Chapter 12. Advanced filters for (re-)classifying packets
As explained in the section on classful queueing disciplines, filters are
needed to classify packets into any of the sub-queues. These filters are
called from within the classful qdisc.
Here is an incomplete list of classifiers available:
- fw
Bases the decision on how the firewall has marked the packet. This can be
the easy way out if you don't want to learn tc filter syntax. See the
Queueing chapter for details.
- u32
Bases the decision on fields within the packet (i.e. source IP address, etc)
- route
Bases the decision on which route the packet will be routed by
- rsvp, rsvp6
Routes packets based on RSVP . Only useful
on networks you control - the Internet does not respect RSVP.
- tcindex
Used in the DSMARK qdisc, see the relevant section.
Note that in general there are many ways in which you can classify packet
and that it generally comes down to preference as to which system you wish
to use.
Classifiers in general accept a few arguments in common. They are listed
here for convenience:
- protocol
The protocol this classifier will accept. Generally you will only be
accepting only IP traffic. Required.
- parent
The handle this classifier is to be attached to. This handle must be
an already existing class. Required.
- prio
The priority of this classifier. Lower numbers get tested first.
- handle
This handle means different things to different filters.
All the following sections will assume you are trying to shape the traffic
going to HostA. They will assume that the root class has been
configured on 1: and that the class you want to send the selected traffic to
is 1:1.
Take our 
