_candidate_free(s->query_candidates); hashmap_free(s->transactions_by_key); 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); sd_event_source_unref(s->announce_event_source); dns_cache_flush(&s->cache); dns_zone_flush(&s->zone); LIST_REMOVE(scopes, s->manager->dns_scopes, s); return mfree(s); } 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) return; 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); } static int dns_scope_emit_one(DnsScope *s, int fd, DnsPacket *p) { union in_addr_union addr; int ifindex = 0, r; int family; uint32_t mtu; assert(s); assert(p); assert(p->protocol == s->protocol); 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: assert(fd >= 0); 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: assert(fd < 0); if (DNS_PACKET_QDCOUNT(p) > 1) return -EOPNOTSUPP; if (!ratelimit_test(&s->ratelimit)) return -EBUSY; family = s->family; 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, LLMNR_PORT, NULL, p); if (r < 0) return r; break; case DNS_PROTOCOL_MDNS: assert(fd < 0); if (!ratelimit_test(&s->ratelimit)) return -EBUSY; family = s->family; if (family == AF_INET) { addr.in = MDNS_MULTICAST_IPV4_ADDRESS; fd = manager_mdns_ipv4_fd(s->manager); } else if (family == AF_INET6) { addr.in6 = MDNS_MULTICAST_IPV6_ADDRESS; fd = manager_mdns_ipv6_fd(s->manager); } else return -EAFNOSUPPORT; if (fd < 0) return fd; r = manager_send(s->manager, fd, ifindex, family, &addr, MDNS_PORT, NULL, p); if (r < 0) return r; break; default: return -EAFNOSUPPORT; } return 1; } int dns_scope_emit_udp(DnsScope *s, int fd, DnsPacket *p) { int r; assert(s); assert(p); assert(p->protocol == s->protocol); assert((s->protocol == DNS_PROTOCOL_DNS) == (fd >= 0)); do { /* If there are multiple linked packets, set the TC bit in all but the last of them */ if (p->more) { assert(p->protocol == DNS_PROTOCOL_MDNS); dns_packet_set_flags(p, true, true); } r = dns_scope_emit_one(s, fd, p); if (r < 0) return r; p = p->more; } while (p); return 0; } static int dns_scope_socket( DnsScope *s, int type, int family, const union in_addr_union *address, DnsServer *server, uint16_t port) { _cleanup_close_ int fd = -1; union sockaddr_union sa = {}; socklen_t salen; static const int one = 1; int ret, r, ifindex; assert(s); if (server) { assert(family == AF_UNSPEC); assert(!address); ifindex = dns_server_ifindex(server); sa.sa.sa_family = server->family; if (server->family == AF_INET) { sa.in.sin_port = htobe16(port); sa.in.sin_addr = server->address.in; salen = sizeof(sa.in); } else if (server->family == AF_INET6) { sa.in6.sin6_port = htobe16(port); sa.in6.sin6_addr = server->address.in6; sa.in6.sin6_scope_id = ifindex; salen = sizeof(sa.in6); } else return -EAFNOSUPPORT; } else { assert(family != AF_UNSPEC); assert(address); sa.sa.sa_family = family; ifindex = s->link ? s->link->ifindex : 0; 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 = ifindex; 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) { be32_t ifindex_be = htobe32(ifindex); if (sa.sa.sa_family == AF_INET) { r = setsockopt(fd, IPPROTO_IP, IP_UNICAST_IF, &ifindex_be, sizeof(ifindex_be)); if (r < 0) return -errno; } else if (sa.sa.sa_family == AF_INET6) { r = setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_IF, &ifindex_be, sizeof(ifindex_be)); 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; ret = fd; fd = -1; return ret; } int dns_scope_socket_udp(DnsScope *s, DnsServer *server, uint16_t port) { return dns_scope_socket(s, SOCK_DGRAM, AF_UNSPEC, NULL, server, port); } int dns_scope_socket_tcp(DnsScope *s, int family, const union in_addr_union *address, DnsServer *server, uint16_t port) { return