/* program to do DNS access 
 * uses the new struct and new commands
 * to handle IPv6 and to be thread safe
 */

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <err.h>

int main(int argc, char **argv) /* argv[1] is domain name */
{
    struct addrinfo hints;         // man getaddrinfo for details
                                   // hints is a struct filled with criteria
                                   // for socket address structs wanted
    struct addrinfo *firsthost = NULL; 
    struct addrinfo *currenthost = NULL;
    struct sockaddr_in *address4;  // to hold return address
    struct sockaddr_in6 *address6; // to hold return address
    int error;

    /* buffer to hold readable IP address */
    char addrbuf[INET6_ADDRSTRLEN]; // man inet_ntop for details

    /* check that we have the correct number of args
     * generate an error message and exit
     */
    if (argc != 2)
    {
        printf("usage: dnsaccess IPaddr|hostname \n");
        exit(1);
    }

    /* 0 memory so that debugging does not find trash */
    memset(&hints, 0, sizeof(hints));

    /* set the flags in the addrinfo struct */
    /* these are important as when 0, various options are invoked
     * as the system gives back info for everything, e.g., UDP, TCP, ...
     */
    hints.ai_flags = AI_CANONNAME;  // want canonical name
    hints.ai_family = AF_UNSPEC;    // any protocol family
    hints.ai_socktype = SOCK_DGRAM; // TCP Socket, need to be there or
                                    // multiple addresses

    /* do the call to get dns info for the host */
    error = getaddrinfo(argv[1], NULL, &hints, &firsthost);
    /* if call failed, error and die */
    if (error)
    {
       errx(1,  "getaddrinfo error");
    }

    /* have the dns info, start by printing first name,
     * which is the canonical name */
    printf("Canonical hostname: %s\n", firsthost->ai_canonname);

    /* print out the other names by climbing down the list of hosts
     * that is created by getaddrinfo */
    for (currenthost = firsthost; currenthost != NULL; currenthost = currenthost->ai_next)
    {
        /* want to handle both v6 and v4 addresses
         */
        switch (currenthost->ai_family)
        {
             case AF_INET:
                 address4 = (struct sockaddr_in*)currenthost->ai_addr;
                 inet_ntop(AF_INET, &address4->sin_addr, addrbuf, sizeof(addrbuf));
                 break;
             case AF_INET6:
                 address6 = (struct sockaddr_in6*)currenthost->ai_addr;
                 inet_ntop(AF_INET6, &address6->sin6_addr, addrbuf, sizeof(addrbuf));
                 break;
             default:
                addrbuf[0] = 0;
        }

        /* print the friggen address */
        printf("An Address: %s\n", addrbuf);
        
        /* for fun, print it all out */
        printf("Address: %s\n\tsocktype: %d\n\tprotocol: %d\n\tfamily: %d\n\tflags: %d\n\taddr: %p\n\tcanonname: %s\n\n",
            addrbuf,
            currenthost->ai_socktype,
            currenthost->ai_protocol,
            currenthost->ai_family,
            currenthost->ai_flags,
            currenthost->ai_addr,
            currenthost->ai_canonname);
    }

    /* another version of the climbing down the list of hosts
     * this one uses getnameinfo which provides for selecting between
     * v4 and v6 without the switch statement
     */
    for (currenthost = firsthost; currenthost != NULL; currenthost = currenthost->ai_next)
    {
        /* want to handle both v6 and v4 addresses
         */
        getnameinfo(currenthost->ai_addr, currenthost->ai_addrlen,
                  addrbuf, sizeof(addrbuf), NULL, 0, NI_NUMERICHOST);
    
        /* print the friggen address */
        printf("getname Address: %s\n", addrbuf);
    }


    /*free the memory allocated by getaddrinfo */
    freeaddrinfo(firsthost);

    /*we are done */
    printf("That's All Folks \n");

    return 0;
}