[PATCH RFC net-next v3 1/8] vsock/dgram: generalize recvmsg and drop transport->dgram_dequeue

[Bobby Eshleman <bobby.eshleman@bytedance.com>]

This commit drops the transport->dgram_dequeue callback and makes
vsock_dgram_recvmsg() generic. It also adds additional transport
callbacks for use by the generic vsock_dgram_recvmsg(), such as for
parsing skbs for CID/port which vary in format per transport.

Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
---
 drivers/vhost/vsock.c                   |  4 +-
 include/linux/virtio_vsock.h            |  3 ++
 include/net/af_vsock.h                  | 13 ++++++-
 net/vmw_vsock/af_vsock.c                | 51 ++++++++++++++++++++++++-
 net/vmw_vsock/hyperv_transport.c        | 17 +++++++--
 net/vmw_vsock/virtio_transport.c        |  4 +-
 net/vmw_vsock/virtio_transport_common.c | 18 +++++++++
 net/vmw_vsock/vmci_transport.c          | 68 +++++++++++++--------------------
 net/vmw_vsock/vsock_loopback.c          |  4 +-
 9 files changed, 132 insertions(+), 50 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 6578db78f0ae..c8201c070b4b 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -410,9 +410,11 @@ static struct virtio_transport vhost_transport = {
 		.cancel_pkt               = vhost_transport_cancel_pkt,
 
 		.dgram_enqueue            = virtio_transport_dgram_enqueue,
-		.dgram_dequeue            = virtio_transport_dgram_dequeue,
 		.dgram_bind               = virtio_transport_dgram_bind,
 		.dgram_allow              = virtio_transport_dgram_allow,
+		.dgram_get_cid		  = virtio_transport_dgram_get_cid,
+		.dgram_get_port		  = virtio_transport_dgram_get_port,
+		.dgram_get_length	  = virtio_transport_dgram_get_length,
 
 		.stream_enqueue           = virtio_transport_stream_enqueue,
 		.stream_dequeue           = virtio_transport_stream_dequeue,
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index c58453699ee9..23521a318cf0 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -219,6 +219,9 @@ bool virtio_transport_stream_allow(u32 cid, u32 port);
 int virtio_transport_dgram_bind(struct vsock_sock *vsk,
 				struct sockaddr_vm *addr);
 bool virtio_transport_dgram_allow(u32 cid, u32 port);
+int virtio_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid);
+int virtio_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port);
+int virtio_transport_dgram_get_length(struct sk_buff *skb, size_t *len);
 
 int virtio_transport_connect(struct vsock_sock *vsk);
 
diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 0e7504a42925..7bedb9ee7e3e 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -120,11 +120,20 @@ struct vsock_transport {
 
 	/* DGRAM. */
 	int (*dgram_bind)(struct vsock_sock *, struct sockaddr_vm *);
-	int (*dgram_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
-			     size_t len, int flags);
 	int (*dgram_enqueue)(struct vsock_sock *, struct sockaddr_vm *,
 			     struct msghdr *, size_t len);
 	bool (*dgram_allow)(u32 cid, u32 port);
+	int (*dgram_get_cid)(struct sk_buff *skb, unsigned int *cid);
+	int (*dgram_get_port)(struct sk_buff *skb, unsigned int *port);
+	int (*dgram_get_length)(struct sk_buff *skb, size_t *length);
+
+	/* The number of bytes into the buffer at which the payload starts, as
+	 * first seen by the receiving socket layer. For example, if the
+	 * transport presets the skb pointers using skb_pull(sizeof(header))
+	 * than this would be zero, otherwise it would be the size of the
+	 * header.
+	 */
+	const size_t dgram_payload_offset;
 
 	/* STREAM. */
 	/* TODO: stream_bind() */
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 413407bb646c..7ec0659c6ae5 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1271,11 +1271,15 @@ static int vsock_dgram_connect(struct socket *sock,
 int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 			size_t len, int flags)
 {
+	const struct vsock_transport *transport;
 #ifdef CONFIG_BPF_SYSCALL
 	const struct proto *prot;
 #endif
 	struct vsock_sock *vsk;
+	struct sk_buff *skb;
+	size_t payload_len;
 	struct sock *sk;
+	int err;
 
 	sk = sock->sk;
 	vsk = vsock_sk(sk);
@@ -1286,7 +1290,52 @@ int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 		return prot->recvmsg(sk, msg, len, flags, NULL);
 #endif
 
