s4 dns: Fix TCP handling in the DNS server

Autobuild-User: Kai Blin <kai@samba.org>
Autobuild-Date: Tue Mar  6 21:17:19 CET 2012 on sn-devel-104

source4/dns_server/dns_server.c

@@ -233,13 +233,13 @@ static void dns_tcp_call_loop(struct tevent_req *subreq)
 		return;
 	}
 
-	DEBUG(10,("Received krb5 TCP packet of length %lu from %s\n",
+	DEBUG(10,("Received DNS TCP packet of length %lu from %s\n",
 		 (long) call->in.length,
 		 tsocket_address_string(dns_conn->conn->remote_address, call)));
 
 	/* skip length header */
-	call->in.data += 4;
+	call->in.data += 2;
-	call->in.length -= 4;
+	call->in.length -= 2;
 
 	/* Call dns */
 	status = dns_process(dns_conn->dns_socket->dns, call, &call->in, &call->out);
@@ -251,9 +251,9 @@ static void dns_tcp_call_loop(struct tevent_req *subreq)
 	}
 
 	/* First add the length of the out buffer */
-	RSIVAL(call->out_hdr, 0, call->out.length);
+	RSSVAL(call->out_hdr, 0, call->out.length);
 	call->out_iov[0].iov_base = (char *) call->out_hdr;
-	call->out_iov[0].iov_len = 4;
+	call->out_iov[0].iov_len = 2;
 
 	call->out_iov[1].iov_base = (char *) call->out.data;
 	call->out_iov[1].iov_len = call->out.length;
@@ -271,14 +271,14 @@ static void dns_tcp_call_loop(struct tevent_req *subreq)
 	tevent_req_set_callback(subreq, dns_tcp_call_writev_done, call);
 
 	/*
-	 * The krb5 tcp pdu's has the length as 4 byte (initial_read_size),
+	 * The dns tcp pdu's has the length as 2 byte (initial_read_size),
-	 * packet_full_request_u32 provides the pdu length then.
+	 * packet_full_request_u16 provides the pdu length then.
 	 */
 	subreq = tstream_read_pdu_blob_send(dns_conn,
 					    dns_conn->conn->event.ctx,
 					    dns_conn->tstream,
-					    4, /* initial_read_size */
+					    2, /* initial_read_size */
-					    packet_full_request_u32,
+					    packet_full_request_u16,
 					    dns_conn);
 	if (subreq == NULL) {
 		dns_tcp_terminate_connection(dns_conn, "dns_tcp_call_loop: "
@@ -358,14 +358,14 @@ static void dns_tcp_accept(struct stream_connection *conn)
 	conn->private_data = dns_conn;
 
 	/*
-	 * The krb5 tcp pdu's has the length as 4 byte (initial_read_size),
+	 * The dns tcp pdu's has the length as 2 byte (initial_read_size),
-	 * packet_full_request_u32 provides the pdu length then.
+	 * packet_full_request_u16 provides the pdu length then.
 	 */
 	subreq = tstream_read_pdu_blob_send(dns_conn,
 					    dns_conn->conn->event.ctx,
 					    dns_conn->tstream,
-					    4, /* initial_read_size */
+					    2, /* initial_read_size */
-					    packet_full_request_u32,
+					    packet_full_request_u16,
 					    dns_conn);
 	if (subreq == NULL) {
 		dns_tcp_terminate_connection(dns_conn, "dns_tcp_accept: "

source4/lib/stream/packet.c

@@ -612,3 +612,15 @@ _PUBLIC_ NTSTATUS packet_full_request_u32(void *private_data, DATA_BLOB blob, si
 	}
 	return NT_STATUS_OK;
 }
+
+_PUBLIC_ NTSTATUS packet_full_request_u16(void *private_data, DATA_BLOB blob, size_t *size)
+{
+	if (blob.length < 2) {
+		return STATUS_MORE_ENTRIES;
+	}
+	*size = 2 + RSVAL(blob.data, 0);
+	if (*size > blob.length) {
+		return STATUS_MORE_ENTRIES;
+	}
+	return NT_STATUS_OK;
+}

source4/lib/stream/packet.h

@@ -61,5 +61,6 @@ void packet_queue_run(struct packet_context *pc);
 */
 NTSTATUS packet_full_request_nbt(void *private_data, DATA_BLOB blob, size_t *size);
 NTSTATUS packet_full_request_u32(void *private_data, DATA_BLOB blob, size_t *size);
+NTSTATUS packet_full_request_u16(void *private_data, DATA_BLOB blob, size_t *size);
 
 

source4/scripting/python/samba/tests/dns.py

@@ -99,6 +99,22 @@ class DNSTest(TestCase):
             if s is not None:
                 s.close()
 
+    def dns_transaction_tcp(self, packet, host=os.getenv('DC_SERVER_IP')):
+        "send a DNS query and read the reply"
+        s = None
+        try:
+            send_packet = ndr.ndr_pack(packet)
+            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
+            s.connect((host, 53))
+            tcp_packet = struct.pack('!H', len(send_packet))
+            tcp_packet += send_packet
+            s.send(tcp_packet, 0)
+            recv_packet = s.recv(0xffff + 2, 0)
+            return ndr.ndr_unpack(dns.name_packet, recv_packet[2:])
+        finally:
+                if s is not None:
+                    s.close()
+
     def test_one_a_query(self):
         "create a query packet containing one query record"
         p = self.make_name_packet(dns.DNS_OPCODE_QUERY)
@@ -117,6 +133,24 @@ class DNSTest(TestCase):
         self.assertEquals(response.answers[0].rdata,
                           os.getenv('DC_SERVER_IP'))
 
+    def test_one_a_query_tcp(self):
+        "create a query packet containing one query record via TCP"
+        p = self.make_name_packet(dns.DNS_OPCODE_QUERY)
+        questions = []
+
+        name = "%s.%s" % (os.getenv('DC_SERVER'), self.get_dns_domain())
+        q = self.make_name_question(name, dns.DNS_QTYPE_A, dns.DNS_QCLASS_IN)
+        print "asking for ", q.name
+        questions.append(q)
+
+        self.finish_name_packet(p, questions)
+        response = self.dns_transaction_tcp(p)
+        self.assert_dns_rcode_equals(response, dns.DNS_RCODE_OK)
+        self.assert_dns_opcode_equals(response, dns.DNS_OPCODE_QUERY)
+        self.assertEquals(response.ancount, 1)
+        self.assertEquals(response.answers[0].rdata,
+                          os.getenv('DC_SERVER_IP'))
+
     def test_two_queries(self):
         "create a query packet containing two query records"
         p = self.make_name_packet(dns.DNS_OPCODE_QUERY)