[dpdk-dev] [RFC] librte_vhost: Add unix domain socket fd registration

[Aaron Conole <aconole@redhat.com>]

Prior to this commit, the only way to add a vhost-user socket to the
system is by relying on librte_vhost to open the unix domain socket and
add it to the unix socket list.  This is problematic for applications
which would like to set the permissions, or applications which are not
directly allowed to open sockets due to policy restrictions.

This patch provides a new API and ABI to allow application developers to
acquire the unix domain socket via whatever mechanism fits and pass it
to the vhost driver registration process.

Signed-off-by: Aaron Conole <aconole@redhat.com>
---
 doc/guides/prog_guide/vhost_lib.rst          |  8 +++++
 lib/librte_vhost/rte_vhost_version.map       |  6 ++++
 lib/librte_vhost/rte_virtio_net.h            |  6 ++++
 lib/librte_vhost/vhost_user/vhost-net-user.c | 47 ++++++++++++++++++----------
 4 files changed, 50 insertions(+), 17 deletions(-)

diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
index 48e1fff..22d0c6d 100644
--- a/doc/guides/prog_guide/vhost_lib.rst
+++ b/doc/guides/prog_guide/vhost_lib.rst
@@ -49,6 +49,14 @@ Vhost API Overview
       For vhost-user, a Unix domain socket server will be created with the parameter as
       the local socket path.
 
+      Alternately, rte_vhost_driver_register_socket registers a unix domain
+      socket into the system.
+      This socket descriptor should be acquired by the host application through
+      some mechanism (either fd passing or by performing the unix domain socket
+      allocation).
+      The file descriptor passed in this way must still be a Unix domain socket
+      server.
+
 *   Vhost session start
 
       rte_vhost_driver_session_start starts the vhost session loop.
diff --git a/lib/librte_vhost/rte_vhost_version.map b/lib/librte_vhost/rte_vhost_version.map
index 3d8709e..fe58967 100644
--- a/lib/librte_vhost/rte_vhost_version.map
+++ b/lib/librte_vhost/rte_vhost_version.map
@@ -20,3 +20,9 @@ DPDK_2.1 {
 	rte_vhost_driver_unregister;
 
 } DPDK_2.0;
+
+DPDK_16.7 {
+	global:
+
+	rte_vhost_driver_register_socket;
+} DPDK_2.1;
diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 600b20b..d2959ff 100644
--- a/lib/librte_vhost/rte_virtio_net.h
+++ b/lib/librte_vhost/rte_virtio_net.h
@@ -236,6 +236,12 @@ int rte_vhost_enable_guest_notification(struct virtio_net *dev, uint16_t queue_i
 /* Register vhost driver. dev_name could be different for multiple instance support. */
 int rte_vhost_driver_register(const char *dev_name);
 
+/* Register vhost driver using the provided unix domain socket. The socket MUST
+ * already be fully created and in a listening state (by calling listen()).
+ */
+int rte_vhost_driver_register_socket(const char *dev_name,
+	int vhost_unix_socket);
+
 /* Unregister vhost driver. This is only meaningful to vhost user. */
 int rte_vhost_driver_unregister(const char *dev_name);
 
diff --git a/lib/librte_vhost/vhost_user/vhost-net-user.c b/lib/librte_vhost/vhost_user/vhost-net-user.c
index df2bd64..0fe72db 100644
--- a/lib/librte_vhost/vhost_user/vhost-net-user.c
+++ b/lib/librte_vhost/vhost_user/vhost-net-user.c
@@ -446,45 +446,58 @@ vserver_message_handler(int connfd, void *dat, int *remove)
 	}
 }
 
+
 /**
- * Creates and initialise the vhost server.
+ * Appends a socket to the vhost server polling list
  */
 int
-rte_vhost_driver_register(const char *path)
+rte_vhost_driver_register_socket(const char *dev_name, int vhost_unix_socket)
 {
 	struct vhost_server *vserver;
 
-	pthread_mutex_lock(&g_vhost_server.server_mutex);
-
-	if (g_vhost_server.vserver_cnt == MAX_VHOST_SERVER) {
-		RTE_LOG(ERR, VHOST_CONFIG,
-			"error: the number of servers reaches maximum\n");
-		pthread_mutex_unlock(&g_vhost_server.server_mutex);
-		return -1;
-	}
-
 	vserver = calloc(sizeof(struct vhost_server), 1);
 	if (vserver == NULL) {
-		pthread_mutex_unlock(&g_vhost_server.server_mutex);
 		return -1;
 	}
 
-	vserver->listenfd = uds_socket(path);
-	if (vserver->listenfd < 0) {
+	vserver->listenfd = vhost_unix_socket;
+	vserver->path = strdup(dev_name);
+	if (!vserver->path) {
 		free(vserver);
-		pthread_mutex_unlock(&g_vhost_server.server_mutex);
 		return -1;
 	}
 
-	vserver->path = strdup(path);
+	pthread_mutex_lock(&g_vhost_server.server_mutex);
+
+	if (g_vhost_server.vserver_cnt == MAX_VHOST_SERVER) {
+		RTE_LOG(ERR, VHOST_CONFIG,
+			"error: the number of servers reaches maximum\n");
+		pthread_mutex_unlock(&g_vhost_server.server_mutex);
+		free(vserver->path);
+		free(vserver);
+		return -1;
+	}
 
 	fdset_add(&g_vhost_server.fdset, vserver->listenfd,
 		vserver_new_vq_conn, NULL, vserver);
 
 	g_vhost_server.server[g_vhost_server.vserver_cnt++] = vserver;
 	pthread_mutex_unlock(&g_vhost_server.server_mutex);
+}
 
-	return 0;
+
+/**
+ * Creates and initialise the vhost server.
+ */
+int
+rte_vhost_driver_register(const char *dev_name)
+{
+
+	int listenfd = uds_socket(dev_name);
+	if (listenfd < 0)
+		return -1;
+
+	return rte_vhost_driver_register_socket(dev_name, listenfd);
 }
 
 
-- 
2.5.5