This patch allows users to pick queue_mapping, range
from A to B. Then we can load balance packets from A
to B tx queue. The range is an unsigned 16bit value
in decimal format.

$ tc filter ... action skbedit queue_mapping skbhash A B

"skbedit queue_mapping QUEUE_MAPPING" (from "man 8 tc-skbedit")
is enhanced with flags: SKBEDIT_F_TXQ_SKBHASH

  +----+      +----+      +----+
  | P1 |      | P2 |      | Pn |
  +----+      +----+      +----+
    |           |           |
    +-----------+-----------+
                |
                | clsact/skbedit
                |      MQ
                v
    +-----------+-----------+
    | q0        | qn        | qm
    v           v           v
  HTB/FQ       FIFO   ...  FIFO

For example:
If P1 sends out packets to different Pods on other host, and
we want distribute flows from qn - qm. Then we can use skb->hash
as hash.

setup commands:
$ NETDEV=eth0
$ ip netns add n1
$ ip link add ipv1 link $NETDEV type ipvlan mode l2
$ ip link set ipv1 netns n1
$ ip netns exec n1 ifconfig ipv1 2.2.2.100/24 up

$ tc qdisc add dev $NETDEV clsact
$ tc filter add dev $NETDEV egress protocol ip prio 1 \
        flower skip_hw src_ip 2.2.2.100 action skbedit queue_mapping skbhash 2 6
$ tc qdisc add dev $NETDEV handle 1: root mq
$ tc qdisc add dev $NETDEV parent 1:1 handle 2: htb
$ tc class add dev $NETDEV parent 2: classid 2:1 htb rate 100kbit
$ tc class add dev $NETDEV parent 2: classid 2:2 htb rate 200kbit
$ tc qdisc add dev $NETDEV parent 1:2 tbf rate 100mbit burst 100mb latency 1
$ tc qdisc add dev $NETDEV parent 1:3 pfifo
$ tc qdisc add dev $NETDEV parent 1:4 pfifo
$ tc qdisc add dev $NETDEV parent 1:5 pfifo
$ tc qdisc add dev $NETDEV parent 1:6 pfifo
$ tc qdisc add dev $NETDEV parent 1:7 pfifo

$ ip netns exec n1 iperf3 -c 2.2.2.1 -i 1 -t 10 -P 10

pick txqueue from 2 - 6:
$ ethtool -S $NETDEV | grep -i tx_queue_[0-9]_bytes
     tx_queue_0_bytes: 42
     tx_queue_1_bytes: 0
     tx_queue_2_bytes: 11442586444
     tx_queue_3_bytes: 7383615334
     tx_queue_4_bytes: 3981365579
     tx_queue_5_bytes: 3983235051
     tx_queue_6_bytes: 6706236461
     tx_queue_7_bytes: 42
     tx_queue_8_bytes: 0
     tx_queue_9_bytes: 0

txqueues 2 - 6 are mapped to classid 1:3 - 1:7
$ tc -s class show dev $NETDEV
...
class mq 1:3 root leaf 8002:
 Sent 11949133672 bytes 7929798 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
class mq 1:4 root leaf 8003:
 Sent 7710449050 bytes 5117279 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
class mq 1:5 root leaf 8004:
 Sent 4157648675 bytes 2758990 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
class mq 1:6 root leaf 8005:
 Sent 4159632195 bytes 2759990 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
class mq 1:7 root leaf 8006:
 Sent 7003169603 bytes 4646912 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
...

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jonathan Lemon <jonathan.lemon@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexander Lobakin <alobakin@pm.me>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Talal Ahmad <talalahmad@google.com>
Cc: Kevin Hao <haokexin@gmail.com>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Antoine Tenart <atenart@kernel.org>
Cc: Wei Wang <weiwan@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>