ccid2.c

LINUX 2.6.17.4的源码

	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);

	/* slow start */
	if (hctx->ccid2hctx_cwnd < hctx->ccid2hctx_ssthresh) {
		hctx->ccid2hctx_acks = 0;

		/* We can increase cwnd at most maxincr [ack_ratio/2] */
		if (*maxincr) {
			/* increase every 2 acks */
			hctx->ccid2hctx_ssacks++;
			if (hctx->ccid2hctx_ssacks == 2) {
				ccid2_change_cwnd(sk, hctx->ccid2hctx_cwnd + 1);
				hctx->ccid2hctx_ssacks = 0;
				*maxincr = *maxincr - 1;
			}
		} else {
			/* increased cwnd enough for this single ack */
			hctx->ccid2hctx_ssacks = 0;
		}
	} else {
		hctx->ccid2hctx_ssacks = 0;
		hctx->ccid2hctx_acks++;

		if (hctx->ccid2hctx_acks >= hctx->ccid2hctx_cwnd) {
			ccid2_change_cwnd(sk, hctx->ccid2hctx_cwnd + 1);
			hctx->ccid2hctx_acks = 0;
		}
	}

	/* update RTO */
	if (hctx->ccid2hctx_srtt == -1 ||
	    (jiffies - hctx->ccid2hctx_lastrtt) >= hctx->ccid2hctx_srtt) {
		unsigned long r = jiffies - seqp->ccid2s_sent;
		int s;

		/* first measurement */
		if (hctx->ccid2hctx_srtt == -1) {
			ccid2_pr_debug("R: %lu Time=%lu seq=%llu\n",
			       	       r, jiffies, seqp->ccid2s_seq);
			hctx->ccid2hctx_srtt = r;
			hctx->ccid2hctx_rttvar = r >> 1;
		} else {
			/* RTTVAR */
			long tmp = hctx->ccid2hctx_srtt - r;
			if (tmp < 0)
				tmp *= -1;

			tmp >>= 2;
			hctx->ccid2hctx_rttvar *= 3;
			hctx->ccid2hctx_rttvar >>= 2;
			hctx->ccid2hctx_rttvar += tmp;

			/* SRTT */
			hctx->ccid2hctx_srtt *= 7;
			hctx->ccid2hctx_srtt >>= 3;
			tmp = r >> 3;
			hctx->ccid2hctx_srtt += tmp;
		}
		s = hctx->ccid2hctx_rttvar << 2;
		/* clock granularity is 1 when based on jiffies */
		if (!s)
			s = 1;
		hctx->ccid2hctx_rto = hctx->ccid2hctx_srtt + s;

		/* must be at least a second */
		s = hctx->ccid2hctx_rto / HZ;
		/* DCCP doesn't require this [but I like it cuz my code sux] */
#if 1
		if (s < 1)
			hctx->ccid2hctx_rto = HZ;
#endif
		/* max 60 seconds */
		if (s > 60)
			hctx->ccid2hctx_rto = HZ * 60;

		hctx->ccid2hctx_lastrtt = jiffies;

		ccid2_pr_debug("srtt: %ld rttvar: %ld rto: %ld (HZ=%d) R=%lu\n",
		       	       hctx->ccid2hctx_srtt, hctx->ccid2hctx_rttvar,
		       	       hctx->ccid2hctx_rto, HZ, r);
		hctx->ccid2hctx_sent = 0;
	}

	/* we got a new ack, so re-start RTO timer */
	ccid2_hc_tx_kill_rto_timer(sk);
	ccid2_start_rto_timer(sk);
}

static void ccid2_hc_tx_dec_pipe(struct sock *sk)
{
	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);

	hctx->ccid2hctx_pipe--;
	BUG_ON(hctx->ccid2hctx_pipe < 0);

	if (hctx->ccid2hctx_pipe == 0)
		ccid2_hc_tx_kill_rto_timer(sk);
}

static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
{
	struct dccp_sock *dp = dccp_sk(sk);
	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
	u64 ackno, seqno;
	struct ccid2_seq *seqp;
	unsigned char *vector;
	unsigned char veclen;
	int offset = 0;
	int done = 0;
	int loss = 0;
	unsigned int maxincr = 0;

	ccid2_hc_tx_check_sanity(hctx);
	/* check reverse path congestion */
	seqno = DCCP_SKB_CB(skb)->dccpd_seq;

	/* XXX this whole "algorithm" is broken.  Need to fix it to keep track
	 * of the seqnos of the dupacks so that rpseq and rpdupack are correct
	 * -sorbo.
	 */
	/* need to bootstrap */
	if (hctx->ccid2hctx_rpdupack == -1) {
		hctx->ccid2hctx_rpdupack = 0;
		hctx->ccid2hctx_rpseq = seqno;
	} else {
		/* check if packet is consecutive */
		if ((hctx->ccid2hctx_rpseq + 1) == seqno)
			hctx->ccid2hctx_rpseq++;
		/* it's a later packet */
		else if (after48(seqno, hctx->ccid2hctx_rpseq)) {
			hctx->ccid2hctx_rpdupack++;

