On 12/10/06, Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxx> wrote:
This simplifies the calculation of a value p for a given fval when the
first loss interval is computed (RFC 3448, 6.3.1). It makes use of the
two new functions scaled_div/scaled_div32 to provide overflow protection.
Additionally, protection against divide-by-zero is extended - in this
case the function will return the maximally possible value of p=100%.
Just discovered an error in this patch. If we can't determine the loss
rate we should set the interval to ~0 as used by
dccp_li_hist_calc_i_mean. We definitely should not use 1000000 as this
signifies we got 1 million packets without loss and will cause
performance to be ramped up in the face of problems! Possibly we
should use 1 as a case if we want to signify we should slow down
things. Thinking about this and writing a patch shortly.
Ian
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index bdd13de..89ef118 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -785,12 +785,12 @@ static u32 ccid3_hc_rx_calc_first_li(str
@@ -834,30 +834,35 @@ found:
+ if (rtt == 0) { /* would result in divide-by-zero */
+ DCCP_WARN("RTT==0, returning 1/p = 1\n");
+ return 1000000;
}
+ if (x_recv == 0) { /* would also trigger divide-by-zero */
+ DCCP_WARN("X_recv==0\n");
+ if ((x_recv = hcrx->ccid3hcrx_x_recv) == 0) {
+ DCCP_BUG("stored value of X_recv is zero");
+ return 1000000;
+ }
}
--
Web: http://wand.net.nz/~iam4
Blog: http://imcdnzl.blogspot.com
WAND Network Research Group
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