Re: [PATCH] libxl: force netback to wait for hotplug execution before connecting

[Durrant, Paul]

On 24/01/2022 16:02, Roger Pau Monne wrote:

By writing an empty "hotplug-status" xenstore node in the backend path
libxl can force Linux netback to wait for hotplug script execution
before proceeding to the 'connected' state.

This is required so that netback doesn't skip state 2 (InitWait) and
thus blocks libxl waiting for such state in order to launch the
hotplug script (see libxl__wait_device_connection).

Reported-by: James Dingwall <james-...@dingwall.me.uk>
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
Tested-by: James Dingwall <james-...@dingwall.me.uk>
---
Cc: Wei Liu <wei....@kernel.org>
Cc: Paul Durrant <p...@xen.org>

Reviewed-by: Paul Durrant <p...@xen.org>

---
  tools/libs/light/libxl_nic.c | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/tools/libs/light/libxl_nic.c b/tools/libs/light/libxl_nic.c
index 0b45469dca..0b9e70c9d1 100644
--- a/tools/libs/light/libxl_nic.c
+++ b/tools/libs/light/libxl_nic.c
@@ -248,6 +248,13 @@ static int libxl__set_xenstore_nic(libxl__gc *gc, uint32_t 
domid,
      flexarray_append(ro_front, "mtu");
      flexarray_append(ro_front, GCSPRINTF("%u", nic->mtu));

+ /*

+     * Force backend to wait for hotplug script execution before switching to
+     * connected state.
+     */
+    flexarray_append(back, "hotplug-status");
+    flexarray_append(back, "");
+
      return 0;
  }