[PATCH v2 1/4] tools/hotplug: add remove_from_bridge() and improve debug output

[Paul Durrant <paul@xxxxxxx>]

From: Paul Durrant <pdurrant@xxxxxxxxxx>

This patch adds a remove_from_bridge() function into xen-network-common.sh
to partner with the existing add_to_bridge() function. The code in
add_to_bridge() is also slightly re-arranged to avoid duplication calls of
'ip link'.

Both add_to_bridge() and remove_from_bridge() will check if their bridge
manipulation operations are necessary and emit a log message if they are not.

NOTE: A call to remove_from_bridge() will be added by a subsequent patch.

Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
---
 tools/hotplug/Linux/xen-network-common.sh | 37 ++++++++++++++++++-----
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/tools/hotplug/Linux/xen-network-common.sh 
b/tools/hotplug/Linux/xen-network-common.sh
index 8dd3a62068..37e71cfa9c 100644
--- a/tools/hotplug/Linux/xen-network-common.sh
+++ b/tools/hotplug/Linux/xen-network-common.sh
@@ -126,19 +126,40 @@ add_to_bridge () {
     local bridge=$1
     local dev=$2
 
-    # Don't add $dev to $bridge if it's already on a bridge.
-    if [ -e "/sys/class/net/${bridge}/brif/${dev}" ]; then
-       ip link set dev ${dev} up || true
-       return
-    fi
-    if which brctl >&/dev/null; then
-        brctl addif ${bridge} ${dev}
+    # Don't add $dev to $bridge if it's already on the bridge.
+    if [ ! -e "/sys/class/net/${bridge}/brif/${dev}" ]; then
+       log debug "adding $dev to bridge $bridge"
+       if which brctl >&/dev/null; then
+            brctl addif ${bridge} ${dev}
+       else
+            ip link set ${dev} master ${bridge}
+       fi
     else
-        ip link set ${dev} master ${bridge}
+       log debug "$dev already on bridge $bridge"
     fi
+
     ip link set dev ${dev} up
 }
 
+remove_from_bridge () {
+    local bridge=$1
+    local dev=$2
+
+    ip link set dev ${dev} down || :
+
+    # Don't remove $dev from $bridge if it's not on the bridge.
+    if [ -e "/sys/class/net/${bridge}/brif/${dev}" ]; then
+       log debug "removing $dev from bridge $bridge"
+       if which brctl >&/dev/null; then
+            brctl delif ${bridge} ${dev}
+       else
+            ip link set ${dev} nomaster
+       fi
+    else
+       log debug "$dev not on bridge $bridge"
+    fi
+}
+
 # Usage: set_mtu bridge dev
 set_mtu () {
     local bridge=$1
-- 
2.20.1