units1=63 #V6plus:15 OCN:63
units2=1024 #V6plus 4096 OCN:1024
IP4='xxx.xxx.xxx.xxx'
PSID='x'
TUNDEV='map-wan'


iptables -t nat -F PREROUTING
iptables -t nat -F OUTPUT
iptables -t nat -F POSTROUTING

rule=1
while [ $rule -le $units1  ] ; do
  mark=`expr $rule + 16`
  pn=`expr $rule - 1`
  portl=`expr $rule \* $units2 + $PSID \* 16`
  portr=`expr $portl + 15`

  iptables -t nat -A PREROUTING -m statistic --mode nth --every $units1 --packet $pn -j MARK --set-mark $mark
  iptables -t nat -A OUTPUT -m statistic --mode nth --every $units1 --packet $pn -j MARK --set-mark $mark

  iptables -t nat -A POSTROUTING -p icmp -o $TUNDEV -m mark --mark $mark -j SNAT --to $IP4:$portl-$portr
  iptables -t nat -A POSTROUTING -p tcp -o $TUNDEV -m mark --mark $mark -j SNAT --to $IP4:$portl-$portr
  iptables -t nat -A POSTROUTING -p udp -o $TUNDEV -m mark --mark $mark -j SNAT --to $IP4:$portl-$portr
  rule=`expr $rule + 1`
done