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From:   Eric Dumazet <edumazet@google.com>
Date:   Fri, 20 Oct 2023 08:06:05 +0200
Message-ID: <CANn89iKU6-htPJh3YwvDEDhnVtkXgPOE+2rvzWCbKCpU25kbDw@mail.gmail.com>
Subject: Re: [PATCH v3 net-next 1/3] ipv6: remove dst_allfrag test on ipv6 output
To:     Yan Zhai <yan@cloudflare.com>
Cc:     netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
        David Ahern <dsahern@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, Aya Levin <ayal@nvidia.com>,
        Tariq Toukan <tariqt@nvidia.com>, linux-kernel@vger.kernel.org,
        kernel-team@cloudflare.com, Florian Westphal <fw@strlen.de>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Alexander H Duyck <alexander.duyck@gmail.com>
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On Fri, Oct 20, 2023 at 7:32=E2=80=AFAM Yan Zhai <yan@cloudflare.com> wrote=
:
>
> dst_allfrag was added before the first git commit:
>
> https://www.mail-archive.com/bk-commits-head@vger.kernel.org/msg03399.htm=
l
>
> The feature would send packets to the fragmentation path if a box
> receives a PMTU value with less than 1280 byte. However, since commit
> 9d289715eb5c ("ipv6: stop sending PTB packets for MTU < 1280"), such
> message would be simply discarded. The feature flag is neither supported
> in iproute2 utility. In theory one can still manipulate it with direct
> netlink message, but it is not ideal because it was based on obsoleted
> guidance of RFC-2460 (replaced by RFC-8200).
>
> The feature test would always return false at the moment, so remove it
> from the output path.

What about other callers of dst_allfrag() ?

This feature seems broken atm.