Re: [PATCH bpf-next v2 1/4] net: add SO_NETNS_COOKIE socket option

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

On 2/19/21 10:51 AM, Lorenz Bauer wrote:
> We need to distinguish which network namespace a socket belongs to.
> BPF has the useful bpf_get_netns_cookie helper for this, but accessing
> it from user space isn't possible. Add a read-only socket option that
> returns the netns cookie, similar to SO_COOKIE. If network namespaces
> are disabled, SO_NETNS_COOKIE returns the cookie of init_net.
> 
> Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
> ---


> diff --git a/net/core/sock.c b/net/core/sock.c
> index 0ed98f20448a..de4644aeb58d 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1614,6 +1614,17 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
>  		v.val = sk->sk_bound_dev_if;
>  		break;
>  
> +	case SO_NETNS_COOKIE:
> +		lv = sizeof(u64);
> +		if (len < lv)
> +			return -EINVAL;

	if (len != lv)
		return -EINVAL;

(There is no reason to support bigger value before at least hundred years)

> +#ifdef CONFIG_NET_NS
> +		v.val64 = sock_net(sk)->net_cookie;
> +#else
> +		v.val64 = init_net.net_cookie;
> +#endif
> +		break;
> +

Why using this ugly #ifdef ?

The following should work just fine, even if CONFIG_NET_NS is not set.

v.val64 = sock_net(sk)->net_cookie;


	

>  	default:
>  		/* We implement the SO_SNDLOWAT etc to not be settable
>  		 * (1003.1g 7).
>