netdev - Re: [PATCH v2 net 3/6] tcp: Fix bind() regression for v4-mapped-v6 non-wildcard address.

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Date: Tue, 12 Sep 2023 06:59:24 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>, 
	Joanne Koong <joannelkoong@...il.com>, Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net 3/6] tcp: Fix bind() regression for v4-mapped-v6
 non-wildcard address.

On Mon, Sep 11, 2023 at 8:38 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> Since bhash2 was introduced, the example below does not work as expected.
> These two bind() should conflict, but the 2nd bind() now succeeds.
>
>   from socket import *
>
>   s1 = socket(AF_INET6, SOCK_STREAM)
>   s1.bind(('::ffff:127.0.0.1', 0))
>
>   s2 = socket(AF_INET, SOCK_STREAM)
>   s2.bind(('127.0.0.1', s1.getsockname()[1]))
>
> During the 2nd bind() in inet_csk_get_port(), inet_bind2_bucket_find()
> fails to find the 1st socket's tb2, so inet_bind2_bucket_create() allocates
> a new tb2 for the 2nd socket.  Then, we call inet_csk_bind_conflict() that
> checks conflicts in the new tb2 by inet_bhash2_conflict().  However, the
> new tb2 does not include the 1st socket, thus the bind() finally succeeds.
>
> In this case, inet_bind2_bucket_match() must check if AF_INET6 tb2 has
> the conflicting v4-mapped-v6 address so that inet_bind2_bucket_find()
> returns the 1st socket's tb2.
>
> Note that if we bind two sockets to 127.0.0.1 and then ::FFFF:127.0.0.1,
> the 2nd bind() fails properly for the same reason mentinoed in the previous
> commit.
>
> Fixes: 28044fc1d495 ("net: Add a bhash2 table hashed by port and address")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@...gle.com>