dns_scope_socket(s, SOCK_STREAM, family, address, server, port); } DnsScopeMatch dns_scope_good_domain(DnsScope *s, int ifindex, uint64_t flags, const char *domain) { DnsSearchDomain *d; DnsServer *dns_server; assert(s); assert(domain); /* Checks if the specified domain is something to look up on * this scope. Note that this accepts non-qualified hostnames, * i.e. those without any search path prefixed yet. */ if (ifindex != 0 && (!s->link || s->link->ifindex != ifindex)) return DNS_SCOPE_NO; if ((SD_RESOLVED_FLAGS_MAKE(s->protocol, s->family, 0) & flags) == 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; /* Never respond to some of the domains listed in RFC6303 */ if (dns_name_endswith(domain, "0.in-addr.arpa") > 0 || dns_name_equal(domain, "255.255.255.255.in-addr.arpa") > 0 || dns_name_equal(domain, "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0) return DNS_SCOPE_NO; /* Never respond to some of the domains listed in RFC6761 */ if (dns_name_endswith(domain, "invalid") > 0) return DNS_SCOPE_NO; /* Always honour search domains for routing queries. Note that * we return DNS_SCOPE_YES here, rather than just * DNS_SCOPE_MAYBE, which means wildcard scopes won't be * considered anymore. */ LIST_FOREACH(domains, d, dns_scope_get_search_domains(s)) if (dns_name_endswith(domain, d->name) > 0) return DNS_SCOPE_YES; /* If the DNS server has route-only domains, don't send other requests * to it. This would be a privacy violation, will most probably fail * anyway, and adds unnecessary load. */ dns_server = dns_scope_get_dns_server(s); if (dns_server && dns_server_limited_domains(dns_server)) return DNS_SCOPE_NO; switch (s->protocol) { case DNS_PROTOCOL_DNS: /* Exclude link-local IP ranges */ if (dns_name_endswith(domain, "254.169.in-addr.arpa") == 0 && dns_name_endswith(domain, "8.e.f.ip6.arpa") == 0 && dns_name_endswith(domain, "9.e.f.ip6.arpa") == 0 && dns_name_endswith(domain, "a.e.f.ip6.arpa") == 0 && dns_name_endswith(domain, "b.e.f.ip6.arpa") == 0 && /* If networks use .local in their private setups, they are supposed to also add .local to their search * domains, which we already checked above. Otherwise, we consider .local specific to mDNS and won't * send such queries ordinary DNS servers. */ dns_name_endswith(domain, "local") == 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_MAYBE; 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_is_single_label(domain) && /* 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"); } } bool dns_scope_good_key(DnsScope *s, const DnsResourceKey *key) { int key_family; assert(s); assert(key); /* Check if it makes sense to resolve the specified key on * this scope. Note that this call assumes as fully qualified * name, i.e. the search suffixes already appended. */ if (key->class != DNS_CLASS_IN) return false; if (s->protocol == DNS_PROTOCOL_DNS) { /* On classic DNS, looking up non-address RRs is always * fine. (Specifically, we want to permit looking up * DNSKEY and DS records on the root and top-level * domains.) */ if (!dns_resource_key_is_address(key)) return true; /* However, we refuse to look up A and AAAA RRs on the * root and single-label domains, under the assumption * that those should be resolved via LLMNR or search * path only, and should not be leaked onto the * internet. */ return !