netdev - Re: [PATCH bpf-next v7 1/3] bpf: Add "live packet" mode for XDP in bpf_prog

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Message-ID: <87czjt8k78.fsf@toke.dk>
Date:   Fri, 11 Feb 2022 17:03:07 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v7 1/3] bpf: Add "live packet" mode for XDP in
 bpf_prog_run()

Martin KaFai Lau <kafai@...com> writes:

> On Wed, Jan 12, 2022 at 05:37:54PM -0800, Alexei Starovoitov wrote:
>> On Sun, Jan 9, 2022 at 4:30 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>> >
>> > I left that out on purpose: I feel it's exposing an internal
>> > implementation detail as UAPI (as you said). And I'm not convinced it
>> > really needed (or helpful) - see below.
>> 
>> It's irrelevant whether it's documented or not.
>> Once this implementation detail is being relied upon
>> by user space it becomes an undocumented uapi that we cannot change.
>> 
>> > I'll try implementing a TCP stream mode in xdp_trafficgen just to make
>> > sure I'm not missing something. But I believe that sending out a stream
>> > of packets that looks like a coherent TCP stream should be simple
>> > enough, at least. Dealing with the full handshake + CWND control loop
>> > will be harder, though, and right now I think it'll require multiple
>> > trips back to userspace.
>> 
>> The patch set looks very close to being able to do such TCP streaming.
>> Let's make sure nothing is missing from API before we land it.
> Hi Toke,  I am also looking at ways to blast tcp packets by using
> bpf to overcome the pktgen udp-only limitation.
> Are you planning to respin with a TCP stream mode in xdp_trafficgen ?
> Thanks !

Yes, working on it! Got sidetracked a bit, but hoping to have something
to show for my efforts sometime next week :)

-Toke