#! /bin/sh
# Connect Docker container to Open vSwitch bridge (auto-created if required)
#
# Inspired by:
# http://fbevmware.blogspot.co.nz/2013/12/coupling-docker-and-open-vswitch.html
#
# and:
# https://github.com/jpetazzo/pipework
#
# but stripped down for our use case, and with more string protection.
#
# Written by Ewen McNeill <ewen@naos.co.nz>, 2014-10-06
# Updated by Ewen McNeill <ewen@naos.co.nz>, 2014-10-07
#----------------------------------------------------------------------------

set -e            # Give up on errors

PATH=/sbin:/usr/bin:/bin
export PATH

# WARNING! active connection is "tcp:IP:PORT", passive connection is 
# inexpecably "ptcp:PORT:IP"!
CONTROLLERS="tcp:127.0.0.1:6633 ptcp:6634"

#---------------------------------------------------------------------------
# Parse arguments

OVS_BRIDGE="$1"
GUEST_NAME="$2"
IP4_ADDR="$3"
IP4_GW="$4"
VLAN_TAG="$5"

if [ -z "${OVS_BRIDGE}" -o -z "${GUEST_NAME}" -o -z "${IP4_ADDR}" ]; then
  echo "Usage: OVS_BRIDGE GUEST_NAME IP4_ADDR [IP4_GW [VLANTAG]]" >&2
  exit 1
fi

#---------------------------------------------------------------------------
# Find container mount point, so we can determine network namespace

CGROUP_MOUNT=$(grep -w devices /proc/mounts | awk '{ print $2; }')

if [ -z "${CGROUP_MOUNT}" ]; then
  echo "Error: could not auto-locate cgroup mount point" >&2
  exit 1
fi

#echo "Found CGROUP MOUNT at: ${CGROUP_MOUNT}"

#---------------------------------------------------------------------------
# Find our container path

CONTAINER=$(find "${CGROUP_MOUNT}" -name "${GUEST_NAME}*")
if [ -z "${CONTAINER}" ]; then
  echo "Error: no container found matching ${GUEST_NAME}" >&2
  exit 1
fi
NUM_FOUND=$(echo "${CONTAINER}" | wc -l)
if [ "${NUM_FOUND}" -eq 1 ]; then
  :  # Expected
else
  echo "Error: multiple containers found matching ${GUEST_NAME}" >&2
  exit 1
fi

#echo "Container found at: ${CONTAINER}"

#---------------------------------------------------------------------------
# Figure out the namespace PID

NSPID=$(head -n 1 "${CONTAINER}/tasks")
if [ -z "${NSPID}" ]; then
  echo "Error: no tasks found in container ${GUEST_NAME}" >&2
  exit 1
fi

#---------------------------------------------------------------------------
# Ensure the Open vSwitch exists, and will speak OpenFlow 1.3, and tell it 
# to speak to a "local" controller (which may also be provided via a Docker
# container), and listen for local connections.
#
ovs-vsctl --may-exist add-br "${OVS_BRIDGE}"
ovs-vsctl set bridge "${OVS_BRIDGE}" protocols=OpenFlow10,OpenFlow13

# Set controller if there is not one already
EXISTING_CONTROLLER=$(ovs-vsctl get-controller "${OVS_BRIDGE}")
if [ -z "${EXISTING_CONTROLLER}" ]; then
  ovs-vsctl set-controller "${OVS_BRIDGE}" ${CONTROLLERS}
fi

#---------------------------------------------------------------------------
# Prepare helper directory for "ip netns" support

mkdir -p /var/run/netns
rm -f "/var/run/netns/${NSPID}"
ln -s "/proc/${NSPID}/ns/net" "/var/run/netns/${NSPID}"

#---------------------------------------------------------------------------
# Create link pair to connect between Open vSwitch and container
# (removing it if it already exists)

HOST_IFNAME="vethp${NSPID}"
GUEST_IFNAME="vethg${NSPID}"

if [ -n "$(ip link show "${HOST_IFNAME}" 2>/dev/null)" ]; then
  ip link delete "${HOST_IFNAME}" type veth
fi

ip link add name "${HOST_IFNAME}" type veth peer name "${GUEST_IFNAME}"
ip link set "${HOST_IFNAME}" up

#---------------------------------------------------------------------------
# Inject guest end of link into the container, as eth0

ip link set "${GUEST_IFNAME}" netns "${NSPID}"
ip netns exec "${NSPID}" ip link set "${GUEST_IFNAME}" name eth0

#---------------------------------------------------------------------------
# Push the host end of the link into the Open vSwitch (optionally with a
# VLAN tag, as an access port)

if [ -n "${VLAN_TAG}" ]; then
  ovs-vsctl add-port "${OVS_BRIDGE}" "${HOST_IFNAME}" "tag=${VLANTAG}"
else
  ovs-vsctl add-port "${OVS_BRIDGE}" "${HOST_IFNAME}"
fi

#---------------------------------------------------------------------------
# Configure networking inside the container

ip netns exec "${NSPID}" ip addr add "${IP4_ADDR}" dev eth0
ip netns exec "${NSPID}" ip link set eth0 up

# Do we need to set up lo?
#ip netns exec "${NSPID}" ip addr add 127.0.0.1/8   dev lo
#ip netns exec "${NSPID}" ip link set lo   up

if [ -n "${IP4_GW}" ]; then
  ip netns exec "${NSPID}" ip route add default via "${IP4_GW}"
fi