netdev - Re: [PATCH bpf-next] xsk: support AF

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Message-ID: <87im33grtt.fsf@toke.dk>
Date:   Fri, 28 May 2021 10:55:58 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Xie He <xie.he.0141@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        John Ogness <john.ogness@...utronix.de>,
        Wang Hai <wanghai38@...wei.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Tanner Love <tannerlove@...gle.com>,
        Eyal Birger <eyal.birger@...il.com>,
        Menglong Dong <dong.menglong@....com.cn>
Subject: Re: [PATCH bpf-next] xsk: support AF_PACKET

Xuan Zhuo <xuanzhuo@...ux.alibaba.com> writes:

> In xsk mode, users cannot use AF_PACKET(tcpdump) to observe the current
> rx/tx data packets. This feature is very important in many cases. So
> this patch allows AF_PACKET to obtain xsk packages.

You can use xdpdump to dump the packets from the XDP program before it
gets redirected into the XSK:
https://github.com/xdp-project/xdp-tools/tree/master/xdp-dump

Doens't currently work on egress, but if/when we get a proper TX hook
that should be doable as well.

Wiring up XSK to AF_PACKET sounds a bit nonsensical: XSK is already a
transport to userspace, why would you need a second one?

-Toke