netdev - Re: [PATCH net 2/3] ipv6: Fix tcp socket connection with DSCP.

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Date:   Thu, 9 Feb 2023 08:39:21 -0700
From:   David Ahern <dsahern@...nel.org>
To:     Guillaume Nault <gnault@...hat.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     netdev@...r.kernel.org, YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH net 2/3] ipv6: Fix tcp socket connection with DSCP.

On 2/8/23 10:14 AM, Guillaume Nault wrote:
> Take into account the IPV6_TCLASS socket option (DSCP) in
> tcp_v6_connect(). Otherwise fib6_rule_match() can't properly
> match the DSCP value, resulting in invalid route lookup.
> 
> For example:
> 
>   ip route add unreachable table main 2001:db8::10/124
> 
>   ip route add table 100 2001:db8::10/124 dev eth0
>   ip -6 rule add dsfield 0x04 table 100
> 
>   echo test | socat - TCP6:[2001:db8::11]:54321,ipv6-tclass=0x04
> 
> Without this patch, socat fails at connect() time ("No route to host")
> because the fib-rule doesn't jump to table 100 and the lookup ends up
> being done in the main table.
> 
> Fixes: 2cc67cc731d9 ("[IPV6] ROUTE: Routing by Traffic Class.")
> Signed-off-by: Guillaume Nault <gnault@...hat.com>
> ---
>  net/ipv6/tcp_ipv6.c | 1 +
>  1 file changed, 1 insertion(+)
> 

Reviewed-by: David Ahern <dsahern@...nel.org>