resolved: rework synthesizing logic

With this change we'll now also generate synthesized RRs for the local
LLMNR hostname (first label of system hostname), the local mDNS hostname
(first label of system hostname suffixed with .local), the "gateway"
hostname and all the reverse PTRs. This hence takes over part of what
nss-myhostname already implemented.

Local hostnames resolve to the set of local IP addresses. Since the
addresses are possibly on different interfaces it is necessary to change
the internal DnsAnswer object to track per-RR interface indexes, and to
change the bus API to always return the interface per-address rather than
per-reply. This change also patches  the existing clients for resolved
accordingly (nss-resolve + systemd-resolve-host).

This also changes the routing logic for queries slightly: we now ensure
that the local hostname is never resolved via LLMNR, thus making it
trustable on the local system.

1 files changed, 29 insertions, 34 deletions

diff --git a/src/resolve/resolved-bus.c b/src/resolve/resolved-bus.c
index 6db12511f9..de5e8e9c29 100644
--- a/src/resolve/resolved-bus.c
+++ b/src/resolve/resolved-bus.c
@@ -91,13 +91,17 @@ static int reply_query_state(DnsQuery *q) {
         }
 }
 
-static int append_address(sd_bus_message *reply, DnsResourceRecord *rr) {
+static int append_address(sd_bus_message *reply, DnsResourceRecord *rr, int ifindex) {
         int r;
 
         assert(reply);
         assert(rr);
 
-        r = sd_bus_message_open_container(reply, 'r', "iay");
+        r = sd_bus_message_open_container(reply, 'r', "iiay");
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append(reply, "i", ifindex);
         if (r < 0)
                 return r;
 
@@ -145,11 +149,7 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
         if (r < 0)
                 goto finish;
 
-        r = sd_bus_message_append(reply, "i", q->answer_ifindex);
-        if (r < 0)
-                goto finish;
-
-        r = sd_bus_message_open_container(reply, 'a', "(iay)");
+        r = sd_bus_message_open_container(reply, 'a', "(iiay)");
         if (r < 0)
                 goto finish;
 
@@ -157,27 +157,27 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
                 answer = dns_answer_ref(q->answer);
 
                 for (i = 0; i < answer->n_rrs; i++) {
-                        r = dns_question_matches_rr(q->question, answer->rrs[i]);
+                        r = dns_question_matches_rr(q->question, answer->items[i].rr);
                         if (r < 0)
                                 goto finish;
                         if (r == 0) {
                                 /* Hmm, if this is not an address record,
                                    maybe it's a cname? If so, remember this */
-                                r = dns_question_matches_cname(q->question, answer->rrs[i]);
+                                r = dns_question_matches_cname(q->question, answer->items[i].rr);
                                 if (r < 0)
                                         goto finish;
                                 if (r > 0)
-                                        cname = dns_resource_record_ref(answer->rrs[i]);
+                                        cname = dns_resource_record_ref(answer->items[i].rr);
 
                                 continue;
                         }
 
-                        r = append_address(reply, answer->rrs[i]);
+                        r = append_address(reply, answer->items[i].rr, answer->items[i].ifindex);
                         if (r < 0)
                                 goto finish;
 
                         if (!canonical)
-                                canonical = dns_resource_record_ref(answer->rrs[i]);
+                                canonical = dns_resource_record_ref(answer->items[i].rr);
 
                         added ++;
                 }
@@ -204,18 +204,18 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
                 /* Before we restart the query, let's see if any of
                  * the RRs we already got already answers our query */
                 for (i = 0; i < answer->n_rrs; i++) {
-                        r = dns_question_matches_rr(q->question, answer->rrs[i]);
+                        r = dns_question_matches_rr(q->question, answer->items[i].rr);
                         if (r < 0)
                                 goto finish;
                         if (r == 0)
                                 continue;
 
-                        r = append_address(reply, answer->rrs[i]);
+                        r = append_address(reply, answer->items[i].rr, answer->items[i].ifindex);
                         if (r < 0)
                                 goto finish;
 
                         if (!canonical)
-                                canonical = dns_resource_record_ref(answer->rrs[i]);
+                                canonical = dns_resource_record_ref(answer->items[i].rr);
 
