getaddrinfoTest.c

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


#define BROKEN_DOMAIN "word-view.beta.officeapps.live.com"
#define BUF_SIZE 500

/*
*  This is adopted from the example echo client code in the getaddrinfo
*	man page, just shortened and modified so it just resolves BROKEN_DOMAIN
*	and prints the IP address to stderr.
*	Compiled with gcc getaddrinfoTest.c ; Ran with ./a.out
*/

void *get_in_addr(struct sockaddr *sa)
{
	if (sa->sa_family == AF_INET)
		return &(((struct sockaddr_in*)sa)->sin_addr);
	return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(int argc, char *argv[])
{
	struct addrinfo hints;
	struct addrinfo *result, *rp;
	int sfd, s, j;
	size_t len;
	ssize_t nread;
	char buf[BUF_SIZE];

	/* Obtain address(es) matching host/port */

	/*
	//How the hints stucture is initialised in the example code
	memset(&hints, 0, sizeof(struct addrinfo));
	hints.ai_family = AF_UNSPEC;    //Allow IPv4 or IPv6 
	hints.ai_socktype = SOCK_DGRAM; // Datagram socket
	hints.ai_flags = 0;
	hints.ai_protocol = 0;          // Any protocol
	*/

	//How the hints stucture is initialised in DNS::hostByAddress
	memset(&hints, 0, sizeof(hints));
	hints.ai_flags = AI_CANONNAME | AI_ADDRCONFIG; //removing AI_ADDRCONFIG prevents the resolution delay
	
	//make the system call
	s = getaddrinfo(BROKEN_DOMAIN, NULL, &hints, &result); //hangs for about 5 seconds
	if (s != 0) {
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
		exit(EXIT_FAILURE);
	}
	char addrString[INET6_ADDRSTRLEN];
	inet_ntop(result->ai_family, get_in_addr((struct sockaddr *)result->ai_addr), addrString, sizeof addrString);
	printf(addrString,"%s"); printf("\n","%s");
}