Send SERVFAIL when nameservers are not listening on TCP port 53

diff --git a/plugins/dnsproxy.c b/plugins/dnsproxy.c
index 135f7f5..f12fd27 100644 (file)
--- a/plugins/dnsproxy.c
+++ b/plugins/dnsproxy.c
@@ -354,6 +354,42 @@ static int forward_dns_reply(unsigned char *reply, int reply_len, int protocol)
        return err;
 }
 
+static void send_response(int sk, unsigned char *buf, int len,
+                               const struct sockaddr *to, socklen_t tolen,
+                               int protocol)
+{
+       struct domain_hdr *hdr;
+       int err, offset;
+
+       switch (protocol) {
+       case IPPROTO_UDP:
+               offset = 0;
+               break;
+
+       case IPPROTO_TCP:
+               offset = 2;
+               break;
+
+       default:
+               return;
+       }
+
+       if (len < 12)
+               return;
+
+       hdr = (void*) (buf + offset);
+
+       DBG("id 0x%04x qr %d opcode %d", hdr->id, hdr->qr, hdr->opcode);
+
+       hdr->qr = 1;
+       hdr->rcode = 2;
+
+       hdr->ancount = 0;
+       hdr->nscount = 0;
+       hdr->arcount = 0;
+
+       err = sendto(sk, buf, len, 0, to, tolen);
+}
 
 static void destroy_server(struct server_data *server)
 {
@@ -410,8 +446,32 @@ static gboolean tcp_server_event(GIOChannel *channel, GIOCondition condition,
                return FALSE;
 
        if (condition & (G_IO_NVAL | G_IO_ERR | G_IO_HUP)) {
+               GSList *list;
+
                DBG("TCP server channel closed");
 
+               for (list = request_list; list; list = list->next) {
+                       struct request_data *req = list->data;
+                       struct domain_hdr *hdr = (void *) (req->request + 2);
+
+                       if (!req->client_sk)
+                               continue;
+
+                       /*
+                        * If we're not waiting for any further response
+                        * from another name server, then we send an error
+                        * response to the client.
+                        */
+                       if (req->numserv && --(req->numserv))
+                               continue;
+
+                       hdr->id = req->srcid;
+                       send_response(req->client_sk, req->request,
+                                       req->request_len, NULL, 0, IPPROTO_TCP);
+
+                       request_list = g_slist_remove(request_list, req);
+               }
+
                server_list = g_slist_remove(server_list, server);
                destroy_server(server);
 
@@ -826,27 +886,6 @@ static int parse_request(unsigned char *buf, int len,
        return 0;
 }
 
-static void send_response(int sk, unsigned char *buf, int len,
-                               const struct sockaddr *to, socklen_t tolen)
-{
-       struct domain_hdr *hdr = (void *) buf;
-       int err;
-
-       if (len < 12)
-               return;
-
-       DBG("id 0x%04x qr %d opcode %d", hdr->id, hdr->qr, hdr->opcode);
-
-       hdr->qr = 1;
-       hdr->rcode = 2;
-
-       hdr->ancount = 0;
-       hdr->nscount = 0;
-       hdr->arcount = 0;
-
-       err = sendto(sk, buf, len, 0, to, tolen);
-}
-
 static gboolean tcp_listener_event(GIOChannel *channel, GIOCondition condition,
                                                        gpointer user_data)
 {
@@ -890,7 +929,7 @@ static gboolean tcp_listener_event(GIOChannel *channel, GIOCondition condition,
        err = parse_request(buf + 2, len - 2, query, sizeof(query));
        if (err < 0 || (g_slist_length(server_list) == 0 &&
                                connman_ondemand_connected())) {
-               send_response(client_sk, buf, len, NULL, 0);
+               send_response(client_sk, buf, len, NULL, 0, IPPROTO_TCP);
                return TRUE;
        }
 
@@ -989,7 +1028,8 @@ static gboolean udp_listener_event(GIOChannel *channel, GIOCondition condition,
        err = parse_request(buf, len, query, sizeof(query));
        if (err < 0 || (g_slist_length(server_list) == 0 &&
                                connman_ondemand_connected())) {
-               send_response(sk, buf, len, (struct sockaddr *) &sin, size);
+               send_response(sk, buf, len, (struct sockaddr *) &sin, size,
+                               IPPROTO_UDP);
                return TRUE;
        }