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

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Message-Id: <2A707577-CBEA-42C9-A234-2C2AB7E7F7BB@yandex-team.ru>
Date:   Fri, 29 Oct 2021 19:19:42 +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


> 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.