netdev - Re: [PATCH bpf-next v3 4/5] bpf: Add helpers to issue and check SYN cookies in XDP

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Message-ID: <CAADnVQL-44zw3MvyuCNm6fn5K6m8hnzYmXWJbBF3aXrLKQFLVQ@mail.gmail.com>
Date:   Fri, 11 Mar 2022 09:30:35 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Maxim Mikityanskiy <maximmi@...dia.com>
Cc:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Martin KaFai Lau <kafai@...com>,
        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>,
        Petar Penkov <ppenkov@...gle.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Joe Stringer <joe@...ium.io>,
        Florent Revest <revest@...omium.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        Toke Høiland-Jørgensen <toke@...e.dk>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Florian Westphal <fw@...len.de>
Subject: Re: [PATCH bpf-next v3 4/5] bpf: Add helpers to issue and check SYN
 cookies in XDP

On Fri, Mar 11, 2022 at 8:36 AM Maxim Mikityanskiy <maximmi@...dia.com> wrote:
>
> > -----Original Message-----
> > From: Alexei Starovoitov <alexei.starovoitov@...il.com>
> > Sent: 27 February, 2022 05:25
> >
> > On Thu, Feb 24, 2022 at 05:11:44PM +0200, Maxim Mikityanskiy wrote:
> > > @@ -7798,6 +7916,14 @@ xdp_func_proto(enum bpf_func_id func_id, const
> > struct bpf_prog *prog)
> > >             return &bpf_tcp_check_syncookie_proto;
> > >     case BPF_FUNC_tcp_gen_syncookie:
> > >             return &bpf_tcp_gen_syncookie_proto;
> > > +   case BPF_FUNC_tcp_raw_gen_syncookie_ipv4:
> > > +           return &bpf_tcp_raw_gen_syncookie_ipv4_proto;
> > > +   case BPF_FUNC_tcp_raw_gen_syncookie_ipv6:
> > > +           return &bpf_tcp_raw_gen_syncookie_ipv6_proto;
> > > +   case BPF_FUNC_tcp_raw_check_syncookie_ipv4:
> > > +           return &bpf_tcp_raw_check_syncookie_ipv4_proto;
> > > +   case BPF_FUNC_tcp_raw_check_syncookie_ipv6:
> > > +           return &bpf_tcp_raw_check_syncookie_ipv6_proto;
> > >  #endif
> >
> > I understand that the main use case for new helpers is XDP specific,
> > but why limit them to XDP?
> > The feature looks generic and applicable to skb too.
>
> That sounds like an extra feature, rather than a limitation. That's out
> of scope of what I planned to do.
>
> Besides, it sounds kind of useless to me, because the intention of the
> new helpers is to accelerate synproxy, and I doubt BPF over SKBs will
> accelerate anything. Maybe someone else has another use case for these
> helpers and SKBs - in that case I leave the opportunity to add this
> feature up to them.

This patchset will not be accepted until the feature is generalized
to both xdp and skb and tested for both.
"I dont have a use case for it" is not an excuse to narrow down the scope.