resolved: fix crash when shutting down

Reported by Cristian Rodríguez

http://lists.freedesktop.org/archives/systemd-devel/2015-May/031626.html

src/resolve/resolved-dns-cache.c

@@ -91,11 +91,8 @@ void dns_cache_flush(DnsCache *c) {
         assert(hashmap_size(c->by_key) == 0);
         assert(prioq_size(c->by_expiry) == 0);
 
-        hashmap_free(c->by_key);
-        c->by_key = NULL;
-
-        prioq_free(c->by_expiry);
-        c->by_expiry = NULL;
+        c->by_key = hashmap_free(c->by_key);
+        c->by_expiry = prioq_free(c->by_expiry);
 }
 
 static void dns_cache_remove(DnsCache *c, DnsResourceKey *key) {

src/resolve/resolved-dns-server.c

@@ -78,23 +78,24 @@ DnsServer* dns_server_free(DnsServer *s)  {
         if (!s)
                 return NULL;
 
-        if (s->manager) {
+        if (s->link) {
                 if (s->type == DNS_SERVER_LINK)
                         LIST_REMOVE(servers, s->link->dns_servers, s);
-                else if (s->type == DNS_SERVER_SYSTEM)
+
+                if (s->link->current_dns_server == s)
+                        link_set_dns_server(s->link, NULL);
+        }
+
+        if (s->manager) {
+                if (s->type == DNS_SERVER_SYSTEM)
                         LIST_REMOVE(servers, s->manager->dns_servers, s);
                 else if (s->type == DNS_SERVER_FALLBACK)
                         LIST_REMOVE(servers, s->manager->fallback_dns_servers, s);
-                else
-                        assert_not_reached("Unknown server type");
 
                 if (s->manager->current_dns_server == s)
                         manager_set_dns_server(s->manager, NULL);
         }
 
-        if (s->link && s->link->current_dns_server == s)
-                link_set_dns_server(s->link, NULL);
-
         free(s);
 
         return NULL;

src/resolve/resolved-link.c

@@ -68,13 +68,13 @@ Link *link_free(Link *l) {
         if (l->manager)
                 hashmap_remove(l->manager->links, INT_TO_PTR(l->ifindex));
 
+        while (l->dns_servers)
+                dns_server_free(l->dns_servers);
+
         dns_scope_free(l->unicast_scope);
         dns_scope_free(l->llmnr_ipv4_scope);
         dns_scope_free(l->llmnr_ipv6_scope);
 
-        while (l->dns_servers)
-                dns_server_free(l->dns_servers);
-
         free(l);
         return NULL;
 }

src/resolve/resolved-manager.c

@@ -534,11 +534,11 @@ Manager *manager_free(Manager *m) {
         while (m->dns_queries)
                 dns_query_free(m->dns_queries);
 
-        dns_scope_free(m->unicast_scope);
-
         manager_flush_dns_servers(m, DNS_SERVER_SYSTEM);
         manager_flush_dns_servers(m, DNS_SERVER_FALLBACK);
 
+        dns_scope_free(m->unicast_scope);
+
         hashmap_free(m->links);
         hashmap_free(m->dns_transactions);