netdev - Re: [PATCH bpf-next v2 1/4] net: add SO_NETNS

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Message-ID: <00f63863-34ae-aa25-6a36-376db62de510@gmail.com>
Date:   Fri, 19 Feb 2021 12:49:30 +0100
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Lorenz Bauer <lmb@...udflare.com>, daniel@...earbox.net,
        ast@...nel.org, andrii@...nel.org
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        kernel-team@...udflare.com
Subject: Re: [PATCH bpf-next v2 1/4] net: add SO_NETNS_COOKIE socket option



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@...udflare.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).
>