linux-kernel - Re: [PATCH] mptcp: Align mptcp_inet6

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Message-ID: <32460611-f05e-43ea-a57c-494a29d85bb3@kernel.org>
Date: Fri, 2 May 2025 19:00:15 +0200
From: Matthieu Baerts <matttbe@...nel.org>
To: Pedro Falcato <pfalcato@...e.de>, Mat Martineau <martineau@...nel.org>,
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
 mptcp@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mptcp: Align mptcp_inet6_sk with other protocols

Hi Pedro,

On 30/04/2025 17:45, Pedro Falcato wrote:
> Ever since commit f5f80e32de12 ("ipv6: remove hard coded limitation on
> ipv6_pinfo") that protocols stopped using the old "obj_size -
> sizeof(struct ipv6_pinfo)" way of grabbing ipv6_pinfo, that severely
> restricted struct layout and caused fun, hard to see issues.
> 
> However, mptcp_inet6_sk wasn't fixed (unlike tcp_inet6_sk). Do so.
> The non-cloned sockets already do the right thing using
> ipv6_pinfo_offset + the generic IPv6 code.
> 
> Signed-off-by: Pedro Falcato <pfalcato@...e.de>
> ---
>  net/mptcp/protocol.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 26ffa06c21e8..c4fd558307f2 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -3142,9 +3142,9 @@ static int mptcp_disconnect(struct sock *sk, int flags)
>  #if IS_ENABLED(CONFIG_MPTCP_IPV6)
>  static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)
>  {
> -	unsigned int offset = sizeof(struct mptcp6_sock) - sizeof(struct ipv6_pinfo);
> +	struct mptcp6_sock *msk6 = container_of(mptcp_sk(sk), struct mptcp6_sock, msk);
>  
> -	return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
> +	return &msk6->np;

Thank you for suggesting this! Good idea, that's clearer!

Reviewed-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>

@Netdev maintainers: this can be applied in net-next directly.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.