[Qemu-devel] [V6 PATCH 4/9] virtio-9p: Add qemu side interfaces for chroot environment

["M. Mohan Kumar" <mohan@in.ibm.com>]

QEMU side interfaces to communicate with chroot daemon process.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
---
 Makefile.objs                   |    2 +-
 hw/9pfs/virtio-9p-chroot-qemu.c |   97 +++++++++++++++++++++++++++++++++++++++
 hw/9pfs/virtio-9p-chroot.h      |    1 +
 3 files changed, 99 insertions(+), 1 deletions(-)
 create mode 100644 hw/9pfs/virtio-9p-chroot-qemu.c

diff --git a/Makefile.objs b/Makefile.objs
index f09cdee..9ea7946 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -283,7 +283,7 @@ hw-obj-$(CONFIG_SOUND) += $(sound-obj-y)
 9pfs-nested-$(CONFIG_VIRTFS) = virtio-9p-debug.o
 9pfs-nested-$(CONFIG_VIRTFS) +=  virtio-9p-local.o virtio-9p-xattr.o
 9pfs-nested-$(CONFIG_VIRTFS) +=   virtio-9p-xattr-user.o virtio-9p-posix-acl.o
-9pfs-nested-$(CONFIG_VIRTFS) +=   virtio-9p-chroot-dm.o
+9pfs-nested-$(CONFIG_VIRTFS) +=   virtio-9p-chroot-dm.o virtio-9p-chroot-qemu.o
 
 hw-obj-$(CONFIG_REALLY_VIRTFS) += $(addprefix 9pfs/, $(9pfs-nested-y))
 $(addprefix 9pfs/, $(9pfs-nested-y)): CFLAGS +=  -I$(SRC_PATH)/hw/
diff --git a/hw/9pfs/virtio-9p-chroot-qemu.c b/hw/9pfs/virtio-9p-chroot-qemu.c
new file mode 100644
index 0000000..d2d8ab9
--- /dev/null
+++ b/hw/9pfs/virtio-9p-chroot-qemu.c
@@ -0,0 +1,97 @@
+/*
+ * Virtio 9p chroot environment for contained access to exported path
+ * Code handles qemu side interfaces to communicate with chroot daemon process
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ * M. Mohan Kumar <mohan@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the copying file in the top-level directory
+ *
+ */
+
+#include <sys/fsuid.h>
+#include <sys/resource.h>
+#include <signal.h>
+#include "virtio.h"
+#include "qemu_socket.h"
+#include "qemu-thread.h"
+#include "qerror.h"
+#include "virtio-9p.h"
+#include "virtio-9p-chroot.h"
+
+/*
+ * Return received file descriptor on success and -errno on failure.
+ * sock_error is set to 1 whenever there is error in socket IO
+ */
+static int v9fs_receivefd(int sockfd, int *sock_error)
+{
+    struct msghdr msg = { };
+    struct iovec iov;
+    union MsgControl msg_control;
+    struct cmsghdr *cmsg;
+    int retval, fd;
+    FdInfo fd_info;
+
+    iov.iov_base = &fd_info;
+    iov.iov_len = sizeof(fd_info);
+
+    *sock_error = 0;
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_iov = &iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = &msg_control;
+    msg.msg_controllen = sizeof(msg_control);
+
+    retval = recvmsg(sockfd, &msg, 0);
+    if (retval < 0) {
+        *sock_error = 1;
+        return -EIO;
+    }
+    if (fd_info.fi_flags & FI_FD_SOCKERR) {
+        *sock_error = 1;
+        return -EIO;
+    }
+    /* If fd is invalid, ancillary data is not present */
+    if (fd_info.fi_fd < 0 || fd_info.fi_flags & FI_FD_INVALID) {
+        return fd_info.fi_fd;
+    }
+
+    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+        if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)) ||
+                cmsg->cmsg_level != SOL_SOCKET ||
+                cmsg->cmsg_type != SCM_RIGHTS) {
+            continue;
+        }
+        fd = *((int *)CMSG_DATA(cmsg));
+        return fd;
+    }
+    *sock_error = 1;
+    return -EIO;
+}
+
+/*
+ * V9fsFileObjectRequest is written into the socket by QEMU process.
+ * Then this request is read by chroot process using v9fs_read_request function
+ */
+static int v9fs_write_request(int sockfd, V9fsFileObjectRequest *request)
+{
+    int retval;
+    retval = qemu_write_full(sockfd, request, sizeof(*request));
+    if (retval != sizeof(*request)) {
+        return -EIO;
+    }
+    return 0;
+}
+
+/*
+ * This patch adds v9fs_receivefd and v9fs_write_request functions,
+ * but there is no callers. To avoid compiler warning message,
+ * refer these two functions
+ */
+void chroot_dummy(void)
+{
+    (void)v9fs_receivefd;
+    (void)v9fs_write_request;
+}
diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
index a5b2a41..bd186dd 100644
--- a/hw/9pfs/virtio-9p-chroot.h
+++ b/hw/9pfs/virtio-9p-chroot.h
@@ -53,5 +53,6 @@ typedef struct V9fsFileObjectRequest
 } V9fsFileObjectRequest;
 
 int v9fs_chroot(FsContext *fs_ctx);
+void chroot_dummy(void);
 
 #endif /* _QEMU_VIRTIO_9P_CHROOT_H */
-- 
1.7.3.4