resolved: also synthesize records for the full local hostname

Previously, we'd only synthesize RRs for the LLMNR and mDNS versions of
the hostnames (i.e. the first label of the kernel hostname, as well as
the first label of the kernel hostname suffixed with .local). With this
change, we also synthesize an RR for the full hostname, which is
relevant in case it has more than one label.

Fixes: #5041

src/resolve/resolved-manager.c

@@ -322,12 +322,13 @@ static int manager_network_monitor_listen(Manager *m) {
         return 0;
 }
 
-static int determine_hostname(char **llmnr_hostname, char **mdns_hostname) {
+static int determine_hostname(char **full_hostname, char **llmnr_hostname, char **mdns_hostname) {
         _cleanup_free_ char *h = NULL, *n = NULL;
         char label[DNS_LABEL_MAX];
         const char *p;
         int r, k;
 
+        assert(full_hostname);
         assert(llmnr_hostname);
         assert(mdns_hostname);
 
@@ -374,32 +375,33 @@ static int determine_hostname(char **llmnr_hostname, char **mdns_hostname) {
         *llmnr_hostname = n;
         n = NULL;
 
+        *full_hostname = h;
+        h = NULL;
+
         return 0;
 }
 
 static int on_hostname_change(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
-        _cleanup_free_ char *llmnr_hostname = NULL, *mdns_hostname = NULL;
+        _cleanup_free_ char *full_hostname = NULL, *llmnr_hostname = NULL, *mdns_hostname = NULL;
         Manager *m = userdata;
         int r;
 
         assert(m);
 
-        r = determine_hostname(&llmnr_hostname, &mdns_hostname);
+        r = determine_hostname(&full_hostname, &llmnr_hostname, &mdns_hostname);
         if (r < 0)
                 return 0; /* ignore invalid hostnames */
 
-        if (streq(llmnr_hostname, m->llmnr_hostname) && streq(mdns_hostname, m->mdns_hostname))
+        if (streq(full_hostname, m->full_hostname) &&
+            streq(llmnr_hostname, m->llmnr_hostname) &&
+            streq(mdns_hostname, m->mdns_hostname))
                 return 0;
 
-        log_info("System hostname changed to '%s'.", llmnr_hostname);
+        log_info("System hostname changed to '%s'.", full_hostname);
 
-        free(m->llmnr_hostname);
-        free(m->mdns_hostname);
-
-        m->llmnr_hostname = llmnr_hostname;
-        m->mdns_hostname = mdns_hostname;
-
-        llmnr_hostname = mdns_hostname = NULL;
+        free_and_replace(m->full_hostname, full_hostname);
+        free_and_replace(m->llmnr_hostname, llmnr_hostname);
+        free_and_replace(m->mdns_hostname, mdns_hostname);
 
         manager_refresh_rrs(m);
 
@@ -428,9 +430,14 @@ static int manager_watch_hostname(Manager *m) {
 
         (void) sd_event_source_set_description(m->hostname_event_source, "hostname");
 
-        r = determine_hostname(&m->llmnr_hostname, &m->mdns_hostname);
+        r = determine_hostname(&m->full_hostname, &m->llmnr_hostname, &m->mdns_hostname);
         if (r < 0) {
                 log_info("Defaulting to hostname 'linux'.");
+
+                m->full_hostname = strdup("linux");
+                if (!m->full_hostname)
+                        return log_oom();
+
                 m->llmnr_hostname = strdup("linux");
                 if (!m->llmnr_hostname)
                         return log_oom();
@@ -439,7 +446,7 @@ static int manager_watch_hostname(Manager *m) {
                 if (!m->mdns_hostname)
                         return log_oom();
         } else
-                log_info("Using system hostname '%s'.", m->llmnr_hostname);
+                log_info("Using system hostname '%s'.", m->full_hostname);
 
         return 0;
 }
@@ -624,6 +631,8 @@ Manager *manager_free(Manager *m) {
 
         sd_event_source_unref(m->hostname_event_source);
         safe_close(m->hostname_fd);
+
+        free(m->full_hostname);
         free(m->llmnr_hostname);
         free(m->mdns_hostname);
 
@@ -1146,8 +1155,14 @@ int manager_is_own_hostname(Manager *m, const char *name) {
                         return r;
         }
 
-        if (m->mdns_hostname)
-                return dns_name_equal(name, m->mdns_hostname);
+        if (m->mdns_hostname) {
+                r = dns_name_equal(name, m->mdns_hostname);
+                if (r != 0)
+                        return r;
+        }
+
+        if (m->full_hostname)
+                return dns_name_equal(name, m->full_hostname);
 
         return 0;
 }

src/resolve/resolved-manager.h

@@ -109,6 +109,7 @@ struct Manager {
         sd_event_source *bus_retry_event_source;
 
         /* The hostname we publish on LLMNR and mDNS */
+        char *full_hostname;
         char *llmnr_hostname;
         char *mdns_hostname;
         DnsResourceKey *llmnr_host_ipv4_key;