forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
702 lines
18 KiB
702 lines
18 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
|
/* |
|
* Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand. |
|
* Copyright (c) 2005 Ian McDonald <[email protected]> |
|
* Copyright (c) 2005 Arnaldo Carvalho de Melo <[email protected]> |
|
* Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon |
|
*/ |
|
|
|
#include <linux/module.h> |
|
#include "../../dccp.h" |
|
#include "tfrc.h" |
|
|
|
#define TFRC_CALC_X_ARRSIZE 500 |
|
#define TFRC_CALC_X_SPLIT 50000 /* 0.05 * 1000000, details below */ |
|
#define TFRC_SMALLEST_P (TFRC_CALC_X_SPLIT/TFRC_CALC_X_ARRSIZE) |
|
|
|
/* |
|
TFRC TCP Reno Throughput Equation Lookup Table for f(p) |
|
|
|
The following two-column lookup table implements a part of the TCP throughput |
|
equation from [RFC 3448, sec. 3.1]: |
|
|
|
s |
|
X_calc = -------------------------------------------------------------- |
|
R * sqrt(2*b*p/3) + (3 * t_RTO * sqrt(3*b*p/8) * (p + 32*p^3)) |
|
|
|
Where: |
|
X is the transmit 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 ACK |
|
|
|
We can assume that b = 1 and t_RTO is 4 * R. The equation now becomes: |
|
|
|
s |
|
X_calc = ------------------------------------------------------- |
|
R * sqrt(p*2/3) + (12 * R * sqrt(p*3/8) * (p + 32*p^3)) |
|
|
|
which we can break down into: |
|
|
|
s |
|
X_calc = --------- |
|
R * f(p) |
|
|
|
where f(p) is given for 0 < p <= 1 by: |
|
|
|
f(p) = sqrt(2*p/3) + 12 * sqrt(3*p/8) * (p + 32*p^3) |
|
|
|
Since this is kernel code, floating-point arithmetic is avoided in favour of |
|
integer arithmetic. This means that nearly all fractional parameters are |
|
scaled by 1000000: |
|
* the parameters p and R |
|
* the return result f(p) |
|
The lookup table therefore actually tabulates the following function g(q): |
|
|
|
g(q) = 1000000 * f(q/1000000) |
|
|
|
Hence, when p <= 1, q must be less than or equal to 1000000. To achieve finer |
|
granularity for the practically more relevant case of small values of p (up to |
|
5%), the second column is used; the first one ranges up to 100%. This split |
|
corresponds to the value of q = TFRC_CALC_X_SPLIT. At the same time this also |
|
determines the smallest resolution possible with this lookup table: |
|
|
|
TFRC_SMALLEST_P = TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE |
|
|
|
The entire table is generated by: |
|
for(i=0; i < TFRC_CALC_X_ARRSIZE; i++) { |
|
lookup[i][0] = g((i+1) * 1000000/TFRC_CALC_X_ARRSIZE); |
|
lookup[i][1] = g((i+1) * TFRC_CALC_X_SPLIT/TFRC_CALC_X_ARRSIZE); |
|
} |
|
|
|
With the given configuration, we have, with M = TFRC_CALC_X_ARRSIZE-1, |
|
lookup[0][0] = g(1000000/(M+1)) = 1000000 * f(0.2%) |
|
lookup[M][0] = g(1000000) = 1000000 * f(100%) |
|
