Maximum number of in-flight (incomplete) assemblies tracked at once. Caps
the memory an attacker can pin by spraying chunks across many distinct
(session_id, packet_id) keys without ever completing a packet. The
worst-case resident memory is therefore bounded by
MAX_CONCURRENT_ASSEMBLIES * MAX_REASSEMBLED_LEN (≈ 64 MiB).
Largest logical packet the assembler will reassemble. Bounds the memory a
single (session_id, packet_id) assembly can pin: at most
MAX_TOTAL_CHUNKS chunks of MAX_UDP_PAYLOAD bytes each.
Maximum fragments per logical packet, derived from the reassembled-size cap.
A frame declaring more than this (up to the u16::MAX the wire allows) is
dropped, so an attacker cannot force a 65 535-entry chunk map.