resolved: make sure we initialize the ifindex of direct zone answers properly

Previously, after checking the local zone for a reply and finding one we'd not
initialize the answer ifindex from that. Let's fix that.

src/resolve/resolved-dns-answer.c

@@ -185,7 +185,7 @@ int dns_answer_add_extend(DnsAnswer **a, DnsResourceRecord *rr, int ifindex, Dns
         return dns_answer_add(*a, rr, ifindex, flags);
 }
 
-int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl) {
+int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl, int ifindex) {
         _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *soa = NULL;
 
         soa = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_SOA, name);
@@ -208,7 +208,7 @@ int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl) {
         soa->soa.expire = 1;
         soa->soa.minimum = ttl;
 
-        return dns_answer_add(a, soa, 0, DNS_ANSWER_AUTHENTICATED);
+        return dns_answer_add(a, soa, ifindex, DNS_ANSWER_AUTHENTICATED);
 }
 
 int dns_answer_match_key(DnsAnswer *a, const DnsResourceKey *key, DnsAnswerFlags *ret_flags) {

src/resolve/resolved-dns-answer.h

@@ -56,7 +56,7 @@ DnsAnswer *dns_answer_unref(DnsAnswer *a);
 
 int dns_answer_add(DnsAnswer *a, DnsResourceRecord *rr, int ifindex, DnsAnswerFlags flags);
 int dns_answer_add_extend(DnsAnswer **a, DnsResourceRecord *rr, int ifindex, DnsAnswerFlags flags);
-int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl);
+int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl, int ifindex);
 
 int dns_answer_match_key(DnsAnswer *a, const DnsResourceKey *key, DnsAnswerFlags *combined_flags);
 int dns_answer_contains_rr(DnsAnswer *a, DnsResourceRecord *rr, DnsAnswerFlags *combined_flags);

src/resolve/resolved-dns-scope.c

@@ -721,7 +721,7 @@ void dns_scope_process_query(DnsScope *s, DnsStream *stream, DnsPacket *p) {
         assert(p->question->n_keys == 1);
         key = p->question->keys[0];
 
-        r = dns_zone_lookup(&s->zone, key, &answer, &soa, &tentative);
+        r = dns_zone_lookup(&s->zone, key, 0, &answer, &soa, &tentative);
         if (r < 0) {
                 log_debug_errno(r, "Failed to lookup key: %m");
                 return;
@@ -1029,3 +1029,12 @@ bool dns_scope_network_good(DnsScope *s) {
 
         return manager_routable(s->manager, AF_UNSPEC);
 }
+
+int dns_scope_ifindex(DnsScope *s) {
+        assert(s);
+
+        if (s->link)
+                return s->link->ifindex;
+
+        return 0;
+}

src/resolve/resolved-dns-scope.h

@@ -107,3 +107,5 @@ DnsSearchDomain *dns_scope_get_search_domains(DnsScope *s);
 bool dns_scope_name_needs_search_domain(DnsScope *s, const char *name);
 
 bool dns_scope_network_good(DnsScope *s);
+
+int dns_scope_ifindex(DnsScope *s);

src/resolve/resolved-dns-transaction.c

@@ -557,8 +557,7 @@ static int dns_transaction_open_tcp(DnsTransaction *t) {
         /* The interface index is difficult to determine if we are
          * connecting to the local host, hence fill this in right away
          * instead of determining it from the socket */
-        if (t->scope->link)
+        t->stream->ifindex = dns_scope_ifindex(t->scope);
-                t->stream->ifindex = t->scope->link->ifindex;
 
         dns_transaction_reset_answer(t);
 
@@ -798,12 +797,9 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
         switch (t->scope->protocol) {
 
         case DNS_PROTOCOL_LLMNR:
-                assert(t->scope->link);
+                /* For LLMNR we will not accept any packets from other interfaces */
 