lookup[0][1] = g(TFRC_SMALLEST_P) = 1000000 * f(0.01%) |
|
lookup[M][1] = g(TFRC_CALC_X_SPLIT) = 1000000 * f(5%) |
|
|
|
In summary, the two columns represent f(p) for the following ranges: |
|
* The first column is for 0.002 <= p <= 1.0 |
|
* The second column is for 0.0001 <= p <= 0.05 |
|
Where the columns overlap, the second (finer-grained) is given preference, |
|
i.e. the first column is used only for p >= 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 }, |
|
{ 136520, 26052 }, |
|
{ 145456, 27348 }, |
|
{ 154316, 28589 }, |
|
{ 163130, 29783 }, |
|
{ 171919, 30935 }, |
|
{ 180704, 32049 }, |
|
{ 189502, 33130 }, |
|
{ 198328, 34180 }, |
|
{ 207194, 35202 }, |
|
{ 216114, 36198 }, |
|
{ 225097, 37172 }, |
|
{ 234153, 38123 }, |
|
{ 243294, 39055 }, |
|
{ 252527, 39968 }, |
|
{ 261861, 40864 }, |
|
{ 271305, 41743 }, |
|
{ 280866, 42607 }, |
|
{ 290553, 43457 }, |
|
{ 300372, 44293 }, |
|
{ 310333, 45117 }, |
|
{ 320441, 45929 }, |
|
{ 330705, 46729 }, |
|
{ 341131, 47518 }, |
|
{ 351728, 48297 }, |
|
{ 362501, 49066 }, |
|
{ 373460, 49826 }, |
|
{ 384609, 50577 }, |
|
{ 395958, 51320 }, |
|
{ 407513, 52054 }, |
|
{ 419281, 52780 }, |
|
{ 431270, 53499 }, |
|
{ 443487, 54211 }, |
|
{ 455940, 54916 }, |
|
{ 468635, 55614 }, |
|
{ 481581, 56306 }, |
|
{ 494785, 56991 }, |
|
{ 508254, 57671 }, |
|
{ 521996, 58345 }, |
|
{ 536019, 59014 }, |
|
{ 550331, 59677 }, |
|
{ 564939, 60335 }, |
|
{ 579851, 60988 }, |
|
{ 595075, 61636 }, |
|
{ 610619, 62279 }, |
|
{ 626491, 62918 }, |
|
{ 642700, 63553 }, |
|
{ 659253, 64183 }, |
|
{ 676158, 64809 }, |
|
{ 693424, 65431 }, |
|
{ 711060, 66050 }, |
|
{ 729073, 66664 }, |
|
{ 747472, 67275 }, |
|
{ 766266, 67882 }, |
|
{ 785464, 68486 }, |
|
{ 805073, 69087 }, |
|
{ 825103, 69684 }, |
|
{ 845562, 70278 }, |
|
{ 866460, 70868 }, |
|
{ 887805, 71456 }, |
|
{ 909606, 72041 }, |
|
{ 931873, 72623 }, |
|
{ 954614, 73202 }, |
|
{ 977839, 73778 }, |
|
{ 1001557, 74352 }, |
|
{ 1025777, 74923 }, |
|
{ 1050508, 75492 }, |
|
{ 1075761, 76058 }, |
|
{ 1101544, 76621 }, |
|
{ 1127867, 77183 }, |
|
{ 1154739, 77741 }, |
|
{ 1182172, 78298 }, |
|
{ 1210173, 78852 }, |
|
{ 1238753, 79405 }, |
|
{ 1267922, 79955 }, |
|
{ 1297689, 80503 }, |
|
{ 1328066, 81049 }, |
|
{ 1359060, 81593 }, |
|
{ 1390684, 82135 }, |
|
{ 1422947, 82675 }, |
|
{ 1455859, 83213 }, |
|
{ 1489430, 83750 }, |
|
{ 1523671, 84284 }, |
|
{ 1558593, 84817 }, |
|
{ 1594205, 85348 }, |
|
{ 1630518, 85878 }, |
|
{ 1667543, 86406 }, |
|
{ 1705290, 86932 }, |
|
{ 1743770, 87457 }, |
|
{ 1782994, 87980 }, |
|
{ 1822973, 88501 }, |
|
{ 1863717, 89021 }, |
|
{ 1905237, 89540 }, |
|
{ 1947545, 90057 }, |
|
{ 1990650, 90573 }, |
|
{ 2034566, 91087 }, |
|
{ 2079301, 91600 }, |
|
{ 2124869, 92111 }, |
|
{ 2171279, 92622 }, |
|
{ 2218543, 93131 }, |
|
{ 2266673, 93639 }, |
