[Xen-devel] [PATCH v4 23/32] libxl_qmp: Respond to QMP greeting

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 tools/libxl/libxl_qmp.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index e649b8054d..83afce3192 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -1309,6 +1309,9 @@ int libxl__qmp_initializations(libxl__gc *gc, uint32_t 
domid,
 
 /* ------------ Implementation of libxl__ev_qmp ---------------- */
 
+/* hard coded message ID used for capability negociation */
+static int qmp_capability_negociation_msgid = 1;
+
 static int qmp_ev_prepare_cmd(libxl__gc *gc,
                               libxl__ev_qmp *ev,
                               const char *cmd,
@@ -1379,7 +1382,7 @@ static int qmp_ev_handle_response(libxl__egc *egc,
     }
 
     id = libxl__json_object_get_integer(o);
-    if (id != ev->id)
+    if (id != ev->id && id != qmp_capability_negociation_msgid)
         return 0;
 
     switch (type) {
@@ -1413,9 +1416,21 @@ static int qmp_ev_handle_response(libxl__egc *egc,
         abort();
     }
 
-    ev->id = -1;
-    ev->callback(egc, ev, response, rc); /* must be last */
-    return 1;
+    /*
+     * Even if the current state is capability_negociation and the correct ID
+     * as been received, call the callback on error.
+     */
+    if (ev->qmp_state == qmp_state_capability_negociation &&
+        id == qmp_capability_negociation_msgid &&
+        rc == 0) {
+        ev->qmp_state = qmp_state_connected;
+        libxl__ev_fd_modify(gc, &ev->qmp_efd, ev->qmp_efd.events | POLLOUT);
+        return 0;
+    } else {
+        ev->id = -1;
+        ev->callback(egc, ev, response, rc); /* must be last */
+        return 1;
+    }
 }
 
 /* return 1 when a user callback as been called */
@@ -1429,6 +1444,11 @@ static int qmp_ev_handle_message(libxl__egc *egc,
     switch (type) {
     case LIBXL__QMP_MESSAGE_TYPE_QMP:
         /* greeting message */
+        assert(ev->qmp_state == qmp_state_connecting);
+        ev->qmp_state = qmp_state_greeting;
+        /* Allow qmp_ev_callback_writable to be called in order to send
+         * qmp_capabilities */
+        libxl__ev_fd_modify(gc, &ev->qmp_efd, ev->qmp_efd.events | POLLOUT);
         return 0;
     case LIBXL__QMP_MESSAGE_TYPE_RETURN:
     case LIBXL__QMP_MESSAGE_TYPE_ERROR:
@@ -1563,7 +1583,11 @@ static int qmp_ev_callback_writable(libxl__gc *gc, 
libxl__ev_qmp *ev, int fd)
      * be send for now will be in this call. */
     libxl__ev_fd_modify(gc, &ev->qmp_efd, ev->qmp_efd.events & ~POLLOUT);
 
-    if (ev->qmp_state == qmp_state_connected) {
+    if (ev->qmp_state == qmp_state_greeting) {
+        buf = qmp_prepare_qmp_cmd(gc, "qmp_capabilities", NULL,
+                                  qmp_capability_negociation_msgid, &len);
+        ev->qmp_state = qmp_state_capability_negociation;
+    } else if (ev->qmp_state == qmp_state_connected) {
         if (!ev->tx_buf)
             return 0;
 
@@ -1703,7 +1727,7 @@ void libxl__ev_qmp_init(libxl__ev_qmp *ev)
     ev->qmp_cfd = NULL;
     libxl__ev_fd_init(&ev->qmp_efd);
     ev->qmp_state = qmp_state_disconnected;
-    ev->last_id_used = 0;
+    ev->last_id_used = qmp_capability_negociation_msgid + 1;
 
     ev->rx_buf = NULL;
     ev->tx_buf = NULL;
-- 
Anthony PERARD


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