From f577111302677e6d1448475821cc19ba8835f60e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@helsinki.fi>
Date: Thu, 15 Nov 2007 19:35:11 -0800
Subject: [TCP]: Extend reordering detection to cover CA_Loss partially
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This implements more accurately what is stated in sacktag's
overall comment:

  "Both of these heuristics are not used in Loss state, when
   we cannot account for retransmits accurately."

When CA_Loss state is entered, the state changer ensures that
undo_marker is only set if no TCPCB_RETRANS skbs were found,
thus having non-zero undo_marker in CA_Loss basically tells
that the R-bits still accurately reflect the current state
of TCP.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/ipv4/tcp_input.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 901240f40688..26713e5d89db 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1511,7 +1511,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 
 	tcp_verify_left_out(tp);
 
-	if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss &&
+	if ((reord < tp->fackets_out) &&
+	    ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&
 	    (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
 		tcp_update_reordering(sk, tp->fackets_out - reord, 0);
 
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