[LARTC] htb not hard limiting correctly

[Abraham van der Merwe <abz@frogfoot.net>]

Hi!

This morning one of our major links died and suddenly I was streaming 1mbit
of traffic through 256kbit (one of our backup links), but it just doesn't
work. The client is still doing in the region of 350kbit/s (the link
capacity is 512kbit). Here is my config:

------------< snip <------< snip <------< snip <------------
tc qdisc add dev eth1 root handle 1: htb default 4 r2q 5
tc class add dev eth1 parent 1: classid 1:1 htb rate 512kbit
tc class add dev eth1 parent 1:1 classid 1:2 htb rate 320kbit ceil 512kbit prio 1
tc qdisc add dev eth1 handle 2: parent 1:2 sfq perturb 10 limit 84
tc class add dev eth1 parent 1:1 classid 1:3 htb rate 64kbit ceil 256kbit prio 3
tc qdisc add dev eth1 handle 3: parent 1:3 sfq perturb 10 limit 42
tc class add dev eth1 parent 1:1 classid 1:4 htb rate 128kbit ceil 512kbit prio 2
tc qdisc add dev eth1 handle 4: parent 1:4 sfq perturb 10 limit 84
tc qdisc add dev eth0 root handle 1: htb default 4 r2q 5
tc class add dev eth0 parent 1: classid 1:1 htb rate 512kbit
tc class add dev eth0 parent 1:1 classid 1:2 htb rate 320kbit ceil 512kbit prio 1
tc qdisc add dev eth0 handle 2: parent 1:2 sfq perturb 10 limit 84
tc class add dev eth0 parent 1:1 classid 1:3 htb rate 64kbit ceil 256kbit prio 3
tc qdisc add dev eth0 handle 3: parent 1:3 sfq perturb 10 limit 42
tc class add dev eth0 parent 1:1 classid 1:4 htb rate 128kbit ceil 512kbit prio 2
tc qdisc add dev eth0 handle 4: parent 1:4 sfq perturb 10 limit 84
------------< snip <------< snip <------< snip <------------

I'm tagging packets with the netfilter CLASSIFY patch. I've got a
user-defined chain in the mangle table and I redirect all traffic from the
POSTROUTING chain into that and add rules like this:

iptables -t mangle -N qos
iptables -t mangle -A POSTROUTING -j qos

and then these rules for the ftc rules above:

------------< snip <------< snip <------< snip <------------
iptables -t mangle -A qos -o eth1 -d 66.8.28.92/30 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth1 -d 66.8.28.160/27 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth1 -d 168.210.55.0/24 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth1 -d 168.210.54.80/29 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth1 -d 168.210.56.0/24 -j CLASSIFY --set-class 1:3
iptables -t mangle -A qos -o eth1 -d 66.8.28.32/27 -j CLASSIFY --set-class 1:3
iptables -t mangle -A qos -o eth0 -s 66.8.28.92/30 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth0 -s 66.8.28.160/27 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth0 -s 168.210.55.0/24 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth0 -s 168.210.54.80/29 -j CLASSIFY --set-class 1:2
iptables -t mangle -A qos -o eth0 -s 168.210.56.0/24 -j CLASSIFY --set-class 1:3
iptables -t mangle -A qos -o eth0 -s 66.8.28.32/27 -j CLASSIFY --set-class 1:3
------------< snip <------< snip <------< snip <------------

The class which is not shaping correctly is 1:3 - it has a rate of 64kbit
and a ceil of 256kbit so it should be limited to 256kbit even if there is
512kbit of traffic available.

Any ideas what I did wrong or is this a bug?

-- 

Regards
 Abraham

Bernard Shaw is an excellent man; he has not an enemy in the world, and
none of his friends like him either.
		-- Oscar Wilde

___________________________________________________
 Abraham vd Merwe - Frogfoot Networks CC
 9 Kinnaird Court, 33 Main Street, Newlands, 7700
 Phone: +27 21 686 1665 Cell: +27 82 565 4451
 Http: http://www.frogfoot.net/ Email: abz@frogfoot.net

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