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, 35 insertions, 46 deletions

diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
index da22f98eba..ef5eb7b4cf 100644
--- a/src/nss-resolve/nss-resolve.c
+++ b/src/nss-resolve/nss-resolve.c
@@ -61,23 +61,21 @@ static bool bus_error_shall_fallback(sd_bus_error *e) {
 }
 
 static int count_addresses(sd_bus_message *m, int af, const char **canonical) {
-        int c = 0, r, ifindex;
+        int c = 0, r;
 
         assert(m);
         assert(canonical);
 
-        r = sd_bus_message_read(m, "i", &ifindex);
+        r = sd_bus_message_enter_container(m, 'a', "(iiay)");
         if (r < 0)
                 return r;
 
-        r = sd_bus_message_enter_container(m, 'a', "(iay)");
-        if (r < 0)
-                return r;
+        while ((r = sd_bus_message_enter_container(m, 'r', "iiay")) > 0) {
+                int family, ifindex;
 
-        while ((r = sd_bus_message_enter_container(m, 'r', "iay")) > 0) {
-                int family;
+                assert_cc(sizeof(int32_t) == sizeof(int));
 
-                r = sd_bus_message_read(m, "i", &family);
+                r = sd_bus_message_read(m, "ii", &ifindex, &family);
                 if (r < 0)
                         return r;
 
@@ -126,7 +124,7 @@ enum nss_status _nss_resolve_gethostbyname4_r(
         const char *canonical = NULL;
         size_t l, ms, idx;
         char *r_name;
-        int c, r, i = 0, ifindex;
+        int c, r, i = 0;
 
         assert(name);
         assert(pat);
@@ -218,28 +216,26 @@ enum nss_status _nss_resolve_gethostbyname4_r(
         /* Second, append addresses */
         r_tuple_first = (struct gaih_addrtuple*) (buffer + idx);
 
-        r = sd_bus_message_read(reply, "i", &ifindex);
-        if (r < 0)
-                goto fail;
-
-        if (ifindex < 0) {
-                r = -EINVAL;
-                goto fail;
-        }
-
-        r = sd_bus_message_enter_container(reply, 'a', "(iay)");
+        r = sd_bus_message_enter_container(reply, 'a', "(iiay)");
         if (r < 0)
                 goto fail;
 
-        while ((r = sd_bus_message_enter_container(reply, 'r', "iay")) > 0) {
-                int family;
+        while ((r = sd_bus_message_enter_container(reply, 'r', "iiay")) > 0) {
+                int family, ifindex;
                 const void *a;
                 size_t sz;
 
-                r = sd_bus_message_read(reply, "i", &family);
+                assert_cc(sizeof(int32_t) == sizeof(int));
+
+                r = sd_bus_message_read(reply, "ii", &ifindex, &family);
                 if (r < 0)
                         goto fail;
 
+                if (ifindex < 0) {
+                        r = -EINVAL;
+                        goto fail;
+                }
+
                 r = sd_bus_message_read_array(reply, 'y', &a, &sz);
                 if (r < 0)
                         goto fail;
@@ -308,7 +304,7 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         _cleanup_bus_flush_close_unref_ sd_bus *bus = NULL;
         size_t l, idx, ms, alen;
         const char *canonical;
-        int c, r, i = 0, ifindex;
+        int c, r, i = 0;
 
         assert(name);
         assert(result);
@@ -420,28 +416,24 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         /* Third, append addresses */
         r_addr = buffer + idx;
 
-        r = sd_bus_message_read(reply, "i", &ifindex);
-        if (r < 0)
-                goto fail;
-
-        if (ifindex < 0) {
-                r = -EINVAL;
-                goto fail;
-        }
-
-        r = sd_bus_message_enter_container(reply, 'a', "(iay)");
+        r = sd_bus_message_enter_container(reply, 'a', "(iiay)");
         if (r < 0)
                 goto fail;
 
-        while ((r = sd_bus_message_enter_container(reply, 'r', "iay")) > 0) {
-                int family;
+        while ((r = sd_bus_message_enter_container(reply, 'r', "iiay")) > 0) {
+                int ifindex, family;
                 const void *a;
                 size_t sz;
 
-                r = sd_bus_message_read(reply, "i", &family);
+                r = sd_bus_message_read(reply, "ii", &ifindex, &family);
                 if (r < 0)
                         goto fail;
 
+                if (ifindex < 0) {
+                        r = -EINVAL;
+                        goto fail;
+                }
+
                 r = sd_bus_message_read_array(reply, 'y', &a, &sz);
                 if (r < 0)
                         goto fail;
@@ -603,20 +595,17 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
                 return NSS_STATUS_UNAVAIL;
         }
 
-        r = sd_bus_message_read(reply, "i", &ifindex);
+        r = sd_bus_message_enter_container(reply, 'a', "(is)");
         if (r < 0)
                 goto fail;
 
-        if (ifindex < 0) {
-                r = -EINVAL;
-                goto fail;
-        }
+        while ((r = sd_bus_message_read(reply, "(is)", &ifindex, &n)) > 0) {
 
-        r = sd_bus_message_enter_container(reply, 'a', "s");
-        if (r < 0)
-                goto fail;
+                if (ifindex < 0) {
+                        r = -EINVAL;
+                        goto fail;
+                }
 
-        while ((r = sd_bus_message_read(reply, "s", &n)) > 0) {
                 c++;
                 ms += ALIGN(strlen(n) + 1);
         }
@@ -661,7 +650,7 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
         /* Fourth, place aliases */
         i = 0;
         r_name = buffer + idx;
-        while ((r = sd_bus_message_read(reply, "s", &n)) > 0) {
+        while ((r = sd_bus_message_read(reply, "(is)", &ifindex, &n)) > 0) {
                 char *p;
                 size_t l;