|
{ 2315680, 94145 }, |
|
{ 2365575, 94650 }, |
|
{ 2416371, 95154 }, |
|
{ 2468077, 95657 }, |
|
{ 2520707, 96159 }, |
|
{ 2574271, 96660 }, |
|
{ 2628782, 97159 }, |
|
{ 2684250, 97658 }, |
|
{ 2740689, 98155 }, |
|
{ 2798110, 98651 }, |
|
{ 2856524, 99147 }, |
|
{ 2915944, 99641 }, |
|
{ 2976382, 100134 }, |
|
{ 3037850, 100626 }, |
|
{ 3100360, 101117 }, |
|
{ 3163924, 101608 }, |
|
{ 3228554, 102097 }, |
|
{ 3294263, 102586 }, |
|
{ 3361063, 103073 }, |
|
{ 3428966, 103560 }, |
|
{ 3497984, 104045 }, |
|
{ 3568131, 104530 }, |
|
{ 3639419, 105014 }, |
|
{ 3711860, 105498 }, |
|
{ 3785467, 105980 }, |
|
{ 3860253, 106462 }, |
|
{ 3936229, 106942 }, |
|
{ 4013410, 107422 }, |
|
{ 4091808, 107902 }, |
|
{ 4171435, 108380 }, |
|
{ 4252306, 108858 }, |
|
{ 4334431, 109335 }, |
|
{ 4417825, 109811 }, |
|
{ 4502501, 110287 }, |
|
{ 4588472, 110762 }, |
|
{ 4675750, 111236 }, |
|
{ 4764349, 111709 }, |
|
{ 4854283, 112182 }, |
|
{ 4945564, 112654 }, |
|
{ 5038206, 113126 }, |
|
{ 5132223, 113597 }, |
|
{ 5227627, 114067 }, |
|
{ 5324432, 114537 }, |
|
{ 5422652, 115006 }, |
|
{ 5522299, 115474 }, |
|
{ 5623389, 115942 }, |
|
{ 5725934, 116409 }, |
|
{ 5829948, 116876 }, |
|
{ 5935446, 117342 }, |
|
{ 6042439, 117808 }, |
|
{ 6150943, 118273 }, |
|
{ 6260972, 118738 }, |
|
{ 6372538, 119202 }, |
|
{ 6485657, 119665 }, |
|
{ 6600342, 120128 }, |
|
{ 6716607, 120591 }, |
|
{ 6834467, 121053 }, |
|
{ 6953935, 121514 }, |
|
{ 7075025, 121976 }, |
|
{ 7197752, 122436 }, |
|
{ 7322131, 122896 }, |
|
{ 7448175, 123356 }, |
|
{ 7575898, 123815 }, |
|
{ 7705316, 124274 }, |
|
{ 7836442, 124733 }, |
|
{ 7969291, 125191 }, |
|
{ 8103877, 125648 }, |
|
{ 8240216, 126105 }, |
|
{ 8378321, 126562 }, |
|
{ 8518208, 127018 }, |
|
{ 8659890, 127474 }, |
|
{ 8803384, 127930 }, |
|
{ 8948702, 128385 }, |
|
{ 9095861, 128840 }, |
|
{ 9244875, 129294 }, |
|
{ 9395760, 129748 }, |
|
{ 9548529, 130202 }, |
|
{ 9703198, 130655 }, |
|
{ 9859782, 131108 }, |
|
{ 10018296, 131561 }, |
|
{ 10178755, 132014 }, |
|
{ 10341174, 132466 }, |
|
{ 10505569, 132917 }, |
|
{ 10671954, 133369 }, |
|
{ 10840345, 133820 }, |
|
{ 11010757, 134271 }, |
|
{ 11183206, 134721 }, |
|
{ 11357706, 135171 }, |
|
{ 11534274, 135621 }, |
|
{ 11712924, 136071 }, |
|
{ 11893673, 136520 }, |
|
{ 12076536, 136969 }, |
|
{ 12261527, 137418 }, |
|
{ 12448664, 137867 }, |
|
{ 12637961, 138315 }, |
|
{ 12829435, 138763 }, |
|
{ 13023101, 139211 }, |
|
{ 13218974, 139658 }, |
|
{ 13417071, 140106 }, |
|
{ 13617407, 140553 }, |
|
{ 13819999, 140999 }, |
|
{ 14024862, 141446 }, |
|
{ 14232012, 141892 }, |
|
{ 14441465, 142339 }, |
|
{ 14653238, 142785 }, |
|
{ 14867346, 143230 }, |
|
{ 15083805, 143676 }, |
|
{ 15302632, 144121 }, |
|
{ 15523842, 144566 }, |
|
{ 15747453, 145011 }, |
|
{ 15973479, 145456 }, |