			/* check if we got enough dupacks */
			if (hctx->ccid2hctx_rpdupack >=
			    hctx->ccid2hctx_numdupack) {
				hctx->ccid2hctx_rpdupack = -1; /* XXX lame */
				hctx->ccid2hctx_rpseq = 0;

				ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio << 1);
			}
		}
	}

	/* check forward path congestion */
	/* still didn't send out new data packets */
	if (hctx->ccid2hctx_seqh == hctx->ccid2hctx_seqt)
		return;

	switch (DCCP_SKB_CB(skb)->dccpd_type) {
	case DCCP_PKT_ACK:
	case DCCP_PKT_DATAACK:
		break;
	default:
		return;
	}

	ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
	seqp = hctx->ccid2hctx_seqh->ccid2s_prev;

	/* If in slow-start, cwnd can increase at most Ack Ratio / 2 packets for
	 * this single ack.  I round up.
	 * -sorbo.
	 */
	maxincr = dp->dccps_l_ack_ratio >> 1;
	maxincr++;

	/* go through all ack vectors */
	while ((offset = ccid2_ackvector(sk, skb, offset,
					 &vector, &veclen)) != -1) {
		/* go through this ack vector */
		while (veclen--) {
			const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
			u64 ackno_end_rl;

			dccp_set_seqno(&ackno_end_rl, ackno - rl);
			ccid2_pr_debug("ackvec start:%llu end:%llu\n", ackno,
				       ackno_end_rl);
			/* if the seqno we are analyzing is larger than the
			 * current ackno, then move towards the tail of our
			 * seqnos.
			 */
			while (after48(seqp->ccid2s_seq, ackno)) {
				if (seqp == hctx->ccid2hctx_seqt) {
					done = 1;
					break;
				}
				seqp = seqp->ccid2s_prev;
			}
			if (done)
				break;

			/* check all seqnos in the range of the vector
			 * run length
			 */
			while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
				const u8 state = (*vector &
						  DCCP_ACKVEC_STATE_MASK) >> 6;

				/* new packet received or marked */
				if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED &&
				    !seqp->ccid2s_acked) {
				    	if (state ==
					    DCCP_ACKVEC_STATE_ECN_MARKED) {
						loss = 1;
					} else
						ccid2_new_ack(sk, seqp,
							      &maxincr);

					seqp->ccid2s_acked = 1;
					ccid2_pr_debug("Got ack for %llu\n",
					       	       seqp->ccid2s_seq);
					ccid2_hc_tx_dec_pipe(sk);
				}
				if (seqp == hctx->ccid2hctx_seqt) {
					done = 1;
					break;
				}
				seqp = seqp->ccid2s_next;
			}
			if (done)
				break;


			dccp_set_seqno(&ackno, ackno_end_rl - 1);
			vector++;
		}
		if (done)
			break;
	}

	/* The state about what is acked should be correct now
	 * Check for NUMDUPACK
	 */
	seqp = hctx->ccid2hctx_seqh->ccid2s_prev;
	done = 0;
	while (1) {
		if (seqp->ccid2s_acked) {
			done++;
			if (done == hctx->ccid2hctx_numdupack)
				break;
		}
		if (seqp == hctx->ccid2hctx_seqt)
			break;
		seqp = seqp->ccid2s_prev;
	}

	/* If there are at least 3 acknowledgements, anything unacknowledged
	 * below the last sequence number is considered lost
	 */
	if (done == hctx->ccid2hctx_numdupack) {
		struct ccid2_seq *last_acked = seqp;

		/* check for lost packets */
		while (1) {
			if (!seqp->ccid2s_acked) {
				loss = 1;
				ccid2_hc_tx_dec_pipe(sk);
			}
			if (seqp == hctx->ccid2hctx_seqt)
				break;
			seqp = seqp->ccid2s_prev;
		}

		hctx->ccid2hctx_seqt = last_acked;
	}

	/* trim acked packets in tail */
	while (hctx->ccid2hctx_seqt != hctx->ccid2hctx_seqh) {
		if (!hctx->ccid2hctx_seqt->ccid2s_acked)
			break;

		hctx->ccid2hctx_seqt = hctx->ccid2hctx_seqt->ccid2s_next;
	}

	if (loss) {
		/* XXX do bit shifts guarantee a 0 as the new bit? */
		ccid2_change_cwnd(sk, hctx->ccid2hctx_cwnd >> 1);
		hctx->ccid2hctx_ssthresh = hctx->ccid2hctx_cwnd;
		if (hctx->ccid2hctx_ssthresh < 2)
			hctx->ccid2hctx_ssthresh = 2;
	}

	ccid2_hc_tx_check_sanity(hctx);
}

static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
{
        struct ccid2_hc_tx_sock *hctx = ccid_priv(ccid);
	int seqcount = ccid2_seq_len;
	int i;

