Re: [RFC] net: add new socket option SO_SETNETNS

[Hillf Danton <hdanton@sina.com>]

On Wed, 1 Feb 2023 19:22:57 +0000 aloktiagi <aloktiagi@gmail.com>
> @@ -1535,6 +1535,52 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
>  		WRITE_ONCE(sk->sk_txrehash, (u8)val);
>  		break;
>  
> +	case SO_SETNETNS:
> +	{
> +		struct net *other_ns, *my_ns;
> +
> +		if (sk->sk_family != AF_INET && sk->sk_family != AF_INET6) {
> +			ret = -EOPNOTSUPP;
> +			break;
> +		}
> +
> +		if (sk->sk_type != SOCK_STREAM && sk->sk_type != SOCK_DGRAM) {
> +			ret = -EOPNOTSUPP;
> +			break;
> +		}
> +
> +		other_ns = get_net_ns_by_fd(val);
> +		if (IS_ERR(other_ns)) {
> +			ret = PTR_ERR(other_ns);
> +			break;
> +		}
> +
> +		if (!ns_capable(other_ns->user_ns, CAP_NET_ADMIN)) {
> +			ret = -EPERM;
> +			goto out_err;
> +		}
> +
> +		/* check that the socket has never been connected or recently disconnected */
> +		if (sk->sk_state != TCP_CLOSE || sk->sk_shutdown & SHUTDOWN_MASK) {
> +			ret = -EOPNOTSUPP;
> +			goto out_err;
> +		}
> +
> +		/* check that the socket is not bound to an interface*/
> +		if (sk->sk_bound_dev_if != 0) {
> +			ret = -EOPNOTSUPP;
> +			goto out_err;
> +		}
> +
> +		my_ns = sock_net(sk);
> +		sock_net_set(sk, other_ns);
> +		put_net(my_ns);
> +		break;

		cpu 0				cpu 2
		---				---
						ns = sock_net(sk);
		my_ns = sock_net(sk);
		sock_net_set(sk, other_ns);
		put_net(my_ns);
						ns is invalid ?

> +out_err:
> +		put_net(other_ns);
> +		break;
> +	}
> +
>  	default:
>  		ret = -ENOPROTOOPT;
>  		break;