[Qemu-devel] [PATCH v2 2/4] qapi: Add passfd QMP command

[Corey Bryant <coreyb@linux.vnet.ibm.com>]

This patch adds the passfd QMP command using the QAPI framework.
Like the getfd command, it is used to pass a file descriptor via
SCM_RIGHTS.  However, the passfd command also returns the received
file descriptor, which is a difference in behavior from the getfd
command, which returns nothing.

The closefd command can be used to close a file descriptor that was
passed with the passfd command.

v2:
 -Introduce new QMP command to pass/return fd (lcapitulino@redhat.com)
 -Use passfd as command name (berrange@redhat.com)

Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com>
---
 monitor.c        |   14 ++++++++++----
 qapi-schema.json |   15 +++++++++++++++
 qmp-commands.hx  |   27 +++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/monitor.c b/monitor.c
index 4c53cb6..980a226 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2182,7 +2182,7 @@ static void do_inject_mce(Monitor *mon, const QDict *qdict)
 }
 #endif
 
-void qmp_getfd(const char *fdname, Error **errp)
+int64_t qmp_passfd(const char *fdname, Error **errp)
 {
     mon_fd_t *monfd;
     int fd;
@@ -2190,13 +2190,13 @@ void qmp_getfd(const char *fdname, Error **errp)
     fd = qemu_chr_fe_get_msgfd(cur_mon->chr);
     if (fd == -1) {
         error_set(errp, QERR_FD_NOT_SUPPLIED);
-        return;
+        return -1;
     }
 
     if (qemu_isdigit(fdname[0])) {
         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdname",
                   "a name not starting with a digit");
-        return;
+        return -1;
     }
 
     QLIST_FOREACH(monfd, &cur_mon->fds, next) {
@@ -2206,7 +2206,7 @@ void qmp_getfd(const char *fdname, Error **errp)
 
         close(monfd->fd);
         monfd->fd = fd;
-        return;
+        return fd;
     }
 
     monfd = g_malloc0(sizeof(mon_fd_t));
@@ -2214,6 +2214,12 @@ void qmp_getfd(const char *fdname, Error **errp)
     monfd->fd = fd;
 
     QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next);
+    return fd;
+}
+
+void qmp_getfd(const char *fdname, Error **errp)
+{
+    qmp_passfd(fdname, errp);
     return;
 }
 
diff --git a/qapi-schema.json b/qapi-schema.json
index 6be1d90..15da1b8 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1864,6 +1864,21 @@
 { 'command': 'netdev_del', 'data': {'id': 'str'} }
 
 ##
+# @passfd:
+#
+# Pass a file descriptor via SCM rights and assign it a name
+#
+# @fdname: file descriptor name
+#
+# Returns: The QEMU file descriptor that was received
+#          If file descriptor was not received, FdNotSupplied
+#          If @fdname is not valid, InvalidParameterType
+#
+# Since: 1.2.0
+##
+{ 'command': 'passfd', 'data': {'fdname': 'str'}, 'returns': 'int' }
+
+##
 # @getfd:
 #
 # Receive a file descriptor via SCM rights and assign it a name
diff --git a/qmp-commands.hx b/qmp-commands.hx
index f8c0f68..338a0b3 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -869,6 +869,33 @@ Example:
 EQMP
 
     {
+        .name       = "passfd",
+        .args_type  = "fdname:s",
+        .params     = "passfd name",
+        .help       = "pass a file descriptor via SCM rights and assign it a name",
+        .mhandler.cmd_new = qmp_marshal_input_passfd,
+    },
+
+SQMP
+passfd
+------
+
+Pass a file descriptor via SCM rights and assign it a name.
+
+Arguments:
+
+- "fdname": file descriptor name (json-string)
+
+Return a json-int with the QEMU file descriptor that was received.
+
+Example:
+
+-> { "execute": "passfd", "arguments": { "fdname": "fd1" } }
+<- { "return": 42 }
+
+EQMP
+
+    {
         .name       = "getfd",
         .args_type  = "fdname:s",
         .params     = "getfd name",
-- 
1.7.10.2