[Qemu-devel] [V4 PATCH 3/8] Add client side interfaces for chroot environment

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

Define QEMU side interfaces used for chroot environment.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
---
 hw/9pfs/virtio-9p-chroot.c |   87 ++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 87 insertions(+), 0 deletions(-)

diff --git a/hw/9pfs/virtio-9p-chroot.c b/hw/9pfs/virtio-9p-chroot.c
index 5150ff0..b466d9a 100644
--- a/hw/9pfs/virtio-9p-chroot.c
+++ b/hw/9pfs/virtio-9p-chroot.c
@@ -111,6 +111,86 @@ static int chroot_read_request(int sockfd, V9fsFileObjectRequest *request)
     return 0;
 }
 
+/* Receive file descriptor and error status from chroot process */
+static int v9fs_receivefd(int sockfd, int *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);
+
+    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) {
+        *error = EIO;
+        return -EIO;
+    }
+
+    if (fd_info.fi_flags & FI_SOCKERR) {
+        return -EIO;
+    }
+
+    /* If error is set, ancillary data is not present */
+    if (fd_info.fi_error) {
+        *error = fd_info.fi_error;
+        return -1;
+    }
+
+    if (!(fd_info.fi_flags & FI_FDVALID)) {
+        return 0;
+    }
+
+    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;
+    }
+
+    *error = EAGAIN;
+    return -1;
+}
+
+/*
+ * V9fsFileObjectRequest is written into the socket by QEMU process.
+ * Then this request is read by chroot process using read_request function
+ */
+static int v9fs_write_request(int sockfd, V9fsFileObjectRequest *request)
+{
+    int retval, length;
+    char *buff, *buffp;
+
+    length = sizeof(request->data) + request->data.path_len +
+                    request->data.oldpath_len;
+
+    buff = qemu_malloc(length);
+    buffp = buff;
+    memcpy(buffp, &request->data, sizeof(request->data));
+    buffp += sizeof(request->data);
+    memcpy(buffp, request->path.path, request->data.path_len);
+    buffp += request->data.path_len;
+    memcpy(buffp, request->path.old_path, request->data.oldpath_len);
+
+    retval = qemu_write_full(sockfd, buff, length);
+    if (retval != length) {
+        return EIO;
+    }
+    return 0;
+}
+
 static int chroot_daemonize(int chroot_sock)
 {
     sigset_t sigset;
@@ -139,6 +219,12 @@ static int chroot_daemonize(int chroot_sock)
     return 0;
 }
 
+static void chroot_dummy(void)
+{
+    (void)v9fs_receivefd;
+    (void)v9fs_write_request;
+}
+
 /*
  * Fork a process and chroot into the share path. Communication
  * between qemu process and chroot process happens via socket
@@ -184,6 +270,7 @@ int v9fs_chroot(FsContext *fs_ctx)
         error = qemu_write_full(chroot_sock, &code, sizeof(code));
         _exit(1);
     }
+    chroot_dummy();
 
     /*
      * Write 0 to chroot socket to indicate chroot process creation is
-- 
1.7.3.4