ccid2.c

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/*
 *  net/dccp/ccids/ccid2.c
 *
 *  Copyright (c) 2005, 2006 Andrea Bittau <[e-mail]>
 *
 *  Changes to meet Linux coding standards, and DCCP infrastructure fixes.
 *
 *  Copyright (c) 2006 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.
 */

/*
 * This implementation should follow RFC 4341
 *
 * BUGS:
 * - sequence number wrapping
 */

#include "../ccid.h"
#include "../dccp.h"
#include "ccid2.h"


#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
static int ccid2_debug;
#define ccid2_pr_debug(format, a...)	DCCP_PR_DEBUG(ccid2_debug, format, ##a)

static void ccid2_hc_tx_check_sanity(const struct ccid2_hc_tx_sock *hctx)
{
	int len = 0;
	int pipe = 0;
	struct ccid2_seq *seqp = hctx->ccid2hctx_seqh;

	/* there is data in the chain */
	if (seqp != hctx->ccid2hctx_seqt) {
		seqp = seqp->ccid2s_prev;
		len++;
		if (!seqp->ccid2s_acked)
			pipe++;

		while (seqp != hctx->ccid2hctx_seqt) {
			struct ccid2_seq *prev = seqp->ccid2s_prev;

			len++;
			if (!prev->ccid2s_acked)
				pipe++;

			/* packets are sent sequentially */
			BUG_ON(dccp_delta_seqno(seqp->ccid2s_seq,
						prev->ccid2s_seq ) >= 0);
			BUG_ON(time_before(seqp->ccid2s_sent,
					   prev->ccid2s_sent));

			seqp = prev;
		}
	}

	BUG_ON(pipe != hctx->ccid2hctx_pipe);
	ccid2_pr_debug("len of chain=%d\n", len);

	do {
		seqp = seqp->ccid2s_prev;
		len++;
	} while (seqp != hctx->ccid2hctx_seqh);

	ccid2_pr_debug("total len=%d\n", len);
	BUG_ON(len != hctx->ccid2hctx_seqbufc * CCID2_SEQBUF_LEN);
}
#else
#define ccid2_pr_debug(format, a...)
#define ccid2_hc_tx_check_sanity(hctx)
#endif

static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hctx)
{
	struct ccid2_seq *seqp;
	int i;

	/* check if we have space to preserve the pointer to the buffer */
	if (hctx->ccid2hctx_seqbufc >= (sizeof(hctx->ccid2hctx_seqbuf) /
					sizeof(struct ccid2_seq*)))
		return -ENOMEM;

	/* allocate buffer and initialize linked list */
	seqp = kmalloc(CCID2_SEQBUF_LEN * sizeof(struct ccid2_seq), gfp_any());
	if (seqp == NULL)
		return -ENOMEM;

	for (i = 0; i < (CCID2_SEQBUF_LEN - 1); i++) {
		seqp[i].ccid2s_next = &seqp[i + 1];
		seqp[i + 1].ccid2s_prev = &seqp[i];
	}
	seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = seqp;
	seqp->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];

	/* This is the first allocation.  Initiate the head and tail.  */
	if (hctx->ccid2hctx_seqbufc == 0)
		hctx->ccid2hctx_seqh = hctx->ccid2hctx_seqt = seqp;
	else {
		/* link the existing list with the one we just created */
		hctx->ccid2hctx_seqh->ccid2s_next = seqp;
		seqp->ccid2s_prev = hctx->ccid2hctx_seqh;

		hctx->ccid2hctx_seqt->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
		seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = hctx->ccid2hctx_seqt;
	}

	/* store the original pointer to the buffer so we can free it */
	hctx->ccid2hctx_seqbuf[hctx->ccid2hctx_seqbufc] = seqp;
	hctx->ccid2hctx_seqbufc++;

	return 0;
}

static int ccid2_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
{
	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);

	ccid2_pr_debug("pipe=%d cwnd=%d\n", hctx->ccid2hctx_pipe,
		       hctx->ccid2hctx_cwnd);

	if (hctx->ccid2hctx_pipe < hctx->ccid2hctx_cwnd) {
		/* OK we can send... make sure previous packet was sent off */
		if (!hctx->ccid2hctx_sendwait) {
			hctx->ccid2hctx_sendwait = 1;
			return 0;
		}
	}

	return 1; /* XXX CCID should dequeue when ready instead of polling */
}

static void ccid2_change_l_ack_ratio(struct sock *sk, int val)
{
	struct dccp_sock *dp = dccp_sk(sk);
	/*
	 * XXX I don't really agree with val != 2.  If cwnd is 1, ack ratio
	 * should be 1... it shouldn't be allowed to become 2.
	 * -sorbo.
	 */
	if (val != 2) {
		const struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
		int max = hctx->ccid2hctx_cwnd / 2;

