[wleeaf]

IPAddr.new and IPAddr#zone_id= only accept \w characters after %. So zone IDs for common interface names raise InvalidAddressError:

IPAddr.new("fe80::1%eth0.100")   # VLAN interface
IPAddr.new("fe80::1%br-lan")     # bridge, e.g. OpenWrt
# => IPAddr::InvalidAddressError: invalid address: fe80::1%br-lan

ip = IPAddr.new("fe80::1")
ip.zone_id = "%br-lan"
# => IPAddr::InvalidAddressError: invalid zone identifier for address

RFC 6874 (cited when zone IDs were added in #24) defines ZoneID = 1*( unreserved / pct-encoded ), where unreserved is ALPHA / DIGIT / "-" / "." / "_" / "~". Resolv::IPv6 in the resolv gem already accepts %[-0-9A-Za-z._~]+, and Python's ipaddress accepts these addresses too. This change uses the same character class in both places. Characters outside it, such as a space or /, are still rejected.

Tests: added cases to test_to_s_with_zone_id and test_zone_id. Both tests fail before the change (2 errors) and pass after it. bundle exec rake test: 41 tests, 607 assertions, 0 failures.

I compared IPAddr.new with Python's ipaddress on about 50k generated and mutated addresses. Apart from deliberate differences (bracketed addresses, address/mask forms, rejected zero-padded prefixes, mixed notation for ::ffff:0:0/96 in to_s), zone IDs like these were the only valid addresses IPAddr rejected. Python also accepts zone IDs containing : or a newline; this change still rejects those.

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[taketo1113]

Although RFC 6874 has been obsoleted by RFC 9844, RFC 9844 does not define which characters are allowed in a zone ID.
Since characters such as . and - are actually used in environments like OpenWrt, I think it is reasonable to base the allowed characters on unreserved, as referenced by RFC 6874.

References:

• RFC 6874: Section 2. Specification

  ZoneID = 1*( unreserved / pct-encoded )

• RFC 3986: Section 2.3. Unreserved Characters

  unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"