[DCCP]: Shift the retransmit timer for active-close into output.c

When performing active close, RFC 4340, 8.3. requires to retransmit the
Close/CloseReq with a backoff-retransmit timer starting at intially 2 RTTs.

This patch shifts the existing code for active-close retransmit timer
into output.c, so that the retransmit timer is started when the first
Close/CloseReq is sent. Previously, the timer was started when, after
releasing the socket in dccp_close(), the actively-closing side had not yet
reached the CLOSED/TIMEWAIT state.

The patch further reduces the initial timeout from 3 seconds to the required
2 RTTs, where - in absence of a known RTT - the fallback value specified in
RFC 4340, 3.4 is used.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 1 deletions

diff --git a/net/dccp/output.c b/net/dccp/output.c
index 7caa7f57bb7e..e97584aa4898 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -574,7 +574,18 @@ void dccp_send_close(struct sock *sk, const int active)
                 dccp_write_xmit(sk, 1);
                 dccp_skb_entail(sk, skb);
                 dccp_transmit_skb(sk, skb_clone(skb, prio));
-                /* FIXME do we need a retransmit timer here? */
+                /*
+                 * Retransmission timer for active-close: RFC 4340, 8.3 requires
+                 * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
+                 * state can be left. The initial timeout is 2 RTTs.
+                 * Since RTT measurement is done by the CCIDs, there is no easy
+                 * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
+                 * is too low (200ms); we use a high value to avoid unnecessary
+                 * retransmissions when the link RTT is > 0.2 seconds.
+                 * FIXME: Let main module sample RTTs and use that instead.
+                 */
+                inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+                                          DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
         } else
                 dccp_transmit_skb(sk, skb);
 }