net/sched: allow flower to match tunnel options

Allow matching on options in Geneve tunnel headers.
This makes use of existing tunnel metadata support.

The options can be described in the form
CLASS:TYPE:DATA/CLASS_MASK:TYPE_MASK:DATA_MASK, where CLASS is
represented as a 16bit hexadecimal value, TYPE as an 8bit
hexadecimal value and DATA as a variable length hexadecimal value.

e.g.
 # ip link add name geneve0 type geneve dstport 0 external
 # tc qdisc add dev geneve0 ingress
 # tc filter add dev geneve0 protocol ip parent ffff: \
     flower \
       enc_src_ip 10.0.99.192 \
       enc_dst_ip 10.0.99.193 \
       enc_key_id 11 \
       geneve_opts 0102:80:1122334421314151/ffff:ff:ffffffffffffffff \
       ip_proto udp \
       action mirred egress redirect dev eth1

This patch adds support for matching Geneve options in the order
supplied by the user. This leads to an efficient implementation in
the software datapath (and in our opinion hardware datapaths that
offload this feature). It is also compatible with Geneve options
matching provided by the Open vSwitch kernel datapath which is
relevant here as the Flower classifier may be used as a mechanism
to program flows into hardware as a form of Open vSwitch datapath
offload (sometimes referred to as OVS-TC). The netlink
Kernel/Userspace API may be extended, for example by adding a flag,
if other matching options are desired, for example matching given
options in any order. This would require an implementation in the
TC software datapath. And be done in a way that drivers that
facilitate offload of the Flower classifier can reject or accept
such flows based on hardware datapath capabilities.

This approach was discussed and agreed on at Netconf 2017 in Seoul.

Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>