/*
 * KTCPVS       An implementation of the TCP Virtual Server daemon inside
 *              kernel for the LINUX operating system. KTCPVS can be used
 *              to build a moderately scalable and highly available server
 *              based on a cluster of servers, with more flexibility.
 *
 * Version:     $Id$
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *
 *              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.
 *
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/ctype.h>

#include <linux/net.h>
#include <linux/sched.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/uaccess.h>

#include "tcp_vs.h"


/*
 * The interface of tcp_vs_http module needs a rewrite!!!
 *   o the definition of http rules for this module
 *   o how to represent those rules and do fast-matching
 *   o how to insert/modify/display those http rules easily?
 *   o a flexible model that other modules can follow too.
 */

static int tcp_vs_http_init_svc(struct tcp_vs_service *svc)
{
	EnterFunction(5);

	if (!(svc->sched_data=(void *)get_free_page(GFP_KERNEL))) {
		MOD_DEC_USE_COUNT;
		return -1;
	}

	LeaveFunction(5);

	return 0;
}


static int tcp_vs_http_done_svc(struct tcp_vs_service *svc)
{
	EnterFunction(5);

	if (svc->sched_data)
		free_page((unsigned long)svc->sched_data);

	LeaveFunction(5);

	return 0;
}


static int tcp_vs_http_update_svc(struct tcp_vs_service *svc)
{
	return 0;
}


static inline struct tcp_vs_dest *
__tcp_vs_http_wlc_schedule(struct list_head *destinations)
{
	register struct list_head *e;
	struct tcp_vs_dest *dest, *least;

	list_for_each (e, destinations) {
		least = list_entry(e, struct tcp_vs_dest, r_list);
		if (least->weight > 0) {
			goto nextstage;
		}
	}
	return NULL;

	/*
	 *    Find the destination with the least load.
	 */
  nextstage:
	for (e=e->next; e!=destinations; e=e->next) {
		dest = list_entry(e, struct tcp_vs_dest, r_list);
		if (atomic_read(&least->conns) * dest->weight >
		    atomic_read(&dest->conns) * least->weight) {
			least = dest;
		}
	}

	return least;
}


static struct tcp_vs_dest *
tcp_vs_http_matchrule(struct tcp_vs_service *svc, const char *request)
{
	struct list_head *l;
	struct tcp_vs_rule *r;
	struct tcp_vs_dest *dest = NULL;

	read_lock(&svc->lock);
	list_for_each(l, &svc->rule_list) {
		r = list_entry(l, struct tcp_vs_rule, list);
		if (!tcp_vs_exp_exec(&r->exp, request)) {
			/* HIT */
			dest = __tcp_vs_http_wlc_schedule(&r->destinations);
			break;
		}
	}
	read_unlock(&svc->lock);

	return dest;
}


/*
 *      Parse HTTP header
 */
int parse_http_header(char *buffer,
		      size_t buflen, char* request, size_t reqlen)
{
	char *eob,*eol,*tmp;

	EnterFunction(5);
	eob = buffer + buflen;

	/* parse only the first header if multiple headers are present */
	tmp = strstr(buffer, "\r\n\r\n");
	if (tmp!=NULL)
		eob = tmp;


	while (buffer < eob) {
		if (isspace(buffer[0])) {
			buffer++;
			continue;
		}

		eol=strchr(buffer, '\n');

		if (eol==NULL)
			eol=eob;

		if (eol-buffer < 4) {
			buffer++;
			continue;
		}

		if (!strncmp("GET ", buffer, 4)) {
			int len;

			buffer += 4;

			tmp=strchr(buffer, ' ');
			if (tmp == NULL)
				tmp=eol-1;

			if (tmp > eob)
				continue;

			len = min((int)(reqlen-1), tmp-buffer);
			strncpy(request, buffer, len);
			request[len] = 0;

			buffer=eol+1;

			LeaveFunction(5);
			return 0;
		}

		/* next line */
		buffer = eol+1;
	}
	LeaveFunction(5);

	return -1;
}


/*
 *    HTTP content-based scheduling
 *    Parse the http request, select a server according to the
 *    request, and create a socket the server finally.
 */
static struct socket *tcp_vs_http_schedule(struct tcp_vs_conn *conn,
					   struct tcp_vs_service *svc)
{
#define REQLEN 1024
	struct tcp_vs_dest *dest;
	struct socket *csock, *dsock;
	int len;
	char *buffer;
	size_t buflen;
	static char request[REQLEN];

	EnterFunction(5);

	buffer = conn->buffer;
	buflen = conn->buflen;
	csock = conn->csock;

	/* Do we have data ? */
	while (skb_queue_empty(&(csock->sk->receive_queue))) {
		interruptible_sleep_on_timeout(&csock->wait, HZ);
	}

	/* fixme: what if the request overlap this receiving buffer */
	len = tcp_vs_recvbuffer(csock, buffer, buflen);
	if (len < 0) {
		TCP_VS_ERR("error reading request from client\n");
		return NULL;
	}

	if (parse_http_header(buffer, len, request, REQLEN)) {
		TCP_VS_ERR("cannot parse http request\n");
		return NULL;
	}

	TCP_VS_DBG(5, "request: GET %s\n", request);

	/*  Head.RemoteHost.s_addr = sock->sk->daddr; */

	dest = tcp_vs_http_matchrule(svc, request);
	if (!dest) {
		TCP_VS_ERR("no suitable destination available\n");
		return NULL;
	}

	TCP_VS_DBG(5, "HTTP: server %d.%d.%d.%d:%d "
		   "conns %d refcnt %d weight %d\n",
		   NIPQUAD(dest->addr), ntohs(dest->port),
		   atomic_read(&dest->conns),
		   atomic_read (&dest->refcnt), dest->weight);

	atomic_inc(&dest->conns);
	conn->dest = dest;
	dsock = tcp_vs_connect2dest(dest);
	if (!dsock) {
		TCP_VS_ERR("The destination is not available\n");
		return NULL;
	}

	if (tcp_vs_sendbuffer(dsock, buffer, len)!=len) {
		TCP_VS_ERR("Error sending buffer\n");
	}

	LeaveFunction(5);

	return dsock;
}


static struct tcp_vs_scheduler tcp_vs_http_scheduler =
{
	{0},                    /* n_list */
	"http",                 /* name */
	THIS_MODULE,		/* this module */
	tcp_vs_http_init_svc,	/* initializer */
	tcp_vs_http_done_svc,	/* done */
	tcp_vs_http_update_svc,	/* update */
	tcp_vs_http_schedule,   /* select a server by http request */
};


static int __init tcp_vs_http_init(void)
{
	INIT_LIST_HEAD(&tcp_vs_http_scheduler.n_list);
	return register_tcp_vs_scheduler(&tcp_vs_http_scheduler);
}

static void __exit tcp_vs_http_cleanup(void)
{
	unregister_tcp_vs_scheduler(&tcp_vs_http_scheduler);
}

module_init(tcp_vs_http_init);
module_exit(tcp_vs_http_cleanup);