Add PacketMatch hooks to the packet filter, allowing extensions to
customize filtering decisions:
- IngressAllowHooks: checked in RunIn after pre() but before the
standard runIn4/runIn6 match rules. Hooks can accept packets to
destinations outside the local IP set. First match wins; the
returned why string is used for logging.
- LinkLocalAllowHooks: checked inside pre() for both ingress and
egress, providing exceptions to the default policy of dropping
link-local unicast packets. First match wins. The GCP DNS address
(169.254.169.254) is always allowed regardless of hooks.
PacketMatch returns (match bool, why string) to provide a log reason
consistent with the existing filter functions.
Hooks are registered via the new FilterHooks struct in ipnext.Hooks
and wired through to filter.Filter in LocalBackend.updateFilterLocked.
Fixestailscale/corp#35989Fixestailscale/corp#37207
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Michael Ben-Ami
811fe7d18e