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/*
* Copyright © 2009 by Daniel Friesel <derf@derf.homelinux.org>
* License: WTFPL <http://sam.zoy.org/wtfpl>
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#define PRINT_USAGE \
fprintf(stderr, "Usage: %s [-46r] <hostname>\n", argv[0])
static inline int addr_to_ip(const struct addrinfo *address, char *ip, int length) {
void *ptr;
switch (address->ai_family) {
case AF_INET:
ptr = &((struct sockaddr_in *) address->ai_addr)->sin_addr;
break;
case AF_INET6:
ptr = &((struct sockaddr_in6 *) address->ai_addr)->sin6_addr;
break;
default:
fprintf(stderr, "Unknown address family: %u\n", address->ai_family);
return 0;
}
if (inet_ntop(address->ai_family, ptr, ip, length) == NULL) {
perror("inet_ntop");
return 0;
}
return 1;
}
int main(int argc, char **argv) {
struct addrinfo hints = { 0, AF_UNSPEC, SOCK_DGRAM, 0, 0, NULL, NULL, NULL };
struct addrinfo *result, *address;
char hostname[NI_MAXHOST];
char ip_address[INET6_ADDRSTRLEN];
int ret;
int show_rdns = 0;
enum {
INPUT_NONE,
INPUT_IP,
INPUT_HOST
} input_type = INPUT_NONE;
signed char option;
while ((option = getopt(argc, argv, "46r")) != -1) {
switch (option) {
case '4':
hints.ai_family = AF_INET;
break;
case '6':
hints.ai_family = AF_INET6;
break;
case 'r':
show_rdns = 1;
break;
default:
PRINT_USAGE;
return EXIT_FAILURE;
}
}
if (optind >= argc) {
PRINT_USAGE;
return EXIT_FAILURE;
}
ret = getaddrinfo(argv[optind], NULL, &hints, &result);
if (ret != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
return EXIT_FAILURE;
}
for (address = result; address != NULL; address = address->ai_next) {
if (addr_to_ip(address, ip_address, sizeof(ip_address)) == 0)
continue;
if (input_type == INPUT_NONE) {
if (strcmp(ip_address, argv[optind]) == 0)
input_type = INPUT_IP;
else
input_type = INPUT_HOST;
}
if (input_type == INPUT_HOST)
puts(ip_address);
if ((input_type == INPUT_IP) || (show_rdns == 1)) {
ret = getnameinfo(address->ai_addr, address->ai_addrlen, hostname, NI_MAXHOST, NULL, 0, 0);
if (ret != 0) {
fprintf(stderr, "getnameinfo: %s\n", gai_strerror(ret));
continue;
}
puts(hostname);
}
}
freeaddrinfo(address);
return(EXIT_SUCCESS);
}
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