/* 
 * Copyright mcmanus@ducksong.com 2008, Under terms of GPLv2 
 * Slightly modified by Paul Wouters <paul@xelerance.com> 2010
 */

#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <net/if.h>


int main()
{
    struct sockaddr_nl addr;
    int nls,len,rtl;
    char buffer[4096];
    struct nlmsghdr *nlh;
    struct ifaddrmsg *ifa;
    struct rtattr *rth;
    
    if ((nls = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) == -1)   perror ("socket failure\n");
    
    memset (&addr,0,sizeof(addr));
    addr.nl_family = AF_NETLINK;
    addr.nl_groups = RTMGRP_IPV4_IFADDR;
    
    if (bind(nls, (struct sockaddr *)&addr, sizeof(addr)) == -1)    perror ("bind failure\n");

    nlh = (struct nlmsghdr *)buffer;
    while ((len = recv (nls,nlh,4096,0)) > 0)
    {
        for (;(NLMSG_OK (nlh, len)) && (nlh->nlmsg_type != NLMSG_DONE); nlh = NLMSG_NEXT(nlh, len))
        {
	    switch(nlh->nlmsg_type)
	    {

		default:
			fprintf(stdout,"unknown kind of announcement from NETLINK_ROUTE\n");
			continue; /* some other kind of announcement */

		case RTM_DELADDR:
		case RTM_NEWADDR:
			ifa = (struct ifaddrmsg *) NLMSG_DATA (nlh);
			rth = IFA_RTA (ifa);
			rtl = IFA_PAYLOAD (nlh);
			for (;rtl && RTA_OK (rth, rtl); rth = RTA_NEXT (rth,rtl))
			{
			 char name[IFNAMSIZ];
			 uint32_t ipaddr;
                
			if (rth->rta_type != IFA_LOCAL) continue;
                
			ipaddr = * ((uint32_t *)RTA_DATA(rth));
			ipaddr = htonl(ipaddr);

			if(nlh->nlmsg_type == RTM_DELADDR)
				fprintf (stdout,"%s removed %X\n",if_indextoname(ifa->ifa_index,name),ipaddr);
			else if(nlh->nlmsg_type == RTM_NEWADDR)
				fprintf (stdout,"%s added %X\n",if_indextoname(ifa->ifa_index,name),ipaddr);
			else fprintf (stdout,"%s changed?? %X\n",if_indextoname(ifa->ifa_index,name),ipaddr);
			}
	    }
        }
    }
}