[PATCH net-next v4 00/14] net: mctp: Add support for gateway routing

[Jeremy Kerr <jk@codeconstruct.com.au>]

This series adds a gateway route type for the MCTP core, allowing
non-local EIDs as the match for a route.

Example setup using the mctp tools:

    mctp route add 9 via mctpi2c0
    mctp neigh add 9 dev mctpi2c0 lladdr 0x1d
    mctp route add 10 gw 9

- will route packets to eid 10 through mctpi2c0, using a dest lladdr
of 0x1d (ie, that of the directly-attached eid 9).

The core change to support this is the introduction of a struct
mctp_dst, which represents the result of a route lookup. Since this
involves a bit of surgery through the routing code, we add a few tests
along the way.

We're introducing an ABI change in the new RTM_{NEW,GET,DEL}ROUTE
netlink formats, with the support for a RTA_GATEWAY attribute. Because
we need a network ID specified to fully-qualify a gateway EID, the
RTA_GATEWAY attribute carries the (net, eid) tuple in full:

    struct mctp_fq_addr {
        unsigned int net;
        mctp_eid_t eid;
    }

Of course, any questions, comments etc are most welcome.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
---
Changes in v4:
- avoid vla detection from const array-size initialiser, reported by ktr
- Link to v3: https://lore.kernel.org/r/20250625-dev-forwarding-v3-0-2061bd3013b3@codeconstruct.com.au

Changes in v3:
- 02/14 (new): Reduce frame size for route_input_cloned_frag kunit test,
  preventing -Wframe-size-larger-than warnings
- Link to v2: https://lore.kernel.org/r/20250619-dev-forwarding-v2-0-3f81801b06c2@codeconstruct.com.au

Changes in v2:
- 12/13: prevent uninitialsed gateway variable in nlparse_common
- 13/13: make test data static
- commit message spelling fixes
- Link to v1: https://lore.kernel.org/r/20250611-dev-forwarding-v1-0-6b69b1feb37f@codeconstruct.com.au

---
Jeremy Kerr (14):
      net: mctp: don't use source cb data when forwarding, ensure pkt_type is set
      net: mctp: test: make cloned_frag buffers more appropriately-sized
      net: mctp: separate routing database from routing operations
      net: mctp: separate cb from direct-addressing routing
      net: mctp: test: Add an addressed device constructor
      net: mctp: test: Add extaddr routing output test
      net: mctp: test: move functions into utils.[ch]
      net: mctp: test: add sock test infrastructure
      net: mctp: test: Add initial socket tests
      net: mctp: pass net into route creation
      net: mctp: remove routes by netid, not by device
      net: mctp: allow NL parsing directly into a struct mctp_route
      net: mctp: add gateway routing support
      net: mctp: test: Add tests for gateway routes

 include/net/mctp.h         |  52 +++-
 include/uapi/linux/mctp.h  |   8 +
 net/mctp/af_mctp.c         |  62 ++---
 net/mctp/route.c           | 563 +++++++++++++++++++++++++++--------------
 net/mctp/test/route-test.c | 612 +++++++++++++++++++++++++++++----------------
 net/mctp/test/sock-test.c  | 229 +++++++++++++++++
 net/mctp/test/utils.c      | 196 ++++++++++++++-
 net/mctp/test/utils.h      |  44 ++++
 8 files changed, 1310 insertions(+), 456 deletions(-)
---
base-commit: 0097c4195b1d0ca57d15979626c769c74747b5a0
change-id: 20250520-dev-forwarding-0711973470bf

Best regards,
-- 
Jeremy Kerr <jk@codeconstruct.com.au>