Codex Notes

Network Direct Dial

Findings:

HBP RPTO options are variable-length in DMRGateway and null-padded options are already trimmed in FreeDMR.
DMRGateway bounds normal Homebrew DMRD packets to fixed length and uses a 300-byte stack buffer for outbound RPTO; a 255-byte receive limit in FreeDMR is conservative and compatible.
FreeDMR can implement repeater-ID network direct dial without a new packet forwarding path by activating an existing #<tg> dial route and reusing the current TG9 rewrite logic.
FreeDMR1 still treats HBP SLOTS as repeater-advertised metadata from the RPTC config packet or legacy PEER config. It is not currently a master-side routing policy knob for dynamic/dial behavior.

Assumptions:

NETWORK_DIRECT_DIAL_SLOT=0 means disabled; 1 presents TG9 TS1; 2 presents TG9 TS2 for DMO/simplex clients.
Network direct dial is client/session-overridable through OPTIONS; the compact alias is NDD_SLOT.
RF-originated traffic must not activate network direct dial.
Invalid NETWORK_DIRECT_DIAL_SLOT values in config should fall back to 0 and log a warning; invalid OPTIONS values should leave the current session value unchanged.

Unresolved questions:

Whether to add a later local CW N notification for blocked network direct dial attempts.
Whether a broader HBP bounds-validation pass should reject all non-exact DMRD lengths rather than only guarding short packets.
Whether FreeDMR2 should promote HBP SLOTS/DMO capability into an explicit access-session capability model. FreeDMR1 should not infer this for network direct dial.

Protocol-sensitive areas:

Network direct dial is a narrow exception to the normal rule that network audio does not change local RF-facing dial state.
It must not override active or hangtime user-selected dial-a-TG state.
It must preserve existing packet rewrite boundaries by using the established TG9 reflector bridge path.

Inferred invariants:

General private voice routing remains disabled.
Repeater/client-directed group-call access is allowed only when explicitly configured and the selected RF slot is idle.
Overlength OPTIONS should be acknowledged but ignored to avoid client reconnect loops while protecting parser state.