[PATCH 4/4] tools/hotplug: modify set_mtu() to inform the frontend via xenstore

[Paul Durrant <paul@xen.org>]

From: Paul Durrant <pdurrant@amazon.com>

set_mtu() currently sets the backend vif MTU but does not inform the frontend
what it is. This patch adds code to write the MTU into a xenstore node. See
netif.h for a specification of the node.

NOTE: There is also a small modification replacing '$mtu' with '${mtu}'
      for style consistency.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wl@xen.org>
---
 tools/hotplug/Linux/vif-bridge            |  2 +-
 tools/hotplug/Linux/xen-network-common.sh | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/tools/hotplug/Linux/vif-bridge b/tools/hotplug/Linux/vif-bridge
index e1d7c49788..b99cc82a21 100644
--- a/tools/hotplug/Linux/vif-bridge
+++ b/tools/hotplug/Linux/vif-bridge
@@ -81,7 +81,7 @@ case "$command" in
         ;&
     online)
         setup_virtual_bridge_port "$dev"
-        set_mtu "$bridge" "$dev"
+        set_mtu "$bridge" "$dev" "$type_if"
         add_to_bridge "$bridge" "$dev"
         ;;
     remove)
diff --git a/tools/hotplug/Linux/xen-network-common.sh b/tools/hotplug/Linux/xen-network-common.sh
index 37e71cfa9c..24fc42d9cf 100644
--- a/tools/hotplug/Linux/xen-network-common.sh
+++ b/tools/hotplug/Linux/xen-network-common.sh
@@ -164,9 +164,21 @@ remove_from_bridge () {
 set_mtu () {
     local bridge=$1
     local dev=$2
+    local type_if=$3
+
     mtu="`ip link show dev ${bridge}| awk '/mtu/ { print $5 }'`"
     if [ -n "$mtu" ] && [ "$mtu" -gt 0 ]
     then
-            ip link set dev ${dev} mtu $mtu || :
+            ip link set dev ${dev} mtu ${mtu} || :
+    fi
+
+    if [ ${type_if} = vif ]
+    then
+       dev_=${dev#vif}
+       domid=${dev_%.*}
+       devid=${dev_#*.}
+
+       XENBUS_PATH="/local/domain/$domid/device/vif/$devid"
+       xenstore_write "$XENBUS_PATH/mtu" ${mtu}
     fi
 }
-- 
2.20.1