connect-scan: raw non-blocking connect() + poll(POLLOUT) + SO_ERROR via std.os.linux (std.Io.net connect-with-timeout is unimplemented in 0.16); own sized std.Io.Threaded with N io.async workers off a mutex+token-bucket dispenser; --backend connect / --connect, --concurrency, --connect-timeout.
cloud/VM detection: two-socket AF_PACKET self-probe (send on one, observe the tagged frame on a second - single-socket cannot see its own send); --backend auto checks CAP_NET_RAW + egress and auto-falls-back to connect with a notice; forced raw backend disables fallback and hard-fails; zero-response raw scan hints --connect.
raw IPv6 SYN: packet.Addr union result + RFC5952 v6 render; Ipv6Hdr + pseudoChecksum6/tcpChecksum6; 128-bit SipHash cookie (generate6/seq6); parseIpv6, resolveSrcIp6 (/proc/net/if_inet6), defaultGateway6 (/proc/net/ipv6_route); Engine6 (bounded prefix, RFC6890 reserved floor, ::/0 reject, host cap); SynTemplate6; classifyTcp6 + ICMPv6 type1; ndp.zig NDP neighbor resolution; runV6Scan dispatch; connect-path v6 rides the connect engine. v6 scope = TCP SYN.
240 tests Debug+ReleaseSafe (-Dxdp on/off); KAT + two-namespace netns e2e proven on the wire; two read-only audits, 0 Critical/High/Medium, all findings fixed in-phase.
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