Re: Can't get tc to limit network traffic

[Andy Furniss <adf.lists@gmail.com>]

Teresa e Junior wrote:

> #!/bin/sh
>
> tc qdisc del dev ifb0  root
> tc qdisc del dev wlan0 ingress
>
> modprobe ifb
>
> tc qdisc  add dev ifb0 root handle 1: prio
> tc qdisc  add dev ifb0 parent 1:1 handle 10: sfq
> tc qdisc  add dev ifb0 parent 1:2 handle 20: tbf rate 20kbit \
>    buffer 1600 limit 3000
> tc qdisc  add dev ifb0 parent 1:3 handle 30: sfq
> tc filter add dev ifb0 protocol ip pref 1 parent 1: handle 1 fw classid 1:1
> tc filter add dev ifb0 protocol ip pref 2 parent 1: handle 2 fw classid 1:2

Well handle 2 would need iptables mark 2 - and I don't think using 
iptables is needed anyway.

Using tc to set it, historically at least, has been a bit hit and miss 
requiring matching versions of things.

TBH this all seems over complicated if all you want to do is send all 
ipv4 to ifb0 and limit to a couple of meg.

Adding a child of sfq or fq_codel will help stop bulk flows blocking eg dns.

I must admit I made up the params for fq_codel below - maybe someone 
will suggest better for 2mbit rate.

tc qdisc add dev ifb0 root handle 1:0 htb default 1
tc class add dev ifb0 parent 1:0  classid 1:1 htb rate 2mbit
tc qdisc add dev ifb0 parent 1:1 handle 10: fq_codel noecn target 50ms 
interval 100ms

I would just delete the action xt line from below.

> tc qdisc  add dev wlan0 ingress
> tc filter add dev wlan0 parent ffff: protocol ip prio 10 u32 \
>    match u32 0 0 flowid 1:1       \
>    action xt -j MARK --set-mark 1 \
>    action mirred egress redirect dev ifb0

More generally I am guessing you are limiting this box to stop it 
hogging the wan bandwidth rather than wireless lan.

If the download speed of the wan is not much higher than what you set 
you may need to set lower.

Wherever/however you shape incoming from wan you need to back off as you 
are at the wrong end of the bottleneck.

How much you have to back off depends on how hard you hit the connection 
eg if your box is downloading one tcp it will work closer to the limit 
than 100 tcps spread out all over the place like bittorrent.