Optional bridge-nf detection

prog/weave-kube/launch.sh

@@ -11,13 +11,14 @@ STATUS_ADDR=${WEAVE_STATUS_ADDR:-0.0.0.0:6782}
 EXPECT_NPC=${EXPECT_NPC:-1}
 
 # kube-proxy requires that bridged traffic passes through netfilter
-if [ ! -f /proc/sys/net/bridge/bridge-nf-call-iptables ] ; then
-    echo /proc/sys/net/bridge/bridge-nf-call-iptables not found >&2
-    exit 1
+if ! BRIDGE_NF_ENABLED=$(cat /proc/sys/net/bridge/bridge-nf-call-iptables); then
+    echo "Cannot detect bridge-nf support - network policy and iptables mode kubeproxy may not work reliably" >&2
+else
+    if [ "$BRIDGE_NF_ENABLED" != "1" ]; then
+        echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables
+    fi
 fi
 
-echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables
-
 SOURCE_BINARY=/usr/bin/weaveutil
 VERSION=$(/home/weave/weaver $EXTRA_ARGS --version | sed -e 's/weave router //')
 PLUGIN="weave-plugin-$VERSION"