Virtualization - Feb 2023 - [RFC PATCH v1 02/12] vsock: read from socket's error queue

On Mon, Feb 06, 2023 at 06:54:51AM +0000, Arseniy Krasnov
wrote:
>This adds handling of MSG_ERRQUEUE input flag for receive call, thus
>skb from socket's error queue is read.
A general tip, add a little more description in the commit messages,
especially to explain why these changes are necessary.
Otherwise, even review becomes difficult because one has to look at all
the patches to understand what the previous ones are for.
I know it's boring, but it's very useful for those who review and even
then if we have to bisect ;-)

Thanks,
Stefano
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov at sberdevices.ru>
>---
> 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