qemu-config: Add new -add-fd command line option
This option can be used for passing file descriptors on the
command line. It mirrors the existing add-fd QMP command which
allows an fd to be passed to QEMU via SCM_RIGHTS and added to an
fd set.
This can be combined with commands such as -drive to link file
descriptors in an fd set to a drive:
qemu-kvm -add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
This example adds dups of fds 3 and 4, and the accompanying opaque
strings to the fd set with ID=2. qemu_open() already knows how
to handle a filename of this format. qemu_open() searches the
corresponding fd set for an fd and when it finds a match, QEMU
goes on to use a dup of that fd just like it would have used an
fd that it opened itself.
Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/vl.c b/vl.c
index ee3c43a..b870caf 100644
--- a/vl.c
+++ b/vl.c
@@ -790,6 +790,78 @@
return 0;
}
+#ifndef _WIN32
+static int parse_add_fd(QemuOpts *opts, void *opaque)
+{
+ int fd, dupfd, flags;
+ int64_t fdset_id;
+ const char *fd_opaque = NULL;
+
+ fd = qemu_opt_get_number(opts, "fd", -1);
+ fdset_id = qemu_opt_get_number(opts, "set", -1);
+ fd_opaque = qemu_opt_get(opts, "opaque");
+
+ if (fd < 0) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "fd option is required and must be non-negative");
+ return -1;
+ }
+
+ if (fd <= STDERR_FILENO) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "fd cannot be a standard I/O stream");
+ return -1;
+ }
+
+ /*
+ * All fds inherited across exec() necessarily have FD_CLOEXEC
+ * clear, while qemu sets FD_CLOEXEC on all other fds used internally.
+ */
+ flags = fcntl(fd, F_GETFD);
+ if (flags == -1 || (flags & FD_CLOEXEC)) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "fd is not valid or already in use");
+ return -1;
+ }
+
+ if (fdset_id < 0) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "set option is required and must be non-negative");
+ return -1;
+ }
+
+#ifdef F_DUPFD_CLOEXEC
+ dupfd = fcntl(fd, F_DUPFD_CLOEXEC, 0);
+#else
+ dupfd = dup(fd);
+ if (dupfd != -1) {
+ qemu_set_cloexec(dupfd);
+ }
+#endif
+ if (dupfd == -1) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "Error duplicating fd: %s", strerror(errno));
+ return -1;
+ }
+
+ /* add the duplicate fd, and optionally the opaque string, to the fd set */
+ monitor_fdset_add_fd(dupfd, true, fdset_id, fd_opaque ? true : false,
+ fd_opaque, NULL);
+
+ return 0;
+}
+
+static int cleanup_add_fd(QemuOpts *opts, void *opaque)
+{
+ int fd;
+
+ fd = qemu_opt_get_number(opts, "fd", -1);
+ close(fd);
+
+ return 0;
+}
+#endif
+
/***********************************************************/
/* QEMU Block devices */
@@ -3309,6 +3381,18 @@
exit(0);
}
break;
+ case QEMU_OPTION_add_fd:
+#ifndef _WIN32
+ opts = qemu_opts_parse(qemu_find_opts("add-fd"), optarg, 0);
+ if (!opts) {
+ exit(0);
+ }
+#else
+ error_report("File descriptor passing is disabled on this "
+ "platform");
+ exit(1);
+#endif
+ break;
default:
os_parse_cmd_args(popt->index, optarg);
}
@@ -3320,6 +3404,16 @@
exit(1);
}
+#ifndef _WIN32
+ if (qemu_opts_foreach(qemu_find_opts("add-fd"), parse_add_fd, NULL, 1)) {
+ exit(1);
+ }
+
+ if (qemu_opts_foreach(qemu_find_opts("add-fd"), cleanup_add_fd, NULL, 1)) {
+ exit(1);
+ }
+#endif
+
if (machine == NULL) {
fprintf(stderr, "No machine found.\n");
exit(1);
