added suppport for unexpected udp/138 packets

I also fixed up the lookup_pdc_name() code so that it now works, even
with a NT server that insists on replying to udp/138.

The method I used to match packets was to use the mailslot string as a
datagram ID. The true dgm_id doesn't work as NT doesn't set it
correctly. uggh.

PS: Jeremy, I had to change your code quite a bit, are you sure this
worked with a Samba PDC?? The code looked broken, it got the offsets
wrong in the SMB portion of the packet and filled in the IP
incorrectly.
(This used to be commit 32f66f4ea6)

source3/libsmb/nmblib.c

@@ -979,7 +979,7 @@ struct packet_struct *receive_packet(int fd,enum packet_type type,int t)
   queue. The packet must be a reply packet and have the specified trn_id
   The timeout is in milliseconds
   ***************************************************************************/
-struct packet_struct *receive_reply_packet(int fd, int t, int trn_id)
+struct packet_struct *receive_nmb_packet(int fd, int t, int trn_id)
 {
 	struct packet_struct *p;
 
@@ -992,7 +992,48 @@ struct packet_struct *receive_reply_packet(int fd, int t, int trn_id)
 	if (p) free_packet(p);
 
 	/* try the unexpected packet queue */
-	return receive_unexpected_137(trn_id);
+	return receive_unexpected(NMB_PACKET, trn_id, NULL);
+}
+
+/****************************************************************************
+  receive a UDP/138 packet either via UDP or from the unexpected packet
+  queue. The packet must be a reply packet and have the specified dgm_id
+  The timeout is in milliseconds
+  ***************************************************************************/
+struct packet_struct *receive_dgram_packet(int fd, int t, char *mailslot_name)
+{
+	struct packet_struct *p;
+
+	p = receive_packet(fd, DGRAM_PACKET, t);
+
+	if (p && match_mailslot_name(p, mailslot_name)) {
+		return p;
+	}
+	if (p) free_packet(p);
+
+	/* try the unexpected packet queue */
+	return receive_unexpected(DGRAM_PACKET, 0, mailslot_name);
+}
+
+
+/****************************************************************************
+ see if a datagram has the right mailslot name
+***************************************************************************/
+BOOL match_mailslot_name(struct packet_struct *p, char *mailslot_name)
+{
+	struct dgram_packet *dgram = &p->packet.dgram;
+	char *buf;
+
+	buf = &dgram->data[0];
+	buf -= 4;
+
+	buf = smb_buf(buf);
+
+	if (memcmp(buf, mailslot_name, strlen(mailslot_name)+1) == 0) {
+		return True;
+	}
+
+	return False;
 }