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Commit 6408d206 authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
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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: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7b0eb22b

net/ipv4/tcp_input.c

+10 −3
Original line number Diff line number Diff line
@@ -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);