docker-veth.sh

#!/bin/bash


usage () {
    cat <<HELP_USAGE

    $0  Show the veth interface associated of containers

    Examples:

    $0 # shows all containers
    $0 --filter "name=nginx" # filter containers

    See docker ps --help docs for more info on filters

HELP_USAGE
}

case "$1" in
    -h|--help)
    usage
    exit 0
    ;;
    *)
    ;;
esac

veth=""

containers=$(docker ps --format '{{.ID}} {{.Names}}' "$@")

get_veth () {
    # This function expects docker container ID as the first argument
    veth=""
    networkmode=$(docker inspect -f "{{.HostConfig.NetworkMode}}" $1)
    if [ "$networkmode" == "host" ]; then
        veth="host"
    else
        pid=$(docker inspect --format '{{.State.Pid}}' "$1")
        ifindex=$(nsenter -t $pid -n ip link | sed -n -e 's/.*eth0@if\([0-9]*\):.*/\1/p')
        if [ -z "$ifindex" ]; then
            veth="not found"
        else
            veth=$(ip -o link | grep ^$ifindex | sed -n -e 's/.*\(veth[[:alnum:]]*@if[[:digit:]]*\).*/\1/p')
        fi
    fi
}

while IFS= read -r line
do
    containerid=$(echo $line | awk '{ print $1 }')
    get_veth $containerid
    echo "$veth $line"
done <<< "$containers"