3.2.3 IPAddressMonitor

The following IPAddressMonitor class is an example to monitor changes of InterfaceAddresses for IPv4 and IPv6.
1. Define your own netlink monitor C++ class.
2. Add a member variable for groups to monitor.
3. Add a member variable of SocketNetlink which can be used as a communication channel to the kernel.
4. Add a member variable of NetlinkReply<T> which includes a netlink message header and ack data from the kernel.
5. Define a contructor to initialize the group member variable.
6. Define a bind method to communicate with the kernel through the SocketNetlink.
7. Define a recv method to receive a notification from the kernel through the SocketNetlink.
8. In main function, create an instance of your monitor class, and call bind and recv mothods for the instance.

// IPAddressMonitor.cpp
//Copyright (c) 2015 Antillia.com TOSHIYUKI ARAI. ALL RIGHTS RESERVED.

#include <oz++/CommonObject.h>
#include <oz++/LocalDateTime.h>
#include <oz++/Exception.h>
#include <oz++/netlink/SocketNetlink.h>
#include <oz++/netlink/SockAddrNetlink.h>

#include <oz++/netlink/NetlinkReply.h>
#include <oz++/netlink/NetlinkMsgHeader.h>
#include <oz++/netlink/InterfaceAddrAttribute.h>
#include <oz++/netlink/InterfaceAddrMsg.h>

namespace OZ {
class IPAddressMonitor :public CommonObject {
  int              rtmGroups;
  SocketNetlink    socketNetlink;
  NetlinkReply<ifaddrmsg> reply;

  IPAddressMonitor(int group = RTMGRP_IPV4_IFADDR|RTMGRP_IPV6_IFADDR)
  int bind()
    SockAddrNetlink  addrNetlink;
    return socketNetlink.bind(addrNetlink);
  void recv()
    while (true) {
      bzero(&reply, sizeof(reply));

      int n = socketNetlink.recv((char*)&reply, sizeof(reply), 0);
      if ( n < 0 ){
      try {         

        NetlinkMsgHeader netlinkMsgHeader(&reply.head);
        if (netlinkMsgHeader.isDone() || netlinkMsgHeader.isError()) {

        do {
          LocalDateTime dateTime;
          CharString now = dateTime.nowToSeconds();
          printf("%s\n", (const char*)now);

          InterfaceAddrMsg addrMsg(&reply.body);
          InterfaceAddrAttribute attribute(netlinkMsgHeader, addrMsg);
          do {
          } while (attribute.next() );


        } while (netlinkMsgHeader.next());
      } catch (Exception& ex) {

int main(int argc, char* argv[])
  try {
    IPAddressMonitor monitor;
    //IPAddressMonitor monitor(RTMGRP_IPV4_IFADDR);
  } catch (Exception& ex) {
  return 0;

Last modified: 29 Aug 2016

 Last modified: 29 Aug2016

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