/* Udns 1.0 - Jean-Marc Zucconi
 * This file is in the public domain
 */


/* usage: Udns  -h hostname -p password IP_Address
 *        example: Udns -h mydomain.com -p f90284f 194.11.98.45
 * if you want to update your IP address whenever the PPP session restarts,
 * simply add this line in your /etc/ppp/ppp.linkup file:
 *
 *    default:
 *      !bg /usr/local/bin/Udns -h <your.domain.here> -p <password> MYADDR
 *
 */

#include <stdio.h> 
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netdb.h>

#define HOST "www.dtdns.net"
#define PORT 80
#define TIMEOUT 300 /* seconds */

char buffer[8192];

int http_open (char *, int), httpget (char *, int, char *);
void parse (int);
int debug = 0;

void
usage ()
{
    extern char *__progname;
    fprintf (stderr, "usage: %s  -h hostname -p password IP_Address\n", 
	     __progname);
    exit (1);
}

main (int argc, char **argv)
{
    int c, len;
    char *password = 0, *name = 0, *ip = 0;
    char *command;

    while ((c = getopt (argc, argv, "dh:p:")) != -1) {
	switch (c) {
	case 'd': 
	    debug = 1;
	    break;
	case 'p': 
	    password = strdup (optarg);
	    break;
	case 'h': 
	    name = strdup (optarg);
	    break;
	default:
	    usage ();
	}
    }
    if (!argv[optind] || argv[optind+1] || !password || !name)
	usage ();
    ip = strdup (argv[optind]);
    len = 0;
    for (c = 1; c <= optind; c++) { /* hide command line */
	int l =  strlen (argv[c]);
	len += l;
	memset (argv[c], ' ', l);
    }
    command = (char *) malloc (len + 1000);
    sprintf (command, "GET /autodns.cfm?id=%s&pw=%s&ip=%s&client=Udns"
	     " HTTP/1.1\n"
	     "Host: %s\n"
	     "User-Agent: Udns\n"
	     "\n",
	     name, password, ip, HOST);
    len = httpget (HOST, PORT, command);
    /* reply looks like
     *   HTTP/1.1 200 OK\r\n
     *   Server: Microsoft-IIS/5.0\r\n
     *   Date: Fri, 27 Oct 2000 15:59:19 GMT\r\n
     *   Connection: close\r\n
     *   Content-type: text/html\n
     *   Page-Completion-Status: Normal\n
     *   Page-Completion-Status: Normal\n
     *   \n
     *   The hostname you supplied is not valid.
     */
    parse (len);
    exit (0);
}    
void
parse (int len)
{
    char *p;
    buffer[len] = 0;

    if (debug)
	printf ("read %d bytes from server: <%s>\n", len, buffer);

    p = strstr (buffer, "\n\n");
    if (!p) /* OK */
	return;
    p += 2;
    printf ("%s\n", p);
    if (strstr (p, "Host already points to this IP"))
	return; /* OK too */
    exit (1);
}
int
httpget (char *host, int port, char *str)
{
    char *cp;
    struct timeval tv;
    time_t tout;
    fd_set fdset;
    int i, s;
    
    s = http_open (host, port);

    if (debug)
	printf ("sending command: <%s>\n", str);
    i = strlen (str);
    if (i != write (s, str, i))
	err (1, "could not send GET command to %s.", host);
    
    FD_ZERO (&fdset);
    FD_SET (s, &fdset);
    tout = TIMEOUT;
    
    tv.tv_sec = tout;
    tv.tv_usec = 0;
    i = select (s+1, &fdset, 0, 0, &tv); 
    switch (i) {
    case 0:
	errx (1, "timeout");
    case 1:
	i = read (s, buffer, sizeof (buffer));
	return i;
    default:
	err (1, "communication error with %s.", host);
    }
}

int
http_open (char *host, int port)
{
    unsigned long a;
    struct sockaddr_in sin, sin2;
    struct hostent *h;
    int s;
    
    if (debug)
	printf ("establishing conection with %s, port %d\n", host, port);

    a = inet_addr (host);
    if (a != INADDR_NONE) {
	sin.sin_family = AF_INET;
	sin.sin_addr.s_addr = a;
    } else {
	h = gethostbyname (host);
	if (!h) 
	    err (1, "could not lookup host %s.", host);
	sin.sin_family = h->h_addrtype;
	bcopy (h->h_addr, (char *) &sin.sin_addr, h->h_length);
    }
    sin.sin_port = htons (port);
    if ((s = socket (sin.sin_family, SOCK_STREAM, 0)) < 0) 
	err (1, "socket");
    bzero ((char *)&sin2, sizeof (sin2));
    sin2.sin_family = AF_INET;
    sin2.sin_port = 0;
    sin2.sin_addr.s_addr = htonl (INADDR_ANY);
    if (bind (s, (struct sockaddr *) &sin2, sizeof (sin2)))
	err (1, "could not bind to socket.");
    
    if (connect (s, (struct sockaddr *) &sin, sizeof(sin)) < 0)
	err (1, "connection failed.");
    return s;
}