v22.0.1

What's Changed

Breaking changes

• setTTL removed — MulticastSocket.setTTL(ttl) is gone. The library hardcodes IP_MULTICAST_TTL = 255 at bind so the RFC 6762 §11 outbound invariant cannot be silently broken at runtime.

RFC 6762 §11

• Multicast-destination exemption now honored — Packets received on the shared multicast socket are accepted regardless of source IP, per RFC 6762 §11's carve-out for multicast-destination packets. This fixes cross-subnet-overlay multicast traffic that was previously being dropped. Packets received on per-interface unicast sockets still receive the source-subnet check.
• README §RFC 6762 §11 rewritten — Crisp SHOULD/MUST mapping, multicast-destination exemption documented, explicit note that the IP_RECVTTL gap in Node's dgram is upstream and not worked around from userspace.

Input validation

• multicastGroup validated upfront — A non-multicast address now throws multicastGroup X is not a multicast address before any socket allocation, instead of surfacing as a late addMembership EADDRNOTAVAIL. New is_multicast helper is exported from @gibme/multicast/helpers.
• compare_IP_addresses throws on mixed-family inputs — Previously returned a meaningless ordering when comparing IPv4 to IPv6.

IPv6 zone-id handling

• fromSelf is now zone-id-tolerant — Node 22's dgram delivers IPv6 link-local rinfo.address with a %iface suffix; the prior exact-string match missed it. dispatch_message now strips the suffix before comparing against bound addresses.
• srcAddress and host normalized — The same zone-id strip is applied at the three sites that match against bound addresses (create() host check, send() unicast-path, send() multicast-path).

Helpers

• get_addresses dedup fixed — Was [...new Set(addresses)] which deduped by object reference (a no-op for freshly-constructed instances); now a Map keyed by .address string.
• get_addresses requires addr.cidr — Throws if os.networkInterfaces() returns an entry without it. Dead-code netmask_to_prefix fallback (IPv4-only dotted-decimal parser) removed.
• is_on_local_link IPv6 link-local comment — Rewritten to acknowledge both RFC 4291 §2.4 (FE80::/10 reserved prefix) and §2.5.6 (link-local format requires middle 54 bits zero), and explain why the wider /10 check is used for inbound filtering.

Documentation

• JSDoc on send() and Send.Options.useMulticastSocket — Concurrency note: combining useMulticastSocket: true with srcAddress mutates per-socket state on the shared multicast socket via setMulticastInterface. Concurrent calls race; serialize them in the caller, or use the default per-interface unicast path (race-free).
• JSDoc on setMulticastLoopback — Explains that it only mutates IP_MULTICAST_LOOP on the shared multicast socket and that the authoritative user-visible loopback gate is the check inside dispatch_message.

Tests

101/101 pass. Added 8 regression tests under a new input validation and dispatch hardening block covering all of the above.

Full Changelog: v22.0.0...v22.0.1