[RFC PATCH net-next v6 01/14] af_vsock: generalize vsock_dgram_recvmsg() to all transports

[Amery Hung]

From: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>

This commit drops the transport->dgram_dequeue callback and makes
vsock_dgram_recvmsg() generic to all transports.

To make this possible, two transport-level changes are introduced:
- transport in the receiving path now stores the cid and port into
  the control buffer of an skb when populating an skb. The information
  later is used to initialize sockaddr_vm structure in recvmsg()
  without referencing vsk->transport.
- transport implementations set the skb->data pointer to the beginning
  of the payload prior to adding the skb to the socket's receive queue.
  That is, they must use skb_pull() before enqueuing. This is an
  agreement between the transport and the socket layer that skb->data
  always points to the beginning of the payload (and not, for example,
  the packet header).

Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
Signed-off-by: Amery Hung <amery.hung@xxxxxxxxxxxxx>
---
 drivers/vhost/vsock.c                   |  1 -
 include/linux/virtio_vsock.h            |  5 ---
 include/net/af_vsock.h                  | 11 ++++-
 net/vmw_vsock/af_vsock.c                | 42 +++++++++++++++++-
 net/vmw_vsock/hyperv_transport.c        |  7 ---
 net/vmw_vsock/virtio_transport.c        |  1 -
 net/vmw_vsock/virtio_transport_common.c |  9 ----
 net/vmw_vsock/vmci_transport.c          | 59 +++----------------------
 net/vmw_vsock/vsock_loopback.c          |  1 -
 9 files changed, 55 insertions(+), 81 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index ec20ecff85c7..97fffa914e66 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -419,7 +419,6 @@ 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,
 
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index c82089dee0c8..8b56b8a19ddd 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -177,11 +177,6 @@ virtio_transport_stream_dequeue(struct vsock_sock *vsk,
 				size_t len,
 				int type);
 int
-virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
-			       struct msghdr *msg,
-			       size_t len, int flags);
-
-int
 virtio_transport_seqpacket_enqueue(struct vsock_sock *vsk,
 				   struct msghdr *msg,
 				   size_t len);
diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 535701efc1e5..7aa1f5f2b1a5 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -120,8 +120,6 @@ 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);
@@ -219,6 +217,15 @@ void vsock_for_each_connected_socket(struct vsock_transport *transport,
 int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk);
 bool vsock_find_cid(unsigned int cid);
 
+struct vsock_skb_cb {
+	unsigned int src_cid;
+	unsigned int src_port;
+};
+
+static inline struct vsock_skb_cb *vsock_skb_cb(struct sk_buff *skb) {
+	return (struct vsock_skb_cb *)skb->cb;
+};
+
 /**** TAP ****/
 
 struct vsock_tap {
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 4b040285aa78..5e7d4d99ea2c 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1273,11 +1273,15 @@ static int vsock_dgram_connect(struct socket *sock,
 int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 			size_t len, int flags)
 {
+	struct vsock_skb_cb *vsock_cb;
 #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);
@@ -1288,7 +1292,43 @@ 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;
+
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return sock_recv_errqueue(sk, msg, len, SOL_VSOCK, 0);
+
+	/* Retrieve the head sk_buff from the socket's receive queue. */
+	err = 0;
+	skb = skb_recv_datagram(sk_vsock(vsk), flags, &err);
+	if (!skb)
+		return err;
+
+	payload_len = skb->len;
+
+	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, 0, 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);
+
+		vsock_cb = vsock_skb_cb(skb);
+		vsock_addr_init(vm_addr, vsock_cb->src_cid, vsock_cb->src_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 e2157e387217..326dd41ee2d5 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -556,12 +556,6 @@ 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)
-{
-	return -EOPNOTSUPP;
-}
-
 static int hvs_dgram_enqueue(struct vsock_sock *vsk,
 			     struct sockaddr_vm *remote, struct msghdr *msg,
 			     size_t dgram_len)
@@ -833,7 +827,6 @@ static struct vsock_transport hvs_transport = {
 	.shutdown                 = hvs_shutdown,
 
 	.dgram_bind               = hvs_dgram_bind,
-	.dgram_dequeue            = hvs_dgram_dequeue,
 	.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 43d405298857..a8c97e95622a 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -508,7 +508,6 @@ 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,
 
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 16ff976a86e3..4bf73d20c12a 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -810,15 +810,6 @@ virtio_transport_seqpacket_enqueue(struct vsock_sock *vsk,
 }
 EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_enqueue);
 
-int
-virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
-			       struct msghdr *msg,
-			       size_t len, int flags)
-{
-	return -EOPNOTSUPP;
-}
-EXPORT_SYMBOL_GPL(virtio_transport_dgram_dequeue);
-
 s64 virtio_transport_stream_has_data(struct vsock_sock *vsk)
 {
 	struct virtio_vsock_sock *vvs = vsk->trans;
diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
index b370070194fa..b39df3ed8c8d 100644
--- a/net/vmw_vsock/vmci_transport.c
+++ b/net/vmw_vsock/vmci_transport.c
@@ -610,6 +610,7 @@ vmci_transport_datagram_create_hnd(u32 resource_id,
 
 static int vmci_transport_recv_dgram_cb(void *data, struct vmci_datagram *dg)
 {
+	struct vsock_skb_cb *vsock_cb;
 	struct sock *sk;
 	size_t size;
 	struct sk_buff *skb;
@@ -637,10 +638,14 @@ static int vmci_transport_recv_dgram_cb(void *data, struct vmci_datagram *dg)
 	if (!skb)
 		return VMCI_ERROR_NO_MEM;
 
+	vsock_cb = vsock_skb_cb(skb);
+	vsock_cb->src_cid = dg->src.context;
+	vsock_cb->src_port = dg->src.resource;
 	/* sk_receive_skb() will do a sock_put(), so hold here. */
 	sock_hold(sk);
 	skb_put(skb, size);
 	memcpy(skb->data, dg, size);
+	skb_pull(skb, VMCI_DG_HEADERSIZE);
 	sk_receive_skb(sk, skb, 0);
 
 	return VMCI_SUCCESS;
@@ -1731,59 +1736,6 @@ 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 err;
-	struct vmci_datagram *dg;
-	size_t payload_len;
-	struct sk_buff *skb;
-
-	if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
-		return -EOPNOTSUPP;
-
-	/* 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;
-
-	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;
-	}
-
-	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, sizeof(*dg), 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);
-		vsock_addr_init(vm_addr, dg->src.context, dg->src.resource);
-		msg->msg_namelen = sizeof(*vm_addr);
-	}
-	err = payload_len;
-
-out:
-	skb_free_datagram(&vsk->sk, skb);
-	return err;
-}
-
 static bool vmci_transport_dgram_allow(u32 cid, u32 port)
 {
 	if (cid == VMADDR_CID_HYPERVISOR) {
@@ -2040,7 +1992,6 @@ 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,
 	.stream_dequeue = vmci_transport_stream_dequeue,
diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
index 6dea6119f5b2..11488887a5cc 100644
--- a/net/vmw_vsock/vsock_loopback.c
+++ b/net/vmw_vsock/vsock_loopback.c
@@ -66,7 +66,6 @@ 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,
 
-- 
2.20.1