-	return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
+	if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
+		return -EOPNOTSUPP;
+
+	transport = vsk->transport;
+
+	/* Retrieve the head sk_buff from the socket's receive queue. */
+	err = 0;
+	skb = skb_recv_datagram(&vsk->sk, flags, &err);
+	if (!skb)
+		return err;
+
+	err = transport->dgram_get_length(skb, &payload_len);
+	if (err)
+		goto out;
+
+	if (payload_len > len) {
+		payload_len = len;
+		msg->msg_flags |= MSG_TRUNC;
+	}
+
+	/* Place the datagram payload in the user's iovec. */
+	err = skb_copy_datagram_msg(skb, transport->dgram_payload_offset, msg, payload_len);
+	if (err)
+		goto out;
+
+	if (msg->msg_name) {
+		/* Provide the address of the sender. */
+		DECLARE_SOCKADDR(struct sockaddr_vm *, vm_addr, msg->msg_name);
+		unsigned int cid, port;
+
+		err = transport->dgram_get_cid(skb, &cid);
+		if (err)
+			goto out;
+
+		err = transport->dgram_get_port(skb, &port);
+		if (err)
+			goto out;
+
+		vsock_addr_init(vm_addr, cid, port);
+		msg->msg_namelen = sizeof(*vm_addr);
+	}
+	err = payload_len;
+
+out:
+	skb_free_datagram(&vsk->sk, skb);
+	return err;
 }
 EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
 
diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index 7cb1a9d2cdb4..ff6e87e25fa0 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -556,8 +556,17 @@ static int hvs_dgram_bind(struct vsock_sock *vsk, struct sockaddr_vm *addr)
 	return -EOPNOTSUPP;
 }
 
-static int hvs_dgram_dequeue(struct vsock_sock *vsk, struct msghdr *msg,
-			     size_t len, int flags)
+static int hvs_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
+{
+	return -EOPNOTSUPP;
+}
+
+static int hvs_dgram_get_port(struct sk_buff *skb, unsigned int *port)
+{
+	return -EOPNOTSUPP;
+}
+
+static int hvs_dgram_get_length(struct sk_buff *skb, size_t *len)
 {
 	return -EOPNOTSUPP;
 }
@@ -833,7 +842,9 @@ static struct vsock_transport hvs_transport = {
 	.shutdown                 = hvs_shutdown,
 
 	.dgram_bind               = hvs_dgram_bind,
-	.dgram_dequeue            = hvs_dgram_dequeue,
+	.dgram_get_cid		  = hvs_dgram_get_cid,
+	.dgram_get_port		  = hvs_dgram_get_port,
+	.dgram_get_length	  = hvs_dgram_get_length,
 	.dgram_enqueue            = hvs_dgram_enqueue,
 	.dgram_allow              = hvs_dgram_allow,
 
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index e95df847176b..5763cdf13804 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -429,9 +429,11 @@ static struct virtio_transport virtio_transport = {
 		.cancel_pkt               = virtio_transport_cancel_pkt,
 
 		.dgram_bind               = virtio_transport_dgram_bind,
-		.dgram_dequeue            = virtio_transport_dgram_dequeue,
 		.dgram_enqueue            = virtio_transport_dgram_enqueue,
 		.dgram_allow              = virtio_transport_dgram_allow,
+		.dgram_get_cid		  = virtio_transport_dgram_get_cid,
+		.dgram_get_port		  = virtio_transport_dgram_get_port,
+		.dgram_get_length	  = virtio_transport_dgram_get_length,
 
 		.stream_dequeue           = virtio_transport_stream_dequeue,
 		.stream_enqueue           = virtio_transport_stream_enqueue,
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index e4878551f140..abd939694a1a 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -797,6 +797,24 @@ int virtio_transport_dgram_bind(struct vsock_sock *vsk,
 }
 EXPORT_SYMBOL_GPL(virtio_transport_dgram_bind);
 
+int virtio_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
+{
+	return -EOPNOTSUPP;
+}
+EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_cid);
+
+int virtio_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port)
+{
+	return -EOPNOTSUPP;
+}
+EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_port);
+
+int virtio_transport_dgram_get_length(struct sk_buff *skb, size_t *len)
+{
+	return -EOPNOTSUPP;
+}
+EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_length);
+
 bool virtio_transport_dgram_allow(u32 cid, u32 port)
 {
 	return false;
diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
index b370070194fa..b6a51afb74b8 100644
--- a/net/vmw_vsock/vmci_transport.c
+++ b/net/vmw_vsock/vmci_transport.c
@@ -1731,57 +1731,40 @@ static int vmci_transport_dgram_enqueue(
 	return err - sizeof(*dg);
 }
 