|
{ 16201939, 145900 }, |
|
{ 16432847, 146345 }, |
|
{ 16666221, 146789 }, |
|
{ 16902076, 147233 }, |
|
{ 17140429, 147677 }, |
|
{ 17381297, 148121 }, |
|
{ 17624696, 148564 }, |
|
{ 17870643, 149007 }, |
|
{ 18119154, 149451 }, |
|
{ 18370247, 149894 }, |
|
{ 18623936, 150336 }, |
|
{ 18880241, 150779 }, |
|
{ 19139176, 151222 }, |
|
{ 19400759, 151664 }, |
|
{ 19665007, 152107 }, |
|
{ 19931936, 152549 }, |
|
{ 20201564, 152991 }, |
|
{ 20473907, 153433 }, |
|
{ 20748982, 153875 }, |
|
{ 21026807, 154316 }, |
|
{ 21307399, 154758 }, |
|
{ 21590773, 155199 }, |
|
{ 21876949, 155641 }, |
|
{ 22165941, 156082 }, |
|
{ 22457769, 156523 }, |
|
{ 22752449, 156964 }, |
|
{ 23049999, 157405 }, |
|
{ 23350435, 157846 }, |
|
{ 23653774, 158287 }, |
|
{ 23960036, 158727 }, |
|
{ 24269236, 159168 }, |
|
{ 24581392, 159608 }, |
|
{ 24896521, 160049 }, |
|
{ 25214642, 160489 }, |
|
{ 25535772, 160929 }, |
|
{ 25859927, 161370 }, |
|
{ 26187127, 161810 }, |
|
{ 26517388, 162250 }, |
|
{ 26850728, 162690 }, |
|
{ 27187165, 163130 }, |
|
{ 27526716, 163569 }, |
|
{ 27869400, 164009 }, |
|
{ 28215234, 164449 }, |
|
{ 28564236, 164889 }, |
|
{ 28916423, 165328 }, |
|
{ 29271815, 165768 }, |
|
{ 29630428, 166208 }, |
|
{ 29992281, 166647 }, |
|
{ 30357392, 167087 }, |
|
{ 30725779, 167526 }, |
|
{ 31097459, 167965 }, |
|
{ 31472452, 168405 }, |
|
{ 31850774, 168844 }, |
|
{ 32232445, 169283 }, |
|
{ 32617482, 169723 }, |
|
{ 33005904, 170162 }, |
|
{ 33397730, 170601 }, |
|
{ 33792976, 171041 }, |
|
{ 34191663, 171480 }, |
|
{ 34593807, 171919 }, |
|
{ 34999428, 172358 }, |
|
{ 35408544, 172797 }, |
|
{ 35821174, 173237 }, |
|
{ 36237335, 173676 }, |
|
{ 36657047, 174115 }, |
|
{ 37080329, 174554 }, |
|
{ 37507197, 174993 }, |
|
{ 37937673, 175433 }, |
|
{ 38371773, 175872 }, |
|
{ 38809517, 176311 }, |
|
{ 39250924, 176750 }, |
|
{ 39696012, 177190 }, |
|
{ 40144800, 177629 }, |
|
{ 40597308, 178068 }, |
|
{ 41053553, 178507 }, |
|
{ 41513554, 178947 }, |
|
{ 41977332, 179386 }, |
|
{ 42444904, 179825 }, |
|
{ 42916290, 180265 }, |
|
{ 43391509, 180704 }, |
|
{ 43870579, 181144 }, |
|
{ 44353520, 181583 }, |
|
{ 44840352, 182023 }, |
|
{ 45331092, 182462 }, |
|
{ 45825761, 182902 }, |
|
{ 46324378, 183342 }, |
|
{ 46826961, 183781 }, |
|
{ 47333531, 184221 }, |
|
{ 47844106, 184661 }, |
|
{ 48358706, 185101 }, |
|
{ 48877350, 185541 }, |
|
{ 49400058, 185981 }, |
|
{ 49926849, 186421 }, |
|
{ 50457743, 186861 }, |
|
{ 50992759, 187301 }, |
|
{ 51531916, 187741 }, |
|
{ 52075235, 188181 }, |
|
{ 52622735, 188622 }, |
|
{ 53174435, 189062 }, |
|
{ 53730355, 189502 }, |
|
{ 54290515, 189943 }, |
|
{ 54854935, 190383 }, |
|
{ 55423634, 190824 }, |
|
{ 55996633, 191265 }, |
|
{ 56573950, 191706 }, |
|
{ 57155606, 192146 }, |
|
{ 57741621, 192587 }, |
|
