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[TCP] FRTO: Ignore some uninteresting ACKs 

Handles RFC4138 shortcoming (in step 2); it should also have case
c) which ignores ACKs that are not duplicates nor advance window
(opposite dir data, winupdate).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Järvinen 2007-02-21 23:04:11 -08:00 committed by David S. Miller
parent 7b0eb22b1d
commit 6408d206c7
1 changed files with 10 additions and 3 deletions
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13
net/ipv4/tcp_input.c
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@ -2495,9 +2495,9 @@ static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
/* F-RTO spurious RTO detection algorithm (RFC4138)
*
* F-RTO affects during two new ACKs following RTO. State (ACK number) is kept
* in frto_counter. When ACK advances window (but not to or beyond highest
* sequence sent before RTO):
* F-RTO affects during two new ACKs following RTO (well, almost, see inline
* comments). State (ACK number) is kept in frto_counter. When ACK advances
* window (but not to or beyond highest sequence sent before RTO):
* On First ACK, send two new segments out.
* On Second ACK, RTO was likely spurious. Do spurious response (response
* algorithm is not part of the F-RTO detection algorithm
@ -2527,6 +2527,13 @@ static void tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag)
if (flag&FLAG_DATA_ACKED)
inet_csk(sk)->icsk_retransmits = 0;
/* RFC4138 shortcoming in step 2; should also have case c): ACK isn't
* duplicate nor advances window, e.g., opposite dir data, winupdate
*/
if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) &&
!(flag&FLAG_FORWARD_PROGRESS))
return;
if (tp->snd_una == prior_snd_una ||
!before(tp->snd_una, tp->frto_highmark)) {
tcp_enter_frto_loss(sk);