NATApp Developer Guide

Overview

NATApp acts as a basic framework for providing NAT functionality to the SDN controller. One can use REST or Java APIs to enter global IP address into YANG Data Store which will be used by the odl-natapp-feature to map local IP to global IP addresses.

NATApp Architecture

NATApp listens on OpenFlow southbound interface for Packet_In messages. The application parses the message for header information. If the received message has a local IP address the application installs rules on the OpenFlow switch for network address translation from local to global IP addresses. NATApp has NATPacketHandler class that implements the PacketProcessing interface to override the OnPacketReceived notification by which the application is notified of Packet_In messages.

NATApp is implemented with the help of a few java classes.

  1. NATPacketHandler
    • Receives Packet_In messages coming to the controller and process them appropriately
  2. NATPacketParsing
    • Decodes Packet_In messages for packet header information (L2, L3 & L4 information)
  3. NATInventoryUtility
    • Decodes Packet_In messages for OpenFlow Switch and Port information
  4. NATFlowBuilder
    • Creates NAT flow rules at the OpenFlow Switch
  5. NATYangStore
    • Reads Global IP entered by user and maps local IP to Global IP information
  6. NATFlowHandler
    • Manages expired flows in the switch and frees up used global IP address for future natting.

Key APIs and Interfaces

  1. RPC APIs
    • Static - Configure Static Natting Functionality
    • Dynamic - Configure Static Dynamic Functionality
    • PAT - Configure PAT Functionality
  2. DataStore APIs
    • StaticNatIp - Configure floating IP addresses for Static Natting
    • StaticIpMapInfo - Mapped Information between floating and private IP addresses in Static Natting
    • DynamicNatIp - Configure floating IP addresses for Dynamic Natting
    • DynamicIpMapInfo - Mapped Information between floating and private IP addresses in Dynamic Natting
    • PatIp - Configure floating IP addresses for Port Address Translation
    • PatIpMapInfo - Mapped Information between TCP Port numbers of floating IP and private IP addresses
  3. Notification APIs
    • DynamicIPExhaustion - Exhaustion of Dynamic Global IP Addresses
    • PatOverConnection - More than 10 TCP or UDP connections from one private IP address