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Simple Linux Load Balancing with `iproute2`
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#!/bin/bash | |
# Load balance multiple internet connections. Requires iproute2, awk and grep. | |
# (C) 2016 Tobias Girstmair, isticktoit.net, GPLv2 | |
# Also useful: speedometer -l -r eth1 -t eth1 -m $(( 1024 * 1024 * 3 / 2 )) | |
# Not much user error checking is done - only pass working network connections | |
# script needs root to work and at least two interfaces to be useful | |
[ $EUID -eq 0 -a $# -ge 2 ] || { | |
echo "Usage (as root): $0 iface1[:weight1] iface2[:weight2] ..." >&2 | |
exit 1 | |
} | |
get_free_tblnum() { # http://stackoverflow.com/a/28702075 | |
awk -v RS='\\s+' '{ a[$1] } END { for(i = 10; i in a; ++i); print i }'</etc/iproute2/rt_tables | |
} | |
loadbal() { | |
IFS=':' read IFACE WEIGHT <<< "$1" | |
TABLE="${IFACE}loadbalance" | |
if ! grep -q -w "$TABLE" /etc/iproute2/rt_tables ; then | |
echo "$(get_free_tblnum) $TABLE" >> /etc/iproute2/rt_tables | |
fi | |
MY_IP=$(ip -o -4 addr show $IFACE |awk -F'(\\s|/)+' '{print $4}') | |
GW_IP=$(ip route show dev $IFACE | awk '/default/ {print $3}') | |
SUBNT=$(ip route show dev $IFACE | awk '/proto kernel/ {print $1}') | |
ip route add $SUBNT dev $IFACE src $MY_IP table $TABLE | |
ip route add default via $GW_IP table $TABLE | |
ip rule add from $MY_IP table $TABLE | |
echo nexthop via $GW_IP dev $IFACE weight ${WEIGHT:-1} | |
} | |
ip route add default scope global $(for IF in "$@"; do loadbal $IF; done) | |
routes are cached !
there should be a way of bypassing cache or not cache at all, otherwise it wont be that much useful
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your enx... interface doesn't have a default gateway (run the script through
sed '/add default via/s/^/test -n "$GW_IP" \&\& /'
should remove that error). "file exists" errors you can ignore. i haven't bothered removing entries; just reboot and you're back to where you started.