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

[Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>]

This adds handling of MSG_ERRQUEUE input flag for receive call, thus
skb from socket's error queue is read.

Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
---
 include/linux/socket.h   |  1 +
 net/vmw_vsock/af_vsock.c | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 13c3a237b9c9..19a6f39fa014 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -379,6 +379,7 @@ 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/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index b5e51ef4a74c..f752b30b71d6 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -110,6 +110,7 @@
 #include <linux/workqueue.h>
 #include <net/sock.h>
 #include <net/af_vsock.h>
+#include <linux/errqueue.h>
 
 static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
 static void vsock_sk_destruct(struct sock *sk);
@@ -2086,6 +2087,27 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
 	return err;
 }
 
+static int vsock_err_recvmsg(struct sock *sk, struct msghdr *msg)
+{
+	struct sock_extended_err *ee;
+	struct sk_buff *skb;
+	int err;
+
+	lock_sock(sk);
+	skb = sock_dequeue_err_skb(sk);
+	release_sock(sk);
+
+	if (!skb)
+		return -EAGAIN;
+
+	ee = &SKB_EXT_ERR(skb)->ee;
+	err = put_cmsg(msg, SOL_VSOCK, 0, sizeof(*ee), ee);
+	msg->msg_flags |= MSG_ERRQUEUE;
+	consume_skb(skb);
+
+	return err;
+}
+
 static int
 vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 			  int flags)
@@ -2096,6 +2118,10 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	int err;
 
 	sk = sock->sk;
+
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return vsock_err_recvmsg(sk, msg);
+
 	vsk = vsock_sk(sk);
 	err = 0;
 
-- 
2.25.1