Simple support script to gather libnetwork info

This script gathers some basic information from a system that might
be useful to help troubleshoot problems.  If added into an image
including the proper binaries, running looks something like this:

    docker run --rm \
        -v /var/run/docker.sock:/var/run/docker.sock \
        -v /var/run/docker/netns:/var/run/docker/netns \
        --privileged --net=host nwsupport /bin/support

Signed-off-by: Daniel Hiltgen <daniel.hiltgen@docker.com>

libnetwork/support.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+# Required tools
+DOCKER="${DOCKER:-docker}"
+NSENTER="${NSENTER:-nsenter}"
+BRIDGE="${BRIDGE:-bridge}"
+BRCTL="${BRCTL:-brctl}"
+IPTABLES="${IPTABLES:-iptables}"
+
+NSDIR=/var/run/docker/netns
+BRIDGEIF=br0
+
+function die {
+    echo $*
+    exit 1
+}
+
+type -P ${DOCKER} > /dev/null || die "This tool requires the docker binary"
+type -P ${NSENTER} > /dev/null || die "This tool requires nsenter"
+type -P ${BRIDGE} > /dev/null || die "This tool requires bridge"
+type -P ${BRCTL} > /dev/null || die "This tool requires brctl"
+type -P ${IPTABLES} > /dev/null || die "This tool requires iptables"
+
+echo "iptables configuration"
+${IPTABLES} -n -v -L -t filter
+${IPTABLES} -n -v -L -t nat
+echo ""
+
+echo "Overlay network configuration"
+for networkID in $(${DOCKER} network ls --filter driver=overlay -q) ; do
+    echo "Network ${networkID}"
+    nspath=(${NSDIR}/*-$(echo ${networkID}| cut -c1-10))
+    ${NSENTER} --net=${nspath[0]} ${BRIDGE} fdb show ${BRIDGEIF}
+    ${NSENTER} --net=${nspath[0]} ${BRCTL} showmacs ${BRIDGEIF}
+    echo ""
+done