In message <4B6B66FF.50108@spaghetti.zurich.ibm.com>, Jeroen Massar writes:

Richard E. Brown wrote:

...

Folks, =20 My company, Dartware, have derived a regex for testing whether an IPv6 address is correct. I've posted it in my blog: =20 http://intermapper.ning.com/profiles/blogs/a-regular-expression-for= -ipv6 =20 =20 This has links to the regular expression, a (Perl) program that tests various correct and malformed addresses, and a Ruby implementation of the same.

You know, link local addresses (fe80::/10) are quite useless without specifying the zone of that address. See section 11 of RFC4007.

The only proper way of "testing" if an address is a valid IPv6 address is to feed it to getaddrinfo() and then use it through that API. Yes, you can make some assumptions, but it has shown that people assuming that everything stayed under 2001::/16 also got it wrong at one point in time. Thus just feed it to getaddrinfo() if you really need it.

Greets, Jeroen

And now for the trick question. Is ::ffff:077.077.077.077 a legal mapped address and if it, does it match 077.077.077.077? Mark -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@isc.org

In message <4B6B7185.2080708@spaghetti.zurich.ibm.com>, Jeroen Massar writes:

Mark Andrews wrote: [..]

...

And now for the trick question. Is ::ffff:077.077.077.077 a legal mapped address and if it, does it match 077.077.077.077?

::ffff:0:0:0:0/96 should never ever be shown to a user, as it is confusing (is it IPv6 or IPv4?) and does not make sense at all. As such whatever one thinks of it, it is "illegal" in that context.

Internally inside a program though using a 128bit sequence of memory is of course a great way to store both IPv6 and IPv4 addresses in one structure and that is where the ::ffff:0:0:0:0::/96 format is very useful and intended for. Of course still the representation to the user of addresses stored that way would be 77.77.77.77 (and thus an IPv4 address and not IPv6) even though internally it is written as an IPv6 address.

You missed the point 077 is octal and 077.077.077.077 is 63.63.63.63 in the IPv4 address whereas it is decimal dotted quad in a mapped address *if* zero padded decimal dotted quad is legal in a IPv6 text form.

As that usage is internal, you don't need any validation of the format as the input will be either an IPv6 or IPv4 address without any of the compatibility stuff, thus one does not need to handle it anyway.

Of course, there should be only limited places where a user can enter or see IP addresses in the first place. There is this great thing called DNS which is what most people should be using.

Greets, Jeroen

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--------------enig57675C04A65E0982D8079586-- -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@isc.org

On Fri, Feb 5, 2010 at 12:15 AM, <sthaug@nethelp.no> wrote:

...

...

And now for the trick question.  Is ::ffff:077.077.077.077 a legal mapped address and if it, does it match 077.077.077.077?

Wasn't there an internet draft on that subject, recently? http://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-04 077.077.077.077 is equivalent to 77.77.77.77 if valid at all RFC 4038 is very clear that the text representation of a mapped IPv4 address is Base 10. http://tools.ietf.org/html/rfc4038#section-5.1 This is a bit like asking if "::ffff:10.1.2" is a valid IP address though. And is it the same as the ip address "10.1.2" ? (Which of course expands to 10.1.0.2, on common implementations of inet_pton, inet_aton, and getaddrinfo) Or ::ffff:0xA010002 I would say these are perfectly valid _shorthands_ and abbreviations for entering an IP address, which may be provided by some systems, but that they are non-canonical text representations for displaying publishing or sharing IP addresses. -- -J

I Just Don't Know What To Do With Myself ----- Original Message ---- From: Jeroen Massar <jeroen@unfix.org> To: Mark Andrews <marka@isc.org> Cc: nanog@nanog.org; Richard E. Brown <Richard.E.Brown@dartware.com> Sent: Fri, February 5, 2010 1:16:53 AM Subject: Re: Regular Expression for IPv6 addresses Mark Andrews wrote: [..]

And now for the trick question. Is ::ffff:077.077.077.077 a legal mapped address and if it, does it match 077.077.077.077?

::ffff:0:0:0:0/96 should never ever be shown to a user, as it is confusing (is it IPv6 or IPv4?) and does not make sense at all. As such whatever one thinks of it, it is "illegal" in that context. Internally inside a program though using a 128bit sequence of memory is of course a great way to store both IPv6 and IPv4 addresses in one structure and that is where the ::ffff:0:0:0:0::/96 format is very useful and intended for. Of course still the representation to the user of addresses stored that way would be 77.77.77.77 (and thus an IPv4 address and not IPv6) even though internally it is written as an IPv6 address. As that usage is internal, you don't need any validation of the format as the input will be either an IPv6 or IPv4 address without any of the compatibility stuff, thus one does not need to handle it anyway. Of course, there should be only limited places where a user can enter or see IP addresses in the first place. There is this great thing called DNS which is what most people should be using. Greets, Jeroen

In message <alpine.DEB.1.10.1002091548170.25663@red.crap.retrofitta.se>, Thomas Habets writes:

On Fri, 5 Feb 2010, Mark Andrews wrote:

...

And now for the trick question. Is ::ffff:077.077.077.077 a legal mapped address and if it, does it match 077.077.077.077?

Forget IPv6. The first question is does 077.077.077.077 match 077.077.077.077 in IPv4?

I think you meant "does 077.077.077.077 match 77.77.77.77 in IPv4".

The answer is a long one full of different answers depending on who's doing the parsing (gethostbyname(), inet_aton(), inet_net_pton(), etc..) and on what OS. And also on many bugs.

Indeed. It's a minefield out there for application developers that want consistancy. Even when you develop your own some OS vendor will go and stuff it up on you.

And don't count on the documentation being right either, or parsers respecting standards (single unix or RFCs, or which one when they conflict). And don't expect an error code if you feed 080.080.080.080 into a parser, even one that *does* read it as octal.

Don't prefix IP (v4) address octets with zero wether you expect it to be treated as octal or not. Just don't. World of hurt and all that.

E.g.: http://kerneltrap.org/mailarchive/openbsd-bugs/2009/6/6/5882713/thread

We should all do like one vendor I've seen where you enter the IP (v4) address in binary... and then pad with zeroes to whatever size html form wanted. Yes, this decade.

--------- typedef struct me_s { char name[] = { "Thomas Habets" }; char email[] = { "thomas@habets.pp.se" }; char kernel[] = { "Linux" }; char *pgpKey[] = { "http://www.habets.pp.se/pubkey.txt" }; char pgp[] = { "A8A3 D1DD 4AE0 8467 7FDE 0945 286A E90A AD48 E854" }; char coolcmd[] = { "echo '. ./_&. ./_'>_;. ./_" }; } me_t; -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@isc.org