Policy Routing Using Linux®

Interactions with Packet Filters

In your testing of the u32 qdisc you came to wonder what interactions exist between the NetFilter mangle and the u32 filter. You know from testing the fwmark that the mangle table can select and mark packets on input using the PREROUTING hook. You know from your u32 testing that the u32 filter can select and mark packets on ingress. Does one override the other or can they coexist?

Example 6.7—Double Play Packet

You decide to try a quick test now that you have seen good examples of both types of packet tagging. You have router1 set up with a 2.4 kernel and both the NetFilter and the DiffServ running. You then run the following set of commands to set up the tagging mechanisms for both iptables and u32:

							tc qdisc add ...