Re: [PATCH mptcp-next] selftests: mptcp: diag: use mptcp_lib_get_info_value

[Matthieu Baerts <matttbe@kernel.org>]

Hi Geliang,

On 03/04/2025 09:46, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> When running diag.sh in a loop, chk_dump_one will report the following
> "grep: write error":
> 
>  13 ....chk 2 cestab                                  [ OK ]
>  grep: write error
>  14 ....chk dump_one                                  [ OK ]
>  15 ....chk 2->0 msk in use after flush               [ OK ]
>  16 ....chk 2->0 cestab after flush                   [ OK ]
> 
> This error is caused by a broken pipe. When the output of 'ss' is processed
> by grep, 'head -n 1' will exit immediately after getting the first line,
> causing the subsequent pipe to close. At this time, if 'grep' is still
> trying to write data to the closed pipe, it will trigger a SIGPIPE signal,
> causing a write error.
> 
> One solution is not to use this problematic "head -n 1" command, but to use
> mptcp_lib_get_info_value() helper defined in mptcp_lib.sh to get the value
> of 'token'.

I was wondering why this helper would help because there will be 2
connections, and it is still required to limit the output to one. Then I
saw this helper does limit to the first entry because of 'sed (...);q'.

I will modify the message here to explain that. And maybe add a comment
in mptcp_lib.sh as well for later.

Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.