Hi all!
I found a rather esotheric bug / misconfiguration, and now I'm lost.
Maybe somebody else has a clue what is going on here.
I am connected to the internet via a typical DSL router with integrated
4-port switch. One of my computers should be able to serve local
machines at full speed, but internet bandwith usage should be limited.
Just for the record, it is running 2.4.27-pre3, but I have checked
several kernel versions (not the 2.6 series, though). Additionally, a
set of firewall rules is active. The system is rather slow with C3
@533MHz, but has 512MB RAM.
Now what happens is the following: With the QoS rules enabled, the
system behaves as anticipated (fast local traffic, limited internet
traffic), but suddenly for a couple of seconds it won't talk to local
computers any longer. ssh connections freeze, no ping, nothing.
Strangely enough, remote connections are still alive. Other systems can
talk with each other and are routed to the internet as well, so I
conclude that this has nothing to do with the router. This mostly
happens when a lot of upstream traffic is going on, that is, the
internet limit is hit. The time of traffic breakdown varies from event
to event and can be as large as a minute. Needless to say that the
system itself is almost idle during that time and that it won't happen
with QoS disabled.
I narrowed down the strange behaviour and can sort of reproduce it with
the following subset of my QoS rules - the exact bandwidth limits do not
really matter, I got this with 50kbit uplink and 400kbit local traffic
and different quantum values as well:
DEV=eth0
LOCAL=192.168.2.0/24
tc qdisc add dev $DEV root handle 1: htb default 2
# Class 1:1 local traffic
tc class add dev $DEV parent 1: classid 1:1 htb prio 1 \
rate 80mbit quantum 32768
# Class 1:2 remote traffic
tc class add dev $DEV parent 1: classid 1:2 htb prio 2 \
rate 80kbit ceil 80kbit burst 2k quantum 1500
# Local traffic goes unconditionally to 1:1
tc filter add dev $DEV parent 1: protocol ip prio 1 \
u32 match ip dst $LOCAL \
flowid 1:1
Any ideas?
Thanks
Matthias
--
Matthias Hopf - Visualization and Interactive Systems Group \ | | /--
University of Stuttgart, \ | | \
Universitaetsstr. 38, 70569 Stuttgart, Germany \| | --/
Phone +49-711-7816-404 Fax -340 mat@xxxxxxxxx www.mshopf.de
