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3.2.3 IPAddressMonitor

The following IPAddressMonitor class is an example to monitor changes of InterfaceAddresses for IPv4 and IPv6.
Note:
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 {
private:
  int              rtmGroups;
  SocketNetlink    socketNetlink;
  NetlinkReply<ifaddrmsg> reply;

public:
  IPAddressMonitor(int group = RTMGRP_IPV4_IFADDR|RTMGRP_IPV6_IFADDR)
  :rtmGroups(group)
  {
  }
    
    
  int bind()
  {
    SockAddrNetlink  addrNetlink;
    addrNetlink.setFamily(AF_NETLINK);
    addrNetlink.setGroups(rtmGroups);
    return socketNetlink.bind(addrNetlink);
  }
    
  void recv()
  {
    while (true) {
      bzero(&reply, sizeof(reply));

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

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

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

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

          addrMsg.display();
          printf("\n");

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

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

Last modified: 29 Aug 2016