util.c

/*
 * File: util.c
 * Author: Andy Sayler
 * Modified: Shiv Mishra
 * Modified: Brian Peterson
 * Project: CSCI 3753 Programming Assignment 3
 * Create Date: 2012/02/01
 * Modify Date: 2012/02/01
 * Modify Date: 2016/09/26
 * Modify Date: 2020/10/26
 * Description:
 * 	This file contains declarations of utility functions for
 *      Programming Assignment 3.
 *  
 */

#include "util.h"

int dnslookup(const char *hostname, char *firstIPstr, int maxSize)
{

	/* Local vars */
	struct addrinfo *headresult = NULL;
	struct addrinfo *result = NULL;
	struct sockaddr_in *ipv4sock = NULL;
	struct in_addr *ipv4addr = NULL;
	char ipv4str[INET_ADDRSTRLEN];
	char ipstr[INET6_ADDRSTRLEN];
	int addrError = 0;

	/* DEBUG: Print Hostname*/
#ifdef UTIL_DEBUG
	fprintf(stderr, "%s\n", hostname);
#endif

	/* Lookup Hostname */
	addrError = getaddrinfo(hostname, NULL, NULL, &headresult);
	if (addrError)
	{
		fprintf(stderr, "Error looking up Address: %s\n",
				gai_strerror(addrError));
		return UTIL_FAILURE;
	}
	/* Loop Through result Linked List */
	for (result = headresult; result != NULL; result = result->ai_next)
	{
		/* Extract IP Address and Convert to String */
		if (result->ai_addr->sa_family == AF_INET)
		{
			/* IPv4 Address Handling */
			ipv4sock = (struct sockaddr_in *)(result->ai_addr);
			ipv4addr = &(ipv4sock->sin_addr);
			if (!inet_ntop(result->ai_family, ipv4addr,
						   ipv4str, sizeof(ipv4str)))
			{
				perror("Error Converting IP to String");
				return UTIL_FAILURE;
			}
#ifdef UTIL_DEBUG
			fprintf(stdout, "%s\n", ipv4str);
#endif
			strncpy(ipstr, ipv4str, sizeof(ipstr));
			ipstr[sizeof(ipstr) - 1] = '\0';
		}
		else if (result->ai_addr->sa_family == AF_INET6)
		{
			/* IPv6 Handling */
#ifdef UTIL_DEBUG
			fprintf(stdout, "IPv6 Address: Not Handled\n");
#endif
			strncpy(ipstr, "UNHANDELED", sizeof(ipstr));
			ipstr[sizeof(ipstr) - 1] = '\0';
		}
		else
		{
			/* Unhandlded Protocol Handling */
#ifdef UTIL_DEBUG
			fprintf(stdout, "Unknown Protocol: Not Handled\n");
#endif
			strncpy(ipstr, "UNHANDELED", sizeof(ipstr));
			ipstr[sizeof(ipstr) - 1] = '\0';
		}
		/* Save First IP Address */
		if (result == headresult)
		{
			strncpy(firstIPstr, ipstr, maxSize);
			firstIPstr[maxSize - 1] = '\0';
		}
	}

	/* Cleanup */
	freeaddrinfo(headresult);

	return UTIL_SUCCESS;
}

FILE *try_fopen(char *filepath, char *mode, char *caller_name, int graceful)
{
	FILE *fp = fopen(filepath, mode);
	if (fp == NULL)
	{
		fprintf(stderr, "in %s: failed to open file: '%s'\n",
				caller_name, filepath);
		if (!graceful)
		{
			exit(1); // TODO: Use pthread_exit
		}
		else
		{
			return NULL;
		}
	}
	// printf("in %s: opened file '%s' \n",
	// 	   caller_name, filepath);
	return fp;
}