path: root/net/ipv4/tcp_timer.c
diff options
authorNandita Dukkipati <nanditad@google.com>2013-03-11 10:00:44 +0000
committerDavid S. Miller <davem@davemloft.net>2013-03-12 08:30:34 -0400
commit9b717a8d245075ffb8e95a2dfb4ee97ce4747457 (patch)
tree08e1ee37c89b11e4c08734c671a2427edb942944 /net/ipv4/tcp_timer.c
parenttcp: Tail loss probe (TLP) (diff)
tcp: TLP loss detection.
This is the second of the TLP patch series; it augments the basic TLP algorithm with a loss detection scheme. This patch implements a mechanism for loss detection when a Tail loss probe retransmission plugs a hole thereby masking packet loss from the sender. The loss detection algorithm relies on counting TLP dupacks as outlined in Sec. 3 of: http://tools.ietf.org/html/draft-dukkipati-tcpm-tcp-loss-probe-01 The basic idea is: Sender keeps track of TLP "episode" upon retransmission of a TLP packet. An episode ends when the sender receives an ACK above the SND.NXT (tracked by tlp_high_seq) at the time of the episode. We want to make sure that before the episode ends the sender receives a "TLP dupack", indicating that the TLP retransmission was unnecessary, so there was no loss/hole that needed plugging. If the sender gets no TLP dupack before the end of the episode, then it reduces ssthresh and the congestion window, because the TLP packet arriving at the receiver probably plugged a hole. Signed-off-by: Nandita Dukkipati <nanditad@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to '')
1 files changed, 2 insertions, 0 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index ecd61d54147f..eeccf795e917 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -356,6 +356,8 @@ void tcp_retransmit_timer(struct sock *sk)
+ tp->tlp_high_seq = 0;
if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
!((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
/* Receiver dastardly shrinks window. Our retransmits