ip: nexthop: Support resilient groups

Support for resilient next-hop groups was recently accepted to Linux kernel[1]. Resilient next-hop groups add a layer of indirection between the SKB hash and the next hop. Thus the hash is used to reference a hash table bucket, which is then used to reference a particular next hop. This allows the system more flexibility when assigning SKB hash space to next hops. Previously, each next hop had to be assigned a continuous range of SKB hash space. With a hash table as an intermediate layer, it is possible to reassign next hops with a hash table bucket granularity. In turn, this mends issues with traffic flow redirection resulting from next hop removal or adjustments in next-hop weights.

In this patch set, introduce support for resilient next-hop groups to iproute2.

- Patch #1 brings include/uapi/linux/nexthop.h and /rtnetlink.h up to date.

- Patches #2 and #3 add new helpers that will be useful later.

- Patch #4 extends the ip/nexthop sub-tool to accept group type as a command line argument, and to dispatch based on the specified type.

- Patch #5 adds the support for resilient next-hop groups.

- Patch #6 adds the support for resilient next-hop group bucket interface.

To illustrate the usage, consider the following commands:

 # ip nexthop add id 1 via 192.0.2.2 dev dummy1
 # ip nexthop add id 2 via 192.0.2.3 dev dummy1
 # ip nexthop add id 10 group 1/2 type resilient \
	buckets 8 idle_timer 60 unbalanced_timer 300

The last command creates a resilient next-hop group. It will have 8 buckets, each bucket will be considered idle when no traffic hits it for at least 60 seconds, and if the table remains out of balance for 300 seconds, it will be forcefully brought into balance.

And this is how the next-hop group bucket interface looks:

 # ip nexthop bucket show id 10
 id 10 index 0 idle_time 5.59 nhid 1
 id 10 index 1 idle_time 5.59 nhid 1
 id 10 index 2 idle_time 8.74 nhid 2
 id 10 index 3 idle_time 8.74 nhid 2
 id 10 index 4 idle_time 8.74 nhid 1
 id 10 index 5 idle_time 8.74 nhid 1
 id 10 index 6 idle_time 8.74 nhid 1
 id 10 index 7 idle_time 8.74 nhid 1

[1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=2a0186a37700b0d5b8cc40be202a62af44f02fa2

v4:
- Patch #2:
- Make print_tv() take a const*.

v3:
- Add missing S-o-b's.

v2:
- Patch #4:
- Add a missing example command to commit message
- Mention in the man page that mpath is the default

Ido Schimmel (3):
nexthop: Add ability to specify group type
nexthop: Add support for resilient nexthop groups
nexthop: Add support for nexthop buckets

Petr Machata (3):
nexthop: Synchronize uAPI files
json_print: Add print_tv()
nexthop: Extract a helper to parse a NH ID

 include/json_print.h           |   1 +
 include/libnetlink.h           |   3 +
 include/uapi/linux/nexthop.h   |  47 +++-
 include/uapi/linux/rtnetlink.h |   7 +
 ip/ip_common.h                 |   1 +
 ip/ipmonitor.c                 |   6 +
 ip/ipnexthop.c                 | 451 ++++++++++++++++++++++++++++++++-
 lib/json_print.c               |  13 +
 lib/libnetlink.c               |  26 ++
 man/man8/ip-nexthop.8          | 113 ++++++++-
 10 files changed, 651 insertions(+), 17 deletions(-)

2.26.2