[Cake] Ingress classification

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Thu Feb 7 11:28:20 EST 2019

> On 6 Feb 2019, at 16:19, Stephen Hemminger <stephen at networkplumber.org> wrote:
>> At this stage I’m wondering if its possible to get tc/cake to classify egress based on connmarks instead of relying on DSCP but my tc filter syntax is failing me at the moment :-)
> It is possible to use a tc ingress filter to remark DSCP.

Hmmm.  I wonder if this would be more efficient to re-mark the DSCP code and let cake use its normal DSCP to tin mapping instead of overriding via an skb priority edit?

My new problem is using fw marks with tc filters changing skb priority on *egress*.  If I could get that to work then I think it would become compatible with software flow offloading.

I can’t get it to work and don’t know if I’m doing something wrong (likely) with my tc incantations or if it’s just not possible.  

I think something like the following should work, assuming the cake instance handling egress on eth0 is 809a: as shown by 

# tc qdisc show dev ifb4eth0
qdisc cake 809b: root refcnt 2 bandwidth 78Mbit diffserv4 dual-dsthost nat nowash ingress no-ack-filter split-gso rtt 100.0ms ptm overhead 26 

So the following should change the skb priority field based on a firewall connmark of 0x01

tc filter add dev eth0 parent 809a: protocol all handle 0x01 fw action skbedit priority 809a:4


Kevin D-B

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