tc: Add support for configuring the taprio scheduler

This traffic scheduler allows traffic classes states (transmission allowed/not allowed, in the simplest case) to be scheduled, according to a pre-generated time sequence. This is the basis of the IEEE 802.1Qbv specification. Example configuration: tc qdisc replace dev enp3s0 parent root handle 100 taprio \ num_tc 3 \ map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \ queues 1@0 1@1 2@2 \ base-time 1528743495910289987 \ sched-entry S 01 300000 \ sched-entry S 02 300000 \ sched-entry S 04 300000 \ clockid CLOCK_TAI The configuration format is similar to mqprio. The main difference is the presence of a schedule, built by multiple "sched-entry" definitions, each entry has the following format: sched-entry <CMD> <GATE MASK> <INTERVAL> The only supported <CMD> is "S", which means "SetGateStates", following the IEEE 802.1Qbv-2015 definition (Table 8-6). <GATE MASK> is a bitmask where each bit is a associated with a traffic class, so bit 0 (the least significant bit) being "on" means that traffic class 0 is "active" for that schedule entry. <INTERVAL> is a time duration in nanoseconds that specifies for how long that state defined by <CMD> and <GATE MASK> should be held before moving to the next entry. This schedule is circular, that is, after the last entry is executed it starts from the first one, indefinitely. The other parameters can be defined as follows: - base-time: specifies the instant when the schedule starts, if 'base-time' is a time in the past, the schedule will start at base-time + (N * cycle-time) where N is the smallest integer so the resulting time is greater than "now", and "cycle-time" is the sum of all the intervals of the entries in the schedule; - clockid: specifies the reference clock to be used; The parameters should be similar to what the IEEE 802.1Q family of specification defines.

VCVinicius Costa Gomes committed 8 years ago