netdev - Re: [PATCH net-next] tcp: Make SYN ACK RTO tunable by BPF programs with TFO

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Date:   Tue, 16 Aug 2022 09:59:33 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Jie Meng <jmeng@...com>
Cc:     netdev@...r.kernel.org, kuba@...nel.org, edumazet@...gle.com,
        bpf@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: Make SYN ACK RTO tunable by BPF programs
 with TFO

On Mon, Aug 15, 2022 at 01:29:00PM -0700, Jie Meng wrote:
> Instead of the hardcoded TCP_TIMEOUT_INIT, this diff calls tcp_timeout_init
> to initiate req->timeout like the non TFO SYN ACK case.
> 
> Tested using the following packetdrill script, on a host with a BPF
> program that sets the initial connect timeout to 10ms.
> 
> `../../common/defaults.sh`
> 
> // Initialize connection
>     0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
>    +0 setsockopt(3, SOL_TCP, TCP_FASTOPEN, [1], 4) = 0
>    +0 bind(3, ..., ...) = 0
>    +0 listen(3, 1) = 0
> 
>    +0 < S 0:0(0) win 32792 <mss 1000,sackOK,FO TFO_COOKIE>
>    +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK>
>    +.01 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK>
>    +.02 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK>
>    +.04 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK>
>    +.01 < . 1:1(0) ack 1 win 32792
> 
>    +0 accept(3, ..., ...) = 4
Acked-by: Martin KaFai Lau <kafai@...com>