		/* round up */
		if (hctx->ccid2hctx_cwnd & 1)
			max++;

		if (val > max)
			val = max;
	}

	ccid2_pr_debug("changing local ack ratio to %d\n", val);
	WARN_ON(val <= 0);
	dp->dccps_l_ack_ratio = val;
}

static void ccid2_change_cwnd(struct ccid2_hc_tx_sock *hctx, u32 val)
{
	/* XXX do we need to change ack ratio? */
	hctx->ccid2hctx_cwnd = val? : 1;
	ccid2_pr_debug("changed cwnd to %u\n", hctx->ccid2hctx_cwnd);
}

static void ccid2_change_srtt(struct ccid2_hc_tx_sock *hctx, long val)
{
	ccid2_pr_debug("change SRTT to %ld\n", val);
	hctx->ccid2hctx_srtt = val;
}

static void ccid2_change_pipe(struct ccid2_hc_tx_sock *hctx, long val)
{
	hctx->ccid2hctx_pipe = val;
}

static void ccid2_start_rto_timer(struct sock *sk);

static void ccid2_hc_tx_rto_expire(unsigned long data)
{
	struct sock *sk = (struct sock *)data;
	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
	long s;

	bh_lock_sock(sk);
	if (sock_owned_by_user(sk)) {
		sk_reset_timer(sk, &hctx->ccid2hctx_rtotimer,
			       jiffies + HZ / 5);
		goto out;
	}

	ccid2_pr_debug("RTO_EXPIRE\n");

	ccid2_hc_tx_check_sanity(hctx);

	/* back-off timer */
	hctx->ccid2hctx_rto <<= 1;

	s = hctx->ccid2hctx_rto / HZ;
	if (s > 60)
		hctx->ccid2hctx_rto = 60 * HZ;

	ccid2_start_rto_timer(sk);

	/* adjust pipe, cwnd etc */
	ccid2_change_pipe(hctx, 0);
	hctx->ccid2hctx_ssthresh = hctx->ccid2hctx_cwnd >> 1;
	if (hctx->ccid2hctx_ssthresh < 2)
		hctx->ccid2hctx_ssthresh = 2;
	ccid2_change_cwnd(hctx, 1);

	/* clear state about stuff we sent */
	hctx->ccid2hctx_seqt	= hctx->ccid2hctx_seqh;
	hctx->ccid2hctx_ssacks	= 0;
	hctx->ccid2hctx_acks	= 0;
	hctx->ccid2hctx_sent	= 0;

	/* clear ack ratio state. */
	hctx->ccid2hctx_arsent	 = 0;
	hctx->ccid2hctx_ackloss  = 0;
	hctx->ccid2hctx_rpseq	 = 0;
	hctx->ccid2hctx_rpdupack = -1;
	ccid2_change_l_ack_ratio(sk, 1);
	ccid2_hc_tx_check_sanity(hctx);
out:
	bh_unlock_sock(sk);
	sock_put(sk);
}

static void ccid2_start_rto_timer(struct sock *sk)
{
	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);

	ccid2_pr_debug("setting RTO timeout=%ld\n", hctx->ccid2hctx_rto);

	BUG_ON(timer_pending(&hctx->ccid2hctx_rtotimer));
	sk_reset_timer(sk, &hctx->ccid2hctx_rtotimer,
		       jiffies + hctx->ccid2hctx_rto);
}

static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
{
	struct dccp_sock *dp = dccp_sk(sk);
	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
	struct ccid2_seq *next;
	u64 seq;

	ccid2_hc_tx_check_sanity(hctx);

	BUG_ON(!hctx->ccid2hctx_sendwait);
	hctx->ccid2hctx_sendwait = 0;
	ccid2_change_pipe(hctx, hctx->ccid2hctx_pipe + 1);
	BUG_ON(hctx->ccid2hctx_pipe < 0);

	/* There is an issue.  What if another packet is sent between
	 * packet_send() and packet_sent().  Then the sequence number would be
	 * wrong.
	 * -sorbo.
	 */
	seq = dp->dccps_gss;

	hctx->ccid2hctx_seqh->ccid2s_seq   = seq;
	hctx->ccid2hctx_seqh->ccid2s_acked = 0;
	hctx->ccid2hctx_seqh->ccid2s_sent  = jiffies;

	next = hctx->ccid2hctx_seqh->ccid2s_next;
	/* check if we need to alloc more space */
	if (next == hctx->ccid2hctx_seqt) {
		if (ccid2_hc_tx_alloc_seq(hctx)) {
			DCCP_CRIT("packet history - out of memory!");
			/* FIXME: find a more graceful way to bail out */
			return;
		}
		next = hctx->ccid2hctx_seqh->ccid2s_next;
		BUG_ON(next == hctx->ccid2hctx_seqt);
	}
	hctx->ccid2hctx_seqh = next;

	ccid2_pr_debug("cwnd=%d pipe=%d\n", hctx->ccid2hctx_cwnd,
		       hctx->ccid2hctx_pipe);

	hctx->ccid2hctx_sent++;

