udp_diag: Fix socket skipping within chain

While working on rhashtable walking I noticed that the UDP diag
dumping code is buggy.  In particular, the socket skipping within
a chain never happens, even though we record the number of sockets
that should be skipped.

As this code was supposedly copied from TCP, this patch does what
TCP does and resets num before we walk a chain.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp_diag.c b/net/ipv4/udp_diag.c
index 7927db0..4a000f1 100644
--- a/net/ipv4/udp_diag.c
+++ b/net/ipv4/udp_diag.c
@@ -99,11 +99,13 @@
 	s_slot = cb->args[0];
 	num = s_num = cb->args[1];
 
-	for (slot = s_slot; slot <= table->mask; num = s_num = 0, slot++) {
+	for (slot = s_slot; slot <= table->mask; s_num = 0, slot++) {
 		struct sock *sk;
 		struct hlist_nulls_node *node;
 		struct udp_hslot *hslot = &table->hash[slot];
 
+		num = 0;
+
 		if (hlist_nulls_empty(&hslot->head))
 			continue;