can get mac address but how to get ip address?

stats.c

/* ipchange.c
 *
 *  Netlink based IP monitor on specific interface.
 *  Executes command on new IPv4 address.
 *
 *  Sebastian Kricner
 *  tuxwave.net
 *  June 2014
 *
*/
#include <libnl3/netlink/netlink.h>
//#include <libnl3/netlink/socket.h>
//  #include <libnl3/netlink/msg.h>
//  #include <libnl3/netlink/errno.h>
#include <libnl3/netlink/route/link.h>
#include <libnl3/netlink/route/addr.h>
//  #include <libnl3/netlink/route/addr.h>
//  #include <libnl3/netlink/route/qdisc.h>
//  
//  #include <net/if.h>
//  
#include <errno.h>
//  #include <unistd.h>
//  #include <stdlib.h>
//  #include <syslog.h>
//  #include <sys/types.h>
//  #include <string.h>



/*
gcc ipchange.c -o ipchange $(pkg-config --cflags --libs libnl-3.0 libnl-route-3.0 libnl-cli-3.0)
*/


int main(int argc, char **argv, char **envp) {

    int err;

    struct nl_sock *sock;
    struct nl_cache *link_cache;
    struct nl_cache *addr_cache;

    struct rtnl_addr *addr;
    struct nl_addr *p_nl_addr;
 
    struct rtnl_link *p_rtnl_link;

    struct addrinfo *result;


    char *pchLinkName;
    char *pchLinkAddr;
    char *pchIPAddr;
    char *interface;
    interface = "enp6s0";
    pchLinkAddr = malloc(40);
    pchIPAddr = malloc(40);
    strcpy(pchLinkAddr,"11:22:33:44:55:66");
    strcpy(pchIPAddr,"123.456.789.abc");





    sock = nl_socket_alloc();
    if (!sock) {
        fprintf(stderr, "Could not allocate netlink socket.\n");
        exit(ENOMEM);
    }



    // Connect to socket
    if(err = nl_connect(sock, NETLINK_ROUTE)) {
        fprintf(stderr, "netlink error: %s\n", nl_geterror(err));
        sock = NULL;
        exit(err);
    }


    // Either choice, the result below is a mac address
    //err = rtnl_link_alloc_cache(sock, AF_UNSPEC, &link_cache);
    err = rtnl_link_alloc_cache(sock, AF_INET, &link_cache);
    if (0 != err) {
        /* error */
	      printf("rtnl_link_alloc_cache failed: %s\n", nl_geterror(err));
	      return(EXIT_FAILURE);
    }

    err = rtnl_addr_alloc_cache(sock, &addr_cache);
    if (0 != err) {
        /* error */
	      printf("rtnl_addr_alloc_cache failed: %s\n", nl_geterror(err));
	      return(EXIT_FAILURE);
    }



    p_rtnl_link = rtnl_link_get_by_name(link_cache, "enp6s0");
    if (NULL == p_rtnl_link) {
        /* error */
	      printf("rtnl_link_get_by_name failed\n");
	      return(EXIT_FAILURE);
    }


    pchLinkName = rtnl_link_get_name(p_rtnl_link);
    if (NULL == pchLinkName) {
        /* error */
	      printf("rtnl_link_get_name failed\n");
	      return(EXIT_FAILURE);
    }
    printf("Returned link name is %s\n",pchLinkName);


    ////////////////////////////////// mac address  
    p_nl_addr = rtnl_link_get_addr(p_rtnl_link);
    if (NULL == p_nl_addr) {
        /* error */
	      printf("rtnl_link_get_addr failed\n");
	      return(EXIT_FAILURE);
    }

    
    pchLinkAddr = nl_addr2str(p_nl_addr, pchLinkAddr, 40);
    if (NULL == pchLinkAddr) {
        /* error */
	      printf("rtnl_link_get_name failed\n");
	      return(EXIT_FAILURE);
    }
    printf("Returned link addr is %s\n",pchLinkAddr);



    ////////////////////////////////// ip address  
    // How to get ip address for a specified interface?
   
    return(EXIT_SUCCESS);
}