path: root/net/dccp/ccids/ccid3.c

/*
 *  net/dccp/ccids/ccid3.c
 *
 *  Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
 *  Copyright (c) 2005-6 Ian McDonald <imcdnzl@gmail.com>
 *
 *  An implementation of the DCCP protocol
 *
 *  This code has been developed by the University of Waikato WAND
 *  research group. For further information please see http://www.wand.net.nz/
 *
 *  This code also uses code from Lulea University, rereleased as GPL by its
 *  authors:
 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
 *
 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
 *  and to make it work as a loadable module in the DCCP stack written by
 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
 *
 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 *
 *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/config.h>
#include "../ccid.h"
#include "../dccp.h"
#include "lib/packet_history.h"
#include "lib/loss_interval.h"
#include "lib/tfrc.h"
#include "ccid3.h"

/*
 * Reason for maths here is to avoid 32 bit overflow when a is big.
 * With this we get close to the limit.
 */
static u32 usecs_div(const u32 a, const u32 b)
{
	const u32 div = a < (UINT_MAX / (USEC_PER_SEC /    10)) ?    10 :
			a < (UINT_MAX / (USEC_PER_SEC /    50)) ?    50 :
			a < (UINT_MAX / (USEC_PER_SEC /   100)) ?   100 :
			a < (UINT_MAX / (USEC_PER_SEC /   500)) ?   500 :
			a < (UINT_MAX / (USEC_PER_SEC /  1000)) ?  1000 :
			a < (UINT_MAX / (USEC_PER_SEC /  5000)) ?  5000 :
			a < (UINT_MAX / (USEC_PER_SEC / 10000)) ? 10000 :
			a < (UINT_MAX / (USEC_PER_SEC / 50000)) ? 50000 :
								 100000;
	const u32 tmp = a * (USEC_PER_SEC / div);
	return (b >= 2 * div) ? tmp / (b / div) : tmp;
}

static int ccid3_debug;

#ifdef CCID3_DEBUG
#define ccid3_pr_debug(format, a...) \
	do { if (ccid3_debug) \
		printk(KERN_DEBUG "%s: " format, __FUNCTION__, ##a); \
	} while (0)
#else
#define ccid3_pr_debug(format, a...)
#endif

static struct dccp_tx_hist *ccid3_tx_hist;
static struct dccp_rx_hist *ccid3_rx_hist;
static struct dccp_li_hist *ccid3_li_hist;

/* TFRC sender states */
enum ccid3_hc_tx_states {
       	TFRC_SSTATE_NO_SENT = 1,
	TFRC_SSTATE_NO_FBACK,
	TFRC_SSTATE_FBACK,
	TFRC_SSTATE_TERM,
};

#ifdef CCID3_DEBUG
static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
{
	static char *ccid3_state_names[] = {
	[TFRC_SSTATE_NO_SENT]  = "NO_SENT",
	[TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
	[TFRC_SSTATE_FBACK]    = "FBACK",
	[TFRC_SSTATE_TERM]     = "TERM",
	};

	return ccid3_state_names[state];
}
#endif

static void ccid3_hc_tx_set_state(struct sock *sk,
				  enum ccid3_hc_tx_states state)
{
	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
	enum ccid3_hc_tx_states oldstate = hctx->ccid3hctx_state;

	ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
		       dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
		       ccid3_tx_state_name(state));
	WARN_ON(state == oldstate);
	hctx->ccid3hctx_state = state;
}

/* Calculate new t_ipi (inter packet interval) by t_ipi = s / X_inst */
static inline void ccid3_calc_new_t_ipi(struct ccid3_hc_tx_sock *hctx)
{
	/*
	 * If no feedback spec says t_ipi is 1 second (set elsewhere and then
	 * doubles after every no feedback timer (separate function)
	 */
	if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
		hctx->ccid3hctx_t_ipi = usecs_div(hctx->ccid3hctx_s,
						  hctx->ccid3hctx_x);
}

/* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
static inline void ccid3_calc_new_delta(struct ccid3_hc_tx_sock *hctx)
{
	hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,
					   TFRC_OPSYS_HALF_TIME_GRAN);
}

/*
 * Update X by
 *    If (p > 0)
 *       x_calc = calcX(s, R, p);
 *       X = max(min(X_calc, 2 * X_recv), s / t_mbi);
 *    Else
 *       If (now - tld >= R)
 *          X = max(min(2 * X, 2 * X_recv), s / R);
 *          tld = now;
 */ 
static void ccid3_hc_tx_update_x(struct sock *sk)
{
	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

	/* To avoid large error in calcX */
	if (hctx->ccid3hctx_p >= TFRC_SMALLEST_P) {
		hctx->ccid3hctx_x_calc = tfrc_calc_x(hctx->ccid3hctx_s,
						     hctx->ccid3hctx_rtt,
						     hctx->ccid3hctx_p);
		hctx->ccid3hctx_x = max_t(u32, min_t(u32, hctx->ccid3hctx_x_calc,
							  2 * hctx->ccid3hctx_x_recv),
					       (hctx->ccid3hctx_s /
					        TFRC_MAX_BACK_OFF_TIME));
	} else {
		struct timeval now;

		dccp_timestamp(sk, &now);
	       	if (timeval_delta(&now, &hctx->ccid3hctx_t_ld) >=
		    hctx->ccid3hctx_rtt) {
			hctx->ccid3hctx_x = max_t(u32, min_t(u32, hctx->ccid3hctx_x_recv,
								  hctx->ccid3hctx_x) * 2,
						       usecs_div(hctx->ccid3hctx_s,
							       	 hctx->ccid3hctx_rtt));
			hctx->ccid3hctx_t_ld = now;
		}
	}
}

static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
{
	struct sock *sk = (struct sock *)data;
	unsigned long next_tmout = 0;
	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

	bh_lock_sock(sk);
	if (sock_owned_by_user(sk)) {
		/* Try again later. */
		/* XXX: set some sensible MIB */
		sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
			       jiffies + HZ / 5);
		goto out;
	}

	ccid3_pr_debug("%s