balancer.sh

#!/bin/bash

# Example:
#
# auto tun0
# iface tun0 inet static
# 	address 192.168.99.10
# 	netmask 255.255.255.255
# 	fakenet 192.168.99.0/24
# 	table 10000 10001
#         rspec 192.168.99.10:10.99.0.10:10.99.1.10 \
#               192.168.99.20:10.99.0.20:10.99.1.20
# 	pre-up ip tuntap add mode tun tun0
# 	post-down ip tuntap del mode tun tun0
 

if [ -z ${IF_TABLE+x} ]; then
    exit 0
fi

count=0
for table in ${IF_TABLE[@]}; do
    ip route flush table $table
    ip rule delete lookup $table || true
    count=$((count+1))
done

for spec in ${IF_RSPEC[@]}; do
    IFS=':' read -ra addr <<< $spec
    dst=${addr[0]}
    addr=("${addr[@]:1}")

    ecmp_str=""
    for table in ${IF_TABLE[@]}; do
        gw=${addr[0]}
        addr=("${addr[@]:1}")

        if [ -n "$gw" ]; then
            ip route add $dst via $gw src $IF_ADDRESS table $table
            ecmp_str="$ecmp_str nexthop via $gw"
        fi
    done

    ip route del $dst || true
    ip route add $dst src $IF_ADDRESS $ecmp_str
done

iptables -t mangle -F

mark=0
for table in ${IF_TABLE[@]}; do
    mark=$((mark+1))
    iptables -t mangle -A OUTPUT -d $IF_FAKENET \
             -m statistic --mode nth --every $count --packet $((mark-1)) \
             -j MARK --set-mark $mark
    ip rule delete fwmark $mark || true
    ip rule add fwmark $mark lookup $table
done