[DCCP]: Introduce tx buffering

This adds transmit buffering to DCCP.

I have tested with CCID2/3 and with loss and rate limiting.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index a5c5475..0a21be4 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -130,7 +130,7 @@
 extern void dccp_send_sync(struct sock *sk, const u64 seq,
 			   const enum dccp_pkt_type pkt_type);
 
-extern int dccp_write_xmit(struct sock *sk, struct sk_buff *skb, long *timeo);
+extern void dccp_write_xmit(struct sock *sk, int block);
 extern void dccp_write_space(struct sock *sk);
 
 extern void dccp_init_xmit_timers(struct sock *sk);