netdev - Re: [PATCH] tcp: Use BPF timeout setting for SYN ACK RTO

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Date:   Fri, 29 Oct 2021 19:29:55 +0300
From:   Akhmat Karakotov <hmukos@...dex-team.ru>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Alexander Azimov <mitradir@...dex-team.ru>, zeil@...dex-team.ru,
        Lawrence Brakmo <brakmo@...com>, netdev@...r.kernel.org,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH] tcp: Use BPF timeout setting for SYN ACK RTO

Excuse me for lots of duplicate messages. I couldn't get default client
to consistently send plain text messages and delivery system kept rejecting
them. I forgot to remove everyone from cc when tried again.

> On Oct 29, 2021, at 19:19, Akhmat Karakotov <hmukos@...dex-team.ru> wrote:
> 
> 
>> On Oct 25, 2021, at 23:48, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> 
>> Also, have you checked if TCP syn cookies would still work
>> if tcp_timeout_init() returns a small value like 5ms ?
>> 
>> tcp_check_req()
>> ...
>> tmp_opt.ts_recent_stamp = ktime_get_seconds() - ((tcp_timeout_init((struct sock *)req)/HZ)<<req->num_timeout);
>> 
>> -> tmp_opt.ts_recent_stamp = ktime_get_seconds()
>> 
>> 
> 
> I may have overlooked this. As long as I remember TCP SYN cookies worked
> but I will recheck this place again. Also could you please tell in what way exactly
> does this relate to syn cookies? I may have misunderstood what the code does.