[Qemu-devel] [PATCH 1/3] qmp/hmp: Add QMP getfd command that returns fd

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

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

Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com>
---
 hmp-commands.hx  |    2 +-
 monitor.c        |   37 ++++++++++++++++++++++++++++++++++++-
 qapi-schema.json |   13 +++++++++++++
 qmp-commands.hx  |    6 ++++--
 4 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 18cb415..dfab369 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1211,7 +1211,7 @@ ETEXI
         .params     = "getfd name",
         .help       = "receive a file descriptor via SCM rights and assign it a name",
         .user_print = monitor_user_noop,
-        .mhandler.cmd_new = do_getfd,
+        .mhandler.cmd_new = hmp_getfd,
     },
 
 STEXI
diff --git a/monitor.c b/monitor.c
index 12a6fe2..6acf5a3 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2199,7 +2199,7 @@ static void do_inject_mce(Monitor *mon, const QDict *qdict)
 }
 #endif
 
-static int do_getfd(Monitor *mon, const QDict *qdict, QObject **ret_data)
+static int hmp_getfd(Monitor *mon, const QDict *qdict, QObject **ret_data)
 {
     const char *fdname = qdict_get_str(qdict, "fdname");
     mon_fd_t *monfd;
@@ -2235,6 +2235,41 @@ static int do_getfd(Monitor *mon, const QDict *qdict, QObject **ret_data)
     return 0;
 }
 
+int64_t qmp_getfd(const char *fdname, Error **errp)
+{
+    mon_fd_t *monfd;
+    int fd;
+
+    fd = qemu_chr_fe_get_msgfd(cur_mon->chr);
+    if (fd == -1) {
+        error_set(errp, QERR_FD_NOT_SUPPLIED);
+        return -1;
+    }
+
+    if (qemu_isdigit(fdname[0])) {
+        error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdname",
+                  "a name not starting with a digit");
+        return -1;
+    }
+
+    QLIST_FOREACH(monfd, &cur_mon->fds, next) {
+        if (strcmp(monfd->name, fdname) != 0) {
+            continue;
+        }
+
+        close(monfd->fd);
+        monfd->fd = fd;
+        return fd;
+    }
+
+    monfd = g_malloc0(sizeof(mon_fd_t));
+    monfd->name = g_strdup(fdname);
+    monfd->fd = fd;
+
+    QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next);
+    return fd;
+}
+
 static int do_closefd(Monitor *mon, const QDict *qdict, QObject **ret_data)
 {
     const char *fdname = qdict_get_str(qdict, "fdname");
diff --git a/qapi-schema.json b/qapi-schema.json
index 2ca7195..5f26ba2 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1755,3 +1755,16 @@
 # Since: 0.14.0
 ##
 { 'command': 'device_del', 'data': {'id': 'str'} }
+
+##
+# @getfd:
+#
+# Receive a file descriptor via SCM rights and assign it a name
+#
+# @fdname: file descriptor name
+#
+# Returns: The QEMU @fd that was received
+#
+# Since: 1.2
+##
+{ 'command': 'getfd', 'data': {'fdname': 'str'}, 'returns': 'int' }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index db980fa..e13d583 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -844,7 +844,7 @@ EQMP
         .params     = "getfd name",
         .help       = "receive a file descriptor via SCM rights and assign it a name",
         .user_print = monitor_user_noop,
-        .mhandler.cmd_new = do_getfd,
+        .mhandler.cmd_new = qmp_marshal_input_getfd,
     },
 
 SQMP
@@ -857,10 +857,12 @@ Arguments:
 
 - "fdname": file descriptor name (json-string)
 
+Return a json-int with the QEMU file descriptor that was received.
+
 Example:
 
 -> { "execute": "getfd", "arguments": { "fdname": "fd1" } }
-<- { "return": {} }
+<- { "return": 42 }
 
 EQMP
 
-- 
1.7.10.2