(dns_name_is_single_label(dns_resource_key_name(key)) || dns_name_is_root(dns_resource_key_name(key))); } /* On mDNS and LLMNR, send A and AAAA queries only on the * respective scopes */ key_family = dns_type_to_af(key->type); if (key_family < 0) return true; return key_family == s->family; } static int dns_scope_multicast_membership(DnsScope *s, bool b, struct in_addr in, struct in6_addr in6) { int fd; assert(s); assert(s->link); if (s->family == AF_INET) { struct ip_mreqn mreqn = { .imr_multiaddr = in, .imr_ifindex = s->link->ifindex, }; if (s->protocol == DNS_PROTOCOL_LLMNR) fd = manager_llmnr_ipv4_udp_fd(s->manager); else fd = manager_mdns_ipv4_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 = in6, .ipv6mr_interface = s->link->ifindex, }; if (s->protocol == DNS_PROTOCOL_LLMNR) fd = manager_llmnr_ipv6_udp_fd(s->manager); else fd = manager_mdns_ipv6_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; } int dns_scope_llmnr_membership(DnsScope *s, bool b) { assert(s); if (s->protocol != DNS_PROTOCOL_LLMNR) return 0; return dns_scope_multicast_membership(s, b, LLMNR_MULTICAST_IPV4_ADDRESS, LLMNR_MULTICAST_IPV6_ADDRESS); } int dns_scope_mdns_membership(DnsScope *s, bool b) { assert(s); if (s->protocol != DNS_PROTOCOL_MDNS) return 0; return dns_scope_multicast_membership(s, b, MDNS_MULTICAST_IPV4_ADDRESS, MDNS_MULTICAST_IPV6_ADDRESS); } 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; int r; assert(s); assert(ret); if (dns_question_isempty(q) && dns_answer_isempty(answer) && dns_answer_isempty(soa)) 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)); r = dns_packet_append_question(p, q); if (r < 0) return r; DNS_PACKET_HEADER(p)->qdcount = htobe16(dns_question_size(q)); r = dns_packet_append_answer(p, answer); if (r < 0) return r; DNS_PACKET_HEADER(p)->ancount = htobe16(dns_answer_size(answer)); r = dns_packet_append_answer(p, soa); if (r < 0) return r; DNS_PACKET_HEADER(p)->arcount = htobe16(dns_answer_size(soa)); *ret = p; p = NULL; return 0; } static void dns_scope_verify_conflicts(DnsScope *s, DnsPacket *p) { DnsResourceRecord *rr; DnsResourceKey *key; assert(s); assert(p); DNS_QUESTION_FOREACH(key, p->question) dns_zone_verify_conflicts(&s->zone, key); DNS_ANSWER_FOREACH(rr, p->answer) dns_zone_verify_conflicts(&s->zone, rr->key); } void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) { _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL, *soa = NULL; _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL; DnsResourceKey *key = NULL; bool tentative = false; int r; 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 resource records 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; } assert(dns_question_size(p->question) == 1); key = p->question->keys[0]; r = dns_zone_lookup(&s->zone, key, 0, &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); if (r < 0) { log_debug_errno(r, "Failed to enqueue reply packet: %m"); return; } /* Let's take an extra reference on this stream, so that it stays around after returning. The reference * will be dangling until the stream is disconnected, and the default completion handler of the stream * will then unref the stream and destroy it */ if (DNS_STREAM_QUEUED(stream)) dns_stream_ref(stream); } else { int fd; 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, NULL, 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_by_key, 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_RCODE_FAILURE) && t->answer_source != DNS_TRANSACTION_NETWORK) 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)); /* For mDNS, the transaction ID should always be 0 */ if (s->protocol != DNS_PROTOCOL_MDNS) 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, 0, NULL); if (r < 0) return r; r = dns_packet_append_rr(p, rr, 0, NULL, 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_udp(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"); (void) sd_event_source_set_description(scope->conflict_event_source, "scope-conflict"); return 0; } void dns_scope_check_conflicts(DnsScope *scope, DnsPacket *p) { unsigned