{ 58332014, 193028 }, |
|
{ 58926806, 193470 }, |
|
{ 59526017, 193911 }, |
|
{ 60129666, 194352 }, |
|
{ 60737774, 194793 }, |
|
{ 61350361, 195235 }, |
|
{ 61967446, 195677 }, |
|
{ 62589050, 196118 }, |
|
{ 63215194, 196560 }, |
|
{ 63845897, 197002 }, |
|
{ 64481179, 197444 }, |
|
{ 65121061, 197886 }, |
|
{ 65765563, 198328 }, |
|
{ 66414705, 198770 }, |
|
{ 67068508, 199213 }, |
|
{ 67726992, 199655 }, |
|
{ 68390177, 200098 }, |
|
{ 69058085, 200540 }, |
|
{ 69730735, 200983 }, |
|
{ 70408147, 201426 }, |
|
{ 71090343, 201869 }, |
|
{ 71777343, 202312 }, |
|
{ 72469168, 202755 }, |
|
{ 73165837, 203199 }, |
|
{ 73867373, 203642 }, |
|
{ 74573795, 204086 }, |
|
{ 75285124, 204529 }, |
|
{ 76001380, 204973 }, |
|
{ 76722586, 205417 }, |
|
{ 77448761, 205861 }, |
|
{ 78179926, 206306 }, |
|
{ 78916102, 206750 }, |
|
{ 79657310, 207194 }, |
|
{ 80403571, 207639 }, |
|
{ 81154906, 208084 }, |
|
{ 81911335, 208529 }, |
|
{ 82672880, 208974 }, |
|
{ 83439562, 209419 }, |
|
{ 84211402, 209864 }, |
|
{ 84988421, 210309 }, |
|
{ 85770640, 210755 }, |
|
{ 86558080, 211201 }, |
|
{ 87350762, 211647 }, |
|
{ 88148708, 212093 }, |
|
{ 88951938, 212539 }, |
|
{ 89760475, 212985 }, |
|
{ 90574339, 213432 }, |
|
{ 91393551, 213878 }, |
|
{ 92218133, 214325 }, |
|
{ 93048107, 214772 }, |
|
{ 93883493, 215219 }, |
|
{ 94724314, 215666 }, |
|
{ 95570590, 216114 }, |
|
{ 96422343, 216561 }, |
|
{ 97279594, 217009 }, |
|
{ 98142366, 217457 }, |
|
{ 99010679, 217905 }, |
|
{ 99884556, 218353 }, |
|
{ 100764018, 218801 }, |
|
{ 101649086, 219250 }, |
|
{ 102539782, 219698 }, |
|
{ 103436128, 220147 }, |
|
{ 104338146, 220596 }, |
|
{ 105245857, 221046 }, |
|
{ 106159284, 221495 }, |
|
{ 107078448, 221945 }, |
|
{ 108003370, 222394 }, |
|
{ 108934074, 222844 }, |
|
{ 109870580, 223294 }, |
|
{ 110812910, 223745 }, |
|
{ 111761087, 224195 }, |
|
{ 112715133, 224646 }, |
|
{ 113675069, 225097 }, |
|
{ 114640918, 225548 }, |
|
{ 115612702, 225999 }, |
|
{ 116590442, 226450 }, |
|
{ 117574162, 226902 }, |
|
{ 118563882, 227353 }, |
|
{ 119559626, 227805 }, |
|
{ 120561415, 228258 }, |
|
{ 121569272, 228710 }, |
|
{ 122583219, 229162 }, |
|
{ 123603278, 229615 }, |
|
{ 124629471, 230068 }, |
|
{ 125661822, 230521 }, |
|
{ 126700352, 230974 }, |
|
{ 127745083, 231428 }, |
|
{ 128796039, 231882 }, |
|
{ 129853241, 232336 }, |
|
{ 130916713, 232790 }, |
|
{ 131986475, 233244 }, |
|
{ 133062553, 233699 }, |
|
{ 134144966, 234153 }, |
|
{ 135233739, 234608 }, |
|
{ 136328894, 235064 }, |
|
{ 137430453, 235519 }, |
|
{ 138538440, 235975 }, |
|
{ 139652876, 236430 }, |
|
{ 140773786, 236886 }, |
|
{ 141901190, 237343 }, |
|
{ 143035113, 237799 }, |
|
{ 144175576, 238256 }, |
|
{ 145322604, 238713 }, |
|
{ 146476218, 239170 }, |
|
{ 147636442, 239627 }, |
|
{ 148803298, 240085 }, |
|
