netdev - Re: [RFC net-next 11/14] tun: run XDP program in tx path

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Message-ID: <c1088bff-e86c-a3c7-6132-eeee23b80a75@gmail.com>
Date:   Wed, 18 Dec 2019 09:29:31 -0700
From:   David Ahern <dsahern@...il.com>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>,
        Prashant Bhole <prashantbhole.linux@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Jason Wang <jasowang@...hat.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        John Fastabend <john.fastabend@...il.com>,
        Toshiaki Makita <toshiaki.makita1@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>, netdev@...r.kernel.org,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>
Subject: Re: [RFC net-next 11/14] tun: run XDP program in tx path

On 12/18/19 3:07 AM, Jesper Dangaard Brouer wrote:
> 
> You have not configured xdp.rxq, thus a BPF-prog accessing this will crash.

yes, I had a note in my early patch about this. The current XDP context
is definitely Rx focused.

> 
> For an XDP TX hook, I want us to provide/give BPF-prog access to some
> more information about e.g. the current tx-queue length, or TC-q number.
> 
> Question to Daniel or Alexei, can we do this and still keep BPF_PROG_TYPE_XDP?
> Or is it better to introduce a new BPF prog type (enum bpf_prog_type)
> for XDP TX-hook ?
> 

That is one of the design questions: can the Tx path re-use the existing
uapi for XDP or do we need to create a new one.