extract IP address, default gateway, and add/del rule to routing table on Android/Linux

setup_via.sh

#!/system/bin/sh
IF=$1
CMD=$2
SERVER_NET='143.248.140.0/24'
IP=`ip -4 addr show $IF | grep 'inet ' | awk '{print $2}' | sed -e 's/\/[0-9]*//'`
DEF_GW=`ip ro show | grep -o "default.*$IF" | head -n1 | awk '{print $3}'`

if [ $# -ne 2 ]
then
  echo "Usage: `basename $0` <network_name> <add|del>"
  exit
fi

echo "IF: $IF"
echo "IP: $IP"
echo "DEF_GW: $DEF_GW"
echo "$CMD rule via $IF"

su -c "ip ro $CMD ta main $SERVER_NET via $DEF_GW dev $IF"