X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=src%2Fresolve%2Fresolved-dns-scope.c;h=1664b1328e2ec6b11d1274160710c39c212d6c2c;hp=42a2fc4c774c3fbc923acc6f8075626c3901d703;hb=1e43061b67336052b5b231840a38508a5397a363;hpb=4e945a6f7971fd7d1f6b2c62ee3afdaff3c95ce4 diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c index 42a2fc4c7..1664b1328 100644 --- a/src/resolve/resolved-dns-scope.c +++ b/src/resolve/resolved-dns-scope.c @@ -28,6 +28,9 @@ #include "resolved-dns-domain.h" #include "resolved-dns-scope.h" +#define MULTICAST_RATELIMIT_INTERVAL_USEC (1*USEC_PER_SEC) +#define MULTICAST_RATELIMIT_BURST 1000 + int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int family) { DnsScope *s; @@ -49,12 +52,16 @@ int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int 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; @@ -75,6 +82,12 @@ DnsScope* dns_scope_free(DnsScope *s) { dns_transaction_free(t); } + 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); @@ -85,7 +98,7 @@ DnsScope* dns_scope_free(DnsScope *s) { return NULL; } -DnsServer *dns_scope_get_server(DnsScope *s) { +DnsServer *dns_scope_get_dns_server(DnsScope *s) { assert(s); if (s->protocol != DNS_PROTOCOL_DNS) @@ -109,7 +122,7 @@ void dns_scope_next_dns_server(DnsScope *s) { manager_next_dns_server(s->manager); } -int dns_scope_send(DnsScope *s, DnsPacket *p) { +int dns_scope_emit(DnsScope *s, DnsPacket *p) { union in_addr_union addr; int ifindex = 0, r; int family; @@ -133,7 +146,7 @@ int dns_scope_send(DnsScope *s, DnsPacket *p) { if (DNS_PACKET_QDCOUNT(p) > 1) return -ENOTSUP; - srv = dns_scope_get_server(s); + srv = dns_scope_get_dns_server(s); if (!srv) return -ESRCH; @@ -161,6 +174,9 @@ int dns_scope_send(DnsScope *s, DnsPacket *p) { if (DNS_PACKET_QDCOUNT(p) > 1) return -ENOTSUP; + if (!ratelimit_test(&s->ratelimit)) + return -EBUSY; + family = s->family; port = 5355; @@ -197,7 +213,7 @@ int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *add if (family == AF_UNSPEC) { DnsServer *srv; - srv = dns_scope_get_server(s); + srv = dns_scope_get_dns_server(s); if (!srv) return -ESRCH; @@ -275,12 +291,18 @@ int dns_scope_tcp_socket(DnsScope *s, int family, const union in_addr_union *add return ret; } -DnsScopeMatch dns_scope_good_domain(DnsScope *s, const char *domain) { +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; + STRV_FOREACH(i, s->domains) if (dns_name_endswith(domain, *i) > 0) return DNS_SCOPE_YES; @@ -343,6 +365,13 @@ int dns_scope_good_key(DnsScope *s, DnsResourceKey *key) { 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, @@ -353,6 +382,12 @@ int dns_scope_llmnr_membership(DnsScope *s, bool b) { 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) + 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; @@ -366,6 +401,9 @@ int dns_scope_llmnr_membership(DnsScope *s, bool b) { if (fd < 0) return fd; + if (b) + 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 @@ -384,7 +422,7 @@ int dns_scope_good_dns_server(DnsScope *s, int family, const union in_addr_union if (s->link) return !!link_find_dns_server(s->link, family, address); else - return manager_known_dns_server(s->manager, family, address); + return !!manager_find_dns_server(s->manager, family, address); } static int dns_scope_make_reply_packet( @@ -402,8 +440,11 @@ static int dns_scope_make_reply_packet( int r; assert(s); + assert(ret); - if (q->n_keys <= 0 && answer->n_rrs <= 0 && soa->n_rrs <= 0) + 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); @@ -458,6 +499,20 @@ static int dns_scope_make_reply_packet( 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->rrs[n]->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; @@ -489,7 +544,8 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) { } if (DNS_PACKET_C(p)) { - /* FIXME: Somebody notified us about a likely conflict */ + /* Somebody notified us about a possible conflict */ + dns_scope_verify_conflicts(s, p); return; } @@ -513,6 +569,9 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) { 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) @@ -526,6 +585,11 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) { 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); } @@ -535,7 +599,7 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) { } } -DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsQuestion *question) { +DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsQuestion *question, bool cache_ok) { DnsTransaction *t; assert(scope); @@ -544,9 +608,190 @@ DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsQuestion *questio /* Try to find an ongoing transaction that is a equal or a * superset of the specified question */ - LIST_FOREACH(transactions_by_scope, t, scope->transactions) + LIST_FOREACH(transactions_by_scope, t, scope->transactions) { + + /* 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) + continue; + if (dns_question_is_superset(t->question, question) > 0) return t; + } return NULL; } + +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("Failed to make conflict packet: %s", strerror(-r)); + return 0; + } + + r = dns_scope_emit(scope, p); + if (r < 0) + log_debug("Failed to send conflict packet: %s", strerror(-r)); + } + + 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) { + log_debug("Failed to queue conflicting RR: %s", strerror(-r)); + return r; + } + + 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) { + log_debug("Failed to add conflict dispatch event: %s", strerror(-r)); + return r; + } + + 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_C(p) != 0) + return; + + if (DNS_PACKET_T(p) != 0) + return; + + if (manager_our_packet(scope->manager, p)) + return; + + r = dns_packet_extract(p); + if (r < 0) { + log_debug("Failed to extract packet: %s", strerror(-r)); + 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->rrs[i]); + 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->rrs[i], p->family, &p->sender); + if (r <= 0) + continue; + + dns_scope_notify_conflict(scope, p->answer->rrs[i]); + } +}