Thread: please help ! IP validation function

hi everyone ..

i must be daft .. (too much programming) please tell me whats wrong in this function i wrote to validate and pass an ip as a pointer..

Code:

char* ip_validation()
{
	struct sockaddr_in ipStore;					
	char *ipVal;                      // this ip number value gets returned to the main program
	int valid_input, exit_flag = 0;	// when valid_input = 1,the date becomes valid and the loop is exited
	char user_input;				// handles user input, single character menu choice
	unsigned b1, b2, b3, b4;		// ip 
	int rc;


	while( exit_flag == 0 ) 
	{
		valid_input = 0;
		printf("\nUse the Default ip 192.168.0.1 (Y/N)?: ");
		scanf("%c",&user_input);
		user_input = toupper( user_input );
			if((user_input == 'Y')||(user_input == 'N'))  
			valid_input = 1;
			else
			printf("\007Error: Invalid choice\n\n"); 
			clear_char();

		switch(user_input)
			{
			case 'Y':
				ipStore.sin_addr.s_addr = inet_addr("127.0.0.1");     // http://cboard.cprogramming.com/showthread.php?t=15179&highlight=store+ip+address
				ipVal = inet_ntoa(ipStore.sin_addr);
				memset(&(ipStore.sin_zero), '\0', 8);  // zero the rest of the struct 
				exit_flag = 1;
				break;
			case 'N':
				valid_input = 0;							// when valid_input = 1,the data becomes valid and the loop is exited 
				while( valid_input == 0 )
				{
				printf("\nEnter a IP address: ");
				rc = scanf("%3u.%3u.%3u.%3u",&b1, &b2, &b3, &b4);
				clear_char();

				if ((rc != 4 && rc != 6) || ((b1 | b2 | b3 | b4) > 255) || (strspn(ipVal, "0123456789.:") < strlen(ipVal)))
					{
					valid_input = 0;
					printf("\007Error: Incorrect IP\n");
					}
				else
					{
					valid_input = 1;
					ipStore.sin_addr.S_un.S_un_b.s_b1 = b1;
					ipStore.sin_addr.S_un.S_un_b.s_b2 = b2;
					ipStore.sin_addr.S_un.S_un_b.s_b3 = b3;
					ipStore.sin_addr.S_un.S_un_b.s_b4 = b4;														
					}	
				}	
				memset(&(ipStore.sin_zero), '\0', 8);  // zero the rest of the struct 
				exit_flag = 1;
				break; //break case 'N'
			}// end switch
	}//end while
ipVal = inet_ntoa(ipStore.sin_addr);
return ipVal;
}//end function


void clear_char(void) 
{
	int ch;
	while((ch = getchar()) != '\n'); 
}

and please ..if you know of any sample codes online which SHOULD be much better than this one .. i would greatly appriciate it thankyou for your time

> printf("\007Error: Invalid choice\n\n");
> clear_char();
1. Don't use 007 to ring the bell. If you really must, use \a.
But there is nothing more annoying than trivial beeping code which you can't silence.
2. The indentation makes it seem clear_char() is part of the else, but it isn't really.

> ipVal = inet_ntoa(ipStore.sin_addr);
If ipVal is pointing to the innards of that data, then you're returning a pointer to a local.
This is a bad thing.

> char* ip_validation()
My suggestion would be to separate input from validation.
Have functions which
- input an IP into a char buffer
- validate the IP address in that buffer