Re: [RFC mptcp-next] selftests: mptcp: Add a test for self-conn fallback

[Matthieu Baerts <matttbe@kernel.org>]

Hi Gang,

On 14/08/2025 10:57, GangYan wrote:
>> On Thu, Aug 14, 2025 at 08:51:13AM +0000, MPTCP CI wrote:
> Hi Matt,
> 
> I noticed the 'MPTCP_MIB_SIMULTCONNFALLBACK' is not coverd by selftests
> through 'code_coverage'. So, I add a test according to issue#35, and I
> would like to seek your advice on the following points:
> 
> -Is it suitable to add a test like this patch to cover this part of code?
> -If yes, please give me some feedback on modification suggestions about
> this patch.

Good idea to cover this.

My fear is that this test might be unstable, no?

Is it not easier to reproduce this with Packetdrill test? e.g.

> `../common/defaults.sh`
> 
>  0 socket(..., SOCK_STREAM|SOCK_NONBLOCK, IPPROTO_MPTCP) = 3
> +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
> 
> +0 > S  0:0(0)                 <mss 1460, sackOK, TS val 100 ecr 0,   nop, wscale 8, mpcapable v1 flags[flag_h] nokey>
> +0 < S  0:0(0) win 1000        <mss 1460, sackOK, TS val 407 ecr 0,   nop, wscale 8, mpcapable v1 flags[flag_h] nokey>
> +0 > S. 0:0(0) ack 1           <mss 1460, sackOK, TS val 330 ecr 0,   nop, wscale 8, mpcapable v1 flags[flag_h] nokey>
> +0 < S. 0:0(0) ack 1 win 65535 <mss 1460, sackOK, TS val 700 ecr 100, nop, wscale 8, mpcapable v1 flags[flag_h] key[skey=2]>
> +0 >  . 1:1(0)     ack 1 <nop, nop, TS val 845707014 ecr 700, nop, nop, sack 0:1>
Then check the MIB counter.

(Note: I didn't check, the alignment is not OK, just wrote it very quickly)

Cheers,
Matt
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