netdev - Re: [PATCH net-next 1/3] vsock: add support for SIOCOUTQ ioctl for all vsock socket types.

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Message-ID: <weigxhmoj4qoiqz45eklm3n5c3gw75l7ml3pt2seq3jiip7xw6@alqavbovpdoy>
Date: Wed, 3 Apr 2024 11:00:02 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Luigi Leonardi <luigi.leonardi@...look.com>
Cc: kvm@...r.kernel.org, jasowang@...hat.com, 
	virtualization@...ts.linux.dev, mst@...hat.com, kuba@...nel.org, xuanzhuo@...ux.alibaba.com, 
	netdev@...r.kernel.org, stefanha@...hat.com, pabeni@...hat.com, davem@...emloft.net, 
	edumazet@...gle.com, Daan De Meyer <daan.j.demeyer@...il.com>
Subject: Re: [PATCH net-next 1/3] vsock: add support for SIOCOUTQ ioctl for
 all vsock socket types.

On Tue, Apr 02, 2024 at 05:05:37PM +0200, Luigi Leonardi wrote:
>This add support for ioctl(s) for SOCK_STREAM SOCK_SEQPACKET and SOCK_DGRAM
>in AF_VSOCK.
>The only ioctl available is SIOCOUTQ/TIOCOUTQ, which returns the number
>of unsent bytes in the socket. This information is transport-specific
>and is delegated to them using a callback.
>
>Suggested-by: Daan De Meyer <daan.j.demeyer@...il.com>
>Signed-off-by: Luigi Leonardi <luigi.leonardi@...look.com>
>---
> include/net/af_vsock.h   |  1 +
> net/vmw_vsock/af_vsock.c | 42 +++++++++++++++++++++++++++++++++++++---
> 2 files changed, 40 insertions(+), 3 deletions(-)
>
>diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>index 535701efc1e5..cd4311abd3c9 100644
>--- a/include/net/af_vsock.h
>+++ b/include/net/af_vsock.h
>@@ -137,6 +137,7 @@ struct vsock_transport {
> 	u64 (*stream_rcvhiwat)(struct vsock_sock *);
> 	bool (*stream_is_active)(struct vsock_sock *);
> 	bool (*stream_allow)(u32 cid, u32 port);
>+	int (*stream_bytes_unsent)(struct vsock_sock *vsk);
>
> 	/* SEQ_PACKET. */
> 	ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 54ba7316f808..991e9edfa743 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -112,6 +112,7 @@
> #include <net/sock.h>
> #include <net/af_vsock.h>
> #include <uapi/linux/vm_sockets.h>
>+#include <uapi/asm-generic/ioctls.h>
>
> static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
> static void vsock_sk_destruct(struct sock *sk);
>@@ -1292,6 +1293,41 @@ int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> }
> EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
>
>+static int vsock_do_ioctl(struct socket *sock, unsigned int cmd,
>+			  int __user *arg)
>+{
>+	struct sock *sk = sock->sk;
>+	int retval = -EOPNOTSUPP;
>+	struct vsock_sock *vsk;
>+
>+	vsk = vsock_sk(sk);
>+
>+	switch (cmd) {
>+	case SIOCOUTQ:
>+		if (vsk->transport->stream_bytes_unsent) {
>+			if (sk->sk_state == TCP_LISTEN)

Maybe we should do this check only if
`sock_type_connectible(sk->sk_type)` is true.

>+				return -EINVAL;
>+			retval = vsk->transport->stream_bytes_unsent(vsk);

IIUC `stream_bytes_unsent()` is used for any type of socket, so I
suggest using a name more generic, something like `unsent_bytes()`.

>+		}
>+		break;
>+	default:
>+		retval = -EOPNOTSUPP;

Should we return -ENOIOCTLCMD in this case?

>+	}
>+
>+	if (retval >= 0) {

IMHO mixing the the ioctl() return value and the value itself is
confusing.

I also suggest to move the put_user() in the `case SIOCOUTQ`,
other ioctls may no needs any value to copy to userspace.

>+		put_user(retval, arg);

put_user() can fail, we should return the failure to the user.

>+		retval = 0;
>+	}
>+
>+	return retval;
>+}
>+
>+static int vsock_ioctl(struct socket *sock, unsigned int cmd,
>+		       unsigned long arg)
>+{
>+	return vsock_do_ioctl(sock, cmd, (int __user *)arg);
>+}
>+
> static const struct proto_ops vsock_dgram_ops = {
> 	.family = PF_VSOCK,
> 	.owner = THIS_MODULE,
>@@ -1302,7 +1338,7 @@ static const struct proto_ops vsock_dgram_ops = {
> 	.accept = sock_no_accept,
> 	.getname = vsock_getname,
> 	.poll = vsock_poll,
>-	.ioctl = sock_no_ioctl,
>+	.ioctl = vsock_ioctl,
> 	.listen = sock_no_listen,
> 	.shutdown = vsock_shutdown,
> 	.sendmsg = vsock_dgram_sendmsg,
>@@ -2286,7 +2322,7 @@ static const struct proto_ops vsock_stream_ops = {
> 	.accept = vsock_accept,
> 	.getname = vsock_getname,
> 	.poll = vsock_poll,
>-	.ioctl = sock_no_ioctl,
>+	.ioctl = vsock_ioctl,
> 	.listen = vsock_listen,
> 	.shutdown = vsock_shutdown,
> 	.setsockopt = vsock_connectible_setsockopt,
>@@ -2308,7 +2344,7 @@ static const struct proto_ops vsock_seqpacket_ops = {
> 	.accept = vsock_accept,
> 	.getname = vsock_getname,
> 	.poll = vsock_poll,
>-	.ioctl = sock_no_ioctl,
>+	.ioctl = vsock_ioctl,
> 	.listen = vsock_listen,
> 	.shutdown = vsock_shutdown,
> 	.setsockopt = vsock_connectible_setsockopt,
>-- 
>2.34.1
>