ccid3.c

linux2.6.16版本

/*
 *  net/dccp/ccids/ccid3.c
 *
 *  Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
 *  Copyright (c) 2005-6 Ian McDonald <[e-mail]>
 *
 *  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 <[e-mail]>.
 *
 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <[e-mail]>
 *
 *  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 inline 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;

static int ccid3_init(struct sock *sk)
{
	return 0;
}

static void ccid3_exit(struct sock *sk)
{
}

/* 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 inline 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, sk=%p, state=%s\n", dccp_role(sk), sk,
		       ccid3_tx_state_name(hctx->ccid3hctx_state));
	
	switch (hctx->ccid3hctx_state) {
	case TFRC_SSTATE_TERM:
		goto out;
	case TFRC_SSTATE_NO_FBACK:
		/* Halve send rate */
		hctx->ccid3hctx_x /= 2;
		if (hctx->ccid3hctx_x < (hctx->ccid3hctx_s /
					 TFRC_MAX_BACK_OFF_TIME))
			hctx->ccid3hctx_x = (hctx->ccid3hctx_s /
					     TFRC_MAX_BACK_OFF_TIME);

		ccid3_pr_debug("%s, sk=%p, state=%s, updated tx rate to %d "
			       "bytes/s\n",
			       dccp_role(sk), sk,
			       ccid3_tx_state_name(hctx->ccid3hctx_state),
			       hctx->ccid3hctx_x);
		next_tmout = max_t(u32, 2 * usecs_div(hctx->ccid3hctx_s,
						      hctx->ccid3hctx_x),
					TFRC_INITIAL_TIMEOUT);
		/*
		 * FIXME - not sure above calculation is correct. See section
		 * 5 of CCID3 11 should adjust tx_t_ipi and double that to
		 * achieve it really
		 */
		break;
	case TFRC_SSTATE_FBACK:
		/*
		 * Check if IDLE since last timeout and recv rate is less than
		 * 4 packets per RTT
		 */
		if (!hctx->ccid3hctx_idle ||
		    (hctx->ccid3hctx_x_recv >=
		     4 * usecs_div(hctx->ccid3hctx_s, hctx->ccid3hctx_rtt))) {
			ccid3_pr_debug("%s, sk=%p, state=%s, not idle\n",
				       dccp_role(sk), sk,
				       ccid3_tx_state_name(hctx->ccid3hctx_state));
			/* Halve sending rate */

			/*  If (X_calc > 2 * X_recv)
			 *    X_recv = max(X_recv / 2, s / (2 * t_mbi));
			 *  Else
			 *    X_recv = X_calc / 4;
			 */
			BUG_ON(hctx->ccid3hctx_p >= TFRC_SMALLEST_P &&
			       hctx->ccid3hctx_x_calc == 0);

			/* check also if p is zero -> x_calc is infinity? */
			if (hctx->ccid3hctx_p < TFRC_SMALLEST_P ||
			    hctx->ccid3hctx_x_calc > 2 * hctx->ccid3hctx_x_recv)
				hctx->ccid3hctx_x_recv = max_t(u32, hctx->ccid3hctx_x_recv / 2,
								    hctx->ccid3hctx_s / (2 * TFRC_MAX_BACK_OFF_TIME));
			else
				hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc / 4;

			/* Update sending rate */
			ccid3_hc_tx_update_x(sk);
		}
		/*
		 * Schedule no feedback timer to expire in
		 * max(4 * R, 2 * s / X)
		 */
		next_tmout = max_t(u32, hctx->ccid3hctx_t_rto, 
					2 * usecs_div(hctx->ccid3hctx_s,
						      hctx->ccid3hctx_x));
		break;
	default:
		printk(KERN_CRIT "%s: %s, sk=%p, Illegal state (%d)!\n",
		       __FUNCTION__, dccp_role(sk), sk, hctx->ccid3hctx_state);
		dump_stack();
		goto out;
	}

	sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer, 
		      jiffies + max_t(u32, 1, usecs_to_jiffies(next_tmout)));
	hctx->ccid3hctx_idle = 1;
out:
	bh_unlock_sock(sk);
	sock_put(sk);
}

static int ccid3_hc_tx_send_packet(struct sock *sk,
				   struct sk_buff *skb, int len)
{
	struct dccp_sock *dp = dccp_sk(sk);
	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
	struct dccp_tx_hist_entry *new_packet;
	struct timeval now;
	long delay;
	int rc = -ENOTCONN;

	BUG_ON(hctx == NULL || hctx->ccid3hctx_state == TFRC_SSTATE_TERM);

	/* Check if pure ACK or Terminating*/
	/*
	 * XXX: We only call this function for DATA and DATAACK, on, these
	 * packets can have zero length, but why the comment about "pure ACK"?
	 */
	if (unlikely(len == 0))
		goto out;