                         added++;
                 }
@@ -373,11 +373,7 @@ static void bus_method_resolve_address_complete(DnsQuery *q) {
         if (r < 0)
                 goto finish;
 
-        r = sd_bus_message_append(reply, "i", q->answer_ifindex);
-        if (r < 0)
-                goto finish;
-
-        r = sd_bus_message_open_container(reply, 'a', "s");
+        r = sd_bus_message_open_container(reply, 'a', "(is)");
         if (r < 0)
                 goto finish;
 
@@ -385,13 +381,13 @@ static void bus_method_resolve_address_complete(DnsQuery *q) {
                 answer = dns_answer_ref(q->answer);
 
                 for (i = 0; i < answer->n_rrs; i++) {
-                        r = dns_question_matches_rr(q->question, answer->rrs[i]);
+                        r = dns_question_matches_rr(q->question, answer->items[i].rr);
                         if (r < 0)
                                 goto finish;
                         if (r == 0)
                                 continue;
 
-                        r = sd_bus_message_append(reply, "s", answer->rrs[i]->ptr.name);
+                        r = sd_bus_message_append(reply, "(is)", answer->items[i].ifindex, answer->items[i].rr->ptr.name);
                         if (r < 0)
                                 goto finish;
 
@@ -525,11 +521,7 @@ static void bus_method_resolve_record_complete(DnsQuery *q) {
         if (r < 0)
                 goto finish;
 
-        r = sd_bus_message_append(reply, "i", q->answer_ifindex);
-        if (r < 0)
-                goto finish;
-
-        r = sd_bus_message_open_container(reply, 'a', "(qqay)");
+        r = sd_bus_message_open_container(reply, 'a', "(iqqay)");
         if (r < 0)
                 goto finish;
 
@@ -540,7 +532,7 @@ static void bus_method_resolve_record_complete(DnsQuery *q) {
                         _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
                         size_t start;
 
-                        r = dns_question_matches_rr(q->question, answer->rrs[i]);
+                        r = dns_question_matches_rr(q->question, answer->items[i].rr);
                         if (r < 0)
                                 goto finish;
                         if (r == 0)
@@ -550,15 +542,18 @@ static void bus_method_resolve_record_complete(DnsQuery *q) {
                         if (r < 0)
                                 goto finish;
 
-                        r = dns_packet_append_rr(p, answer->rrs[i], &start);
+                        r = dns_packet_append_rr(p, answer->items[i].rr, &start);
                         if (r < 0)
                                 goto finish;
 
-                        r = sd_bus_message_open_container(reply, 'r', "qqay");
+                        r = sd_bus_message_open_container(reply, 'r', "iqqay");
                         if (r < 0)
                                 goto finish;
 
-                        r = sd_bus_message_append(reply, "qq", answer->rrs[i]->key->class, answer->rrs[i]->key->type);
+                        r = sd_bus_message_append(reply, "iqq",
+                                                  answer->items[i].ifindex,
+                                                  answer->items[i].rr->key->class,
+                                                  answer->items[i].rr->key->type);
                         if (r < 0)
                                 goto finish;
 
@@ -662,9 +657,9 @@ static int bus_method_resolve_record(sd_bus_message *message, void *userdata, sd
 
 static const sd_bus_vtable resolve_vtable[] = {
         SD_BUS_VTABLE_START(0),
-        SD_BUS_METHOD("ResolveHostname", "isit", "ia(iay)st", bus_method_resolve_hostname, SD_BUS_VTABLE_UNPRIVILEGED),
-        SD_BUS_METHOD("ResolveAddress", "iiayt", "iast", bus_method_resolve_address, SD_BUS_VTABLE_UNPRIVILEGED),
-        SD_BUS_METHOD("ResolveRecord", "isqqt", "ia(qqay)t", bus_method_resolve_record, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("ResolveHostname", "isit", "a(iiay)st", bus_method_resolve_hostname, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("ResolveAddress", "iiayt", "a(is)t", bus_method_resolve_address, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("ResolveRecord", "isqqt", "a(iqqay)t", bus_method_resolve_record, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_VTABLE_END,
 };