@@ -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);
}
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 <christian.samsel@rwth-aachen.de> --- net/ipv4/tcp_input.c | 16 ++++++++++++++++ 1 files changed, 16 insertions(+), 0 deletions(-)