	/* XXX init variables with proper values */
	hctx->ccid2hctx_cwnd	  = 1;
	hctx->ccid2hctx_ssthresh  = 10;
	hctx->ccid2hctx_numdupack = 3;

	/* XXX init ~ to window size... */
	hctx->ccid2hctx_seqbuf = kmalloc(sizeof(*hctx->ccid2hctx_seqbuf) *
					 seqcount, gfp_any());
	if (hctx->ccid2hctx_seqbuf == NULL)
		return -ENOMEM;

	for (i = 0; i < (seqcount - 1); i++) {
		hctx->ccid2hctx_seqbuf[i].ccid2s_next =
					&hctx->ccid2hctx_seqbuf[i + 1];
		hctx->ccid2hctx_seqbuf[i + 1].ccid2s_prev =
					&hctx->ccid2hctx_seqbuf[i];
	}
	hctx->ccid2hctx_seqbuf[seqcount - 1].ccid2s_next =
					hctx->ccid2hctx_seqbuf;
	hctx->ccid2hctx_seqbuf->ccid2s_prev =
					&hctx->ccid2hctx_seqbuf[seqcount - 1];

	hctx->ccid2hctx_seqh	 = hctx->ccid2hctx_seqbuf;
	hctx->ccid2hctx_seqt	 = hctx->ccid2hctx_seqh;
	hctx->ccid2hctx_sent	 = 0;
	hctx->ccid2hctx_rto	 = 3 * HZ;
	hctx->ccid2hctx_srtt	 = -1;
	hctx->ccid2hctx_rttvar	 = -1;
	hctx->ccid2hctx_lastrtt  = 0;
	hctx->ccid2hctx_rpdupack = -1;

	hctx->ccid2hctx_rtotimer.function = &ccid2_hc_tx_rto_expire;
	hctx->ccid2hctx_rtotimer.data	  = (unsigned long)sk;
	init_timer(&hctx->ccid2hctx_rtotimer);

	ccid2_hc_tx_check_sanity(hctx);
	return 0;
}

static void ccid2_hc_tx_exit(struct sock *sk)
{
        struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);

	ccid2_hc_tx_kill_rto_timer(sk);
	kfree(hctx->ccid2hctx_seqbuf);
	hctx->ccid2hctx_seqbuf = NULL;
}

static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
{
	const struct dccp_sock *dp = dccp_sk(sk);
	struct ccid2_hc_rx_sock *hcrx = ccid2_hc_rx_sk(sk);

	switch (DCCP_SKB_CB(skb)->dccpd_type) {
	case DCCP_PKT_DATA:
	case DCCP_PKT_DATAACK:
		hcrx->ccid2hcrx_data++;
		if (hcrx->ccid2hcrx_data >= dp->dccps_r_ack_ratio) {
			dccp_send_ack(sk);
			hcrx->ccid2hcrx_data = 0;
		}
		break;
	}
}

static struct ccid_operations ccid2 = {
	.ccid_id		= 2,
	.ccid_name		= "ccid2",
	.ccid_owner		= THIS_MODULE,
	.ccid_hc_tx_obj_size	= sizeof(struct ccid2_hc_tx_sock),
	.ccid_hc_tx_init	= ccid2_hc_tx_init,
	.ccid_hc_tx_exit	= ccid2_hc_tx_exit,
	.ccid_hc_tx_send_packet	= ccid2_hc_tx_send_packet,
	.ccid_hc_tx_packet_sent	= ccid2_hc_tx_packet_sent,
	.ccid_hc_tx_packet_recv	= ccid2_hc_tx_packet_recv,
	.ccid_hc_rx_obj_size	= sizeof(struct ccid2_hc_rx_sock),
	.ccid_hc_rx_packet_recv	= ccid2_hc_rx_packet_recv,
};

module_param(ccid2_debug, int, 0444);
MODULE_PARM_DESC(ccid2_debug, "Enable debug messages");

static __init int ccid2_module_init(void)
{
	return ccid_register(&ccid2);
}
module_init(ccid2_module_init);

static __exit void ccid2_module_exit(void)
{
	ccid_unregister(&ccid2);
}
module_exit(ccid2_module_exit);

MODULE_AUTHOR("Andrea Bittau <[e-mail]>");
MODULE_DESCRIPTION("DCCP TCP-Like (CCID2) CCID");
MODULE_LICENSE("GPL");
MODULE_ALIAS("net-dccp-ccid-2");