[PATCH v3 3/8] tools/hotplug/Linux: add remove_from_bridge()

[Paul Durrant <paul@xen.org>]

From: Paul Durrant <pdurrant@amazon.com>

This patch adds a remove_from_bridge() function into xen-network-common.sh
to partner with the existing add_to_bridge() function. The vif-bridge
script is then modified to use it.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wl@xen.org>

v3:
 - Re-factored from "tools/hotplug: add remove_from_bridge() and improve
   debug output" and "tools/hotplug: combine add/online and remove/offline
   in vif-bridge..." in v2
---
 tools/hotplug/Linux/vif-bridge            |  7 +------
 tools/hotplug/Linux/xen-network-common.sh | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/tools/hotplug/Linux/vif-bridge b/tools/hotplug/Linux/vif-bridge
index e722090ca8..c3e409926d 100644
--- a/tools/hotplug/Linux/vif-bridge
+++ b/tools/hotplug/Linux/vif-bridge
@@ -84,12 +84,7 @@ case "$command" in
         ;;
 
     offline)
-        if which brctl >&/dev/null; then
-            do_without_error brctl delif "$bridge" "$dev"
-        else
-            do_without_error ip link set "$dev" nomaster
-        fi
-        do_without_error ifconfig "$dev" down
+        remove_from_bridge "$bridge" "$dev"
         ;;
 
     add)
diff --git a/tools/hotplug/Linux/xen-network-common.sh b/tools/hotplug/Linux/xen-network-common.sh
index ec3bd4ec4a..6a0904361f 100644
--- a/tools/hotplug/Linux/xen-network-common.sh
+++ b/tools/hotplug/Linux/xen-network-common.sh
@@ -141,6 +141,25 @@ add_to_bridge () {
     ip link set dev ${dev} up
 }
 
+remove_from_bridge () {
+    local bridge=$1
+    local dev=$2
+
+    do_without_error 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
+            do_without_error brctl delif ${bridge} ${dev}
+        else
+            do_without_error 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