[dpdk-dev] [RFC 03/24] vhost: allocate per-socket transport state

[Stefan Hajnoczi <stefanha@redhat.com>]

vhost-user transports have per-socket state (like file descriptors).
Make it possible for transports to keep state beyond what is included in
struct vhost_user_socket.

This patch makes it possible to move AF_UNIX-specific fields from struct
vhost_user_socket into trans_af_unix.c in later patches.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 lib/librte_vhost/vhost.h         | 9 +++++++++
 lib/librte_vhost/socket.c        | 6 ++++--
 lib/librte_vhost/trans_af_unix.c | 5 +++++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 8c6d6e524..e5279a572 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -210,6 +210,9 @@ struct virtio_net;
  * A structure containing function pointers for transport-specific operations.
  */
 struct vhost_transport_ops {
+	/** Size of struct vhost_user_socket-derived per-socket state */
+	size_t socket_size;
+
 	/**
 	 * Notify the guest that used descriptors have been added to the vring.
 	 * The VRING_AVAIL_F_NO_INTERRUPT flag has already been checked so this
@@ -273,6 +276,11 @@ TAILQ_HEAD(vhost_user_connection_list, vhost_user_connection);
 /*
  * Every time rte_vhost_driver_register() is invoked, an associated
  * vhost_user_socket struct will be created.
+ *
+ * Transport-specific per-socket state can be kept by embedding this struct at
+ * the beginning of a transport-specific struct.  Set
+ * vhost_transport_ops->socket_size to the size of the transport-specific
+ * struct.
  */
 struct vhost_user_socket {
 	struct vhost_user_connection_list conn_list;
@@ -296,6 +304,7 @@ struct vhost_user_socket {
 	uint64_t features;
 
 	struct vhost_device_ops const *notify_ops;
+	struct vhost_transport_ops const *trans_ops;
 };
 
 struct vhost_user_connection {
diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
index d681f9cae..fffffc663 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -128,6 +128,7 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
 {
 	int ret = -1;
 	struct vhost_user_socket *vsocket;
+	const struct vhost_transport_ops *trans_ops = &af_unix_trans_ops;
 
 	if (!path)
 		return -1;
@@ -140,10 +141,11 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
 		goto out;
 	}
 
-	vsocket = malloc(sizeof(struct vhost_user_socket));
+	vsocket = malloc(trans_ops->socket_size);
 	if (!vsocket)
 		goto out;
-	memset(vsocket, 0, sizeof(struct vhost_user_socket));
+	memset(vsocket, 0, trans_ops->socket_size);
+	vsocket->trans_ops = trans_ops;
 	vsocket->path = strdup(path);
 	if (vsocket->path == NULL) {
 		RTE_LOG(ERR, VHOST_CONFIG,
diff --git a/lib/librte_vhost/trans_af_unix.c b/lib/librte_vhost/trans_af_unix.c
index 636f69916..5e3c5ab2a 100644
--- a/lib/librte_vhost/trans_af_unix.c
+++ b/lib/librte_vhost/trans_af_unix.c
@@ -42,6 +42,10 @@
 
 #define MAX_VIRTIO_BACKLOG 128
 
+struct af_unix_socket {
+	struct vhost_user_socket socket; /* must be the first field! */
+};
+
 static void vhost_user_read_cb(int connfd, void *dat, int *remove);
 
 /* return bytes# of read on success or negative val on failure. */
@@ -496,5 +500,6 @@ af_unix_vring_call(struct virtio_net *dev __rte_unused,
 }
 
 const struct vhost_transport_ops af_unix_trans_ops = {
+	.socket_size = sizeof(struct af_unix_socket),
 	.vring_call = af_unix_vring_call,
 };
-- 
2.14.3