[PATCH] early retransmit
From: Christian Samsel <hidden>
Date: 2009-09-15 11:31:17
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
This patch implements draft-ietf-tcpm-early-rexmt. It prevents a rto by lowering the dupack threshold in case we expect less dupacks then the usual threshold. Signed-off-by: Christian Samsel <redacted> --- net/ipv4/tcp_input.c | 16 ++++++++++++++++ 1 files changed, 16 insertions(+), 0 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index af6d6fa..c0cc4fd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c@@ -2913,6 +2913,7 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag) int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && (tcp_fackets_out(tp) > tp->reordering)); int fast_rexmit = 0, mib_idx; + u32 in_flight; if (WARN_ON(!tp->packets_out && tp->sacked_out)) tp->sacked_out = 0;
@@ -3062,6 +3063,21 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag) if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) tcp_update_scoreboard(sk, fast_rexmit); tcp_cwnd_down(sk, flag); + + + /* draft-ietf-tcpm-early-rexmt: lowers dup ack threshold to prevent rto + * in case we don't expect enough dup ack. if number of outstanding + * packets is less than four and there is either no unsent data ready + * for transmission or the advertised window does not permit new + * segments. + */ + in_flight = tcp_packets_in_flight(tp); + if ( in_flight < 4 && (skb_queue_empty(&sk->sk_write_queue) || + tcp_may_send_now(sk) == 0) ) + tp->reordering = in_flight - 1; + else if (tp->reordering != sysctl_tcp_reordering) + tp->reordering = sysctl_tcp_reordering; + tcp_xmit_retransmit_queue(sk); }
--
1.6.4.1