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#!/bin/sh
#
# A post-up/down hook to automatically create/delete a 'sec' VLAN
# device, and a dedicated, host-scoped, IP for IPSec (v4 only).
#
# Copyright 2013 Guilhem Moulin <guilhem@fripost.org>
#
# Licensed under the GNU GPL version 3 or higher.
#
set -ue
PATH=/usr/sbin:/usr/bin:/sbin:/bin
ifsec=sec0
ipsec=172.16.0.1/32
# /!\ This mark much match that in /usr/local/sbin/update-firewall.sh.
secmark=0xA99
# Ignore the loopback interface and non inet4 families.
[ "$IFACE" != lo -a "$ADDRFAM" = inet ] || exit 0
# Only the device with the default, globally-scoped route, is of
# interest here.
[ "$( /bin/ip -4 route show to default scope global \
| sed -nr '/^default via \S+ dev (\S+).*/ {s//\1/p;q}' )" \
= \
"$IFACE" ] || exit 0
case "$MODE" in
start) # Don't create $ifsec if it's already there
if ! /bin/ip -o link show | grep -qE "^[0-9]+:\s+$ifsec"; then
# Create a new VLAN $IFACE on physical device $ifsec. This is
# required otherwise charon thinks the left peer is that
# host-scoped, non-routable IP.
/bin/ip link add link "$IFACE" name "$ifsec" type vlan id 2713
/bin/ip address add "$ipsec" dev "$ifsec" scope host
/bin/ip link set dev "$ifsec" up
fi
# If a packet retained its mark that far, it means it has
# been SNAT'ed from $ipsec, and didn't have a xfrm
# association. Hence we nullroute it to avoid to leak data
# intented to be tunneled through IPSec. /!\ The priority
# must be >220 (strongSwan IPSec's policy) since xfrm lookup
# must take precedence.
/bin/ip rule add fwmark "$secmark" table 666 priority 666 || true
/bin/ip route add prohibit default table 666 || true
;;
stop) if /bin/ip -o link show | grep -qE "^[0-9]+:\s+$ifsec"; then
# Deactivate the VLAN
/bin/ip link set dev "$ifsec" down
fi
# Delete the 'prohibit' rule
/bin/ip rule del fwmark "$secmark" table 666 priority 666 || true
/bin/ip route flush table 666
;;
esac
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