Public bug reported:
Using IPVS with One-Packet Scheduling on UDP causes CPU soft lockup on
traffic.
Steps to reproduce:
1. Install ipvsadm and netcat-openbsd
2. Execute `ipvsadm -a -u 127.0.0.1:1234 -s rr --ops && ipvsadm -A -u
127.0.0.1:1234 -r 127.0.0.1:1235 -m -w 1`
3. Execute `nc -l -k -u 1235` to actually have a listening service
4. In another terminal, generate traffic `while sleep 0.01; do date | nc -u -w
0 127.0.0.1 1234; done`
In only takes several packets (around 100 in my tests) to cause the soft
lockup to appear. Even with lower packet rates (sleep 1 for example),
the bug occurs.
This problem is already fixed in the current 4.20 vanilla kernel but is
present in the 4.15 vanilla kernel (tested packages from the kernel-
ppa). So basically, this would be a backport.
Ubuntu release: Ubuntu 18.04.1 LTS
Kernel version: Ubuntu 4.15.0-43.46-generic 4.15.18
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "version.log"
https://bugs.launchpad.net/bugs/1811226/+attachment/5228243/+files/version.log
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https://bugs.launchpad.net/bugs/1811226
Title:
ipvsadm --ops causes CPU soft lockup on traffic
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