[CCID3]: Interface CCID3 code with newer Loss Intervals Database

This hooks up the TFRC Loss Interval database with CCID 3 packet reception.
In addition, it makes the CCID-specific computation of the first loss
interval (which requires access to all the guts of CCID3) local to ccid3.c.

The patch also fixes an omission in the DCCP code, that of a default /
fallback RTT value (defined in section 3.4 of RFC 4340 as 0.2 sec); while
at it, the  upper bound of 4 seconds for an RTT sample has  been reduced to
match the initial TCP RTO value of 3 seconds from[RFC 1122, 4.2.3.1].

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 60 insertions, 12 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 8266dfde89c..8f112d18d45 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -1,6 +1,7 @@
 /*
  *  net/dccp/ccids/ccid3.c
  *
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
  *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
  *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
  *
@@ -33,11 +34,7 @@
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
-#include "../ccid.h"
 #include "../dccp.h"
-#include "lib/packet_history.h"
-#include "lib/loss_interval.h"
-#include "lib/tfrc.h"
 #include "ccid3.h"
 
 #include <asm/unaligned.h>
@@ -757,6 +754,46 @@ static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
 	return 0;
 }
 
+/** ccid3_first_li  -  Implements [RFC 3448, 6.3.1]
+ *
+ * Determine the length of the first loss interval via inverse lookup.
+ * Assume that X_recv can be computed by the throughput equation
+ *		    s
+ *	X_recv = --------
+ *		 R * fval
+ * Find some p such that f(p) = fval; return 1/p (scaled).
+ */
+static u32 ccid3_first_li(struct sock *sk)
+{
+	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
+	u32 x_recv, p, delta;
+	u64 fval;
+
+	if (hcrx->ccid3hcrx_rtt == 0) {
+		DCCP_WARN("No RTT estimate available, using fallback RTT\n");
+		hcrx->ccid3hcrx_rtt = DCCP_FALLBACK_RTT;
+	}
+
+	delta = ktime_to_us(net_timedelta(hcrx->ccid3hcrx_tstamp_last_feedback));
+	x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
+	if (x_recv == 0) {		/* would also trigger divide-by-zero */
+		DCCP_WARN("X_recv==0\n");
+		if ((x_recv = hcrx->ccid3hcrx_x_recv) == 0) {
+			DCCP_BUG("stored value of X_recv is zero");
+			return ~0U;
+		}
+	}
+
+	fval = scaled_div(hcrx->ccid3hcrx_s, hcrx->ccid3hcrx_rtt);
+	fval = scaled_div32(fval, x_recv);
+	p = tfrc_calc_x_reverse_lookup(fval);
+
+	ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
+		       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
+
+	return p == 0 ? ~0U : scaled_div(1, p);
+}
+
 static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
@@ -794,6 +831,14 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 	/*
 	 * Handle pending losses and otherwise check for new loss
 	 */
+	if (tfrc_rx_hist_loss_pending(&hcrx->ccid3hcrx_hist) &&
+	    tfrc_rx_handle_loss(&hcrx->ccid3hcrx_hist,
+				&hcrx->ccid3hcrx_li_hist,
+				skb, ndp, ccid3_first_li, sk) ) {
+		do_feedback = CCID3_FBACK_PARAM_CHANGE;
+		goto done_receiving;
+	}
+
 	if (tfrc_rx_hist_new_loss_indicated(&hcrx->ccid3hcrx_hist, skb, ndp))
 		goto update_records;
 
@@ -803,7 +848,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 	if (unlikely(!is_data_packet))
 		goto update_records;
 
-	if (list_empty(&hcrx->ccid3hcrx_li_hist)) {  /* no loss so far: p = 0 */
+	if (!tfrc_lh_is_initialised(&hcrx->ccid3hcrx_li_hist)) {
 		const u32 sample = tfrc_rx_hist_sample_rtt(&hcrx->ccid3hcrx_hist, skb);
 		/*
 		 * Empty loss history: no loss so far, hence p stays 0.
@@ -812,6 +857,13 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 		 */
 		if (sample != 0)
 			hcrx->ccid3hcrx_rtt = tfrc_ewma(hcrx->ccid3hcrx_rtt, sample, 9);
+
+	} else if (tfrc_lh_update_i_mean(&hcrx->ccid3hcrx_li_hist, skb)) {
+		/*
+		 * Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
+		 * has decreased (resp. p has increased), send feedback now.
+		 */
+		do_feedback = CCID3_FBACK_PARAM_CHANGE;
 	}
 
 	/*
@@ -823,6 +875,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 update_records:
 	tfrc_rx_hist_add_packet(&hcrx->ccid3hcrx_hist, skb, ndp);
 
+done_receiving:
 	if (do_feedback)
 		ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
 }
@@ -831,10 +884,8 @@ static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid_priv(ccid);
 
-	ccid3_pr_debug("entry\n");
-
 	hcrx->ccid3hcrx_state = TFRC_RSTATE_NO_DATA;
-	INIT_LIST_HEAD(&hcrx->ccid3hcrx_li_hist);
+	tfrc_lh_init(&hcrx->ccid3hcrx_li_hist);
 	return tfrc_rx_hist_alloc(&hcrx->ccid3hcrx_hist);
 }
 
@@ -844,11 +895,8 @@ static void ccid3_hc_rx_exit(struct sock *sk)
 
 	ccid3_hc_rx_set_state(sk, TFRC_RSTATE_TERM);
 
-	/* Empty packet history */
 	tfrc_rx_hist_purge(&hcrx->ccid3hcrx_hist);
-
-	/* Empty loss interval history */
-	dccp_li_hist_purge(&hcrx->ccid3hcrx_li_hist);
+	tfrc_lh_cleanup(&hcrx->ccid3hcrx_li_hist);
 }
 
 static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)