Merge branch 'tc-ets-qdisc' into next

Petr Machata  says:

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A new Qdisc, "ETS", has been accepted into Linux at kernel commit
6bff00170277 ("Merge branch 'ETS-qdisc'"). Add iproute2 support for this
Qdisc.

Patch #1, changes libnetlink to admit NLA_F_NESTED in nested attributes.
Patch #2 then adds ETS support as such.

Examples (taken from the kernel patchset):

- Add a Qdisc with 6 bands, 3 strict and 3 ETS with 45%-30%-25% weights:

    # tc qdisc add dev swp1 root handle 1: \
	ets strict 3 quanta 4500 3000 2500 priomap 0 1 1 1 2 3 4 5
    # tc qdisc sh dev swp1
    qdisc ets 1: root refcnt 2 bands 6 strict 3 quanta 4500 3000 2500 priomap 0 1 1 1 2 3 4 5 5 5 5 5 5 5 5 5

- Tweak quantum of one of the classes of the previous Qdisc:

    # tc class ch dev swp1 classid 1:4 ets quantum 1000
    # tc qdisc sh dev swp1
    qdisc ets 1: root refcnt 2 bands 6 strict 3 quanta 1000 3000 2500 priomap 0 1 1 1 2 3 4 5 5 5 5 5 5 5 5 5
    # tc class ch dev swp1 classid 1:3 ets quantum 1000
    Error: Strict bands do not have a configurable quantum.

- Purely strict Qdisc with 1:1 mapping between priorities and TCs:

    # tc qdisc add dev swp1 root handle 1: \
	ets strict 8 priomap 7 6 5 4 3 2 1 0
    # tc qdisc sh dev swp1
    qdisc ets 1: root refcnt 2 bands 8 strict 8 priomap 7 6 5 4 3 2 1 0 7 7 7 7 7 7 7 7

- Use "bands" to specify number of bands explicitly. Underspecified bands
  are implicitly ETS and their quantum is taken from MTU. The following
  thus gives each band the same weight:

    # tc qdisc add dev swp1 root handle 1: \
	ets bands 8 priomap 7 6 5 4 3 2 1 0
    # tc qdisc sh dev swp1
    qdisc ets 1: root refcnt 2 bands 8 quanta 1514 1514 1514 1514 1514 1514 1514 1514 priomap 7 6 5 4 3 2 1 0 7 7 7 7 7 7 7 7

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Signed-off-by: David Ahern <dsahern@gmail.com>