getaddrinfo-example.c

/*
 *  Example of getaddrinfo() and inet_ntop()
 *  Copyright (C) 2020 David M. Syzdek <david@syzdek.net>
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are
 *  met:
 *
 *     1. Redistributions of source code must retain the above copyright
 *        notice, this list of conditions and the following disclaimer.
 *
 *     2. Redistributions in binary form must reproduce the above copyright
 *        notice, this list of conditions and the following disclaimer in the
 *        documentation and/or other materials provided with the distribution.
 *
 *     3. Neither the name of the copyright holder nor the names of its
 *        contributors may be used to endorse or promote products derived from
 *        this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 *  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 *  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 *  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 *  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*
 *  Simple Build:
 *     CFLAGS='-std=gnu11 -pedantic -W -Wall -Werror -Weverything'
 *     gcc ${CFLAGS} -c getaddrinfo-example.c
 *     gcc ${CFLAGS} -o getaddrinfo-example getaddrinfo-example.o
 *
 *  Libtool Build:
 *     CFLAGS='-std=gnu11 -pedantic -W -Wall -Werror -Weverything'
 *     libtool --mode=compile --tag=CC gcc ${CFLAGS} -c getaddrinfo-example.c
 *     libtool --mode=link    --tag=CC gcc ${CFLAGS} -o getaddrinfo-example \
 *             getaddrinfo-example.lo
 *
 *  Libtool Clean:
 *     libtool --mode=clean rm -f getaddrinfo-example.lo getaddrinfo-example
 */


///////////////
//           //
//  Headers  //
//           //
///////////////

#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <strings.h>
#include <arpa/inet.h>
#include <getopt.h>


//////////////////
//              //
//  Prototypes  //
//              //
//////////////////

int main(int argc, char * argv[]);


/////////////////
//             //
//  Functions  //
//             //
/////////////////

int main(int argc, char * argv[])
{
   int                   c;
   int                   rc;
   int                   count;
   int                   opt_index;
   char                * ptr;
   const char          * prog_name;
   char                  addrstr[INET6_ADDRSTRLEN];
   char                * hostnam;
   char                * service;
   struct addrinfo     * res;
   struct addrinfo     * info;
   struct addrinfo       hints;

   union
   {
      struct sockaddr         * sa;
      struct sockaddr_in      * sin;
      struct sockaddr_in6     * sin6;
      struct sockaddr_storage * ss;
   } sau;

   static struct option long_opt[] =
   {
      {"help",          no_argument,       0, 'h'},
      {"version",       no_argument,       0, 'V'},
      {NULL,            0,                 0, 0  }
   };


   // initializes variables
   hostnam = NULL;
   service = NULL;
   prog_name = argv[0];
   if ((ptr = rindex(argv[0], '/')) != NULL)
      prog_name = &ptr[1];


   // innitializes hints for getaddrinfo()
   bzero(&hints, sizeof(struct addrinfo));
   //hints.ai_flags     = AI_ADDRCONFIG | AI_V4MAPPED | AI_ALL;
   hints.ai_flags     = AI_UNUSABLE;
   hints.ai_family    = PF_UNSPEC;
   hints.ai_socktype  = SOCK_DGRAM;
   hints.ai_protocol  = IPPROTO_UDP;


   // processes CLI arguments
   while((c = getopt_long(argc, argv, "46hV", long_opt, &opt_index)) != -1)
   {
      switch(c)
      {
         case -1:       // no more arguments
         case 0:        // long options toggles
         break;

         case '4':
         hints.ai_family = PF_INET;
         break;

         case '6':
         hints.ai_family = PF_INET6;
         break;

         case 'h':
         printf("Usage: %s [options] hostname [service]\n", prog_name);
         printf("OPTIONS:\n");
         printf("  -4                        resolve IPv4 only\n");
         printf("  -6                        resolve IPv6 only\n");
         printf("  -h, --help                print this help and exit\n");
         printf("  -V, --version             print version number and exit\n");
         printf("\n");
         return(0);

         case 'V':
         return(0);

         case '?':
         fprintf(stderr, "Try `%s --help' for more information.\n", prog_name);
         return(1);

         default:
         fprintf(stderr, "%s: unrecognized option `--%c'", prog_name, c);
         fprintf(stderr, "`%s --help' for more information.\n", prog_name);
         return(1);
      };
   };
   if (optind == argc)
   {
      fprintf(stderr, "%s: missing required argument\n", prog_name);
      fprintf(stderr, "`%s --help' for more information.\n", prog_name);
      return(1);
   };
   hostnam = argv[optind++];
   if (optind < argc)
      service = argv[optind++];


   // resolves specified hosts
   if ((rc = getaddrinfo(hostnam, service, &hints, &res)) != 0)
   {
      fprintf(stderr, "%s: getaddrinfo(): %s\n", prog_name, gai_strerror(rc));
      return(1);
   };


   // displays results
   count = 0;
   for(info = res; ((info)); info = info->ai_next)
   {
      count++;
      bzero(addrstr, sizeof(addrstr));
      sau.sa = info->ai_addr;
      switch(sau.sa->sa_family)
      {
         case AF_INET:
         inet_ntop(AF_INET,  &sau.sin->sin_addr,   addrstr, sizeof(addrstr));
         printf("%i: %s:%hu\n", count, addrstr, ntohs(sau.sin->sin_port));
         break;

         default:
         inet_ntop(AF_INET6, &sau.sin6->sin6_addr, addrstr, sizeof(addrstr));
         printf("%i: [%s]:%hu\n", count, addrstr, ntohs(sau.sin6->sin6_port));
         break;
      };
   };


   // frees results
   freeaddrinfo(res);


   return(0);
}


/* end of source */