[DCCP]: Move the calc_X routines to dccp_tfrc_lib

Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/dccp/ccids/ccid3.c

···
 #include "../dccp.h"
 #include "lib/packet_history.h"
 #include "lib/loss_interval.h"
+#include "lib/tfrc.h"
 #include "ccid3.h"
 
 /*
···
 	hctx->ccid3hctx_state = state;
 }
 
-#define CALCX_ARRSIZE 500
-
-#define CALCX_SPLIT 50000
-/* equivalent to 0.05 */
-
-static const u32 calcx_lookup[CALCX_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 }
-};
-
-/* 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.
-
-*/
-static u32 ccid3_calc_x(u16 s, u32 R, u32 p)
-{
-	int index;
-	u32 f;
-	u64 tmp1, tmp2;
-
-	if (p < CALCX_SPLIT)
-		index = (p / (CALCX_SPLIT / CALCX_ARRSIZE)) - 1;
-	else
-		index = (p / (1000000 / CALCX_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 >= CALCX_ARRSIZE);
-
-	if (p >= CALCX_SPLIT)
-		f = calcx_lookup[index][0];
-	else
-		f = calcx_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; 
-}
-
 /* Calculate new t_ipi (inter packet interval) by t_ipi = s / X_inst */
 static inline void ccid3_calc_new_t_ipi(struct ccid3_hc_tx_sock *hctx)
 {
···
 
 	/* To avoid large error in calcX */
 	if (hctx->ccid3hctx_p >= TFRC_SMALLEST_P) {
-		hctx->ccid3hctx_x_calc = ccid3_calc_x(hctx->ccid3hctx_s,
-						      hctx->ccid3hctx_rtt,
-						      hctx->ccid3hctx_p);
+		hctx->ccid3hctx_x_calc = tfrc_calc_x(hctx->ccid3hctx_s,
+						     hctx->ccid3hctx_rtt,
+						     hctx->ccid3hctx_p);
 		hctx->ccid3hctx_x = max_t(u32, min_t(u32, hctx->ccid3hctx_x_calc,
 							  2 * hctx->ccid3hctx_x_recv),
 					       (hctx->ccid3hctx_s /
···
 			   &x_recv, sizeof(x_recv));
 }
 
-/*
- * 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
- */
-static u32 calcx_reverse_lookup(u32 fvalue) {
-	int ctr = 0;
-	int small;
-
-	if (fvalue < calcx_lookup[0][1])
-		return 0;
-	if (fvalue <= calcx_lookup[CALCX_ARRSIZE-1][1])
-		small = 1;
-	else if (fvalue > calcx_lookup[CALCX_ARRSIZE-1][0])
-		return 1000000;
-	else
-		small = 0;
-	while (fvalue > calcx_lookup[ctr][small])
-		ctr++;
-	if (small)
-		return (CALCX_SPLIT * ctr / CALCX_ARRSIZE);
-	else
-		return (1000000 * ctr / CALCX_ARRSIZE) ;
-}
-
 /* calculate first loss interval
  *
  * returns estimated loss interval in usecs */
···
 	tmp2 = (u32)tmp1;
 	fval = (hcrx->ccid3hcrx_s * 100000) / tmp2;
 	/* do not alter order above or you will get overflow on 32 bit */
-	p = calcx_reverse_lookup(fval);
+	p = tfrc_calc_x_reverse_lookup(fval);
 	ccid3_pr_debug("%s, sk=%p, receive rate=%u bytes/s, implied "
 		       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
 

net/dccp/ccids/lib/Makefile

···
 obj-$(CONFIG_IP_DCCP_TFRC_LIB) += dccp_tfrc_lib.o
 
-dccp_tfrc_lib-y := loss_interval.o packet_history.o
+dccp_tfrc_lib-y := loss_interval.o packet_history.o tfrc_equation.o

net/dccp/ccids/lib/tfrc.h

···
+#ifndef _TFRC_H_
+#define _TFRC_H_
+/*
+ *  net/dccp/ccids/lib/tfrc.h
+ *
+ *  Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
+ *  Copyright (c) 2005 Ian McDonald <[e-mail]>
+ *  Copyright (c) 2005 Arnaldo Carvalho de Melo <[e-mail]>
+ *  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/types.h>
+
+extern u32 tfrc_calc_x(u16 s, u32 R, u32 p);
+extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue);
+
+#endif /* _TFRC_H_ */

net/dccp/ccids/lib/tfrc_equation.c

···
+/*
+ *  net/dccp/ccids/lib/tfrc_equation.c
+ *
+ *  Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
+ *  Copyright (c) 2005 Ian McDonald <[e-mail]>
+ *  Copyright (c) 2005 Arnaldo Carvalho de Melo <[e-mail]>
+ *  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 },
+	{    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 },
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+	{  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 },
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+	{  59526017, 193911 },
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+	{  76722586, 205417 },
+	{  77448761, 205861 },
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+	{  84211402, 209864 },
+	{  84988421, 210309 },
+	{  85770640, 210755 },
+	{  86558080, 211201 },
+	{  87350762, 211647 },
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+	{  88951938, 212539 },
+	{  89760475, 212985 },
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+	{  92218133, 214325 },
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+	{  99884556, 218353 },
+	{ 100764018, 218801 },
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+	{ 104338146, 220596 },
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+	{ 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 }
+};
+
+/* 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);