- * Overall structure of dummynet (with WF2Q+):
-
-In dummynet, packets are selected with the firewall rules, and passed
-to two different objects: PIPE or QUEUE.
-
-A QUEUE is just a queue with configurable size and queue management
-policy. It is also associated with a mask (to discriminate among
-different flows), a weight (used to give different shares of the
-bandwidth to different flows) and a "pipe", which essentially
-supplies the transmit clock for all queues associated with that
-pipe.
-
-A PIPE emulates a fixed-bandwidth link, whose bandwidth is
-configurable. The "clock" for a pipe can come from either an
-internal timer, or from the transmit interrupt of an interface.
-A pipe is also associated with one (or more, if masks are used)
-queue, where all packets for that pipe are stored.
-
-The bandwidth available on the pipe is shared by the queues
-associated with that pipe (only one in case the packet is sent
-to a PIPE) according to the WF2Q+ scheduling algorithm and the
-configured weights.
-
-In general, incoming packets are stored in the appropriate queue,
-which is then placed into one of a few heaps managed by a scheduler
-to decide when the packet should be extracted.
-The scheduler (a function called dummynet()) is run at every timer
-tick, and grabs queues from the head of the heaps when they are
-ready for processing.
-
-There are three data structures definining a pipe and associated queues:
-
- + dn_pipe, which contains the main configuration parameters related
- to delay and bandwidth;
- + dn_flow_set, which contains WF2Q+ configuration, flow
- masks, plr and RED configuration;
- + dn_flow_queue, which is the per-flow queue (containing the packets)
-
-Multiple dn_flow_set can be linked to the same pipe, and multiple
-dn_flow_queue can be linked to the same dn_flow_set.
-All data structures are linked in a linear list which is used for
-housekeeping purposes.
-
-During configuration, we create and initialize the dn_flow_set
-and dn_pipe structures (a dn_pipe also contains a dn_flow_set).
-
-At runtime: packets are sent to the appropriate dn_flow_set (either
-WFQ ones, or the one embedded in the dn_pipe for fixed-rate flows),
-which in turn dispatches them to the appropriate dn_flow_queue
-(created dynamically according to the masks).
-
-The transmit clock for fixed rate flows (ready_event()) selects the
-dn_flow_queue to be used to transmit the next packet. For WF2Q,
-wfq_ready_event() extract a pipe which in turn selects the right
-flow using a number of heaps defined into the pipe itself.
-
- *