{ 149976809, 240542 }, |
|
{ 151156999, 241000 }, |
|
{ 152343890, 241459 }, |
|
{ 153537506, 241917 }, |
|
{ 154737869, 242376 }, |
|
{ 155945002, 242835 }, |
|
{ 157158929, 243294 }, |
|
{ 158379673, 243753 }, |
|
{ 159607257, 244213 }, |
|
{ 160841704, 244673 }, |
|
{ 162083037, 245133 }, |
|
{ 163331279, 245593 }, |
|
{ 164586455, 246054 }, |
|
{ 165848586, 246514 }, |
|
{ 167117696, 246975 }, |
|
{ 168393810, 247437 }, |
|
{ 169676949, 247898 }, |
|
{ 170967138, 248360 }, |
|
{ 172264399, 248822 }, |
|
{ 173568757, 249284 }, |
|
{ 174880235, 249747 }, |
|
{ 176198856, 250209 }, |
|
{ 177524643, 250672 }, |
|
{ 178857621, 251136 }, |
|
{ 180197813, 251599 }, |
|
{ 181545242, 252063 }, |
|
{ 182899933, 252527 }, |
|
{ 184261908, 252991 }, |
|
{ 185631191, 253456 }, |
|
{ 187007807, 253920 }, |
|
{ 188391778, 254385 }, |
|
{ 189783129, 254851 }, |
|
{ 191181884, 255316 }, |
|
{ 192588065, 255782 }, |
|
{ 194001698, 256248 }, |
|
{ 195422805, 256714 }, |
|
{ 196851411, 257181 }, |
|
{ 198287540, 257648 }, |
|
{ 199731215, 258115 }, |
|
{ 201182461, 258582 }, |
|
{ 202641302, 259050 }, |
|
{ 204107760, 259518 }, |
|
{ 205581862, 259986 }, |
|
{ 207063630, 260454 }, |
|
{ 208553088, 260923 }, |
|
{ 210050262, 261392 }, |
|
{ 211555174, 261861 }, |
|
{ 213067849, 262331 }, |
|
{ 214588312, 262800 }, |
|
{ 216116586, 263270 }, |
|
{ 217652696, 263741 }, |
|
{ 219196666, 264211 }, |
|
{ 220748520, 264682 }, |
|
{ 222308282, 265153 }, |
|
{ 223875978, 265625 }, |
|
{ 225451630, 266097 }, |
|
{ 227035265, 266569 }, |
|
{ 228626905, 267041 }, |
|
{ 230226576, 267514 }, |
|
{ 231834302, 267986 }, |
|
{ 233450107, 268460 }, |
|
{ 235074016, 268933 }, |
|
{ 236706054, 269407 }, |
|
{ 238346244, 269881 }, |
|
{ 239994613, 270355 }, |
|
{ 241651183, 270830 }, |
|
{ 243315981, 271305 } |
|
}; |
|
|
|
/* return largest index i such that fval <= lookup[i][small] */ |
|
static inline u32 tfrc_binsearch(u32 fval, u8 small) |
|
{ |
|
u32 try, low = 0, high = TFRC_CALC_X_ARRSIZE - 1; |
|
|
|
while (low < high) { |
|
try = (low + high) / 2; |
|
if (fval <= tfrc_calc_x_lookup[try][small]) |
|
high = try; |
|
else |
|
low = try + 1; |
|
} |
|
return high; |
|
} |
|
|
|
/** |
|
* tfrc_calc_x - Calculate the send rate as per section 3.1 of RFC3448 |
|
* @s: packet size in bytes |
|
* @R: RTT scaled by 1000000 (i.e., microseconds) |
|
* @p: loss ratio estimate scaled by 1000000 |
|
* |
|
* Returns X_calc in bytes per second (not scaled). |
|
*/ |
|
u32 tfrc_calc_x(u16 s, u32 R, u32 p) |
|
{ |
|
u16 index; |
|
u32 f; |
|
u64 result; |
|
|
|
/* check against invalid parameters and divide-by-zero */ |
|
BUG_ON(p > 1000000); /* p must not exceed 100% */ |
|
BUG_ON(p == 0); /* f(0) = 0, divide by zero */ |
|
if (R == 0) { /* possible divide by zero */ |
|
