netdev - Re: [PATCH net] tcp: md5: fix IPv4-mapped support

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Message-ID: <b2d5dc2b-c525-44b4-48cf-7d56add05a14@arista.com>
Date:   Tue, 26 Jul 2022 18:13:34 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Brian Vazquez <brianvv@...gle.com>,
        David Ahern <dsahern@...nel.org>,
        Leonard Crestez <cdleonard@...il.com>
Subject: Re: [PATCH net] tcp: md5: fix IPv4-mapped support

On 7/26/22 12:57, Eric Dumazet wrote:
> After the blamed commit, IPv4 SYN packets handled
> by a dual stack IPv6 socket are dropped, even if
> perfectly valid.
> 
> $ nstat | grep MD5
> TcpExtTCPMD5Failure             5                  0.0
> 
> For a dual stack listener, an incoming IPv4 SYN packet
> would call tcp_inbound_md5_hash() with @family == AF_INET,
> while tp->af_specific is pointing to tcp_sock_ipv6_specific.
> 
> Only later when an IPv4-mapped child is created, tp->af_specific
> is changed to tcp_sock_ipv6_mapped_specific.

Makes sense. Sorry, I didn't spot it at that moment.

> 
> Fixes: 7bbb765b7349 ("net/tcp: Merge TCP-MD5 inbound callbacks")
> Reported-by: Brian Vazquez <brianvv@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Dmitry Safonov <dima@...sta.com>
> Cc: David Ahern <dsahern@...nel.org>
> Cc: Leonard Crestez <cdleonard@...il.com>

Reviewed-by: Dmitry Safonov <dima@...sta.com>

Thanks,
           Dmitry