fix localhost resolution

src/lib/ares_addrinfo_localhost.c

@@ -49,6 +49,19 @@
 #  endif
 #endif
 
+static ares_bool_t ares_ai_has_family(int aftype,
+                                      const struct ares_addrinfo_node *nodes)
+{
+  const struct ares_addrinfo_node *node;
+
+  for (node = nodes; node != NULL; node = node->ai_next) {
+    if (node->ai_family == aftype)
+      return ARES_TRUE;
+  }
+
+  return ARES_FALSE;
+}
+
 ares_status_t ares_append_ai_node(int aftype, unsigned short port,
                                   unsigned int ttl, const void *adata,
                                   struct ares_addrinfo_node **nodes)
@@ -107,7 +120,8 @@ static ares_status_t
 {
   ares_status_t status = ARES_SUCCESS;
 
-  if (aftype == AF_UNSPEC || aftype == AF_INET6) {
+  if ((aftype == AF_UNSPEC || aftype == AF_INET6) &&
+      !ares_ai_has_family(AF_INET6, *nodes)) {
     struct ares_in6_addr addr6;
     ares_inet_pton(AF_INET6, "::1", &addr6);
     status = ares_append_ai_node(AF_INET6, port, 0, &addr6, nodes);
@@ -116,7 +130,8 @@ static ares_status_t
     }
   }
 
-  if (aftype == AF_UNSPEC || aftype == AF_INET) {
+  if ((aftype == AF_UNSPEC || aftype == AF_INET) &&
+      !ares_ai_has_family(AF_INET, *nodes)) {
     struct in_addr addr4;
     ares_inet_pton(AF_INET, "127.0.0.1", &addr4);
     status = ares_append_ai_node(AF_INET, port, 0, &addr4, nodes);
@@ -150,11 +165,13 @@ static ares_status_t
       continue;
     }
 
-    if (table->Table[i].Address.si_family == AF_INET) {
+    if (table->Table[i].Address.si_family == AF_INET &&
+        !ares_ai_has_family(AF_INET, *nodes)) {
       status =
         ares_append_ai_node(table->Table[i].Address.si_family, port, 0,
                             &table->Table[i].Address.Ipv4.sin_addr, nodes);
-    } else if (table->Table[i].Address.si_family == AF_INET6) {
+    } else if (table->Table[i].Address.si_family == AF_INET6 &&
+               !ares_ai_has_family(AF_INET6, *nodes)) {
       status =
         ares_append_ai_node(table->Table[i].Address.si_family, port, 0,
                             &table->Table[i].Address.Ipv6.sin6_addr, nodes);
@@ -195,8 +212,7 @@ ares_status_t ares_addrinfo_localhost(const char *name, unsigned short port,
                                       const struct ares_addrinfo_hints *hints,
                                       struct ares_addrinfo             *ai)
 {
-  struct ares_addrinfo_node *nodes = NULL;
-  ares_status_t              status;
+  ares_status_t status;
 
   /* Validate family */
   switch (hints->ai_family) {
@@ -210,24 +226,17 @@ ares_status_t ares_addrinfo_localhost(const char *name, unsigned short port,
 
   ai->name = ares_strdup(name);
   if (!ai->name) {
-    goto enomem; /* LCOV_EXCL_LINE: OutOfMemory */
+    status = ARES_ENOMEM;
+    goto done; /* LCOV_EXCL_LINE: OutOfMemory */
   }
 
-  status = ares_system_loopback_addrs(hints->ai_family, port, &nodes);
-
-  if (status == ARES_ENOTFOUND) {
-    status = ares_default_loopback_addrs(hints->ai_family, port, &nodes);
+  status = ares_system_loopback_addrs(hints->ai_family, port, &ai->nodes);
+  if (status != ARES_SUCCESS && status != ARES_ENOTFOUND) {
+    goto done;
   }
 
-  ares_addrinfo_cat_nodes(&ai->nodes, nodes);
+  status = ares_default_loopback_addrs(hints->ai_family, port, &ai->nodes);
 
+done:
   return status;
-
-/* LCOV_EXCL_START: OutOfMemory */
-enomem:
-  ares_freeaddrinfo_nodes(nodes);
-  ares_free(ai->name);
-  ai->name = NULL;
-  return ARES_ENOMEM;
-  /* LCOV_EXCL_STOP */
 }

src/lib/ares_getaddrinfo.c

@@ -418,9 +418,13 @@ static ares_status_t file_lookup(struct host_query *hquery)
    * SHOULD recognize localhost names as special and SHOULD always return the
    * IP loopback address for address queries".
    * We will also ignore ALL errors when trying to resolve localhost, such
-   * as permissions errors reading /etc/hosts or a malformed /etc/hosts */
-  if (status != ARES_SUCCESS && status != ARES_ENOMEM &&
-      ares_is_localhost(hquery->name)) {
+   * as permissions errors reading /etc/hosts or a malformed /etc/hosts.
+   *
+   * Also, just because the query itself returned success from /etc/hosts
+   * lookup doesn't mean it returned everything it needed to for all requested
+   * address families. As long as we're not on a critical out of memory
+   * condition pass it through to fill in any other address classes. */
+  if (status != ARES_ENOMEM && ares_is_localhost(hquery->name)) {
     return ares_addrinfo_localhost(hquery->name, hquery->port, &hquery->hints,
                                    hquery->ai);
   }

src/lib/ares_gethostbyname.c

@@ -307,9 +307,13 @@ static ares_status_t ares_gethostbyname_file_int(ares_channel_t *channel,
    * SHOULD recognize localhost names as special and SHOULD always return the
    * IP loopback address for address queries".
    * We will also ignore ALL errors when trying to resolve localhost, such
-   * as permissions errors reading /etc/hosts or a malformed /etc/hosts */
-  if (status != ARES_SUCCESS && status != ARES_ENOMEM &&
-      ares_is_localhost(name)) {
+   * as permissions errors reading /etc/hosts or a malformed /etc/hosts.
+   *
+   * Also, just because the query itself returned success from /etc/hosts
+   * lookup doesn't mean it returned everything it needed to for all requested
+   * address families. As long as we're not on a critical out of memory
+   * condition pass it through to fill in any other address classes. */
+  if (status != ARES_ENOMEM && ares_is_localhost(name)) {
     return ares_hostent_localhost(name, family, host);
   }
 

src/lib/ares_hosts_file.c

@@ -845,7 +845,7 @@ ares_status_t ares_hosts_entry_to_addrinfo(const ares_hosts_entry_t *entry,
                                            ares_bool_t           want_cnames,
                                            struct ares_addrinfo *ai)
 {
-  ares_status_t               status;
+  ares_status_t               status  = ARES_ENOTFOUND;
   struct ares_addrinfo_cname *cnames  = NULL;
   struct ares_addrinfo_node  *ainodes = NULL;
   ares_llist_node_t          *node;
@@ -888,6 +888,11 @@ ares_status_t ares_hosts_entry_to_addrinfo(const ares_hosts_entry_t *entry,
     }
   }
 
+  /* Might be ARES_ENOTFOUND here if no ips matched requested address family */
+  if (status != ARES_SUCCESS) {
+    goto done;
+  }
+
   if (want_cnames) {
     status = ares_hosts_ai_append_cnames(entry, &cnames);
     if (status != ARES_SUCCESS) {