DCCP_CRIT("WARNING: RTT is 0, returning maximum X_calc."); |
|
return ~0U; |
|
} |
|
|
|
if (p <= TFRC_CALC_X_SPLIT) { /* 0.0000 < p <= 0.05 */ |
|
if (p < TFRC_SMALLEST_P) { /* 0.0000 < p < 0.0001 */ |
|
DCCP_WARN("Value of p (%d) below resolution. " |
|
"Substituting %d\n", p, TFRC_SMALLEST_P); |
|
index = 0; |
|
} else /* 0.0001 <= p <= 0.05 */ |
|
index = p/TFRC_SMALLEST_P - 1; |
|
|
|
f = tfrc_calc_x_lookup[index][1]; |
|
|
|
} else { /* 0.05 < p <= 1.00 */ |
|
index = p/(1000000/TFRC_CALC_X_ARRSIZE) - 1; |
|
|
|
f = tfrc_calc_x_lookup[index][0]; |
|
} |
|
|
|
/* |
|
* Compute X = s/(R*f(p)) in bytes per second. |
|
* Since f(p) and R are both scaled by 1000000, we need to multiply by |
|
* 1000000^2. To avoid overflow, the result is computed in two stages. |
|
* This works under almost all reasonable operational conditions, for a |
|
* wide range of parameters. Yet, should some strange combination of |
|
* parameters result in overflow, the use of scaled_div32 will catch |
|
* this and return UINT_MAX - which is a logically adequate consequence. |
|
*/ |
|
result = scaled_div(s, R); |
|
return scaled_div32(result, f); |
|
} |
|
|
|
/** |
|
* tfrc_calc_x_reverse_lookup - try to find p given f(p) |
|
* @fvalue: function value to match, scaled by 1000000 |
|
* |
|
* Returns closest match for p, also scaled by 1000000 |
|
*/ |
|
u32 tfrc_calc_x_reverse_lookup(u32 fvalue) |
|
{ |
|
int index; |
|
|
|
if (fvalue == 0) /* f(p) = 0 whenever p = 0 */ |
|
return 0; |
|
|
|
/* Error cases. */ |
|
if (fvalue < tfrc_calc_x_lookup[0][1]) { |
|
DCCP_WARN("fvalue %u smaller than resolution\n", fvalue); |
|
return TFRC_SMALLEST_P; |
|
} |
|
if (fvalue > tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][0]) { |
|
DCCP_WARN("fvalue %u exceeds bounds!\n", fvalue); |
|
return 1000000; |
|
} |
|
|
|
if (fvalue <= tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][1]) { |
|
index = tfrc_binsearch(fvalue, 1); |
|
return (index + 1) * TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE; |
|
} |
|
|
|
/* else ... it must be in the coarse-grained column */ |
|
index = tfrc_binsearch(fvalue, 0); |
|
return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE; |
|
} |
|
|
|
/** |
|
* tfrc_invert_loss_event_rate - Compute p so that 10^6 corresponds to 100% |
|
* @loss_event_rate: loss event rate to invert |
|
* When @loss_event_rate is large, there is a chance that p is truncated to 0. |
|
* To avoid re-entering slow-start in that case, we set p = TFRC_SMALLEST_P > 0. |
|
*/ |
|
u32 tfrc_invert_loss_event_rate(u32 loss_event_rate) |
|
{ |
|
if (loss_event_rate == UINT_MAX) /* see RFC 4342, 8.5 */ |
|
return 0; |
|
if (unlikely(loss_event_rate == 0)) /* map 1/0 into 100% */ |
|
return 1000000; |
|
return max_t(u32, scaled_div(1, loss_event_rate), TFRC_SMALLEST_P); |
|
}
|
|
|