	/* Ack Ratio.  Need to maintain a concept of how many windows we sent */
	hctx->ccid2hctx_arsent++;
	/* We had an ack loss in this window... */
	if (hctx->ccid2hctx_ackloss) {
		if (hctx->ccid2hctx_arsent >= hctx->ccid2hctx_cwnd) {
			hctx->ccid2hctx_arsent	= 0;
			hctx->ccid2hctx_ackloss	= 0;
		}
	} else {
		/* No acks lost up to now... */
		/* decrease ack ratio if enough packets were sent */
		if (dp->dccps_l_ack_ratio > 1) {
			/* XXX don't calculate denominator each time */
			int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
				    dp->dccps_l_ack_ratio;

			denom = hctx->ccid2hctx_cwnd * hctx->ccid2hctx_cwnd / denom;

			if (hctx->ccid2hctx_arsent >= denom) {
				ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
				hctx->ccid2hctx_arsent = 0;
			}
		} else {
			/* we can't increase ack ratio further [1] */
			hctx->ccid2hctx_arsent = 0; /* or maybe set it to cwnd*/
		}
	}

	/* setup RTO timer */
	if (!timer_pending(&hctx->ccid2hctx_rtotimer))
		ccid2_start_rto_timer(sk);

#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
	ccid2_pr_debug("pipe=%d\n", hctx->ccid2hctx_pipe);
	ccid2_pr_debug("Sent: seq=%llu\n", (unsigned long long)seq);
	do {
		struct ccid2_seq *seqp = hctx->ccid2hctx_seqt;

		while (seqp != hctx->ccid2hctx_seqh) {
			ccid2_pr_debug("out seq=%llu acked=%d time=%lu\n",
				       (unsigned long long)seqp->ccid2s_seq,
				       seqp->ccid2s_acked, seqp->ccid2s_sent);
			seqp = seqp->ccid2s_next;
		}
	} while (0);
	ccid2_pr_debug("=========\n");
	ccid2_hc_tx_check_sanity(hctx);
#endif
}

/* XXX Lame code duplication!
 * returns -1 if none was found.
 * else returns the next offset to use in the function call.
 */
static int ccid2_ackvector(struct sock *sk, struct sk_buff *skb, int offset,
			   unsigned char **vec, unsigned char *veclen)
{
	const struct dccp_hdr *dh = dccp_hdr(skb);
	unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
	unsigned char *opt_ptr;
	const unsigned char *opt_end = (unsigned char *)dh +
					(dh->dccph_doff * 4);
	unsigned char opt, len;
	unsigned char *value;

	BUG_ON(offset < 0);
	options += offset;
	opt_ptr = options;
	if (opt_ptr >= opt_end)
		return -1;

	while (opt_ptr != opt_end) {
		opt   = *opt_ptr++;
		len   = 0;
		value = NULL;

		/* Check if this isn't a single byte option */
		if (opt > DCCPO_MAX_RESERVED) {
			if (opt_ptr == opt_end)
				goto out_invalid_option;

			len = *opt_ptr++;
			if (len < 3)
				goto out_invalid_option;
			/*
			 * Remove the type and len fields, leaving
			 * just the value size
			 */
			len     -= 2;
			value   = opt_ptr;
			opt_ptr += len;

			if (opt_ptr > opt_end)
				goto out_invalid_option;
		}

		switch (opt) {
		case DCCPO_ACK_VECTOR_0:
		case DCCPO_ACK_VECTOR_1:
			*vec	= value;
			*veclen = len;
			return offset + (opt_ptr - options);
		}
	}

	return -1;

out_invalid_option:
	DCCP_BUG("Invalid option - this should not happen (previous parsing)!");
	return -1;
}

static void ccid2_hc_tx_kill_rto_timer(struct sock *sk)
{
	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);

	sk_stop_timer(sk, &hctx->ccid2hctx_rtotimer);
	ccid2_pr_debug("deleted RTO timer\n");
}

static inline void ccid2_new_ack(struct sock *sk,
				 struct ccid2_seq *seqp,
				 unsigned int *maxincr)