netdev - Re: [PATCH bpf] bpf: correctly set initial window on active Fast Open sender

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Message-ID: <6262C910-E27D-40A8-8462-60F93ED0A4CB@fb.com>
Date:   Wed, 9 Jan 2019 23:06:01 +0000
From:   Lawrence Brakmo <brakmo@...com>
To:     Yuchung Cheng <ycheng@...gle.com>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "ncardwell@...gle.com" <ncardwell@...gle.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>
Subject: Re: [PATCH bpf] bpf: correctly set initial window on active Fast Open
 sender

On 1/8/19, 6:13 PM, "netdev-owner@...r.kernel.org on behalf of Yuchung Cheng" <netdev-owner@...r.kernel.org on behalf of ycheng@...gle.com> wrote:

    The existing BPF TCP initial congestion window (TCP_BPF_IW) does not
    to work on (active) Fast Open sender. This is because it changes the
    (initial) window only if data_segs_out is zero -- but data_segs_out
    is also incremented on SYN-data.  This patch fixes the issue by
    proerly accounting for SYN-data additionally.
    
    Fixes: fc7478103c84 ("bpf: Adds support for setting initial cwnd")
    Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
    Reviewed-by: Neal Cardwell <ncardwell@...gle.com>
    ---
     net/core/filter.c | 2 +-
     1 file changed, 1 insertion(+), 1 deletion(-)
    
    diff --git a/net/core/filter.c b/net/core/filter.c
    index 447dd1bad31f..2b3b436ef545 100644
    --- a/net/core/filter.c
    +++ b/net/core/filter.c
    @@ -4203,7 +4203,7 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
     			/* Only some options are supported */
     			switch (optname) {
     			case TCP_BPF_IW:
    -				if (val <= 0 || tp->data_segs_out > 0)
    +				if (val <= 0 || tp->data_segs_out > tp->syn_data)
     					ret = -EINVAL;
     				else
     					tp->snd_cwnd = val;
    -- 
    2.20.1.97.g81188d93c3-goog
    
Looks good to me. 

Acked-by: Lawrence Brakmo <brakmo@...com>