diff options
| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 07:30:19 +0200 |
|---|---|---|
| committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 07:45:34 +0200 |
| commit | 535c55df136ad2783d444e54d518a8fae8bdbf79 (patch) | |
| tree | 8f7b18bc7b82270e78061c4c22bf722534b743a1 /net/dccp/ccids/lib | |
| parent | 3306c781ff13aea89606435c134ec84e3c608681 (diff) | |
dccp tfrc/ccid-3: Computing Loss Rate from Loss Event Rate
This adds a function to take care of the following cases occurring in the
computation of the Loss Rate p:
* 1/(2^32-1) is mapped into 0% as per RFC 4342, 8.5;
* 1/0 is mapped into the maximum of 100%;
* we want to avoid that p = 1/x is rounded down to 0 when x is very large,
since this means accidentally re-entering slow-start (indicated by p==0).
In the last case, the minimum-resolution value of p is returned.
Furthermore, a bug in ccid3_hc_rx_getsockopt is fixed (1/0 was mapped into ~0U),
which now allows to consistently print the scaled p-values as
printf("Loss Event Rate = %u.%04u %%\n", rx_info.tfrcrx_p / 10000,
rx_info.tfrcrx_p % 10000);
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp/ccids/lib')
| -rw-r--r-- | net/dccp/ccids/lib/tfrc.h | 1 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/tfrc_equation.c | 17 |
2 files changed, 16 insertions, 2 deletions
diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h index ed9857527acf..bb47146ac7d1 100644 --- a/net/dccp/ccids/lib/tfrc.h +++ b/net/dccp/ccids/lib/tfrc.h @@ -58,6 +58,7 @@ static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight) extern u32 tfrc_calc_x(u16 s, u32 R, u32 p); extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue); +extern u32 tfrc_invert_loss_event_rate(u32 loss_event_rate); extern int tfrc_tx_packet_history_init(void); extern void tfrc_tx_packet_history_exit(void); diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c index 2f20a29cffe4..bc3dc2b2a849 100644 --- a/net/dccp/ccids/lib/tfrc_equation.c +++ b/net/dccp/ccids/lib/tfrc_equation.c @@ -658,7 +658,6 @@ u32 tfrc_calc_x(u16 s, u32 R, u32 p) result = scaled_div(s, R); return scaled_div32(result, f); } - EXPORT_SYMBOL_GPL(tfrc_calc_x); /** @@ -693,5 +692,19 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue) index = tfrc_binsearch(fvalue, 0); return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE; } - EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup); + +/** + * tfrc_invert_loss_event_rate - Compute p so that 10^6 corresponds to 100% + * 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); +} +EXPORT_SYMBOL_GPL(tfrc_invert_loss_event_rate); |