[DCCP]: Initial feature negotiation implementation

Still needs more work, but boots and doesn't crashes, even
does some negotiation!

18:38:52.174934  127.0.0.1.43458 > 127.0.0.1.5001: request <change_l ack_ratio 2, change_r ccid 2, change_l ccid 2>
18:38:52.218526  127.0.0.1.5001 > 127.0.0.1.43458: response <nop, nop, change_l ack_ratio 2, confirm_r ccid 2 2, confirm_l ccid 2 2, confirm_r ack_ratio 2>
18:38:52.185398  127.0.0.1.43458 > 127.0.0.1.5001: <nop, confirm_r ack_ratio 2, ack_vector0 0x00, elapsed_time 212>

:-)

Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index aa34b576e228..d7c786608ec6 100644
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -141,6 +141,17 @@ static void dccp_retransmit_timer(struct sock *sk)
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
 
+        /* retransmit timer is used for feature negotiation throughout
+         * connection.  In this case, no packet is re-transmitted, but rather an
+         * ack is generated and pending changes are splaced into its options.
+         */
+        if (sk->sk_send_head == NULL) {
+                dccp_pr_debug("feat negotiation retransmit timeout %p\n", sk);
+                if (sk->sk_state == DCCP_OPEN)
+                        dccp_send_ack(sk);
+                goto backoff;
+        }
+
         /*
          * sk->sk_send_head has to have one skb with
          * DCCP_SKB_CB(skb)->dccpd_type set to one of the retransmittable DCCP
@@ -177,6 +188,7 @@ static void dccp_retransmit_timer(struct sock *sk)
                 goto out;
         }
 
+backoff:
         icsk->icsk_backoff++;
         icsk->icsk_retransmits++;