net: nexthop: Expose nexthop group HW stats to user space

Add netlink support for reading NH group hardware stats.

Stats collection is done through a new notifier,
NEXTHOP_EVENT_HW_STATS_REPORT_DELTA. Drivers that implement HW counters for
a given NH group are thereby asked to collect the stats and report back to
core by calling nh_grp_hw_stats_report_delta(). This is similar to what
netdevice L3 stats do.

Besides exposing number of packets that passed in the HW datapath, also
include information on whether any driver actually realizes the counters.
The core can tell based on whether it got any _report_delta() reports from
the drivers. This allows enabling the statistics at the group at any time,
with drivers opting into supporting them. This is also in line with what
netdevice L3 stats are doing.

So as not to waste time and space, tie the collection and reporting of HW
stats with a new op flag, NHA_OP_FLAG_DUMP_HW_STATS.

Co-developed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Kees Cook <keescook@chromium.org> # For the __counted_by bits
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: nexthop: Add ability to enable / disable hardware statistics

Add netlink support for enabling collection of HW statistics on nexthop
groups.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: nexthop: Expose nexthop group stats to user space

Add netlink support for reading NH group stats.

This data is only for statistics of the traffic in the SW datapath. HW
nexthop group statistics will be added in the following patches.

Emission of the stats is keyed to a new op_stats flag to avoid cluttering
the netlink message with stats if the user doesn't need them:
NHA_OP_FLAG_DUMP_STATS.

Co-developed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: nexthop: Add NHA_OP_FLAGS

In order to add per-nexthop statistics, but still not increase netlink
message size for consumers that do not care about them, there needs to be a
toggle through which the user indicates their desire to get the statistics.
To that end, add a new attribute, NHA_OP_FLAGS. The idea is to be able to
use the attribute for carrying of arbitrary operation-specific flags, i.e.
not make it specific for get / dump.

Add the new attribute to get and dump policies, but do not actually allow
any flags yet -- those will come later as the flags themselves are defined.
Add the necessary parsing code.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

nexthop: Add netlink defines and enumerators for resilient NH groups

- RTM_NEWNEXTHOP et.al. that handle resilient groups will have a new nested
attribute, NHA_RES_GROUP, whose elements are attributes NHA_RES_GROUP_*.

- RTM_NEWNEXTHOPBUCKET et.al. is a suite of new messages that will
currently serve only for dumping of individual buckets of resilient next
hop groups. For nexthop group buckets, these messages will carry a nested
attribute NHA_RES_BUCKET, whose elements are attributes NHA_RES_BUCKET_*.

There are several reasons why a new suite of messages is created for
nexthop buckets instead of overloading the information on the existing
RTM_{NEW,DEL,GET}NEXTHOP messages.

First, a nexthop group can contain a large number of nexthop buckets (4k
is not unheard of). This imposes limits on the amount of information that
can be encoded for each nexthop bucket given a netlink message is limited
to 64k bytes.

Second, while RTM_NEWNEXTHOPBUCKET is only used for notifications at
this point, in the future it can be extended to provide user space with
control over nexthop buckets configuration.

- The new group type is NEXTHOP_GRP_TYPE_RES. Note that nexthop code is
adjusted to bounce groups with that type for now.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

nexthop: support for fdb ecmp nexthops

This patch introduces ecmp nexthops and nexthop groups
for mac fdb entries. In subsequent patches this is used
by the vxlan driver fdb entries. The use case is
E-VPN multihoming [1,2,3] which requires bridged vxlan traffic
to be load balanced to remote switches (vteps) belonging to
the same multi-homed ethernet segment (This is analogous to
a multi-homed LAG but over vxlan).

Changes include new nexthop flag NHA_FDB for nexthops
referenced by fdb entries. These nexthops only have ip.
This patch includes appropriate checks to avoid routes
referencing such nexthops.

example:
$ip nexthop add id 12 via 172.16.1.2 fdb
$ip nexthop add id 13 via 172.16.1.3 fdb
$ip nexthop add id 102 group 12/13 fdb

$bridge fdb add 02:02:00:00:00:13 dev vxlan1000 nhid 101 self

[1] E-VPN https://tools.ietf.org/html/rfc7432
[2] E-VPN VxLAN: https://tools.ietf.org/html/rfc8365
[3] LPC talk with mention of nexthop groups for L2 ecmp
http://vger.kernel.org/lpc_net2018_talks/scaling_bridge_fdb_database_slidesV3.pdf

v4 - fixed uninitialized variable reported by kernel test robot
Reported-by: kernel test robot <rong.a.chen@intel.com>

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: nexthop uapi

New UAPI for nexthops as standalone objects:
- defines netlink ancillary header, struct nhmsg
- RTM commands for nexthop objects, RTM_*NEXTHOP,
- RTNLGRP for nexthop notifications, RTNLGRP_NEXTHOP,
- Attributes for creating nexthops, NHA_*
- Attribute for route specs to specify a nexthop by id, RTA_NH_ID.

The nexthop attributes and semantics follow the route and RTA ones for
device, gateway and lwt encap. Unique to nexthop objects are a blackhole
and a group which contains references to other nexthop objects. With the
exception of blackhole and group, nexthop objects MUST contain a device.
Gateway and encap are optional. Nexthop groups can only reference other
pre-existing nexthops by id. If the NHA_ID attribute is present that id
is used for the nexthop. If not specified, one is auto assigned.

Dump requests can include attributes:
- NHA_GROUPS to return only nexthop groups,
- NHA_MASTER to limit dumps to nexthops with devices enslaved to the
given master (e.g., VRF)
- NHA_OIF to limit dumps to nexthops using given device

nlmsg_route_perms in selinux code is updated for the new RTM comands.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>