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From:   Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date:   Wed, 22 Jul 2020 11:49:40 -0400
Message-ID: <CA+FuTSdQWKFam0KwCg_REZdhNB6+BOwAHL00eRgrJ2FwPDRjcA@mail.gmail.com>
Subject: Re: linux-next: manual merge of the bpf-next tree with the net tree
To:     Jakub Sitnicki <jakub@cloudflare.com>
Cc:     Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Kuniyuki Iwashima <kuniyu@amazon.co.jp>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        David Miller <davem@davemloft.net>,
        kernel-team <kernel-team@cloudflare.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linux-Next Mailing List <linux-next@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>
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On Wed, Jul 22, 2020 at 11:25 AM Jakub Sitnicki <jakub@cloudflare.com> wrote:
>
> On Wed, Jul 22, 2020 at 05:05 PM CEST, Willem de Bruijn wrote:
> > On Wed, Jul 22, 2020 at 11:02 AM Jakub Sitnicki <jakub@cloudflare.com> wrote:
> >>
> >> On Wed, Jul 22, 2020 at 04:42 PM CEST, Kuniyuki Iwashima wrote:
> >> > Can I submit a patch to net tree that rewrites udp[46]_lib_lookup2() to
> >> > use only 'result' ?
> >>
> >> Feel free. That should make the conflict resolution even easier later
> >> on.
> >
> > Thanks for the detailed analysis, Jakub.
> >
> > Would it be easier to fix this wholly in bpf-next, by introducing
> > reuseport_result there?
>
> Did you mean replicating the Kuniyuki fix in bpf-next, or just
> introducing the intermediate 'reuseport_result' var?
>
> I'm assuming the former, so that the conflict resolving later on will
> reduce to selecting everything from bpf-next side.

Indeed. Since you are already adding a patch to bpf-next to move the
reuseport_has_conns check back. At the same time, it can introduce
reuseport_result:

                if (score > badness) {
                        reuseport_result = lookup_reuseport(net, sk,
skb, saddr, sport, daddr, hnum);
                        if (reuseport_result && !reuseport_has_conns(sk, false))
                                return reuseport_result;

                        result = reuseport_result ? : sk;
                        badness = score;
                }

> TBH, I don't what is the preferred way to handle it. Perhaps DaveM or
> Alexei/Daniel can say what would make their life easiest?

Good point.

With the above, there still remains a merge conflict, of course. But
then we can take bpf-next as is, so I think it would save a separate
patch to net. But not sure whether that helps anything. It does add an
unnecessary variable.