Setup Linux namespace network with virtual bridge

setup_namespace_network.sh

#!/bin/bash
# (C) Pekka Järvinen 2022

# Name for bridge which virtual namespaces will use to communicate with each other
BRIDGENAME="gamebr0"
# Prefix for network
NETPREFIX="192.168.255."

# Starting IP (NETPREFIX + this)
let STARTIP=10

# How many virtual player namespaces to create
# 4 is good for 2 x 2 screen
let PLAYERCOUNT=4

# Old cleanup
if [[ -d "/sys/class/net/$BRIDGENAME" ]]
then
    ip link del dev $BRIDGENAME
fi

while read NS; do
  ip netns delete $NS
done < <(ip netns list | grep "^player" )

# Remove player* interfaces
find /sys/class/net -maxdepth 1 -iname "player*" -printf "%f\n" | xargs -I{} ip link del dev {}

# Setup

echo "Setting up bridge $BRIDGENAME"
ip link add $BRIDGENAME type bridge
ip addr add ${NETPREFIX}1/24 dev $BRIDGENAME
ip link set $BRIDGENAME up

echo ""

let PIP=$STARTIP
for (( i=0; i<=$PLAYERCOUNT; i++ )) do
  echo "Setting up player #$i network namespace..."
  echo "  Adding namespace: player$i"
  ip netns add player$i
  # Bring lo up
  ip netns exec player$i ip link set lo up
  echo "  Adding virtual ethernet device player${i}eth and TAP player${i}tap0"
  ip link add player${i}eth type veth peer name player${i}tap0
  ip link set player${i}tap0 up
  echo "  Attaching player${i}tap0 to $BRIDGENAME"
  ip link set player${i}tap0 master $BRIDGENAME
  echo "  Moving player${i}eth to namespace player$i"
  ip link set player${i}eth netns player$i
  echo "  Setting IP address to ${NETPREFIX}${PIP}/24"
  ip netns exec player$i ip address add "${NETPREFIX}${PIP}/24" dev player${i}eth
  ((PIP=PIP+1))
  # Bring veth up
  ip netns exec player$i ip link set player${i}eth up
  # Show address to user
  ip netns exec player$i ip addr show player${i}eth
  echo "-----------------------------------------"
done

echo ""
echo "Testing network with ping..."
for (( i=0; i<=$PLAYERCOUNT; i++ )) do
  let NStoBErr=0
  let BtoNSErr=0

  # Ping bridge from namespace
  ip netns exec player$i ping -q -n -c1 ${NETPREFIX}1 > /dev/null || NStoBErr=1 

  # Ping namespace from bridge
  ping -I $BRIDGENAME -q -n -c1 ${NETPREFIX}$(expr $STARTIP + $i) > /dev/null || BtoNSErr=1
  
  if [ $NStoBErr -eq 1 ] 
  then
    echo "!! Failed to ping ${NETPREFIX}1 ($BRIDGENAME) from NS player$i. Please check your firewall and IP forwarding kernel settings."
    exit 1
  fi

  if [ $BtoNSErr -eq 1 ] 
  then
    echo "!! Failed to ping ${NETPREFIX}$(expr $STARTIP + $i) (NS player$i) from $BRIDGENAME. Please check your firewall and IP forwarding kernel settings."
    exit 1
  fi
  
done

echo "Player network added successfully!"
echo ""
echo "Bridge:"
ip addr show $BRIDGENAME
echo ""

echo "Done."
echo ""
echo "Test that namespace networking works with:"
echo "  ping -I $BRIDGENAME ${NETPREFIX}1"
echo "  ping -I $BRIDGENAME ${NETPREFIX}$STARTIP"
echo "  ping -I $BRIDGENAME ${NETPREFIX}$(expr $STARTIP + 1)"
echo "  sudo ip netns exec player1 ping ${NETPREFIX}1"
echo "  sudo ip netns exec player2 ping ${NETPREFIX}1"
echo "  sudo ip netns exec player1 ping ${NETPREFIX}$(expr $STARTIP + 1)"
echo "  sudo ip netns exec player2 ping ${NETPREFIX}$STARTIP"

echo ""
echo "Show namespaces with:"
echo "  ip netns"
echo ""

echo "Delete networks and namespaces after use (or just reboot):"
for (( i=0; i<=$PLAYERCOUNT; i++ )) do
  echo "  sudo ip netns delete player${i}"
  #echo "sudo ip link del dev player${i}tap0"
done

echo "sudo ip link del dev $BRIDGENAME"