[Cake] squash option

[Jonathan Morton]

> On 13 Apr, 2015, at 01:20, Dave Taht <dave.taht at gmail.com> wrote:
> 
> Inbound diffserv markings cannot be trusted. A simple remark to
> dscp & ECT(3) of diffserv is kind of a must for cake.

As I noted previously, cake can trivially be configured to ignore Diffserv.  A simple iptables rule would then suffice to remove the mark for downstream consumers if desired.

More useful would be the ability to re-mark packets according to local Diffserv policy before cake’s classifier acts on it.  Iptables doesn’t help here, because it runs *after* ingress qdiscs (even in ifb).  Unfortunately, the likely complexity of the configuration mechanism for such a device runs counter to cake’s deliberately simple configuration interface.

However, I have no objection to a second qdisc which could be run in series with cake to perform that function.  This would be a qdisc which performs no queueing of its own, and simply performs the re-marking before passing the packet up the qdisc stack.  The configuration mechanism of this can be relatively complex, but narrowly focused on the re-marking task.  Call it “icing” or “cherry” or whatever, to emphasise that it goes on top of cake.

 - Jonathan Morton