-static int vmci_transport_dgram_dequeue(struct vsock_sock *vsk,
-					struct msghdr *msg, size_t len,
-					int flags)
+int vmci_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
 {
-	int err;
 	struct vmci_datagram *dg;
-	size_t payload_len;
-	struct sk_buff *skb;
 
-	if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
-		return -EOPNOTSUPP;
+	dg = (struct vmci_datagram *)skb->data;
+	if (!dg)
+		return -EINVAL;
 
-	/* Retrieve the head sk_buff from the socket's receive queue. */
-	err = 0;
-	skb = skb_recv_datagram(&vsk->sk, flags, &err);
-	if (!skb)
-		return err;
+	*cid = dg->src.context;
+	return 0;
+}
+
+int vmci_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port)
+{
+	struct vmci_datagram *dg;
 
 	dg = (struct vmci_datagram *)skb->data;
 	if (!dg)
-		/* err is 0, meaning we read zero bytes. */
-		goto out;
-
-	payload_len = dg->payload_size;
-	/* Ensure the sk_buff matches the payload size claimed in the packet. */
-	if (payload_len != skb->len - sizeof(*dg)) {
-		err = -EINVAL;
-		goto out;
-	}
+		return -EINVAL;
 
-	if (payload_len > len) {
-		payload_len = len;
-		msg->msg_flags |= MSG_TRUNC;
-	}
+	*port = dg->src.resource;
+	return 0;
+}
 
-	/* Place the datagram payload in the user's iovec. */
-	err = skb_copy_datagram_msg(skb, sizeof(*dg), msg, payload_len);
-	if (err)
-		goto out;
+int vmci_transport_dgram_get_length(struct sk_buff *skb, size_t *len)
+{
+	struct vmci_datagram *dg;
 
-	if (msg->msg_name) {
-		/* Provide the address of the sender. */
-		DECLARE_SOCKADDR(struct sockaddr_vm *, vm_addr, msg->msg_name);
-		vsock_addr_init(vm_addr, dg->src.context, dg->src.resource);
-		msg->msg_namelen = sizeof(*vm_addr);
-	}
-	err = payload_len;
+	dg = (struct vmci_datagram *)skb->data;
+	if (!dg)
+		return -EINVAL;
 
-out:
-	skb_free_datagram(&vsk->sk, skb);
-	return err;
+	*len = dg->payload_size;
+	return 0;
 }
 
 static bool vmci_transport_dgram_allow(u32 cid, u32 port)
@@ -2040,9 +2023,12 @@ static struct vsock_transport vmci_transport = {
 	.release = vmci_transport_release,
 	.connect = vmci_transport_connect,
 	.dgram_bind = vmci_transport_dgram_bind,
-	.dgram_dequeue = vmci_transport_dgram_dequeue,
 	.dgram_enqueue = vmci_transport_dgram_enqueue,
 	.dgram_allow = vmci_transport_dgram_allow,
+	.dgram_get_cid = vmci_transport_dgram_get_cid,
+	.dgram_get_port = vmci_transport_dgram_get_port,
+	.dgram_get_length = vmci_transport_dgram_get_length,
+	.dgram_payload_offset = sizeof(struct vmci_datagram),
 	.stream_dequeue = vmci_transport_stream_dequeue,
 	.stream_enqueue = vmci_transport_stream_enqueue,
 	.stream_has_data = vmci_transport_stream_has_data,
diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
index e3afc0c866f5..136061f622b8 100644
--- a/net/vmw_vsock/vsock_loopback.c
+++ b/net/vmw_vsock/vsock_loopback.c
@@ -63,9 +63,11 @@ static struct virtio_transport loopback_transport = {
 		.cancel_pkt               = vsock_loopback_cancel_pkt,
 
 		.dgram_bind               = virtio_transport_dgram_bind,
-		.dgram_dequeue            = virtio_transport_dgram_dequeue,
 		.dgram_enqueue            = virtio_transport_dgram_enqueue,
 		.dgram_allow              = virtio_transport_dgram_allow,
+		.dgram_get_cid		  = virtio_transport_dgram_get_cid,
+		.dgram_get_port		  = virtio_transport_dgram_get_port,
+		.dgram_get_length	  = virtio_transport_dgram_get_length,
 
 		.stream_dequeue           = virtio_transport_stream_dequeue,
 		.stream_enqueue           = virtio_transport_stream_enqueue,

-- 
2.30.2