[PATCH net v3 0/6] amt: relay tunnel lifetime, validation and request-path hardening

[Omar Ramadan <omar@blockcast.net>]

Six fixes to the AMT relay data and control paths, found while adding an
IPv6 outer transport (that feature follows for net-next, rebased on this).
All are independent of the IPv6 work and belong in net with stable in mind.

1/6 is the most serious: a Membership Update can re-arm the gc timer of a
tunnel amt_tunnel_expire() is already freeing, firing a delayed_work in
freed memory.  2/6 and 3/6 close two input-validation holes (a gateway
Query/Data from 0.0.0.0 before a relay is learned; a 16-byte IPv6 literal
accepted into an IPv4 netlink attribute).  4/6-6/6 harden the relay's
tunnel table: key it on the (address, port) endpoint RFC 7450 defines,
surface silently-dropped pre-Query reports, and stop allocating tunnel
state for unauthenticated (spoofable) Requests, which closes a table-
exhaustion / ICMP-reflector / session-desync primitive and moves the
max_tunnels bound onto verified gateways.

Each patch carries a Fixes: tag.  Verified W=1 clean and with a
KASAN + lockdep + PROVE_RCU boot of the amt selftests, no splat, and
of amt.sh with max_tunnels 1, which keeps the tunnel table full while
the gateway keeps sending Requests.

v3:
- Add 1/6-3/6, found in review of v2 and of the net-next IPv6
  series [1]: the gc_wq re-arm use-after-free, and the IPv4 halves of
  two input-validation bugs.  The IPv6 series will be rebased on this.
- 4/6: do not count the invalid-MAC drop in rx_dropped; amt_rcv()
  already counts it.
- 5/6: commit message: the Query supplies the response MAC that the
  Update echoes, not the nonce.
- 6/6: keep three secrets so a response MAC outlives the advertised
  QQIC; cap the tunnels one source can hold in the locked re-check (a
  fixed limit, no new UAPI); when the table is full, answer a gateway
  that holds no tunnel with ICMP and no Query, so it rediscovers; seed
  the secret before the socket is created; refresh last_seen rather
  than re-arming gc_wq (see 1/6).
v2: https://lore.kernel.org/netdev/20261009201455.1904698-1-omar@blockcast.net/
v1: https://lore.kernel.org/netdev/20261008003606.3666617-1-omar@blockcast.net/

[1] https://lore.kernel.org/netdev/20261009122426.551178-1-omar@blockcast.net/

Omar Ramadan (6):
  amt: fix use-after-free when a Membership Update re-arms a freed tunnel
  amt: reject a gateway Query or Data from 0.0.0.0 before a relay is learned
  amt: reject an IPv6 address passed in an IPv4 address attribute
  amt: key relay tunnel state on the (address, port) endpoint, not the address
  amt: make pre-query report drops visible
  amt: do not create tunnel state for unauthenticated Requests