Date:   Thu, 16 Feb 2023 11:11:10 +0100
From:   Stefano Garzarella <sgarzare@redhat.com>
To:     Bobby Eshleman <bobby.eshleman@bytedance.com>
Cc:     Stefan Hajnoczi <stefanha@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Mykola Lysenko <mykolal@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Bobby Eshleman <bobbyeshleman@gmail.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
        jakub@cloudflare.com, hdanton@sina.com, cong.wang@bytedance.com
Subject: Re: [PATCH RFC net-next v2 1/3] vsock: support sockmap
Message-ID: <20230216101110.fnwci5u5cwbkg2u5@sgarzare-redhat>
References: <20230118-support-vsock-sockmap-connectible-v2-0-58ffafde0965@bytedance.com>
 <20230118-support-vsock-sockmap-connectible-v2-1-58ffafde0965@bytedance.com>
MIME-Version: 1.0
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In-Reply-To: <20230118-support-vsock-sockmap-connectible-v2-1-58ffafde0965@bytedance.com>
Precedence: bulk

On Mon, Jan 30, 2023 at 08:35:12PM -0800, Bobby Eshleman wrote:
>This patch adds sockmap support for vsock sockets. It is intended to be
>usable by all transports, but only the virtio transport is implemented.
>
>Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
>---
> drivers/vhost/vsock.c                   |   1 +
> include/linux/virtio_vsock.h            |   1 +
> include/net/af_vsock.h                  |  17 ++++
> net/vmw_vsock/Makefile                  |   1 +
> net/vmw_vsock/af_vsock.c                |  55 ++++++++--
> net/vmw_vsock/virtio_transport.c        |   2 +
> net/vmw_vsock/virtio_transport_common.c |  24 +++++
> net/vmw_vsock/vsock_bpf.c               | 175 ++++++++++++++++++++++++++++++++
> net/vmw_vsock/vsock_loopback.c          |   2 +
> 9 files changed, 272 insertions(+), 6 deletions(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 1f3b89c885cc..3c6dc036b904 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -439,6 +439,7 @@ static struct virtio_transport vhost_transport = {
> 		.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
> 		.notify_buffer_size       = virtio_transport_notify_buffer_size,
>
>+		.read_skb = virtio_transport_read_skb,
> 	},
>
> 	.send_pkt = vhost_transport_send_pkt,
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 3f9c16611306..c58453699ee9 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -245,4 +245,5 @@ u32 virtio_transport_get_credit(struct virtio_vsock_sock *vvs, u32 wanted);
> void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit);
> void virtio_transport_deliver_tap_pkt(struct sk_buff *skb);
> int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *list);
>+int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t read_actor);
> #endif /* _LINUX_VIRTIO_VSOCK_H */
>diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>index 568a87c5e0d0..a73f5fbd296a 100644
>--- a/include/net/af_vsock.h
>+++ b/include/net/af_vsock.h
>@@ -75,6 +75,7 @@ struct vsock_sock {
> 	void *trans;
> };
>
>+s64 vsock_connectible_has_data(struct vsock_sock *vsk);
> s64 vsock_stream_has_data(struct vsock_sock *vsk);
> s64 vsock_stream_has_space(struct vsock_sock *vsk);
> struct sock *vsock_create_connected(struct sock *parent);
>@@ -173,6 +174,9 @@ struct vsock_transport {
>
> 	/* Addressing. */
> 	u32 (*get_local_cid)(void);
>+
>+	/* Read a single skb */
>+	int (*read_skb)(struct vsock_sock *, skb_read_actor_t);
> };
>
> /**** CORE ****/
>@@ -225,5 +229,18 @@ int vsock_init_tap(void);
> int vsock_add_tap(struct vsock_tap *vt);
> int vsock_remove_tap(struct vsock_tap *vt);
> void vsock_deliver_tap(struct sk_buff *build_skb(void *opaque), void *opaque);
>+int vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>+			      int flags);
>+int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
>+			       size_t len, int flags);

checkpatch complains: "CHECK: Alignment should match open parenthesis"

