[CCID3]: Call sk->sk_write_space(sk) when receiving a feedback packet

This makes the send rate calculations behave way more closely to what
is specified, with the jitter previously seen on x and x_recv
disappearing completely on non lossy setups.

This resembles the tcp_data_snd_check code, that possibly we'll end up
using in DCCP as well, perhaps moving this code to
inet_connection_sock.

For now I'm doing the simplest implementation tho.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 3cf2cbc..3fc75db 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -1280,6 +1280,7 @@
 	dccp_init_xmit_timers(sk);
 	inet_csk(sk)->icsk_rto = DCCP_TIMEOUT_INIT;
 	sk->sk_state = DCCP_CLOSED;
+	sk->sk_write_space = dccp_write_space;
 	dp->dccps_mss_cache = 536;
 	dp->dccps_role = DCCP_ROLE_UNDEFINED;