Merge branch 'psp-add-support-for-dev-assoc-disassoc'

Wei Wang says:

====================
psp: Add support for dev-assoc/disassoc

The main purpose of this feature is to associate virtual devices like
veth or netkit with a real PSP device, so we could provide PSP
functionality to the application running with virtual devices.

A typical deployment that works with this feature is as follows:
     Host Namespace:
     psp_dev_local  ←──physically linked──→ psp_dev_peer
	  (PSP device)
	       │
	       │ BPF on psp_dev_local ingress: bpf_redirect_peer() to nk_guest
	       │
	  nk_host / veth_host
	       │
	       │ BPF on nk_host ingress: bpf_redirect_neigh() to psp_dev_local
	       │
      Guest Namespace (netns):
	       │
	  nk_guest / veth_guest
	  ★ PSP application run here

      Remote Namespace (_netns):
	  psp_dev_peer
	  ★ PSP server application runs here

Note:
The general requirement for this feature to work:
For PSP to work correctly, the egress device at validate_xmit_skb()
time must have psp_dev matching the association's psd. Any device
stacking or traffic redirection that changes the egress device will
cause either:
1. TX validation failure (SKB_DROP_REASON_PSP_OUTPUT) - fail-safe
2. RX policy failure after tx-assoc - packets without PSP extension
   are rejected by receiver expecting encrypted traffic

Here are a few examples that this feature would not work:
- Bonding with load balancing in round-robin, XOR, 802.3ad mode across
  multiple PSP devices, or mixed PSP and non-PSP devices
- Bonding with active-backup mode might work without PSP migration for
  failover case.
- ipvlan/macvlan in bridge mode would not work given packets are
  loopbacked locally without going through the PSP device.
====================

Link: https://patch.msgid.link/20260608233118.2694144-1-weibunny.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>