Linux Virtualization - Sep 2023 - [PATCH net-next v1 02/12] vsock: read from socket's error queue

On Fri, Sep 22, 2023 at 08:24:18AM +0300, Arseniy Krasnov
wrote:
>This adds handling of MSG_ERRQUEUE input flag in receive call. This flag
>is used to read socket's error queue instead of data queue. Possible
>scenario of error queue usage is receiving completions for transmission
>with MSG_ZEROCOPY flag. This patch also adds new defines:
'SOL_VSOCK'
>and 'VSOCK_RECVERR'.
>
>Signed-off-by: Arseniy Krasnov <avkrasnov at salutedevices.com>
>---
> Changelog:
> v5(big patchset) -> v1:
>  * R-b tag removed, due to added defines to
'include/uapi/linux/vsock.h'.
>    Both 'SOL_VSOCK' and 'VSOCK_RECVERR' are needed by
userspace, so
>    they were placed to 'include/uapi/linux/vsock.h'. At the same
time,
>    the same define for 'SOL_VSOCK' was placed to
'include/linux/socket.h'.
>    This is needed because this file contains SOL_XXX defines for different
>    types of socket, so it prevents situation when another new SOL_XXX
>    will use constant 287.
>
> include/linux/socket.h     | 1 +
> include/uapi/linux/vsock.h | 9 +++++++++
> net/vmw_vsock/af_vsock.c   | 6 ++++++
> 3 files changed, 16 insertions(+)
> create mode 100644 include/uapi/linux/vsock.h
>
>diff --git a/include/linux/socket.h b/include/linux/socket.h
>index 39b74d83c7c4..cfcb7e2c3813 100644
>--- a/include/linux/socket.h
>+++ b/include/linux/socket.h
>@@ -383,6 +383,7 @@ struct ucred {
> #define SOL_MPTCP	284
> #define SOL_MCTP	285
> #define SOL_SMC		286
>+#define SOL_VSOCK	287
>
> /* IPX options */
> #define IPX_TYPE	1
>diff --git a/include/uapi/linux/vsock.h b/include/uapi/linux/vsock.h
>new file mode 100644
>index 000000000000..b25c1347a3b8
>--- /dev/null
>+++ b/include/uapi/linux/vsock.h
We already have include/uapi/linux/vm_sockets.h

Should we include these changes there instead of creating a new header?
>@@ -0,0 +1,9 @@
>+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>+#ifndef _UAPI_LINUX_VSOCK_H
>+#define _UAPI_LINUX_VSOCK_H
>+
>+#define SOL_VSOCK	287
Why we need to re-define this also here?

In that case, should we protect with some guards to avoid double
defines?
>+
>+#define VSOCK_RECVERR	1
>+
>+#endif /* _UAPI_LINUX_VSOCK_H */
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index d841f4de33b0..4fd11bf34bc7 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -110,6 +110,8 @@
> #include <linux/workqueue.h>
> #include <net/sock.h>
> #include <net/af_vsock.h>
>+#include <linux/errqueue.h>
>+#include <uapi/linux/vsock.h>
>
> static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
> static void vsock_sk_destruct(struct sock *sk);
>@@ -2137,6 +2139,10 @@ vsock_connectible_recvmsg(struct socket *sock, struct
msghdr *msg, size_t len,
> 	int err;
>
> 	sk = sock->sk;
>+
>+	if (unlikely(flags & MSG_ERRQUEUE))
>+		return sock_recv_errqueue(sk, msg, len, SOL_VSOCK, VSOCK_RECVERR);
>+
> 	vsk = vsock_sk(sk);
> 	err = 0;
>
>-- 
>2.25.1
>