netdev - Re: [PATCH] net: inet_diag: always export IPV6

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Date:	Thu, 09 Jul 2015 14:57:57 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Phil Sutter <phil@....cc>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH] net: inet_diag: always export IPV6_V6ONLY sockopt

On Thu, 2015-07-09 at 10:42 +0200, Phil Sutter wrote:
> Reconsidering my commit 20462155 "net: inet_diag: export IPV6_V6ONLY
> sockopt", I am not happy with the limitations it causes for socket
> analysing code in userspace. Exporting the value only if it is set makes
> it hard for userspace to decide whether the option is not set or the
> kernel does not support exporting the option at all.
> 
> From an auditor's perspective, the interesting question for AF_INET6
> sockets is: "Does it NOT have IPV6_V6ONLY set?" Because it is the
> unexpected case. This patch allows to answer this question reliably.
> 
> Signed-off-by: Phil Sutter <phil@....cc>
> Cc: Eric Dumazet <edumazet@...gle.com>
> ---
>  net/ipv4/inet_diag.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
> index 9bc2667..e622d2e 100644
> --- a/net/ipv4/inet_diag.c
> +++ b/net/ipv4/inet_diag.c
> @@ -152,8 +152,7 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
>  				       inet6_sk(sk)->tclass) < 0)
>  				goto errout;
>  
> -		if (ipv6_only_sock(sk) &&
> -		    nla_put_u8(skb, INET_DIAG_SKV6ONLY, 1))
> +		if (nla_put_u8(skb, INET_DIAG_SKV6ONLY, ipv6_only_sock(sk)))
>  			goto errout;
>  	}
>  #endif

Okay, I guess you don't dump millions of sockets.

Can you remind me why this attribute is useful for non listening
sockets ?

It looks you are interested to know if a _listener_ is v6 only or not.




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