	/* See if last packet allocated was not sent */
	new_packet = dccp_tx_hist_head(&hctx->ccid3hctx_hist);
	if (new_packet == NULL || new_packet->dccphtx_sent) {
		new_packet = dccp_tx_hist_entry_new(ccid3_tx_hist,
						    SLAB_ATOMIC);

		rc = -ENOBUFS;
		if (unlikely(new_packet == NULL)) {
			LIMIT_NETDEBUG(KERN_WARNING "%s: %s, sk=%p, not enough "
				       "mem to add to history, send refused\n",
				       __FUNCTION__, dccp_role(sk), sk);
			goto out;
		}

		dccp_tx_hist_add_entry(&hctx->ccid3hctx_hist, new_packet);
	}

	dccp_timestamp(sk, &now);

	switch (hctx->ccid3hctx_state) {
	case TFRC_SSTATE_NO_SENT:
		hctx->ccid3hctx_no_feedback_timer.function = ccid3_hc_tx_no_feedback_timer;
		hctx->ccid3hctx_no_feedback_timer.data     = (unsigned long)sk;
		sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
			       jiffies + usecs_to_jiffies(TFRC_INITIAL_TIMEOUT));
		hctx->ccid3hctx_last_win_count	 = 0;
		hctx->ccid3hctx_t_last_win_count = now;
		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
		hctx->ccid3hctx_t_ipi = TFRC_INITIAL_IPI;

		/* Set nominal send time for initial packet */
		hctx->ccid3hctx_t_nom = now;
		timeval_add_usecs(&hctx->ccid3hctx_t_nom,
				  hctx->ccid3hctx_t_ipi);
		ccid3_calc_new_delta(hctx);
		rc = 0;
		break;
	case TFRC_SSTATE_NO_FBACK:
	case TFRC_SSTATE_FBACK:
		delay = (timeval_delta(&now, &hctx->ccid3hctx_t_nom) -
		         hctx->ccid3hctx_delta);
		delay /= -1000;
		/* divide by -1000 is to convert to ms and get sign right */
		rc = delay > 0 ? delay : 0;
		break;
	default:
		printk(KERN_CRIT "%s: %s, sk=%p, Illegal state (%d)!\n",
		       __FUNCTION__, dccp_role(sk), sk, hctx->ccid3hctx_state);
		dump_stack();
		rc = -EINVAL;
		break;
	}

	/* Can we send? if so add options and add to packet history */
	if (rc == 0) {
		dp->dccps_hc_tx_insert_options = 1;
		new_packet->dccphtx_ccval =
			DCCP_SKB_CB(skb)->dccpd_ccval =
				hctx->ccid3hctx_last_win_count;
	}
out:
	return rc;
}

static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, int len)
{
	const struct dccp_sock *dp = dccp_sk(sk);
	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
	struct timeval now;

	BUG_ON(hctx == NULL || hctx->ccid3hctx_state == TFRC_SSTATE_TERM);

	dccp_timestamp(sk, &now);

	/* check if we have sent a data packet */
	if (len > 0) {
		unsigned long quarter_rtt;
		struct dccp_tx_hist_entry *packet;

		packet = dccp_tx_hist_head(&hctx->ccid3hctx_hist);
		if (unlikely(packet == NULL)) {
			LIMIT_NETDEBUG(KERN_WARNING "%s: packet doesn't "
				       "exists in history!\n", __FUNCTION__);
			return;
		}
		if (unlikely(packet->dccphtx_sent)) {
			LIMIT_NETDEBUG(KERN_WARNING "%s: no unsent packet in "
				       "history!\n", __FUNCTION__);
			return;
		}
		packet->dccphtx_tstamp = now;
		packet->dccphtx_seqno  = dp->dccps_gss;
		/*
		 * Check if win_count have changed
		 * Algorithm in "8.1. Window Counter Valuer" in
		 * draft-ietf-dccp-ccid3-11.txt
		 */
		quarter_rtt = timeval_delta(&now, &hctx->ccid3hctx_t_last_win_count);
		if (likely(hctx->ccid3hctx_rtt > 8))
			quarter_rtt /= hctx->ccid3hctx_rtt / 4;

		if (quarter_rtt > 0) {
			hctx->ccid3hctx_t_last_win_count = now;
			hctx->ccid3hctx_last_win_count	 = (hctx->ccid3hctx_last_win_count +
							    min_t(unsigned long, quarter_rtt, 5)) % 16;
			ccid3_pr_debug("%s, sk=%p, window changed from "
				       "%u to %u!\n",
				       dccp_role(sk), sk,
				       packet->dccphtx_ccval,
				       hctx->ccid3hctx_last_win_count);
		}

		hctx->ccid3hctx_idle = 0;
		packet->dccphtx_rtt  = hctx->ccid3hctx_rtt;
		packet->dccphtx_sent = 1;
	} else
		ccid3_pr_debug("%s, sk=%p, seqno=%llu NOT inserted!\n",
			       dccp_role(sk), sk, dp->dccps_gss);

	switch (hctx->ccid3hctx_state) {
	case TFRC_SSTATE_NO_SENT:
		/* if first wasn't pure ack */
		if (len != 0)
			printk(KERN_CRIT "%s: %s, First packet sent is noted "
					 "as a data packet\n",
			       __FUNCTION__, dccp_role(sk));
		return;
	case TFRC_SSTATE_NO_FBACK: