Re: [PATCH net-next v1 08/12] vsock: enable setting SO_ZEROCOPY

[Stefano Garzarella]

On Fri, Sep 22, 2023 at 08:24:24AM +0300, Arseniy Krasnov wrote:
> For AF_VSOCK, zerocopy tx mode depends on transport, so this option must
> be set in AF_VSOCK implementation where transport is accessible (if
> transport is not set during setting SO_ZEROCOPY: for example socket is
> not connected, then SO_ZEROCOPY will be enabled, but once transport will
> be assigned, support of this type of transmission will be checked).
>
> To handle SO_ZEROCOPY, AF_VSOCK implementation uses SOCK_CUSTOM_SOCKOPT
> bit, thus handling SOL_SOCKET option operations, but all of them except
> SO_ZEROCOPY will be forwarded to the generic handler by calling
> 'sock_setsockopt()'.
>
> Signed-off-by: Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx>
> ---
> Changelog:
> v5(big patchset) -> v1:
>  * Compact 'if' conditions.
>  * Rename 'zc_val' to 'zerocopy'.
>  * Use 'zerocopy' value directly in 'sock_valbool_flag()', without
>    ?: operator.
>  * Set 'SOCK_CUSTOM_SOCKOPT' bit for connectible sockets only, as
>    suggested by Bobby Eshleman <bobbyeshleman@xxxxxxxxx>.
>
> net/vmw_vsock/af_vsock.c | 46 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index 482300eb88e0..c05a42e02a17 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -1406,8 +1406,16 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
> 			goto out;
> 		}
>
> -		if (vsock_msgzerocopy_allow(transport))
> +		if (vsock_msgzerocopy_allow(transport)) {
> 			set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
> +		} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
> +			/* If this option was set before 'connect()',
> +			 * when transport was unknown, check that this
> +			 * feature is supported here.
> +			 */
> +			err = -EOPNOTSUPP;
> +			goto out;
> +		}
>
> 		err = vsock_auto_bind(vsk);
> 		if (err)
> @@ -1643,7 +1651,7 @@ static int vsock_connectible_setsockopt(struct socket *sock,
> 	const struct vsock_transport *transport;
> 	u64 val;
>
> -	if (level != AF_VSOCK)
> +	if (level != AF_VSOCK && level != SOL_SOCKET)
> 		return -ENOPROTOOPT;
>
> #define COPY_IN(_v)                                       \
> @@ -1666,6 +1674,34 @@ static int vsock_connectible_setsockopt(struct socket *sock,
>
> 	transport = vsk->transport;
>
> +	if (level == SOL_SOCKET) {
> +		int zerocopy;
> +
> +		if (optname != SO_ZEROCOPY) {
> +			release_sock(sk);
> +			return sock_setsockopt(sock, level, optname, optval, optlen);
> +		}
> +
> +		/* Use 'int' type here, because variable to
> +		 * set this option usually has this type.
> +		 */
> +		COPY_IN(zerocopy);
> +
> +		if (zerocopy < 0 || zerocopy > 1) {
> +			err = -EINVAL;
> +			goto exit;
> +		}
> +
> +		if (transport && !vsock_msgzerocopy_allow(transport)) {
> +			err = -EOPNOTSUPP;
> +			goto exit;
> +		}
> +
> +		sock_valbool_flag(sk, SOCK_ZEROCOPY,
> +				  zerocopy);

it's not necessary to wrap this call.

> +		goto exit;
> +	}
> +
> 	switch (optname) {
> 	case SO_VM_SOCKETS_BUFFER_SIZE:
> 		COPY_IN(val);
> @@ -2322,6 +2358,12 @@ static int vsock_create(struct net *net, struct socket *sock,
> 		}
> 	}
>
> +	/* SOCK_DGRAM doesn't have 'setsockopt' callback set in its
> +	 * proto_ops, so there is no handler for custom logic.
> +	 */
> +	if (sock_type_connectible(sock->type))
> +		set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
> +
> 	vsock_insert_unbound(vsk);
>
> 	return 0;
> --
> 2.25.1