#!/bin/sh
# ip source routing ifupdown script
# (C) 2015 Nirgal Vourgère
# GPL-3+
#
# This script set up source routing for a given interface
# Optionnal argument $1: The gateway. If missing, the interface gateway is required.
# Example usage: In /etc/network/interfaces
# iface eth7 inet static
#     address 192.168.5.42/24
#     post-up source-route 192.168.1.1
# or
# iface eth7 inet static
#     address 192.168.5.42/24
#     gateway 192.168.5.1
#     post-up source-route

#set -x 
RTTABLE=from$IFACE
LOGGER="logger -t source-route -s"

if test "$VERBOSITY" = 1
then
	$LOGGER -p user.debug -- IFACE=$IFACE LOGICAL=$LOGICAL ADDRFAM=$ADDRFAM METHOD=$METHOD MODE=$MODE PHASE=$PHASE VERBOSITY=$VERBOSITY PATH=$PATH
fi

if ! which ipv4calc >/dev/null
then
	$LOGGER -p user.crit -- "ipv4calc not found: apt-get install libnetwork-ipv4addr-perl"
	exit 2
fi
if ! which ipv6calc >/dev/null
then
	$LOGGER -p user.crit -- "ipv6calc not found: apt-get install ipv6calc"
	exit 2
fi
if test -z "$IFACE"
then
	$LOGGER -p user.crit -- "\$IFACE is empty. Are you really running from /etc/network/interfaces ?"
	exit 2
fi
if test "$PHASE" != "post-up"
then
	$LOGGER -p user.error -- "Invalid \$PHASE. $0 is only valid in 'post-up'. Ignoring."
	exit 0  # Soft failure
fi

RT_TABLES=/etc/iproute2/rt_tables
if ! grep -q $RTTABLE /etc/iproute2/rt_tables
then
	$LOGGER -p user.crit -- "$RT_TABLES does not have $RTTABLE entry."
	exit 2
fi

case $ADDRFAM in
inet)
	IPFLAG=-4
	;;
inet6)
	IPFLAG=-6
	;;
*)
	$LOGGER -p user.error -- "\$ADDRFAM must be inet or inet6. Ignoring."
   	exit 0  # Soft failure
	;;
esac
IPADDR=$(ip $IPFLAG -o addr show $IFACE | grep -w $ADDRFAM | grep global | sed -re "s/.*$ADDRFAM (.*)\/.*/\1/")
IPCIDR=$(ip $IPFLAG -o addr show $IFACE | grep -w $ADDRFAM | grep global | sed -re "s/.*$ADDRFAM .*\/([^ ]*).*/\1/")
if test "$ADDRFAM" = "inet6"
then
	IPNET=$(ipv6calc --in ipv6 --out ipv6 --maskprefix $IPADDR/$IPCIDR)
else
	IPNET=$(ipv4calc --network $IPADDR/$IPCIDR)/$IPCIDR
fi
if test -n "$1"
then
	IPGW=$1
else
	IPGW=$(ip $IPFLAG -o route show | grep default | sed -re "s/.*via ([^ ]*) .*/\1/")
fi
if test -z "$IPGW"
then
	$LOGGER -p user.crit "Could not find the gateway and none was given."
	exit 2
fi

# Setting up source routing on $IFACE, so that packets from $IFACE don't get answered on another interface
$LOGGER -- "Setting up source routing on $IFACE: from $IPADDR -> route $IPNET via $IPGW"

if ! ip $IPFLAG route show table $RTTABLE | grep -q default  # Once only
then
	if test "$VERBOSITY" = 1
	then
        	$LOGGER -p user.debug -- ip $IPFLAG route add $IPNET dev "$IFACE" scope link table $RTTABLE
        	$LOGGER -p user.debug -- ip $IPFLAG route add default via "$IPGW" dev "$IFACE" table $RTTABLE
	fi
        ip $IPFLAG route add $IPNET dev "$IFACE" scope link table $RTTABLE
        ip $IPFLAG route add default via "$IPGW" dev "$IFACE" table $RTTABLE
fi
if ! ip $IPFLAG rule show | grep -q $RTTABLE  # Once only
then
	if test "$VERBOSITY" = 1
	then
        	$LOGGER -p user.debug -- ip $IPFLAG rule add from $IPADDR table $RTTABLE
	fi
        ip $IPFLAG rule add from $IPADDR table $RTTABLE
fi

ip $IPFLAG route flush cache