tree 95ab0dc853b2f68d529162e5f1dfd5e0cb5e37a9
parent 6079a463cf95fafcc704a4e5e92a4da12444bd3c
author Gerrit Renker <gerrit@erg.abdn.ac.uk> 1211895234 -0700
committer David S. Miller <davem@davemloft.net> 1211895234 -0700

dccp ccid-3: Fix "t_ipi explosion" bug

The identification of this bug is thanks to Cheng Wei and Tomasz
Grobelny.

To avoid divide-by-zero, the implementation previously ignored RTTs
smaller than 4 microseconds when performing integer division RTT/4.

When the RTT reached a value less than 4 microseconds (as observed on
loopback), this prevented the Window Counter CCVal value from
advancing. As a result, the receiver stopped sending feedback. This in
turn caused non-ending expiries of the nofeedback timer at the sender,
so that the sending rate was progressively reduced until reaching the
minimum of one packet per 64 seconds.

The patch fixes this bug by handling integer division more
intelligently. Due to consistent use of dccp_sample_rtt(),
divide-by-zero-RTT is avoided.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>