Setup the openwrt networks

setup-net.sh

#!/bin/bash

set -eo pipefail

# List of bridges to create space delimited
bridges="sw-r0-eth0 sw-r0-eth1 sw-r0-eth2 sw-r0-eth3"
# Veths peirs to create with the following format, space delimited
# <veth dev 1>[|options]:<veth dev 1>[|options]
# where options are a comma delimited key=values pair
# options: master=<master bridge> or dhcp
veths="veth0:dhcp|veth1:master=sw-r0-eth1"

#wan_bridge="$(echo ${bridges} | cut -d\  -f 1)"
wan_bridge="virbr0"

action=$1


function _help {
    cat<<EOF
${0} usage: Creates the necessary bridges and interfaces necessary for the virtualbox infrastructure

${0} <start|stop|dhcp|stop-dhcp|show-wan|help>
- start: creates the bridges and veths, and sets them up
- stop: tears everything down
- dhcp: runs dhclient on the dhcp interfaces
- stop-dhcp: kill running dhcp processes
- show-wan: shows the wan interface
- help: displays this help message
EOF
}
if [ -z "${action}" ]; then
    _help
    exit 1
fi;

wan_interface=$(ip r | grep default | grep dev | sed -e 's/^.*dev \([^ ]*\) .*$/\1/')

if [ -z "${wan_interface}" ]; then
    echo "could not determine the wan interface"
    exit 1
fi;

function _start {
    for bridge in ${bridges}; do
        if ! ip link show "${bridge}" >/dev/null 2>&1; then
            sudo ip link add "${bridge}" type bridge stp_state 1
        fi;
    done;

    for veth in ${veths}; do
        veth0=$(echo "${veth}" | cut -f1 -d\| | cut -f1 -d:)
        veth1=$(echo "${veth}" | cut -f2 -d\| | cut -f1 -d:)
        if [ -z "${veth0}" ] || [ -z "${veth1}" ]; then
            echo "invalid veth interface spec ${veth}, should be like veth0:veth1:br-master"
            exit 1
        fi;

        if ! ip link show "${veth0}" >/dev/null 2>&1 || ! ip link show "${veth1}" >/dev/null 2>&1; then
            echo "(re)-creating the pair ${veth}"
            sudo ip link del "${veth0}" 2>/dev/null || true
            sudo ip link del "${veth1}" 2>/dev/null || true
            sudo ip link add "${veth0}" type veth peer name "${veth1}"
        fi;
        sudo ip link set up dev "${veth0}"
        sudo ip link set up dev "${veth1}"
        for cfgVeth in $(echo "${veth}" | tr '|' ' '); do
            local vethName
            vethName="$(echo "${cfgVeth}" | cut -d: -f1)"
            echo "configuring veth ${vethName}"
            for opt in $(echo "${cfgVeth}" | cut -d: -f2 | tr ',' ' '); do
                if ! echo "${cfgVeth}" | grep -q ":"; then 
                    continue
                fi;
                case ${opt} in
                    dhcp)
                    if [ -n "${DO_DHCP}" ]; then
                        echo " - running dhclient"
                        sudo dhclient -4 -v "${vethName}"
                        echo "removing default routes set by dhclient"
                        route=$(ip route | grep default | grep "${vethName}")
                        if [ -n "${route}" ]; then
                            # shellcheck disable=SC2086
                            sudo ip route del ${route}
                        fi;
                    else
                        echo " - DHCP would be enabled by ${0} dhcp"
                    fi;
                ;;
                    master=*)
                    local masterBridge
                    masterBridge="$(echo "${opt}" | cut -d= -f2)"
                    echo " - setting ${vethName} as a port of ${masterBridge}"
                     if ! ip link show "${masterBridge}" >/dev/null 2>&1; then
                        echo "bridge ${masterBridge} does not exist"
                        exit 1
                    fi;

                    sudo ip link set master "${masterBridge}" dev "${vethName}"
                ;;
                    *)
                    echo "Invalid option ${opt}"
                ;;
                esac
            done;
        done;
    done;

    for bridge in ${bridges}; do
        sudo ip link set up dev "${bridge}"
    done;
}

function _dhcp {
    DO_DHCP=1 _start
}

function _stop {
    for veth in ${veths}; do
        veth0=$(echo "${veth}" | cut -f1 -d\| | cut -f1 -d:)
        veth1=$(echo "${veth}" | cut -f2 -d\| | cut -f1 -d:)
        if [ -z "${veth0}" ] || [ -z "${veth1}" ]; then
            echo "Invalid veth interface spec ${veth}, should be like veth0:<options>|veth1:<options>"
            exit 1
        fi;

        sudo ip link del "${veth0}" || true
        sudo ip link del "${veth1}" || true
    done;

    for bridge in ${bridges}; do
        sudo ip link del "${bridge}" || true
    done;
}

function _stop_dhcp {
    for veth in ${veths}; do
        veth0=$(echo "${veth}" | cut -f1 -d\| | cut -f1 -d:)
        veth1=$(echo "${veth}" | cut -f2 -d\| | cut -f1 -d:)
        if [ -z "${veth0}" ] || [ -z "${veth1}" ]; then
            echo "Invalid veth interface spec ${veth}, should be like veth0:<options>|veth1:<options>"
            exit 1
        fi;

        # shellcheck disable=SC2009
        pid="$(ps faux | grep 'dhclient -4 -v veth0' |grep -v grep | awk '{ print $2 }')"
        if [ -n "${pid}" ]; then
            echo "killing dhclient with pid ${pid}"
            sudo kill "${pid}"
        fi;
    done;
}

function _iptables {
    sudo iptables -I FORWARD -i ${wan_bridge} -o "${wan_interface}" -j ACCEPT
    sudo iptables -I FORWARD -o ${wan_bridge} -i "${wan_interface}" -j ACCEPT
    sudo iptables -t nat -I POSTROUTING -o "${wan_interface}" -j MASQUERADE
}

case ${action} in
    start)
        _start
        exit 0
    ;;
    stop)
        _stop
        _stop_dhcp
        exit 0
    ;;
    iptables)
        _iptables
        exit 0
    ;;
    dhcp)
        _dhcp
        exit 0
    ;;
    stop-dhcp)
        _stop_dhcp
        exit 0
    ;;
    show-wan)
        echo "${wan_interface}"
        exit 0
    ;;
    help)
        _help
        exit 0
    ;;
    *)
        echo "Unrecognised action ${action}"
        exit 1
    ;;
esac