Re: Hit regression with TCP_TW REUSE/RECYCLE

From: Eric Dumazet
Date: Tue Nov 17 2015 - 07:07:57 EST


On Tue, 2015-11-17 at 14:35 +0800, Ethan Zhao wrote:
> Tested the same case with 4.4-RC1, it was fixed in 4.4-RC1.
> But don't know which commit fixed it.
>
> # echo 1024 65535 > /proc/sys/net/ipv4/ip_local_port_range
> # cat /proc/sys/net/ipv4/ip_local_port_range
> 1024 65535
> # echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse
> # cat /proc/sys/net/ipv4/tcp_tw_reuse
> 1
> # echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle
> # cat /proc/sys/net/ipv4/tcp_tw_reuse
> 1
> # ./accept -n 5 -r &
> [1] 11866
> # port: 7954
> ninst: 5
> reuseport: 1
>
> # ./connect -i 127.0.0.1 -n 5 -d 10
> 78578.50
> # uname -a
> Linux localhost.localdomain 4.4.0-rc1 #49 SMP Tue Nov 17 15:04:18 KST
> 2015 x86_64 x86_64 x86_64 GNU/Linux

Maybe run a reverse bisection ?

tcp_tw_reuse and tcp_tw_recycle both set to one have never been
supported in linux.

tcp_tw_recycle - BOOLEAN
Enable fast recycling TIME-WAIT sockets. Default value is 0.
It should not be changed without advice/request of technical
experts.

tcp_tw_reuse - BOOLEAN
Allow to reuse TIME-WAIT sockets for new connections when it is
safe from protocol viewpoint. Default value is 0.
It should not be changed without advice/request of technical
experts.

Thanks.


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