>+
>+#ifdef CONFIG_BPF_SYSCALL
>+extern struct proto vsock_proto;
>+int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
>+void __init vsock_bpf_build_proto(void);
>+#else
>+static inline void __init vsock_bpf_build_proto(void)
>+{}
>+#endif
>
> #endif /* __AF_VSOCK_H__ */
>diff --git a/net/vmw_vsock/Makefile b/net/vmw_vsock/Makefile
>index 6a943ec95c4a..5da74c4a9f1d 100644
>--- a/net/vmw_vsock/Makefile
>+++ b/net/vmw_vsock/Makefile
>@@ -8,6 +8,7 @@ obj-$(CONFIG_HYPERV_VSOCKETS) += hv_sock.o
> obj-$(CONFIG_VSOCKETS_LOOPBACK) += vsock_loopback.o
>
> vsock-y += af_vsock.o af_vsock_tap.o vsock_addr.o
>+vsock-$(CONFIG_BPF_SYSCALL) += vsock_bpf.o
>
> vsock_diag-y += diag.o
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 19aea7cba26e..f2cc04fb8b13 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -116,10 +116,13 @@ static void vsock_sk_destruct(struct sock *sk);
> static int vsock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
>
> /* Protocol family. */
>-static struct proto vsock_proto = {
>+struct proto vsock_proto = {
> 	.name = "AF_VSOCK",
> 	.owner = THIS_MODULE,
> 	.obj_size = sizeof(struct vsock_sock),
>+#ifdef CONFIG_BPF_SYSCALL
>+	.psock_update_sk_prot = vsock_bpf_update_proto,
>+#endif
> };
>
> /* The default peer timeout indicates how long we will wait for a peer response
>@@ -865,7 +868,7 @@ s64 vsock_stream_has_data(struct vsock_sock *vsk)
> }
> EXPORT_SYMBOL_GPL(vsock_stream_has_data);
>
>-static s64 vsock_connectible_has_data(struct vsock_sock *vsk)
>+s64 vsock_connectible_has_data(struct vsock_sock *vsk)
> {
> 	struct sock *sk = sk_vsock(vsk);
>
>@@ -874,6 +877,7 @@ static s64 vsock_connectible_has_data(struct vsock_sock *vsk)
> 	else
> 		return vsock_stream_has_data(vsk);
> }
>+EXPORT_SYMBOL_GPL(vsock_connectible_has_data);
>
> s64 vsock_stream_has_space(struct vsock_sock *vsk)
> {
>@@ -1131,6 +1135,13 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
> 	return mask;
> }
>
>+static int vsock_read_skb(struct sock *sk, skb_read_actor_t read_actor)
>+{
>+	struct vsock_sock *vsk = vsock_sk(sk);
>+
>+	return vsk->transport->read_skb(vsk, read_actor);
>+}
>+
> static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
> 			       size_t len)
> {
>@@ -1241,19 +1252,34 @@ static int vsock_dgram_connect(struct socket *sock,
>
> 	memcpy(&vsk->remote_addr, remote_addr, sizeof(vsk->remote_addr));
> 	sock->state = SS_CONNECTED;
>+	sk->sk_state = TCP_ESTABLISHED;
>
> out:
> 	release_sock(sk);
> 	return err;
> }
>
>-static int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
>-			       size_t len, int flags)
>+int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
>+			size_t len, int flags)
> {
>-	struct vsock_sock *vsk = vsock_sk(sock->sk);
>+#ifdef CONFIG_BPF_SYSCALL
>+	const struct proto *prot;
>+#endif
>+	struct vsock_sock *vsk;
>+	struct sock *sk;
>+
>+	sk = sock->sk;
>+	vsk = vsock_sk(sk);
>+
>+#ifdef CONFIG_BPF_SYSCALL
>+	prot = READ_ONCE(sk->sk_prot);
>+	if (prot != &vsock_proto)
>+		return prot->recvmsg(sk, msg, len, flags, NULL);
>+#endif
>
> 	return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
> }
>+EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
>
