fix-docker-route.sh

#!/bin/bash

###############################################################################
# Shell script to help deal with problems with VirtualBox and network routing
# issues when running Docker, mainly caused by VPN software.  The symptom is
# "docker-machine env" or "boot2docker env" hanging instead of returning
# environment variables. It might help with Vagrant as well.
#
# Tested on OS/X Yosemite with GNU coreutils installed via Homebrew, which
# might (or might not) affect the operation of the script.
#
# Owen Berry
###############################################################################

# Likely candidate for the network in my experience
VBOX_SUBNET="192.168.99"

# Try to detect the VirtualBox network interface
VBOX_INTERFACE=$(ifconfig | grep -B2 "${VBOX_SUBNET}" | head -n 1 | cut -f 1 -d:)
# And the VirtualBox gateway, which could show as a VPN gateway
ROUTE_GATEWAY=$(route get ${VBOX_SUBNET}.100 | grep gateway | cut -f2 -d:)

# curses stuff
bold=$(tput bold)
nbold=$(tput sgr0)

###################### Functions #####################

function check_for_existing_route {
    if [ -z "${ROUTE_GATEWAY}" ]; then
        echo
        echo "${bold}It looks like there might already be a route for docker:${nbold}"
        echo "---------------------------------------------------------"
        echo
        route get ${VBOX_SUBNET}.100
        echo

        while true; do
            read -r -p "Carry on (y/n)? " yn
            case $yn in
                [Yy]* ) yn=x; break;;
                * ) remove_route_message; exit;;
            esac
        done
    fi
}

function confirm_add_route {
    local route_interface
    route_interface=$(route get ${VBOX_SUBNET}.100 | grep interface | cut -f2 -d:)

    echo
    echo "${bold}Possible network interface:${nbold}"
    echo "---------------------------"
    echo
    ifconfig | grep -B2 "${VBOX_SUBNET}"
    echo
    echo "${bold}Current route interface:${nbold} ${route_interface}"
    echo "${bold}Current route gateway:${nbold} ${ROUTE_GATEWAY}"
    echo

    while true; do
        read -r -p "Add route for interface ${VBOX_INTERFACE} (y/n)? " yn
        case $yn in
            [Yy]* ) break;;
            [Nn]* ) exit;;
            * ) echo "Please answer y/n.";;
        esac
    done
}

function add_route {
    echo
    echo "You may need to enter your password to add the route now"
    sudo route add -net ${VBOX_SUBNET}.0/24 -interface "${VBOX_INTERFACE}"
}

function remove_route_message {
    echo
    echo "${bold}To remove the route:${nbold}"
    echo "    sudo route delete -net ${VBOX_SUBNET}.0/24 -interface \"${VBOX_INTERFACE}\""
    echo
}

###################### Start #####################

check_for_existing_route
confirm_add_route
add_route
remove_route_message

##################### End #####################

Unfortunately, this does not always work with Cisco AnyConnect. Sometimes adding the route seems to have no effect at all, and I'm not sure why right now. Try rebooting. :-/