switchdev: add IPv4 routing offload

From: Scott Feldman <[email protected]>

v4:

- Add NETIF_F_NETNS_LOCAL to rocker port feature list to keep rocker ports in the default netns. Rocker hardware can't be partitioned to support multiple namespaces, currently. It would be interesting to add netns support to rocker device by basically adding another match field to each table to match on some unique netns ID, with a port knowing it's netns ID. Future work TDB.
- Up-level the RTNH_F_EXTERNAL marking of routes installed to offload device from driver to switchdev common code. Now driver can't skip routes. Either it can install the route or it cannot. Yes or No. If no on any route, all offloading is aborted by removing routes from offload device and setting ipv4.fib_offload_disabled so no more routes can be offloaded. This is harsh, but it's our starting point. We can refine the policies in follow-up work.
- Add new net.ipv4.fib_offload_disabled bool that is set if anything goes wrong with route offloading. We can refine this later to make the setting per-device or per-device-port-netdev, but let's start here simple and refine in follow-up work.
- Rebase against Alex's latest FIB changes. I think I did everything correctly, and didn't run into any issues with testing, but I'd like Alex to look over the changes and maybe follow-up with any cleanups.

v3:

Changes based on v2 review comments:

- Move check for custom rules up earlier in patch set, to keep git bisect safe.
- Simplify the route add/modify failure handling to simple try until failure, and then on failure, undo everything. The switchdev driver will return err when route can normally be installed to device, but the install fails for one reason or another (no space left on device, etc). If a failure happens, uninstall all routes from the device, punting forwarding for all routes back to the kernel.
- Scan route's full nexthop list, ensuring all nexthop devs belong to the same switchdev device, otherwise don't try to install route to device.

v2:

Changes based on v1 review comments and discussions at netconf:

- Allow route modification, but use same ndo op used for adding route. Driver/device is expected to modify route in-place, if it can, to avoid interruption of service.
- Add new RTNH_F_EXTERNAL flag to mark FIB entries offloaded externally.
- Don't offload routes if using custom IP rules. If routes are already offloaded, and custom IP rules are turned on, flush routes from offload device. (Offloaded routes are marked with RTNH_F_EXTERNAL).
- Use kernel's neigh resolution code to resolve route's nexthops' neigh MAC addrs. (Thanks davem, works great!).
- Use fib->fib_priority in rocker driver to give priorities to routes in OF-DPA unicast route table.

v1:

This patch set adds L3 routing offload support for IPv4 routes. The idea is to mirror routes installed in the kernel's FIB down to a hardware switch device to offload the data forwarding path for L3. Only the data forwarding path is intercepted. Control and management of the kernel's FIB remains with the kernel.

Scott Feldman (8):
rtnetlink: add RTNH_F_EXTERNAL flag for fib offload
netdevice: add IPv4 fib add/del ops
switchdev: add IPv4 fib ndo ops wrappers
switchdev: don't support custom ip rules, for now
switchdev: implement IPv4 fib ndo wrappers
ipv4: add net bool fib_offload_disabled
fib: hook IPv4 fib for hardware offload
rocker: implement IPv4 fib offloading

 drivers/net/ethernet/rocker/rocker.c |  483 ++++++++++++++++++++++++++++++----
 include/linux/netdevice.h            |   22 ++
 include/net/ip_fib.h                 |    2 +
 include/net/netns/ipv4.h             |    1 +
 include/net/switchdev.h              |   24 ++
 include/uapi/linux/rtnetlink.h       |    1 +
 net/ipv4/fib_frontend.c              |   13 +
 net/ipv4/fib_rules.c                 |    3 +
 net/ipv4/fib_trie.c                  |   92 ++++++-
 net/switchdev/switchdev.c            |  161 ++++++++++++
 10 files changed, 754 insertions(+), 48 deletions(-)

1.7.10.4