netdev - Re: [PATCH net 1/2] udp: Copy has_conns in reuseport

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Date:   Tue, 21 Jul 2020 08:25:04 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.co.jp>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Craig Gallek <kraig@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Network Development <netdev@...r.kernel.org>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        Benjamin Herrenschmidt <benh@...zon.com>,
        osa-contribution-log@...zon.com
Subject: Re: [PATCH net 1/2] udp: Copy has_conns in reuseport_grow().

On Tue, Jul 21, 2020 at 2:16 AM Kuniyuki Iwashima <kuniyu@...zon.co.jp> wrote:
>
> If an unconnected socket in a UDP reuseport group connect()s, has_conns is
> set to 1. Then, when a packet is received, udp[46]_lib_lookup2() scans all
> sockets in udp_hslot looking for the connected socket with the highest
> score.
>
> However, when the number of sockets bound to the port exceeds max_socks,
> reuseport_grow() resets has_conns to 0. It can cause udp[46]_lib_lookup2()
> to return without scanning all sockets, resulting in that packets sent to
> connected sockets may be distributed to unconnected sockets.
>
> Therefore, reuseport_grow() should copy has_conns.
>
> Fixes: acdcecc61285 ("udp: correct reuseport selection with connected sockets")
> CC: Willem de Bruijn <willemb@...gle.com>
> Reviewed-by: Benjamin Herrenschmidt <benh@...zon.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>

Acked-by: Willem de Bruijn <willemb@...gle.com>

Thanks. Yes, I missed this resize operation when adding the field.