[PATCH 15/30] virtiofsd: Open vhost connection instead of mounting

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

When run with vhost-user options we conect to the QEMU instead
via a socket.  Start this off by creating the socket.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 contrib/virtiofsd/fuse_i.h        |  7 ++-
 contrib/virtiofsd/fuse_lowlevel.c | 53 +++-------------------
 contrib/virtiofsd/fuse_virtio.c   | 75 +++++++++++++++++++++++++++++++
 contrib/virtiofsd/fuse_virtio.h   | 23 ++++++++++
 4 files changed, 110 insertions(+), 48 deletions(-)
 create mode 100644 contrib/virtiofsd/fuse_virtio.c
 create mode 100644 contrib/virtiofsd/fuse_virtio.h

diff --git a/contrib/virtiofsd/fuse_i.h b/contrib/virtiofsd/fuse_i.h
index d65af06ff0..27fa50274d 100644
--- a/contrib/virtiofsd/fuse_i.h
+++ b/contrib/virtiofsd/fuse_i.h
@@ -6,9 +6,10 @@
   See the file COPYING.LIB
 */
 
-#define FUSE_USE_VERSION 31
-
+#ifndef FUSE_I_H
+#define FUSE_I_H
 
+#define FUSE_USE_VERSION 31
 #include "fuse.h"
 #include "fuse_lowlevel.h"
 
@@ -119,3 +120,5 @@ void fuse_session_process_buf_int(struct fuse_session *se,
 
 /* room needed in buffer to accommodate header */
 #define FUSE_BUFFER_HEADER_SIZE 0x1000
+
+#endif
diff --git a/contrib/virtiofsd/fuse_lowlevel.c b/contrib/virtiofsd/fuse_lowlevel.c
index d47e4438f3..247667e3f4 100644
--- a/contrib/virtiofsd/fuse_lowlevel.c
+++ b/contrib/virtiofsd/fuse_lowlevel.c
@@ -13,6 +13,7 @@
 #include "fuse_kernel.h"
 #include "fuse_opt.h"
 #include "fuse_misc.h"
+#include "fuse_virtio.h"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -2152,6 +2153,11 @@ struct fuse_session *fuse_session_new(struct fuse_args *args,
 		goto out4;
 	}
 
+	if (!se->vu_socket_path) {
+		fprintf(stderr, "fuse: missing -o vhost_user_socket option\n");
+		goto out4;
+	}
+
 	se->bufsize = FUSE_MAX_MAX_PAGES * getpagesize() +
 		FUSE_BUFFER_HEADER_SIZE;
 
@@ -2175,52 +2181,7 @@ out1:
 
 int fuse_session_mount(struct fuse_session *se)
 {
-	int fd;
-
-	/*
-	 * Make sure file descriptors 0, 1 and 2 are open, otherwise chaos
-	 * would ensue.
-	 */
-	do {
-		fd = open("/dev/null", O_RDWR);
-		if (fd > 2)
-			close(fd);
-	} while (fd >= 0 && fd <= 2);
-
-	/*
-	 * To allow FUSE daemons to run without privileges, the caller may open
-	 * /dev/fuse before launching the file system and pass on the file
-	 * descriptor by specifying /dev/fd/N as the mount point. Note that the
-	 * parent process takes care of performing the mount in this case.
-	 */
-	fd = fuse_mnt_parse_fuse_fd(mountpoint);
-	if (fd != -1) {
-		if (fcntl(fd, F_GETFD) == -1) {
-			fuse_log(FUSE_LOG_ERR,
-				"fuse: Invalid file descriptor /dev/fd/%u\n",
-				fd);
-			return -1;
-		}
-		se->fd = fd;
-		return 0;
-	}
-
-	/* Open channel */
-	fd = fuse_kern_mount(mountpoint, se->mo);
-	if (fd == -1)
-		return -1;
-	se->fd = fd;
-
-	/* Save mountpoint */
-	se->mountpoint = strdup(mountpoint);
-	if (se->mountpoint == NULL)
-		goto error_out;
-
-	return 0;
-
-error_out:
-	fuse_kern_unmount(mountpoint, fd);
-	return -1;
+	return virtio_session_mount(se);
 }
 
 int fuse_session_fd(struct fuse_session *se)
diff --git a/contrib/virtiofsd/fuse_virtio.c b/contrib/virtiofsd/fuse_virtio.c
new file mode 100644
index 0000000000..da8451faa7
--- /dev/null
+++ b/contrib/virtiofsd/fuse_virtio.c
@@ -0,0 +1,75 @@
+/*
+ * virtio-fs glue for FUSE
+ * Copyright (C) 2018 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ *   Dave Gilbert  <dgilbert@redhat.com>
+ *
+ * Implements the glue between libfuse and libvhost-user
+ *
+ * This program can be distributed under the terms of the GNU LGPLv2.
+ * See the file COPYING.LIB
+ */
+
+#include "fuse_i.h"
+#include "fuse_kernel.h"
+#include "fuse_misc.h"
+#include "fuse_opt.h"
+#include "fuse_virtio.h"
+
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+/* From spec */
+struct virtio_fs_config {
+    char tag[36];
+    uint32_t num_queues;
+};
+
+int virtio_session_mount(struct fuse_session *se)
+{
+    struct sockaddr_un un;
+
+    if (strlen(se->vu_socket_path) >= sizeof(un.sun_path)) {
+        fuse_log(FUSE_LOG_ERR, "Socket path too long\n");
+        return -1;
+    }
+
+    /*
+     * Poison the fuse FD so we spot if we accidentally use it;
+     * DO NOT check for this value, check for fuse_lowlevel_is_virtio()
+     */
+    se->fd = 0xdaff0d11;
+
+    /*
+     * Create the Unix socket to communicate with qemu
+     * based on QEMU's vhost-user-bridge
+     */
+    unlink(se->vu_socket_path);
+    strcpy(un.sun_path, se->vu_socket_path);
+    size_t addr_len = sizeof(un.sun_family) + strlen(se->vu_socket_path);
+
+    int listen_sock = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (listen_sock == -1) {
+        fuse_log(FUSE_LOG_ERR, "vhost socket creation: %m\n");
+        return -1;
+    }
+    un.sun_family = AF_UNIX;
+
+    if (bind(listen_sock, (struct sockaddr *)&un, addr_len) == -1) {
+        fuse_log(FUSE_LOG_ERR, "vhost socket bind: %m\n");
+        return -1;
+    }
+
+    if (listen(listen_sock, 1) == -1) {
+        fuse_log(FUSE_LOG_ERR, "vhost socket listen: %m\n");
+        return -1;
+    }
+
+    return -1;
+}
diff --git a/contrib/virtiofsd/fuse_virtio.h b/contrib/virtiofsd/fuse_virtio.h
new file mode 100644
index 0000000000..6652e609e0
--- /dev/null
+++ b/contrib/virtiofsd/fuse_virtio.h
@@ -0,0 +1,23 @@
+/*
+  virtio-fs glue for FUSE
+  Copyright (C) 2018 Red Hat, Inc. and/or its affiliates
+
+  Authors:
+    Dave Gilbert  <dgilbert@redhat.com>
+
+  Implements the glue between libfuse and libvhost-user
+
+  This program can be distributed under the terms of the GNU LGPLv2.
+  See the file COPYING.LIB
+*/
+
+#ifndef FUSE_VIRTIO_H
+#define FUSE_VIRTIO_H
+
+#include "fuse_i.h"
+
+struct fuse_session;
+
+int virtio_session_mount(struct fuse_session *se);
+
+#endif
-- 
2.23.0