MIME-Version: 1.0
References: <20220111192952.49040-1-ivan@cloudflare.com>
In-Reply-To: <20220111192952.49040-1-ivan@cloudflare.com>
From:   Song Liu <song@kernel.org>
Date:   Tue, 11 Jan 2022 13:47:49 -0800
Message-ID: <CAPhsuW5ynK+XZkUm2jDE2LcpMbqPcQJDJHmFyU_WbBQyBKN38g@mail.gmail.com>
Subject: Re: [PATCH bpf-next] tcp: bpf: Add TCP_BPF_RCV_SSTHRESH for bpf_setsockopt
To:     Ivan Babrou <ivan@cloudflare.com>
Cc:     bpf <bpf@vger.kernel.org>, Networking <netdev@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        kernel-team@cloudflare.com, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Eric Dumazet <edumazet@google.com>
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On Tue, Jan 11, 2022 at 11:29 AM Ivan Babrou <ivan@cloudflare.com> wrote:
>
> This patch adds bpf_setsockopt(TCP_BPF_RCV_SSTHRESH) to allow setting
> rcv_ssthresh value for TCP connections. Combined with increased
> window_clamp via tcp_rmem[1], it allows to advertise initial scaled
> TCP window larger than 64k. This is useful for high BDP connections,
> where it allows to push data with fewer roundtrips, reducing latency.
>
> For active connections the larger window is advertised in the first
> non-SYN ACK packet as the part of the 3 way handshake.
>
> For passive connections the larger window is advertised whenever
> there's any packet to send after the 3 way handshake.
>
> See: https://lkml.org/lkml/2021/12/22/652

I guess this is [1] mentioned above. Please use lore link instead, e.g.

[1] https://lore.kernel.org/all/CABWYdi0qBQ57OHt4ZbRxMtdSzhubzkPaPKkYzdNfu4+cgPyXCA@mail.gmail.com/

Can we add a selftests for this? Something similar to

tools/testing/selftests/bpf/progs/test_misc_tcp_hdr_options.c

Thanks,
Song

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