Re: SFQ flow classifier, works for imq0, not for eth1

[Patrick McHardy <kaber@trash.net>]

On 12.11.2010 15:57, Ben Pfountz wrote:
> Hey Everyone,
> 
> Any direction with this problem would be greatly appreciated.  For some
> reason when I add a SFQ flow classifier using tc filter, the sfq qdisc
> stops forwarding packets.  (strangely though, a few packets are
> forwarded before things stop working)
> 
> I am working with an openwrt based router, trying to add SFQ flow
> classifier support to openwrt's qos-scripts.  I have simplified the TC
> commands down to these to try to find the problem.
> 
> tc qdisc add dev eth1 root handle 1: htb default 7
> tc class add dev eth1 parent 1: classid 1:7 htb rate 500mbit ceil
> 1000mbit prio 3
> tc qdisc add dev eth1 parent 1:7 handle 10: sfq perturb 10
> tc filter add dev eth1 protocol ip parent 10: handle 2 flow hash keys
> src,dst divisor 1024
> 
> 
> 
> Without the last line, packets flow normally as shown by
> 
> # tc -s -d qdisc show dev eth1
> qdisc htb 1: root refcnt 2 r2q 10 default 7 direct_packets_stat 0 ver 3.17
>  Sent 856 bytes 11 pkt (dropped 0, overlimits 0 requeues 0)
>  rate 0bit 0pps backlog 0b 0p requeues 0
> qdisc sfq 10: parent 1:7 limit 127p quantum 1514b flows 127/1024 perturb
> 10sec
>  Sent 856 bytes 11 pkt (dropped 0, overlimits 0 requeues 0)
>  rate 0bit 0pps backlog 0b 0p requeues 0
> 
> 
> With the last line, I see this
> 
> tc -s -d qdisc show dev eth1
> qdisc htb 1: root refcnt 2 r2q 10 default 7 direct_packets_stat 0 ver 3.17
>  Sent 5019 bytes 53 pkt (dropped 40, overlimits 0 requeues 0)
>  rate 0bit 0pps backlog 0b 0p requeues 0
> qdisc sfq 10: parent 1:7 limit 127p quantum 1514b flows 127/1024 perturb
> 10sec
>  Sent 5019 bytes 53 pkt (dropped 40, overlimits 0 requeues 0)
>  rate 0bit 0pps backlog 0b 0p requeues 0
> 
> 
> I have tried every combination of hash keys and divisor I can think of,
> but the problem remains.
> 
> The system is linux 2.6.32.25, iproute 2.6.35, and cls_flow is loaded.
> 
> Does anyone have any suggestions?

IMQ hooks into the netfilter hooks and thus receives IP packets only.
On eth0 you have to take care of classifying ARP packets as well,
otherwise packet flow will stop eventually.