Re: [PATCH net-next] sockopt: Make SO_BINDTODEVICE readable

[Eric Dumazet <eric.dumazet@gmail.com>]

On Fri, 2012-10-19 at 13:55 +0400, Pavel Emelyanov wrote:
> The SO_BINDTODEVICE option is the only SOL_SOCKET one that can be set, but
> cannot be get via sockopt API. The only way we can find the device id a
> socket is bound to is via sock-diag interface. But the diag works only on
> hashed sockets, while the opt in question can be set for yet unhashed one.
> 
> That said, in order to know what device a socket is bound to (we do want
> to know this in checkpoint-restore project) I propose to make this option
> getsockopt-able and report the respective device index.
> 
> Another solution to the problem might be to teach the sock-diag reporting
> info on unhashed sockets. Should I go this way instead?
> 
> Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
> 
> ---
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 8a146cf..c49412c 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1074,6 +1074,9 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
>  	case SO_NOFCS:
>  		v.val = sock_flag(sk, SOCK_NOFCS);
>  		break;
> +	case SO_BINDTODEVICE:
> +		v.val = sk->sk_bound_dev_if;
> +		break;
>  	default:
>  		return -ENOPROTOOPT;
>  	}

This looks quite reasonable to me.

Acked-by: Eric Dumazet <edumazet@google.com>