netsukuku/src/getaddrinfodnstest.c

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>		/* getaddrinfo, getnameinfo */
#include <stdio.h>		/* fprintf, printf */
#include <stdlib.h>		/* exit */
#include <string.h>		/* memset */
 
int
getaddrinfodnsresolution(char *domain)
{
	struct addrinfo hints, *res, *res0;
	int error;
	char host[NI_MAXHOST];
 
	/*
	 * Request only one socket type from getaddrinfo(). Else we
	 * would get both SOCK_DGRAM and SOCK_STREAM, and print two
	 * copies of each numeric address.
	 */
	memset(&hints, 0, sizeof hints);
	hints.ai_family = PF_UNSPEC;     /* IPv4, IPv6, or anything */
	hints.ai_socktype = SOCK_DGRAM;  /* Dummy socket type */

	/*
	 * Use getaddrinfo() to resolve domain and allocate
	 * a linked list of addresses.
	 */
	error = getaddrinfo(domain, NULL, &hints, &res0);
	if (error) {
		fprintf(stderr, "%s\n", gai_strerror(error));
		exit(1);
	}
 
	/* Iterate the linked list. */
	for (res = res0; res; res = res->ai_next) {
		/*
		 * Use getnameinfo() to convert res->ai_addr to a
		 * printable string.
		 *
		 * NI_NUMERICHOST means to present the numeric address
		 * without doing reverse DNS to get a domain name.
		 */
		error = getnameinfo(res->ai_addr, res->ai_addrlen,
		    host, sizeof host, NULL, 0, NI_NUMERICHOST);
 
		if (error) {
			fprintf(stderr, "%s\n", gai_strerror(error));
		} else {
			/* Print the numeric address. */
			printf("%s\n", host);
		}
	}
 
	/* Free the linked list. */
	freeaddrinfo(res0);
 
	return 0;
}