net/dccp/ccids/lib/tfrc.h

   1 #ifndef _TFRC_H_
   2 #define _TFRC_H_
   3 /*
   4  *  net/dccp/ccids/lib/tfrc.h
   5  *
   6  *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
   7  *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
   8  *  Copyright (c) 2005-6 Ian McDonald <ian.mcdonald@jandi.co.nz>
   9  *  Copyright (c) 2005   Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  10  *  Copyright (c) 2003   Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
  11  *
  12  *  This program is free software; you can redistribute it and/or modify
  13  *  it under the terms of the GNU General Public License as published by
  14  *  the Free Software Foundation; either version 2 of the License, or
  15  *  (at your option) any later version.
  16  */
  17 #include <linux/types.h>
  18 #include <linux/math64.h>
  19 #include "../../dccp.h"
  20 /* internal includes that this module exports: */
  21 #include "loss_interval.h"
  22 #include "packet_history.h"
  23
  24 #ifdef CONFIG_IP_DCCP_TFRC_DEBUG
  25 extern int tfrc_debug;
  26 #define tfrc_pr_debug(format, a...)     DCCP_PR_DEBUG(tfrc_debug, format, ##a)
  27 #else
  28 #define tfrc_pr_debug(format, a...)
  29 #endif
  30
  31 /* integer-arithmetic divisions of type (a * 1000000)/b */
  32 static inline u64 scaled_div(u64 a, u64 b)
  33 {
  34         BUG_ON(b==0);
  35         return div64_u64(a * 1000000, b);
  36 }
  37
  38 static inline u32 scaled_div32(u64 a, u64 b)
  39 {
  40         u64 result = scaled_div(a, b);
  41
  42         if (result > UINT_MAX) {
  43                 DCCP_CRIT("Overflow: %llu/%llu > UINT_MAX",
  44                           (unsigned long long)a, (unsigned long long)b);
  45                 return UINT_MAX;
  46         }
  47         return result;
  48 }
  49
  50 /**
  51  * tfrc_scaled_sqrt  -  Compute scaled integer sqrt(x) for 0 < x < 2^22-1
  52  * Uses scaling to improve accuracy of the integer approximation of sqrt(). The
  53  * scaling factor of 2^10 limits the maximum @sample to 4e6; this is okay for
  54  * clamped RTT samples (dccp_sample_rtt).
  55  * Should best be used for expressions of type sqrt(x)/sqrt(y), since then the
  56  * scaling factor is neutralised. For this purpose, it avoids returning zero.
  57  */
  58 static inline u16 tfrc_scaled_sqrt(const u32 sample)
  59 {
  60         const unsigned long non_zero_sample = sample ? : 1;
  61
  62         return int_sqrt(non_zero_sample << 10);
  63 }
  64
  65 /**
  66  * tfrc_ewma  -  Exponentially weighted moving average
  67  * @weight: Weight to be used as damping factor, in units of 1/10
  68  */
  69 static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight)
  70 {
  71         return avg ? (weight * avg + (10 - weight) * newval) / 10 : newval;
  72 }
  73
  74 extern u32  tfrc_calc_x(u16 s, u32 R, u32 p);
  75 extern u32  tfrc_calc_x_reverse_lookup(u32 fvalue);
  76 extern u32  tfrc_invert_loss_event_rate(u32 loss_event_rate);
  77
  78 extern int  tfrc_tx_packet_history_init(void);
  79 extern void tfrc_tx_packet_history_exit(void);
  80 extern int  tfrc_rx_packet_history_init(void);
  81 extern void tfrc_rx_packet_history_exit(void);
  82
  83 extern int  tfrc_li_init(void);
  84 extern void tfrc_li_exit(void);
  85 #endif /* _TFRC_H_ */