> static const struct proto_ops vsock_dgram_ops = {
> 	.family = PF_VSOCK,
>@@ -1272,6 +1298,7 @@ static const struct proto_ops vsock_dgram_ops = {
> 	.recvmsg = vsock_dgram_recvmsg,
> 	.mmap = sock_no_mmap,
> 	.sendpage = sock_no_sendpage,
>+	.read_skb = vsock_read_skb,
> };
>
> static int vsock_transport_cancel_pkt(struct vsock_sock *vsk)
>@@ -2086,13 +2113,16 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
> 	return err;
> }
>
>-static int
>+int
> vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 			  int flags)
> {
> 	struct sock *sk;
> 	struct vsock_sock *vsk;
> 	const struct vsock_transport *transport;
>+#ifdef CONFIG_BPF_SYSCALL
>+	const struct proto *prot;
>+#endif
> 	int err;
>
> 	sk = sock->sk;
>@@ -2139,6 +2169,14 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 		goto out;
> 	}
>
>+#ifdef CONFIG_BPF_SYSCALL
>+	prot = READ_ONCE(sk->sk_prot);
>+	if (prot != &vsock_proto) {
>+		release_sock(sk);
>+		return prot->recvmsg(sk, msg, len, flags, NULL);
>+	}
>+#endif
>+
> 	if (sk->sk_type == SOCK_STREAM)
> 		err = __vsock_stream_recvmsg(sk, msg, len, flags);
> 	else
>@@ -2148,6 +2186,7 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 	release_sock(sk);
> 	return err;
> }
>+EXPORT_SYMBOL_GPL(vsock_connectible_recvmsg);
>
> static int vsock_set_rcvlowat(struct sock *sk, int val)
> {
>@@ -2188,6 +2227,7 @@ static const struct proto_ops vsock_stream_ops = {
> 	.mmap = sock_no_mmap,
> 	.sendpage = sock_no_sendpage,
> 	.set_rcvlowat = vsock_set_rcvlowat,
>+	.read_skb = vsock_read_skb,
> };
>
> static const struct proto_ops vsock_seqpacket_ops = {
>@@ -2209,6 +2249,7 @@ static const struct proto_ops vsock_seqpacket_ops = {
> 	.recvmsg = vsock_connectible_recvmsg,
> 	.mmap = sock_no_mmap,
> 	.sendpage = sock_no_sendpage,
>+	.read_skb = vsock_read_skb,
> };
>
> static int vsock_create(struct net *net, struct socket *sock,
>@@ -2348,6 +2389,8 @@ static int __init vsock_init(void)
> 		goto err_unregister_proto;
> 	}
>
>+	vsock_bpf_build_proto();
>+
> 	return 0;
>
> err_unregister_proto:
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index 28b5a8e8e094..e95df847176b 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -457,6 +457,8 @@ static struct virtio_transport virtio_transport = {
> 		.notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
> 		.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
> 		.notify_buffer_size       = virtio_transport_notify_buffer_size,
>+
>+		.read_skb = virtio_transport_read_skb,
> 	},
>
> 	.send_pkt = virtio_transport_send_pkt,
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index a1581c77cf84..82bdaf61ee02 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -1388,6 +1388,30 @@ int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *queue)
> }
> EXPORT_SYMBOL_GPL(virtio_transport_purge_skbs);
>
>+int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_actor)
>+{
>+	struct virtio_vsock_sock *vvs = vsk->trans;
>+	struct sock *sk = sk_vsock(vsk);
>+	struct sk_buff *skb;
>+	int off = 0;
>+	int copied;
>+	int err;
>+
>+	spin_lock_bh(&vvs->rx_lock);
>+	/* Use __skb_recv_datagram() for race-free handling of the receive. It
>+	 * works for types other than dgrams. */

