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Yuchung Cheng 0eb96bf754 tcp: fix tcp_fastretrans_alert warning
This patch fixes the cause of an WARNING indicatng TCP has pending
retransmission in Open state in tcp_fastretrans_alert().

The root cause is a bad interaction between path mtu probing,
if enabled, and the RACK loss detection. Upong receiving a SACK
above the sequence of the MTU probing packet, RACK could mark the
probe packet lost in tcp_fastretrans_alert(), prior to calling
tcp_simple_retransmit().

tcp_simple_retransmit() only enters Loss state if it newly marks
the probe packet lost. If the probe packet is already identified as
lost by RACK, the sender remains in Open state with some packets
marked lost and retransmitted. Then the next SACK would trigger
the warning. The likely scenario is that the probe packet was
lost due to its size or network congestion. The actual impact of
this warning is small by potentially entering fast recovery an
ACK later.

The simple fix is always entering recovery (Loss) state if some
packet is marked lost during path MTU probing.

Fixes: a0370b3f3f ("tcp: enable RACK loss detection to trigger recovery")
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Reported-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-11-10 18:09:19 +09:00
arch x86/mm: Unbreak modules that rely on external PAGE_KERNEL availability 2017-11-08 13:52:36 -08:00
block
certs
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-11-06 09:05:03 -08:00
Documentation
drivers Final power management fixes for v4.14 2017-11-09 11:16:28 -08:00
firmware
fs
include sound fixes for 4.14 2017-11-09 09:58:11 -08:00
init
ipc
kernel Final power management fixes for v4.14 2017-11-09 11:16:28 -08:00
lib KEYS: fix NULL pointer dereference during ASN.1 parsing [ver #2] 2017-11-09 00:38:21 +11:00
mm
net tcp: fix tcp_fastretrans_alert warning 2017-11-10 18:09:19 +09:00
samples
scripts scripts: add leaking_addresses.pl 2017-11-06 11:46:42 -08:00
security apparmor: fix off-by-one comparison on MAXMAPPED_SIG 2017-11-08 10:56:22 -08:00
sound sound fixes for 4.14 2017-11-09 09:58:11 -08:00
tools
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MAINTAINERS scripts: add leaking_addresses.pl 2017-11-06 11:46:42 -08:00
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README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
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See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.