[V5,4/8] virtio-9p: Add support to open a file in chroot environment

diff --git a/hw/9pfs/virtio-9p-chroot-clnt.c b/hw/9pfs/virtio-9p-chroot-clnt.c
index ac65f03..7f72add 100644
--- a/hw/9pfs/virtio-9p-chroot-clnt.c
+++ b/hw/9pfs/virtio-9p-chroot-clnt.c
@@ -88,9 +88,23 @@  static int v9fs_write_request(int sockfd, V9fsFileObjectRequest *request)
     return 0;
 }
 
-void chroot_dummy(void)
+/* Return opened file descriptor on success or -1 on error */
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *request,
+                        int *error)
 {
-    (void)v9fs_receivefd;
-    (void)v9fs_write_request;
+    int fd;
+    qemu_mutex_lock(&fs_ctx->chroot_mutex);
+    if (fs_ctx->chroot_ioerror) {
+        *error = EIO;
+        fd = -1;
+        goto unlock;
+    }
+    v9fs_write_request(fs_ctx->chroot_socket, request);
+    fd = v9fs_receivefd(fs_ctx->chroot_socket, error);
+    if (fd == -EIO && *error == EIO) {
+        fs_ctx->chroot_ioerror = 1;
+    }
+unlock:
+    qemu_mutex_unlock(&fs_ctx->chroot_mutex);
+    return fd;
 }
-
diff --git a/hw/9pfs/virtio-9p-chroot-sv.c b/hw/9pfs/virtio-9p-chroot-sv.c
index 86d10cd..e9952b3 100644
--- a/hw/9pfs/virtio-9p-chroot-sv.c
+++ b/hw/9pfs/virtio-9p-chroot-sv.c
@@ -70,6 +70,21 @@  static int chroot_read_request(int sockfd, V9fsFileObjectRequest *request)
     return 0;
 }
 
+/*
+ * Helper routine to open a file and return fd and error status in
+ * FdInfo structure
+ */
+static void chroot_do_open(V9fsFileObjectRequest *request, FdInfo *fd_info)
+{
+    fd_info->fi_fd = open(request->path.path, request->data.flags);
+    if (fd_info->fi_fd < 0) {
+        fd_info->fi_error = errno;
+    } else {
+        fd_info->fi_error = 0;
+        fd_info->fi_flags = FI_FDVALID;
+    }
+}
+
 static int chroot_daemonize(int chroot_sock)
 {
     sigset_t sigset;
@@ -164,6 +179,17 @@  int v9fs_chroot(FsContext *fs_ctx)
             fd_info.fi_error = EIO;
             fd_info.fi_flags = FI_SOCKERR;
             chroot_sendfd(chroot_sock, &fd_info);
+            continue;
+        }
+        switch (request.data.type) {
+        case T_OPEN:
+            chroot_do_open(&request, &fd_info);
+            break;
+        default:
+            fd_info.fi_fd = 0;
+            fd_info.fi_error = EIO;
+            break;
         }
+        chroot_sendfd(chroot_sock, &fd_info);
     }
 }
diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
index 9122edc..057dcde 100644
--- a/hw/9pfs/virtio-9p-chroot.h
+++ b/hw/9pfs/virtio-9p-chroot.h
@@ -53,6 +53,6 @@  typedef struct V9fsFileObjectRequest
 } V9fsFileObjectRequest;
 
 int v9fs_chroot(FsContext *fs_ctx);
-void chroot_dummy(void);
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *or, int *error);
 
 #endif /* _QEMU_VIRTIO_9P_CHROOT_H */
diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
index 0a015de..bef0272 100644
--- a/hw/9pfs/virtio-9p-local.c
+++ b/hw/9pfs/virtio-9p-local.c
@@ -13,6 +13,9 @@ 
 #include "virtio.h"
 #include "virtio-9p.h"
 #include "virtio-9p-xattr.h"
+#include "qemu_socket.h"
+#include "fsdev/qemu-fsdev.h"
+#include "virtio-9p-chroot.h"
 #include <arpa/inet.h>
 #include <pwd.h>
 #include <grp.h>
@@ -20,6 +23,35 @@ 
 #include <sys/un.h>
 #include <attr/xattr.h>
 
+/* Helper routine to fill V9fsFileObjectRequest structure */
+static void fill_request(V9fsFileObjectRequest *request, const char *path,
+                FsCred *credp)
+{
+    memset(request, 0, sizeof(*request));
+    request->data.path_len = strlen(path);
+    strcpy(request->path.path, (path));
+    if (credp) {
+        request->data.mode = credp->fc_mode;
+        request->data.uid = credp->fc_uid;
+        request->data.gid = credp->fc_gid;
+        request->data.dev = credp->fc_rdev;
+    }
+}
+
+static int passthrough_open(FsContext *fs_ctx, const char *path, int flags)
+{
+    V9fsFileObjectRequest request;
+    int fd, error = 0;
+
+    fill_request(&request, path, NULL);
+    request.data.flags = flags;
+    request.data.type = T_OPEN;
+    fd = v9fs_request(fs_ctx, &request, &error);
+    if (fd < 0) {
+        errno = error;
+    }
+    return fd;
+}
 
 static int local_lstat(FsContext *fs_ctx, const char *path, struct stat *stbuf)
 {
@@ -138,14 +170,27 @@  static int local_closedir(FsContext *ctx, DIR *dir)
     return closedir(dir);
 }
 
-static int local_open(FsContext *ctx, const char *path, int flags)
+static int local_open(FsContext *fs_ctx, const char *path, int flags)
 {
-    return open(rpath(ctx, path), flags);
+    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        return passthrough_open(fs_ctx, path, flags);
+    } else {
+        return open(rpath(fs_ctx, path), flags);
+    }
 }
 
-static DIR *local_opendir(FsContext *ctx, const char *path)
+static DIR *local_opendir(FsContext *fs_ctx, const char *path)
 {
-    return opendir(rpath(ctx, path));
+    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        int fd;
+        fd = passthrough_open(fs_ctx, path, O_DIRECTORY);
+        if (fd < 0) {
+            return NULL;
+        }
+        return fdopendir(fd);
+    } else {
+        return opendir(rpath(fs_ctx, path));
+    }
 }
 
 static void local_rewinddir(FsContext *ctx, DIR *dir)