Checkpatch:
   WARNING: Block comments use a trailing */ on a separate line

Since we also use this convention in the other comments in this file,
I would follow it.

>+	skb = __skb_recv_datagram(sk, &vvs->rx_queue, MSG_DONTWAIT, &off, &err);
>+	spin_unlock_bh(&vvs->rx_lock);
>+
>+	if (!skb)
>+		return err;
>+
>+	copied = recv_actor(sk, skb);
>+	kfree_skb(skb);
>+	return copied;
>+}
>+EXPORT_SYMBOL_GPL(virtio_transport_read_skb);
>+
> MODULE_LICENSE("GPL v2");
> MODULE_AUTHOR("Asias He");
> MODULE_DESCRIPTION("common code for virtio vsock");
>diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
>new file mode 100644
>index 000000000000..ee92a1f42031
>--- /dev/null
>+++ b/net/vmw_vsock/vsock_bpf.c
>@@ -0,0 +1,175 @@
>+// SPDX-License-Identifier: GPL-2.0
>+/* Copyright (c) 2022 Bobby Eshleman <bobby.eshleman@bytedance.com>
>+ *
>+ * Based off of net/unix/unix_bpf.c
>+ */
>+
>+#include <linux/bpf.h>
>+#include <linux/module.h>
>+#include <linux/skmsg.h>
>+#include <linux/socket.h>
>+#include <linux/wait.h>
>+#include <net/af_vsock.h>
>+#include <net/sock.h>
>+
>+#define vsock_sk_has_data(__sk, __psock)				\
>+		({	!skb_queue_empty(&__sk->sk_receive_queue) ||	\
>+			!skb_queue_empty(&__psock->ingress_skb) ||	\
>+			!list_empty(&__psock->ingress_msg);		\
>+		})

Some suggestions from checkpatch that I would fix:

CHECK: Macro argument '__sk' may be better as '(__sk)' to avoid precedence issues
CHECK: Macro argument '__psock' may be better as '(__psock)' to avoid precedence issues

>+
>+static struct proto *vsock_prot_saved __read_mostly;
>+static DEFINE_SPINLOCK(vsock_prot_lock);
>+static struct proto vsock_bpf_prot;
>+
>+static bool vsock_has_data(struct sock *sk, struct sk_psock *psock)
>+{
>+	struct vsock_sock *vsk = vsock_sk(sk);
>+	s64 ret;
>+
>+	ret = vsock_connectible_has_data(vsk);
>+	if (ret > 0)
>+		return true;
>+
>+	return vsock_sk_has_data(sk, psock);
>+}
>+
>+static int vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo)

IIUC now this function returns 0 when there isn't data and 1 when there
is data, maybe better to change the return type to bool.

>+{
>+	int ret = 0;
>+
>+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
>+
>+	if (sk->sk_shutdown & RCV_SHUTDOWN)
>+		return 1;
>+
>+	if (!timeo)
>+		return ret;
>+
>+	add_wait_queue(sk_sleep(sk), &wait);
>+	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
>+	ret = vsock_has_data(sk, psock);
>+	if (!ret) {
>+		wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
>+		ret = vsock_has_data(sk, psock);
>+	}
>+	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
>+	remove_wait_queue(sk_sleep(sk), &wait);
>+	return ret;
>+}
>+
>+static int __vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags)
>+{
>+	struct socket *sock = sk->sk_socket;
>+	int err;
>+
>+	if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
>+		err = vsock_connectible_recvmsg(sock, msg, len, flags);
>+	else if (sk->sk_type == SOCK_DGRAM)
>+		err = vsock_dgram_recvmsg(sock, msg, len, flags);
>+	else
>+		err = -EPROTOTYPE;
>+
>+	return err;
>+}
>+
>+static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
>+			     size_t len, int flags, int *addr_len)
>+{
>+	struct sk_psock *psock;
>+	int copied;
>+
>+	psock = sk_psock_get(sk);
>+	lock_sock(sk);
>+	if (unlikely(!psock)) {
>+		release_sock(sk);

I'm not sure we need the lock to check psock, so can we move this
block before the lock_sock?

>+		return __vsock_recvmsg(sk, msg, len, flags);
>+	}
>+
>+	if (vsock_has_data(sk, psock) && sk_psock_queue_empty(psock)) {
>+		release_sock(sk);
>+		sk_psock_put(sk, psock);
>+		return __vsock_recvmsg(sk, msg, len, flags);
>+	}
>+
>+msg_bytes_ready:

I saw that this code is also in unix_bpf.c and tcp_bpf.c, so I guess
it's acceptable, but I would have avoided using a label to go back.
I prefer a to use goto only for centralized exiting of functions.