-                /* For LLMNR we will not accept any packets from other
+                if (p->ifindex != dns_scope_ifindex(t->scope))
-                 * interfaces */
-
-                if (p->ifindex != t->scope->link->ifindex)
                         return;
 
                 if (p->family != t->scope->family)
@@ -820,10 +816,9 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
                 break;
 
         case DNS_PROTOCOL_MDNS:
-                assert(t->scope->link);
-
                 /* For mDNS we will not accept any packets from other interfaces */
-                if (p->ifindex != t->scope->link->ifindex)
+
+                if (p->ifindex != dns_scope_ifindex(t->scope))
                         return;
 
                 if (p->family != t->scope->family)
@@ -1246,7 +1241,7 @@ static int dns_transaction_prepare(DnsTransaction *t, usec_t ts) {
          * for probing or verifying a zone item. */
         if (set_isempty(t->notify_zone_items)) {
 
-                r = dns_zone_lookup(&t->scope->zone, t->key, &t->answer, NULL, NULL);
+                r = dns_zone_lookup(&t->scope->zone, t->key, dns_scope_ifindex(t->scope), &t->answer, NULL, NULL);
                 if (r < 0)
                         return r;
                 if (r > 0) {

src/resolve/resolved-dns-zone.c

@@ -287,13 +287,16 @@ int dns_zone_put(DnsZone *z, DnsScope *s, DnsResourceRecord *rr, bool probe) {
         return 0;
 }
 
-int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, DnsAnswer **ret_answer, DnsAnswer **ret_soa, bool *ret_tentative) {
+int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, int ifindex, DnsAnswer **ret_answer, DnsAnswer **ret_soa, bool *ret_tentative) {
         _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL, *soa = NULL;
         unsigned n_answer = 0;
         DnsZoneItem *j, *first;
         bool tentative = true, need_soa = false;
         int r;
 
+        /* Note that we don't actually need the ifindex for anything. However when it is passed we'll initialize the
+         * ifindex field in the answer with it */
+
         assert(z);
         assert(key);
         assert(ret_answer);
@@ -389,7 +392,7 @@ int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, DnsAnswer **ret_answer, Dns
                         if (k < 0)
                                 return k;
                         if (k > 0) {
-                                r = dns_answer_add(answer, j->rr, 0, DNS_ANSWER_AUTHENTICATED);
+                                r = dns_answer_add(answer, j->rr, ifindex, DNS_ANSWER_AUTHENTICATED);
                                 if (r < 0)
                                         return r;
 
@@ -398,7 +401,7 @@ int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, DnsAnswer **ret_answer, Dns
                 }
 
                 if (found && !added) {
-                        r = dns_answer_add_soa(soa, dns_resource_key_name(key), LLMNR_DEFAULT_TTL);
+                        r = dns_answer_add_soa(soa, dns_resource_key_name(key), LLMNR_DEFAULT_TTL, ifindex);
                         if (r < 0)
                                 return r;
                 }
@@ -415,7 +418,7 @@ int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, DnsAnswer **ret_answer, Dns
                         if (j->state != DNS_ZONE_ITEM_PROBING)
                                 tentative = false;
 
-                        r = dns_answer_add(answer, j->rr, 0, DNS_ANSWER_AUTHENTICATED);
+                        r = dns_answer_add(answer, j->rr, ifindex, DNS_ANSWER_AUTHENTICATED);
                         if (r < 0)
                                 return r;
                 }
@@ -435,7 +438,7 @@ int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, DnsAnswer **ret_answer, Dns
                         }
 
                         if (add_soa) {
-                                r = dns_answer_add_soa(soa, dns_resource_key_name(key), LLMNR_DEFAULT_TTL);
+                                r = dns_answer_add_soa(soa, dns_resource_key_name(key), LLMNR_DEFAULT_TTL, ifindex);
                                 if (r < 0)
                                         return r;
                         }

src/resolve/resolved-dns-zone.h

@@ -65,7 +65,7 @@ void dns_zone_flush(DnsZone *z);
 int dns_zone_put(DnsZone *z, DnsScope *s, DnsResourceRecord *rr, bool probe);
 void dns_zone_remove_rr(DnsZone *z, DnsResourceRecord *rr);
 
-int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, DnsAnswer **answer, DnsAnswer **soa, bool *tentative);
+int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, int ifindex, DnsAnswer **answer, DnsAnswer **soa, bool *tentative);
 
 void dns_zone_item_conflict(DnsZoneItem *i);
 void dns_zone_item_notify(DnsZoneItem *i);