[PATCH v2 1/2] libxl: fix usage of backend parameter and run_hotplug_scripts

[Roger Pau Monne <roger.pau@citrix.com>]

vif interfaces allows the user to specify the domain that should run
the backend (also known as driver domain) using the 'backend'
parameter. This is not compatible with run_hotplug_scripts=1, since
libxl can only run the hotplug scripts from the Domain 0.

Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
---
Changes since v1:

 * Remove references to xl.conf, since it's a layering violation.

 * Move the docs update to next patch (that includes xl changes).
---
 tools/libxl/libxl.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 8ea3478..47b1fb9 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -2474,6 +2474,8 @@ out:
 int libxl__device_nic_setdefault(libxl__gc *gc, libxl_device_nic *nic,
                                  uint32_t domid)
 {
+    int run_hotplug_scripts;
+
     if (!nic->mtu)
         nic->mtu = 1492;
     if (!nic->model) {
@@ -2503,6 +2505,18 @@ int libxl__device_nic_setdefault(libxl__gc *gc, libxl_device_nic *nic,
                                   libxl__xen_script_dir_path()) < 0 )
         return ERROR_FAIL;
 
+    run_hotplug_scripts = libxl__hotplug_settings(gc, XBT_NULL);
+    if (run_hotplug_scripts < 0) {
+        LOG(ERROR, "unable to get current hotplug scripts execution setting");
+        return run_hotplug_scripts;
+    }
+    if (nic->backend_domid != LIBXL_TOOLSTACK_DOMID && run_hotplug_scripts) {
+        LOG(ERROR, "cannot use a backend domain different than %d if"
+                   "hotplug scripts are executed from libxl",
+                   LIBXL_TOOLSTACK_DOMID);
+        return ERROR_FAIL;
+    }
+
     switch (libxl__domain_type(gc, domid)) {
     case LIBXL_DOMAIN_TYPE_HVM:
         if (!nic->nictype)
-- 
1.7.7.5 (Apple Git-26)