Bring up IPv6 through ISATAP tunnel.

isatap

#!/bin/bash
# vim730: set tw=80 cc=+1:

# Bring up IPv6 through ISATAP tunnel.

version="1.0"

usage() {
cat <<EOF
USAGE:
	$0 [-d -i interface -s solution]
	$0 -h/--help/-v/--version

When -d is specified, it will delete sit1 interface. Otherwise it will set up
(possibly override exsiting) isatap interface.

When no interface is specified, it will use the first global IPv4 address found
in 'ip addr'.

The solution of isatap service can be one of: thu/wlan/sjtu. When no solution is
specified, it will default to thu.
EOF
}

# Default values.
iface=""
sln="thu"
action="add"

args=$(getopt -o "dhvi:s:" -l "help,version" -- "$@")
if [ $? -ne 0 ]; then
	usage
	exit 1
fi
eval set -- "$args"

while [ ! -z "$1" ]; do
	case "$1" in
		-d)
			action="delete"
			;;
		-i)
			shift
			iface="$1"
			;;
		-s)
			shift
			sln="$1"
			;;
		-v|--version)
			echo "$(basename $0) $version"
			exit 0
			;;
		-h|--help)
			usage
			exit 0
			;;
		--)
			shift
			break
			;;
	esac
	shift
done

if [ $# -ne 0 ]; then
	printf "Error: unrecognized arguments $@.\n" >&2
	usage
	exit 1
fi

# Get IPv4 address.
if [ -n "$iface" ]; then
	line="`ip addr show dev "$iface" | grep 'inet .*scope global' \
		| head -n 1`"
else
	line="`ip addr | grep 'inet .*scope global' | head -n 1`"
fi

# Get global ipv4 address in 'addr/prefix' format.
if [ -z "$line" ]; then
	if [ -z "$iface" ]; then
		printf "Error: no valid IPv4 address found.\n" >&2
	else
		printf "Error: no valid IPv4 address found on $iface.\n" >&2
	fi
	exit 5
fi
yourip="`echo $line | awk '{print $2}'`"
# Strip trailing "/prefix" part.
yourip="${yourip%/*}"
if [ -z "$iface" ]; then
	iface="`echo $line | awk '{print $NF}'`"
fi

echo "Given local ip $yourip on interface $iface."
echo "Given solution $sln."
echo "Given action $action."

do_delete ()
{
	if sudo ip tunnel show sit1 >/dev/null 2>&1; then
		sudo ip tunnel del sit1
	fi
}

if [ "$action" = "delete" ]; then
	do_delete
	exit $?
fi

if [ "$sln" = "thu" ]; then
	IsatapIPv4=59.66.4.50
	IsatapIPv6Prefix=2001:da8:200:900e:0:5efe
	IsatapIPv6Router=2001:da8:200:900e::1
elif [ "$sln" = "wlan" ]; then
	IsatapIPv4=166.111.21.1 # isatap.tsinghua.edu.cn
	IsatapIPv6Prefix=2001:da8:200:900e:0:5efe
	IsatapIPv6Router=2001:da8:200:900e::1
elif [ "$sln" = "sjtu" ]; then
	# This works!
	# From: http://bbs.sjtu.edu.cn/bbstcon?board=SJTUnet&reid=1212259140
	IsatapIPv4=202.120.58.150
	# IPv4 addr of isatap.sjtu.edu.cn
	# do not work...
	#IsatapIPv4=202.112.26.246
	IsatapIPv6Prefix=2001:da8:8000:d010:0:5efe
	IsatapIPv6Router=2001:da8:8000:d010::1
else
	echo "Unkown solution: $sln"
	exit 1
fi

# Add new isatap interface.
do_delete
echo "Adding new sit1..."
sudo ip tunnel add sit1 mode sit remote $IsatapIPv4 local $yourip
sudo ifconfig sit1 up
sudo ifconfig sit1 add $IsatapIPv6Prefix:$yourip/64
# Make sure to remove default route through original interface.
while [ -n "$(sudo ip -6 route show ::/0 dev ${iface})" ]; do
	sudo ip route del ::/0 dev ${iface}
	sleep 1
done
sudo ip route add ::/0 via $IsatapIPv6Router metric 1