PACKET_TX_RING (PACKET_MMAP, TPACKET_V2) over AF_PACKET with
PACKET_QDISC_BYPASS: socket + version + TX_RING setsockopt + mmap'd ring,
errno-gated, fail-closed on missing CAP_NET_RAW. ratelimit.zig integer
token bucket (banked-nanoseconds, no float, saturating, exact KATs).
template.zig SYN frame template: stamp dst IP/port + SipHash seq, recompute
IP + TCP checksums (reuses the M1 RFC 1071 + cookie code, both self-verify).
afpacket.zig pure Ring slot bookkeeping (inline tpacket2_hdr, comptime size
assert, reserve/fill/atomic-status, self-defending bounds, kernel-drain
reuse) split from the privileged Backend so the hot-path accounting is
unit-tested over an in-process buffer. tx.zig transmit engine generic over
an injected Sink + Clock: the M2 cyclic-group bijection is proven to survive
stamp -> ratelimit -> submit end-to-end via a fake sink + fake clock.
Privileged tx subcommand for on-hardware benchmarking (setcap + tcpdump/perf).
Green Debug + ReleaseSafe, leak-free, 45/45 tests.
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