[DCCP]: Retrieve packet sequence number for error reporting

This fixes a problem when analysing erroneous packets in dccp_v{4,6}_err:
* dccp_hdr_seq currently takes an skb
* however, the transport headers in the skb are shifted, due to the
  preceding IPv4/v6 header.
Fixed for v4 and v6 by changing dccp_hdr_seq to take a struct dccp_hdr as
argument. Verified that the correct sequence number is now reported in the
error handler.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index bbadd66..62428ff 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -173,7 +173,7 @@
 
 	icmpv6_err_convert(type, code, &err);
 
-	seq = DCCP_SKB_CB(skb)->dccpd_seq;
+	seq = dccp_hdr_seq(dh);
 	/* Might be for an request_sock */
 	switch (sk->sk_state) {
 		struct request_sock *req, **prev;
@@ -787,7 +787,7 @@
 
 	dh = dccp_hdr(skb);
 
-	DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(skb);
+	DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 	DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 
 	if (dccp_packet_without_ack(skb))