/* webdump6.c -- Copyright (C) 2001 Paul Stauffer <paulds@bu.edu>
 * A primitive IPv6 HTTP client.  Connects to the specified server on the
 * standard HTTP port, using the IPv6 protocol at the network layer,
 * requests a document, and dumps the resulting document to stdout.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

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

#define INPUT_BUFSIZ BUFSIZ*10
#define MAXTRIES 3
#define TIMEOUT_SECS 20
#define TIMEOUT_USECS 0

int main(int argc, char* argv[]) {
	
	int s;						/* socket descriptor */
	int alen;					/* length of an AF_INET6 address */
	int offset = 0;				/* memory offset */
	int retval = 0;				/* value returned by select */
	int tries = 0;				/* number of attempts to make */
	/* Note that the default size of the input buffer will not actually
	   accommodate the length of many modern web pages.  For production
	   purposes, increase this by a large multiplicative factor, but this
	   will be good enough for demonstration purposes. */
	char inbuf[INPUT_BUFSIZ];	/* input buffer */
	char outbuf[BUFSIZ];		/* output buffer */
	char* host;					/* hostname of server */
	char* url = "/index.html";	/* URL to request */
	struct sockaddr_in6 saddr;	/* socket structure */
	struct hostent* servdata;	/* data returned by gethostbyname */
	fd_set readset;				/* for select */
	struct timeval timeout;		/* timeout value waiting for server */
	
	switch(argc) {
		case 3:
			url = argv[2];
			host = argv[1];
			break;
		case 2:
			host = argv[1];
			break;
		default:
			fprintf(stderr, "usage: webdump host [url]\n");
			return(1);
	}
	
	/* To be safe, zero out these items */
	memset(inbuf, '\0', INPUT_BUFSIZ);
	memset(outbuf, '\0', BUFSIZ);
	memset(&saddr, 0, sizeof(saddr));
	
	/* lookup host data */
	if ((servdata = gethostbyname2(host, AF_INET6)) == NULL) {
		fprintf(stderr, "Error looking up host: %s\n", hstrerror(h_errno));
		return(1);
	}
	
	/* set up the server address */
	memcpy(&saddr.sin6_addr, servdata->h_addr, servdata->h_length);
	saddr.sin6_family = AF_INET6;
	saddr.sin6_port = htons(80);		/* HTTP port, currently hard-coded */
	alen = sizeof(saddr);
	
	/* create socket */
	if ((s = socket(PF_INET6, SOCK_STREAM, 0)) < 0) {
		fprintf(stderr, "Error creating socket\n");
		return(1);
	}
	
	/* connect to server */
	if ((connect(s, &saddr, alen)) < 0) {
		fprintf(stderr, "Error connecting to server: %s\n", strerror(errno));
		close(s);
		return(1);
	}
	
	/* set up the request string */
	strcat(outbuf, "GET ");
	strncat(outbuf, url, strlen(url));
	strcat(outbuf, " HTTP/1.0\r\n\r\n");
	
	while (retval == 0) {
		
		send(s, outbuf, strlen(outbuf), 0);
		
		/* set up for the select */
		memset(&timeout, 0, sizeof(timeout));
		timeout.tv_sec = TIMEOUT_SECS;
		timeout.tv_usec = TIMEOUT_USECS;
		FD_ZERO(&readset);
		FD_SET(s, &readset);
		
		if ((retval = select(s+1, &readset, NULL, NULL, &timeout)) < 0) {
			fprintf(stderr, "Error on select\n");
			close(s);
			return(1);
		}
		else if (retval == 0) {
			tries++;
			fprintf(stderr, "Attempt %i timed out.\n", tries);
			
			if (tries == MAXTRIES) {
				fprintf(stderr, "Server not responding, giving up.\n");
				close(s);
				return(1);
			}
		}
	}
	
	recv(s, inbuf, INPUT_BUFSIZ-1, 0);
	
	/* Step through the received buffer, looking for the byte pattern that
	   indicates the end of the HTTP header. */
	while(strncmp(inbuf+offset, "\r\n\r\n", 4) != 0) {
		offset++;
	}
	
	/* Anything other than "200" at this location indicates some sort of */
	/*  HTTP error */
	if (strncmp(inbuf+9, "200", 3) != 0) {
		
		/* Set the next byte after the HTTP header to a NULL, so that */
		/*  output will stop when it gets to this point. */
		memset(inbuf+offset+4, '\0', 1);
		fprintf(stdout, inbuf);		/* Print the HTTP headers. */
		close(s);
		return(1);
	}
	
	/* Print the response, starting 4 bytes after the location we identified
	   as the beginning of the "\r\n\r\n" string. */
	fprintf(stdout, inbuf+offset+4);
	
	close(s);
	return(0);
}