57 lines
2.2 KiB
Diff
57 lines
2.2 KiB
Diff
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From c448ca01367916741662b9e6af54d5d3f189d4fa Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Christoph=20B=C3=B6hmwalder?=
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<christoph.boehmwalder@linbit.com>
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Date: Mon, 25 Mar 2024 15:39:44 +0100
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Subject: [PATCH 1/3] portblock: remove write to tcp_tw_recycle
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Currently, the portblock resource agent enables the
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net.ipv4.tcp_tw_recycle option before sending a tickle ACK packet.
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This option is supposed to recycle TCP sockets that are left in the
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TIME_WAIT state. On the host that initiates the closing of a TCP
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connection, a socket will be left in this state for about 60 seconds
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before it finally gets removed (and freed up for further use). This is
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by design, and it is generally considered useful. [0]
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The tcp_tw_recycle option is supposed to shorten the time that a socket
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spends in the TIME_WAIT state, allowing its slot to be reused more
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quickly.
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Unfortunately, there are no hints left by the previous author about the
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rationale behind setting this option. One can only guess that they
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somehow managed to exhaust the number of TCP sockets during testing, and
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setting this option resolved that immediate issue. It is not entirely
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clear how this would happen in an actual real-world scenario, since it
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would require many switchovers in a relatively short period of time.
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The problem is that this option has been completely broken starting from
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Linux 4.10 (since it started randomizing TCP timestamp offsets), and
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even before that for NAT connections.
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Finally, the option has been completely removed in Linux 4.12, which now
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leads to annoying "No such file or directory" errors whenever the
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portblock agent runs on a semi-modern kernel.
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Thus, remove the line enabling the option.
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[0] https://vincent.bernat.ch/en/blog/2014-tcp-time-wait-state-linux
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---
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heartbeat/portblock | 1 -
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1 file changed, 1 deletion(-)
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diff --git a/heartbeat/portblock b/heartbeat/portblock
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index 7b9f5ca3..e88ecc2a 100755
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--- a/heartbeat/portblock
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+++ b/heartbeat/portblock
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@@ -328,7 +328,6 @@ save_tcp_connections()
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tickle_remote()
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{
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[ -z "$OCF_RESKEY_tickle_dir" ] && return
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- echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle
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f=$OCF_RESKEY_tickle_dir/$OCF_RESKEY_ip
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[ -r $f ] || return
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$TICKLETCP -n 3 < $f
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--
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2.25.1
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