resolved: enforce ratelimit on LLMNR traffic

[elogind.git] / src / resolve / resolved-dns-scope.c

diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index 4c53edb5a034efe9c563ab4ecdcb88fb46380ede..8d16101dc7042bd84ff9ecce84b6ec179d8aff59 100644 (file)
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -28,7 +28,8 @@
 #include "resolved-dns-domain.h"
 #include "resolved-dns-scope.h"
 
-#define SEND_TIMEOUT_USEC (2*USEC_PER_SEC)
+#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;
@@ -51,12 +52,15 @@ 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) {
-        DnsQueryTransaction *t;
+        DnsTransaction *t;
 
         if (!s)
                 return NULL;
@@ -71,10 +75,10 @@ DnsScope* dns_scope_free(DnsScope *s) {
                  * freed while we still look at it */
 
                 t->block_gc++;
-                dns_query_transaction_complete(t, DNS_QUERY_ABORTED);
+                dns_transaction_complete(t, DNS_TRANSACTION_ABORTED);
                 t->block_gc--;
 
-                dns_query_transaction_free(t);
+                dns_transaction_free(t);
         }
 
         dns_cache_flush(&s->cache);
@@ -87,7 +91,7 @@ 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)
@@ -135,7 +139,7 @@ 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;
 
@@ -163,6 +167,9 @@ 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;
 
@@ -199,7 +206,7 @@ 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;
 
@@ -355,6 +362,12 @@ 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;
 
@@ -368,6 +381,9 @@ 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
@@ -389,14 +405,25 @@ int dns_scope_good_dns_server(DnsScope *s, int family, const union in_addr_union
                 return !!manager_find_dns_server(s->manager, family, address);
 }
 
-static int dns_scope_make_reply_packet(DnsScope *s, uint16_t id, int rcode, DnsQuestion *q, DnsAnswer *answer, DnsAnswer *soa, DnsPacket **ret) {
+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);
 
-        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);
@@ -409,7 +436,7 @@ static int dns_scope_make_reply_packet(DnsScope *s, uint16_t id, int rcode, DnsQ
                                                               0 /* opcode */,
                                                               0 /* c */,
                                                               0 /* tc */,
-                                                              0 /* t */,
+                                                              tentative,
                                                               0 /* (ra) */,
                                                               0 /* (ad) */,
                                                               0 /* (cd) */,
@@ -454,6 +481,7 @@ static int dns_scope_make_reply_packet(DnsScope *s, uint16_t id, int rcode, DnsQ
 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);
@@ -485,7 +513,7 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
                 return;
         }
 
-        r = dns_zone_lookup(&s->zone, p->question, &answer, &soa);
+        r = dns_zone_lookup(&s->zone, p->question, &answer, &soa, &tentative);
         if (r < 0) {
                 log_debug("Failed to lookup key: %s", strerror(-r));
                 return;
@@ -496,7 +524,7 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
         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, &reply);
+        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("Failed to build reply packet: %s", strerror(-r));
                 return;
@@ -505,6 +533,9 @@ 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)
@@ -526,3 +557,29 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
                 return;
         }
 }
+
+DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsQuestion *question, bool cache_ok) {
+        DnsTransaction *t;
+
+        assert(scope);
+        assert(question);
+
+        /* 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) {
+
+                /* 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;
+}