[DCCP]: Move the calc_X routines to dccp_tfrc_lib

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 644 insertions, 0 deletions

diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c
new file mode 100644
index 00000000000..d2b5933b451
--- /dev/null
+++ b/net/dccp/ccids/lib/tfrc_equation.c
@@ -0,0 +1,644 @@
+/*
+ *  net/dccp/ccids/lib/tfrc_equation.c
+ *
+ *  Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
+ *  Copyright (c) 2005 Ian McDonald <iam4@cs.waikato.ac.nz>
+ *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
+ *
+ *  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.
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+
+#include <asm/bug.h>
+#include <asm/div64.h>
+
+#include "tfrc.h"
+
+#define TFRC_CALC_X_ARRSIZE 500
+
+#define TFRC_CALC_X_SPLIT 50000
+/* equivalent to 0.05 */
+
+static const u32 tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE][2] = {
+	{     37172,   8172 },
+	{     53499,  11567 },
+	{     66664,  14180 },
+	{     78298,  16388 },
+	{     89021,  18339 },
+	{     99147,  20108 },
+	{    108858,  21738 },
+	{    118273,  23260 },
+	{    127474,  24693 },
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+	{    145456,  27348 },
+	{    154316,  28589 },
+	{    163130,  29783 },
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+	{    180704,  32049 },
+	{    189502,  33130 },
+	{    198328,  34180 },
+	{    207194,  35202 },
+	{    216114,  36198 },
+	{    225097,  37172 },
+	{    234153,  38123 },
+	{    243294,  39055 },
+	{    252527,  39968 },
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+};
+
+/* Calculate the send rate as per section 3.1 of RFC3448
+ 
+Returns send rate in bytes per second
+
+Integer maths and lookups are used as not allowed floating point in kernel
+
+The function for Xcalc as per section 3.1 of RFC3448 is:
+
+X =                            s
+     -------------------------------------------------------------
+     R*sqrt(2*b*p/3) + (t_RTO * (3*sqrt(3*b*p/8) * p * (1+32*p^2)))
+
+where 
+X is the trasmit rate in bytes/second
+s is the packet size in bytes
+R is the round trip time in seconds
+p is the loss event rate, between 0 and 1.0, of the number of loss events 
+  as a fraction of the number of packets transmitted
+t_RTO is the TCP retransmission timeout value in seconds
+b is the number of packets acknowledged by a single TCP acknowledgement
+
+we can assume that b = 1 and t_RTO is 4 * R. With this the equation becomes:
+
+X =                            s
+     -----------------------------------------------------------------------
+     R * sqrt(2 * p / 3) + (12 * R * (sqrt(3 * p / 8) * p * (1 + 32 * p^2)))
+
+
+which we can break down into:
+
+X =     s
+     --------
+     R * f(p)
+
+where f(p) = sqrt(2 * p / 3) + (12 * sqrt(3 * p / 8) * p * (1 + 32 * p * p))
+
+Function parameters:
+s - bytes
+R - RTT in usecs
+p - loss rate (decimal fraction multiplied by 1,000,000)
+
+Returns Xcalc in bytes per second
+
+DON'T alter this code unless you run test cases against it as the code
+has been manipulated to stop underflow/overlow.
+
+*/
+u32 tfrc_calc_x(u16 s, u32 R, u32 p)
+{
+	int index;
+	u32 f;
+	u64 tmp1, tmp2;
+
+	if (p < TFRC_CALC_X_SPLIT)
+		index = (p / (TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE)) - 1;
+	else
+		index = (p / (1000000 / TFRC_CALC_X_ARRSIZE)) - 1;
+
+	if (index < 0)
+		/* p should be 0 unless there is a bug in my code */
+		index = 0;
+
+	if (R == 0)
+		R = 1; /* RTT can't be zero or else divide by zero */
+
+	BUG_ON(index >= TFRC_CALC_X_ARRSIZE);
+
+	if (p >= TFRC_CALC_X_SPLIT)
+		f = tfrc_calc_x_lookup[index][0];
+	else
+		f = tfrc_calc_x_lookup[index][1];
+
+	tmp1 = ((u64)s * 100000000);
+	tmp2 = ((u64)R * (u64)f);
+	do_div(tmp2, 10000);
+	do_div(tmp1, tmp2); 
+	/* Don't alter above math unless you test due to overflow on 32 bit */
+
+	return (u32)tmp1; 
+}
+
+EXPORT_SYMBOL_GPL(tfrc_calc_x);
+
+/*
+ * args: fvalue - function value to match
+ * returns: p closest to that value
+ *
+ * both fvalue and p are multiplied by 1,000,000 to use ints
+ */
+u32 tfrc_calc_x_reverse_lookup(u32 fvalue)
+{
+	int ctr = 0;
+	int small;
+
+	if (fvalue < tfrc_calc_x_lookup[0][1])
+		return 0;
+
+	if (fvalue <= tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][1])
+		small = 1;
+	else if (fvalue > tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][0])
+		return 1000000;
+	else
+		small = 0;
+
+	while (fvalue > tfrc_calc_x_lookup[ctr][small])
+		ctr++;
+
+	if (small)
+		return TFRC_CALC_X_SPLIT * ctr / TFRC_CALC_X_ARRSIZE;
+	else
+		return 1000000 * ctr / TFRC_CALC_X_ARRSIZE;
+}
+
+EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);