netdev - Re: [PATCH v1 net] tcp: Don't flag tcp_sk(sk)->rx_opt.saw

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Message-ID: <343d737fde9caa4aba549ed5eaa59c05965da927.camel@redhat.com>
Date: Thu, 04 Jul 2024 12:05:42 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>, "David S. Miller"
	 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	 <kuba@...nel.org>
Cc: David Ahern <dsahern@...nel.org>, Dmitry Safonov <0x7f454c46@...il.com>,
  Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net] tcp: Don't flag tcp_sk(sk)->rx_opt.saw_unknown
 for TCP AO.

On Tue, 2024-07-02 at 20:35 -0700, Kuniyuki Iwashima wrote:
> When we process segments with TCP AO, we don't check it in
> tcp_parse_options().  Thus, opt_rx->saw_unknown is set to 1,
> which unconditionally triggers the BPF TCP option parser.
> 
> Let's avoid the unnecessary BPF invocation.
> 
> Fixes: 0a3a809089eb ("net/tcp: Verify inbound TCP-AO signed segments")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
>  net/ipv4/tcp_input.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index e67cbeeeb95b..77294fd5fd3e 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -4223,6 +4223,13 @@ void tcp_parse_options(const struct net *net,
>  				 * checked (see tcp_v{4,6}_rcv()).
>  				 */
>  				break;
> +#endif
> +#ifdef CONFIG_TCP_AO
> +			case TCPOPT_AO:
> +				/* TCP AO has already been checked
> +				 * (see tcp_inbound_ao_hash()).
> +				 */
> +				break;
>  #endif
>  			case TCPOPT_FASTOPEN:
>  				tcp_parse_fastopen_option(

[not strictly related to this patch] possibly even MPTCP could benefit
from a similar change, but I'm unsure if we want to add even more cases
to this statement.

Cheers,

Paolo