diff options
Diffstat (limited to 'src/resolve/resolved-dns-scope.c')
| -rw-r--r-- | src/resolve/resolved-dns-scope.c | 198 |
1 files changed, 196 insertions, 2 deletions
diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c index 40c326a81d..174249a9f7 100644 --- a/src/resolve/resolved-dns-scope.c +++ b/src/resolve/resolved-dns-scope.c @@ -61,6 +61,7 @@ int dns_scope_new(Manager *m, DnsScope **ret, Link *l, DnsProtocol protocol, int DnsScope* dns_scope_free(DnsScope *s) { DnsTransaction *t; + DnsResourceRecord *rr; if (!s) return NULL; @@ -81,6 +82,12 @@ DnsScope* dns_scope_free(DnsScope *s) { dns_transaction_free(t); } + while ((rr = hashmap_steal_first(s->conflict_queue))) + dns_resource_record_unref(rr); + + hashmap_free(s->conflict_queue); + sd_event_source_unref(s->conflict_event_source); + dns_cache_flush(&s->cache); dns_zone_flush(&s->zone); @@ -115,7 +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; @@ -420,6 +427,7 @@ static int dns_scope_make_reply_packet( int r; assert(s); + assert(ret); if ((!q || q->n_keys <= 0) && (!answer || answer->n_rrs <= 0) @@ -478,6 +486,20 @@ 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; @@ -509,7 +531,8 @@ 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; } @@ -588,3 +611,174 @@ DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsQuestion *questio 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 = 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 = hashmap_ensure_allocated(&scope->conflict_queue, dns_resource_key_hash_func, dns_resource_key_compare_func); + 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 = 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]); + } +} |