app connector packets
We introduce the Conn25PacketHooks interface to be used as a nil-able
field in userspaceEngine. The engine then plumbs through the functions
to the corresponding tstun.Wrapper intercepts.
The new intercepts run pre-filter when egressing toward WireGuard,
and post-filter when ingressing from WireGuard. This is preserve the
design invariant that the filter recognizes the traffic as interesting
app connector traffic.
This commit does not plumb through implementation of the interface, so
should be a functional no-op.
Fixestailscale/corp#35985
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
5a5572e48a