tree 2afd0d3fba79620b889935b678ac8c024e10c19d
parent a23c37f1110d8912d4d0a66e78197e9195bb36d4
author stephen hemminger <shemminger@vyatta.com> 1300089132 +0000
committer David S. Miller <davem@davemloft.net> 1300143278 -0700

tcp: fix RTT for quick packets in congestion control

In the congestion control interface, the callback for each ACK
includes an estimated round trip time in microseconds.
Some algorithms need high resolution (Vegas style) but most only
need jiffie resolution.  If RTT is not accurate (like a retransmission)
-1 is used as a flag value.

When doing coarse resolution if RTT is less than a a jiffie
then 0 should be returned rather than no estimate. Otherwise algorithms
that expect good ack's to trigger slow start (like CUBIC Hystart)
will be confused.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>