One possible refactoring (not tested):

         copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
         while (!copied) {
                 long timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);

                 if (!vsock_msg_wait_data(sk, psock, timeo)) {
                         copied = -EAGAIN;
                         break;
                 }

                 if (sk_psock_queue_empty(psock)) {
                         release_sock(sk);
                         sk_psock_put(sk, psock);
                         return __vsock_recvmsg(sk, msg, len, flags);
                 }

                 copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
         }
         ...

I'm not sure why we need to call release_sock() and sk_psock_put()
before __vsock_recvmsg(). If it is not needed we can simplify more the
previous code.

The rest LGTM.

Thanks,
Stefano

>+	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
>+	if (!copied) {
>+		long timeo;
>+		int data;
>+
>+		timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
>+		data = vsock_msg_wait_data(sk, psock, timeo);
>+		if (data) {
>+			if (!sk_psock_queue_empty(psock))
>+				goto msg_bytes_ready;
>+			release_sock(sk);
>+			sk_psock_put(sk, psock);
>+			return __vsock_recvmsg(sk, msg, len, flags);
>+		}
>+		copied = -EAGAIN;
>+	}
>+	release_sock(sk);
>+	sk_psock_put(sk, psock);
>+
>+	return copied;
>+}
>+
>+/* Copy of original proto with updated sock_map methods */
>+static struct proto vsock_bpf_prot = {
>+	.close = sock_map_close,
>+	.recvmsg = vsock_bpf_recvmsg,
>+	.sock_is_readable = sk_msg_is_readable,
>+	.unhash = sock_map_unhash,
>+};
>+
>+static void vsock_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
>+{
>+	*prot        = *base;
>+	prot->close  = sock_map_close;
>+	prot->recvmsg = vsock_bpf_recvmsg;
>+	prot->sock_is_readable = sk_msg_is_readable;
>+}
>+
>+static void vsock_bpf_check_needs_rebuild(struct proto *ops)
>+{
>+	/* Paired with the smp_store_release() below. */
>+	if (unlikely(ops != smp_load_acquire(&vsock_prot_saved))) {
>+		spin_lock_bh(&vsock_prot_lock);
>+		if (likely(ops != vsock_prot_saved)) {
>+			vsock_bpf_rebuild_protos(&vsock_bpf_prot, ops);
>+			/* Make sure proto function pointers are updated before publishing the
>+			 * pointer to the struct.
>+			 */
>+			smp_store_release(&vsock_prot_saved, ops);
>+		}
>+		spin_unlock_bh(&vsock_prot_lock);
>+	}
>+}
>+
>+int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
>+{
>+	struct vsock_sock *vsk;
>+
>+	if (restore) {
>+		sk->sk_write_space = psock->saved_write_space;
>+		sock_replace_proto(sk, psock->sk_proto);
>+		return 0;
>+	}
>+
>+	vsk = vsock_sk(sk);
>+	if (!vsk->transport)
>+		return -ENODEV;
>+
>+	if (!vsk->transport->read_skb)
>+		return -EOPNOTSUPP;
>+
>+	vsock_bpf_check_needs_rebuild(psock->sk_proto);
>+	sock_replace_proto(sk, &vsock_bpf_prot);
>+	return 0;
>+}
>+
>+void __init vsock_bpf_build_proto(void)
>+{
>+	vsock_bpf_rebuild_protos(&vsock_bpf_prot, &vsock_proto);
>+}
>diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
>index 671e03240fc5..40753b661c13 100644
>--- a/net/vmw_vsock/vsock_loopback.c
>+++ b/net/vmw_vsock/vsock_loopback.c
>@@ -94,6 +94,8 @@ static struct virtio_transport loopback_transport = {
> 		.notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
> 		.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
> 		.notify_buffer_size       = virtio_transport_notify_buffer_size,
>+
>+		.read_skb = virtio_transport_read_skb,
> 	},
>
> 	.send_pkt = vsock_loopback_send_pkt,
>
>-- 
>2.35.1
>