sch_cake: Add DiffServ handling
This adds support for DiffServ-based priority queueing to CAKE. If the shaper is in use, each priority tier gets its own virtual clock, which limits that tier's rate to a fraction of the overall shaped rate, to discourage trying to game the priority mechanism. CAKE defaults to a simple, three-tier mode that interprets most code points as "best effort", but places CS1 traffic into a low-priority "bulk" tier which is assigned 1/16 of the total rate, and a few code points indicating latency-sensitive or control traffic (specifically TOS4, VA, EF, CS6, CS7) into a "latency sensitive" high-priority tier, which is assigned 1/4 rate. The other supported DiffServ modes are a 4-tier mode matching the 802.11e precedence rules, as well as two 8-tier modes, one of which implements strict precedence of the eight priority levels. This commit also adds an optional DiffServ 'wash' mode, which will zero out the DSCP fields of any packet passing through CAKE. While this can technically be done with other mechanisms in the kernel, having the feature available in CAKE significantly decreases configuration complexity; and the implementation cost is low on top of the other DiffServ-handling code. Filters and applications can set the skb->priority field to override the DSCP-based classification into tiers. If TC_H_MAJ(skb->priority) matches CAKE's qdisc handle, the minor number will be interpreted as a priority tier if it is less than or equal to the number of configured priority tiers. Signed-off-by:Toke Høiland-Jørgensen <toke@toke.dk> Signed-off-by:
David S. Miller <davem@davemloft.net>
parent
ea825115
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