dccp tfrc/ccid-3: computing the loss rate from the Loss Event Rate
This adds a function to take care of the following, separate 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 100%, the maximum;
* 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, the minimum
resolution value of p is now returned instead;
* a bug in ccid3_hc_rx_getsockopt is fixed: 1/0 was mapped into ~0U.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 90bc0a7..9715eeb 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -400,10 +400,10 @@
/* Update loss event rate (which is scaled by 1e6) */
pinv = opt_recv->ccid3or_loss_event_rate;
- if (pinv == ~0U || pinv == 0) /* see RFC 4342, 8.5 */
+ if (pinv == 0)
hc->tx_p = 0;
- else /* can not exceed 100% */
- hc->tx_p = scaled_div(1, pinv);
+ else
+ hc->tx_p = tfrc_invert_loss_event_rate(pinv);
/*
* Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
@@ -834,8 +834,7 @@
return -EINVAL;
rx_info.tfrcrx_x_recv = hc->rx_x_recv;
rx_info.tfrcrx_rtt = hc->rx_rtt;
- rx_info.tfrcrx_p = hc->rx_pinv == 0 ? ~0U :
- scaled_div(1, hc->rx_pinv);
+ rx_info.tfrcrx_p = tfrc_invert_loss_event_rate(hc->rx_pinv);
len = sizeof(rx_info);
val = &rx_info;
break;