i; int r; assert(scope); assert(p); if (!IN_SET(p->protocol, DNS_PROTOCOL_LLMNR, DNS_PROTOCOL_MDNS)) return; if (DNS_PACKET_RRCOUNT(p) <= 0) return; if (p->protocol == DNS_PROTOCOL_LLMNR) { 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); } } void dns_scope_dump(DnsScope *s, FILE *f) { assert(s); if (!f) f = stdout; fputs("[Scope protocol=", f); fputs(dns_protocol_to_string(s->protocol), f); if (s->link) { fputs(" interface=", f); fputs(s->link->name, f); } if (s->family != AF_UNSPEC) { fputs(" family=", f); fputs(af_to_name(s->family), f); } fputs("]\n", f); if (!dns_zone_is_empty(&s->zone)) { fputs("ZONE:\n", f); dns_zone_dump(&s->zone, f); } if (!dns_cache_is_empty(&s->cache)) { fputs("CACHE:\n", f); dns_cache_dump(&s->cache, f); } } DnsSearchDomain *dns_scope_get_search_domains(DnsScope *s) { assert(s); if (s->protocol != DNS_PROTOCOL_DNS) return NULL; if (s->link) return s->link->search_domains; return s->manager->search_domains; } bool dns_scope_name_needs_search_domain(DnsScope *s, const char *name) { assert(s); if (s->protocol != DNS_PROTOCOL_DNS) return false; return dns_name_is_single_label(name); } bool dns_scope_network_good(DnsScope *s) { /* Checks whether the network is in good state for lookups on this scope. For mDNS/LLMNR/Classic DNS scopes * bound to links this is easy, as they don't even exist if the link isn't in a suitable state. For the global * DNS scope we check whether there are any links that are up and have an address. */ if (s->link) return true; return manager_routable(s->manager, AF_UNSPEC); } int dns_scope_ifindex(DnsScope *s) { assert(s); if (s->link) return s->link->ifindex; return 0; } static int on_announcement_timeout(sd_event_source *s, usec_t usec, void *userdata) { DnsScope *scope = userdata; assert(s); scope->announce_event_source = sd_event_source_unref(scope->announce_event_source); (void) dns_scope_announce(scope, false); return 0; } int dns_scope_announce(DnsScope *scope, bool goodbye) { _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL; _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; LinkAddress *a; int r; if (!scope) return 0; if (scope->protocol != DNS_PROTOCOL_MDNS) return 0; answer = dns_answer_new(scope->link->n_addresses * 2); if (!answer) return log_oom(); LIST_FOREACH(addresses, a, scope->link->addresses) { r = dns_answer_add(answer, a->mdns_address_rr, 0, goodbye ? DNS_ANSWER_GOODBYE : DNS_ANSWER_CACHE_FLUSH); if (r < 0) return log_debug_errno(r, "Failed to add address RR to answer: %m"); r = dns_answer_add(answer, a->mdns_ptr_rr, 0, goodbye ? DNS_ANSWER_GOODBYE : DNS_ANSWER_CACHE_FLUSH); if (r < 0) return log_debug_errno(r, "Failed to add PTR RR to answer: %m"); } if (dns_answer_isempty(answer)) return 0; r = dns_scope_make_reply_packet(scope, 0, DNS_RCODE_SUCCESS, NULL, answer, NULL, false, &p); if (r < 0) return log_debug_errno(r, "Failed to build reply packet: %m"); r = dns_scope_emit_udp(scope, -1, p); if (r < 0) return log_debug_errno(r, "Failed to send reply packet: %m"); /* In section 8.3 of RFC6762: "The Multicast DNS responder MUST send at least two unsolicited * responses, one second apart." */ if (!scope->announced) { usec_t ts; scope->announced = true; assert_se(sd_event_now(scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); ts += MDNS_ANNOUNCE_DELAY; r = sd_event_add_time( scope->manager->event, &scope->announce_event_source, clock_boottime_or_monotonic(), ts, MDNS_JITTER_RANGE_USEC, on_announcement_timeout, scope); if (r < 0) return log_debug_errno(r, "Failed to schedule second announcement: %m"); (void) sd_event_source_set_description(scope->announce_event_source, "mdns-announce"); } return 0; }