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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2008-09-04 01:30:19 -0400
committerGerrit Renker <gerrit@erg.abdn.ac.uk>2008-09-04 01:45:34 -0400
commit535c55df136ad2783d444e54d518a8fae8bdbf79 (patch)
tree8f7b18bc7b82270e78061c4c22bf722534b743a1 /net/dccp
parent3306c781ff13aea89606435c134ec84e3c608681 (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')
-rw-r--r--net/dccp/ccids/ccid3.c9
-rw-r--r--net/dccp/ccids/lib/tfrc.h1
-rw-r--r--net/dccp/ccids/lib/tfrc_equation.c17
3 files changed, 20 insertions, 7 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 4c422fb2189f..206204551f4d 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -410,10 +410,10 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
410 410
411 /* Update loss event rate (which is scaled by 1e6) */ 411 /* Update loss event rate (which is scaled by 1e6) */
412 pinv = opt_recv->ccid3or_loss_event_rate; 412 pinv = opt_recv->ccid3or_loss_event_rate;
413 if (pinv == ~0U || pinv == 0) /* see RFC 4342, 8.5 */ 413 if (pinv == 0)
414 hctx->p = 0; 414 hctx->p = 0;
415 else /* can not exceed 100% */ 415 else
416 hctx->p = scaled_div(1, pinv); 416 hctx->p = tfrc_invert_loss_event_rate(pinv);
417 417
418 /* 418 /*
419 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3 419 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
@@ -854,8 +854,7 @@ static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
854 return -EINVAL; 854 return -EINVAL;
855 rx_info.tfrcrx_x_recv = hcrx->x_recv; 855 rx_info.tfrcrx_x_recv = hcrx->x_recv;
856 rx_info.tfrcrx_rtt = hcrx->rtt; 856 rx_info.tfrcrx_rtt = hcrx->rtt;
857 rx_info.tfrcrx_p = hcrx->p_inverse == 0 ? ~0U : 857 rx_info.tfrcrx_p = tfrc_invert_loss_event_rate(hcrx->p_inverse);
858 scaled_div(1, hcrx->p_inverse);
859 len = sizeof(rx_info); 858 len = sizeof(rx_info);
860 val = &rx_info; 859 val = &rx_info;
861 break; 860 break;
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)
58 58
59extern u32 tfrc_calc_x(u16 s, u32 R, u32 p); 59extern u32 tfrc_calc_x(u16 s, u32 R, u32 p);
60extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue); 60extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue);
61extern u32 tfrc_invert_loss_event_rate(u32 loss_event_rate);
61 62
62extern int tfrc_tx_packet_history_init(void); 63extern int tfrc_tx_packet_history_init(void);
63extern void tfrc_tx_packet_history_exit(void); 64extern 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)
658 result = scaled_div(s, R); 658 result = scaled_div(s, R);
659 return scaled_div32(result, f); 659 return scaled_div32(result, f);
660} 660}
661
662EXPORT_SYMBOL_GPL(tfrc_calc_x); 661EXPORT_SYMBOL_GPL(tfrc_calc_x);
663 662
664/** 663/**
@@ -693,5 +692,19 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue)
693 index = tfrc_binsearch(fvalue, 0); 692 index = tfrc_binsearch(fvalue, 0);
694 return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE; 693 return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE;
695} 694}
696
697EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup); 695EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);
696
697/**
698 * tfrc_invert_loss_event_rate - Compute p so that 10^6 corresponds to 100%
699 * When @loss_event_rate is large, there is a chance that p is truncated to 0.
700 * To avoid re-entering slow-start in that case, we set p = TFRC_SMALLEST_P > 0.
701 */
702u32 tfrc_invert_loss_event_rate(u32 loss_event_rate)
703{
704 if (loss_event_rate == UINT_MAX) /* see RFC 4342, 8.5 */
705 return 0;
706 if (unlikely(loss_event_rate == 0)) /* map 1/0 into 100% */
707 return 1000000;
708 return max_t(u32, scaled_div(1, loss_event_rate), TFRC_SMALLEST_P);
709}
710EXPORT_SYMBOL_GPL(tfrc_invert_loss_event_rate);