[Xen-devel] [RFC 1/4] libxl: Learned to send FD through QMP to QEMU

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

Adding the ability to send a file descriptor from libxl to QEMU via the
QMP interface. This will be use with the "add-fd" QMP command.

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 tools/libxl/libxl_qmp.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index d03cb51668..5bf5236240 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -80,6 +80,9 @@ struct libxl__qmp_handler {
         int minor;
         int micro;
     } version;
+
+    /* File descriptor to send to QEMU on the next command */
+    int fd_to_send;
 };
 
 static int qmp_send(libxl__qmp_handler *qmp,
@@ -378,6 +381,8 @@ static libxl__qmp_handler *qmp_init_handler(libxl__gc *gc, 
uint32_t domid)
 
     LIBXL_STAILQ_INIT(&qmp->callback_list);
 
+    qmp->fd_to_send = -1;
+
     return qmp;
 }
 
@@ -602,9 +607,16 @@ static int qmp_send(libxl__qmp_handler *qmp,
         goto out;
     }
 
-    if (libxl_write_exactly(qmp->ctx, qmp->qmp_fd, buf, strlen(buf),
-                            "QMP command", "QMP socket"))
-        goto out;
+    if (qmp->fd_to_send >= 0) {
+        if (libxl__sendmsg_fds(gc, qmp->qmp_fd, buf, strlen(buf),
+                               1, &qmp->fd_to_send, "QMP socket"))
+            goto out;
+        qmp->fd_to_send = -1;
+    } else {
+        if (libxl_write_exactly(qmp->ctx, qmp->qmp_fd, buf, strlen(buf),
+                                "QMP command", "QMP socket"))
+            goto out;
+    }
     if (libxl_write_exactly(qmp->ctx, qmp->qmp_fd, "\r\n", 2,
                             "CRLF", "QMP socket"))
         goto out;
-- 
Anthony PERARD


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