Find the default IPv6 gateway and start forwarding traffic on OpenBSD and Comcast (XFinity)

start_inet6.sh

#!/bin/sh
egress=$1
internal=$2

# This should set up ipv6 on XFinity or Comcast on OpenBSD 6.1

# Stop everything
/usr/bin/pkill dhcp6c
route -qn delete -inet6 default
ifconfig $egress -inet6

# Turn on autoconf so we can find our default gateway
/sbin/ifconfig $egress inet6 autoconf

# Wait until we get a gateway
gateway=
while [ -z "$gateway" ]; do
 sleep 1
 gateway=$( route -qn get -inet6 default | awk '/gateway/ { print $2 }' )
done

# Now, add the default gateway statically,
# for reasons I don't understand
route -qn add -inet6 default $gateway
/usr/local/sbin/dhcp6c $egress $internal