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

[Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxxx>
---
 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
@@ -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
+
+#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