classify.zig pure frame parser: SYN-ACK -> open, RST/ACK -> closed,
ICMP type-3 {1,2,3,9,10,13} -> filtered, every verdict gated on a
wrapping SipHash cookie re-check (ack == seq+1 for replies, inner seq
== cookie for ICMP) so spoofed/stale frames are dropped state-free;
byte-offset readInt parsing, fully length-guarded. dedup.zig power-of-2
open-addressed (ip,port) set, single-owned allocator, grows at load
factor with a bounded probe (never wedges). rx.zig receive engine
generic over an injected Source + Sink (proven over hand-built frames),
Io.Queue found-host handoff across producer/consumer fibers, and a
privileged AF_PACKET Receiver (poll-bounded drain with a hard deadline,
ignore-outgoing, EINTR-retry, errno-gated, fail-closed on missing
CAP_NET_RAW). scan subcommand shares one per-run cookie across the TX
template + RX validation; consumer uses a dedicated allocator to keep
the producer/consumer fibers race-free. netutil.zig factors the shared
arg-parse/iface-resolve helpers out of txcmd. Proven end-to-end with a
live SYN scan inside a unshare -r -n netns over a veth pair
(open/closed against a real listener, dedup verified). Green Debug +
ReleaseSafe, leak-free, 61 unit tests.
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