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Fix fast path for uni directional transfers

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pure ACK case:

drag snd_wl2 along so only newer
ACKs can update the window size.
also avoids the state where snd_wl2
is eventually larger than th_ack and thus
blocking the window update mechanism and
the connection gets stuck for a loooong
time in the zero sized send window state.

see PR/kern 55567

ok thorpej@, also found in FreeBSD
This commit is contained in:
kardel 2020-09-02 15:08:46 +00:00
parent 9f4a03f995
commit eff3797159
1 changed files with 15 additions and 2 deletions
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17
sys/netinet/tcp_input.c
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@ -1,4 +1,4 @@
/* $NetBSD: tcp_input.c,v 1.418 2020/07/06 18:49:12 christos Exp $ */
/* $NetBSD: tcp_input.c,v 1.419 2020/09/02 15:08:46 kardel Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@ -148,7 +148,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.418 2020/07/06 18:49:12 christos Exp $");
__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.419 2020/09/02 15:08:46 kardel Exp $");
#ifdef _KERNEL_OPT
#include "opt_inet.h"
@ -1897,6 +1897,19 @@ after_listen:
tp->snd_fack = tp->snd_una;
if (SEQ_LT(tp->snd_high, tp->snd_una))
tp->snd_high = tp->snd_una;
/*
* drag snd_wl2 along so only newer
* ACKs can update the window size.
* also avoids the state where snd_wl2
* is eventually larger than th_ack and thus
* blocking the window update mechanism and
* the connection gets stuck for a loooong
* time in the zero sized send window state.
*
* see PR/kern 55567
*/
tp->snd_wl2 = tp->snd_una;
m_freem(m);
/*