pub const REBIND_VALIDATION_PATH_ID: u8 = 255;Expand description
Reserved path_id for validating a passive NAT rebind (M-3).
A passive rebind (the peer’s source address changes without it calling
migrate()) keeps path_id = 0 — the implicit, permanently-Validated
handshake path. Because path 0 is always Validated, the path-id-gated
challenge logic would skip it and the new source would never be validated,
promoted, or used for the downstream direction (a stall). The server detects
the rebind by address (an AEAD-authenticated frame whose source differs
from the established peer) and challenges that candidate on this dedicated
reserved id, which the registry can take through Validating → Validated
independently of the always-Validated path 0.
This id is carved permanently out of the active-migration id space:
Session::next_migration_path_id never returns it (it wraps 254 → 1,
skipping both 0 and 255), so a client-driven migration and a passive
rebind can never share this registry slot.