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From: Karl Auer <kauer@biplane.com.au> To: nanog@nanog.org Date: Fri, 02 Nov 2012 10:52:10 +1100 In-Reply-To: <B054B0DE-9D2F-4AD1-BE75-2DE89CA0A1B8@delong.com> Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org --=-Sm+N8xUSds63WZ8YzmfP Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable On Thu, 2012-11-01 at 07:07 -0700, Owen DeLong wrote: > I agree with you that we shouldn't introduce partially decimal format, but I > don't see why you say IPv6 addresses are difficult to parse. They are not simple to parse, but not particularly difficult either. > 1. Tokenize (on : boundaries). > 2. If n(tokens) < 8, expand null token to 9-n tokens. It's a bit harder than that. You need to deal with the positioning of the "::", which may be at the beginning or end. Scope identifiers need to be handled. On output, you need to handle the requirements of RFC 5952. > You really shouldn't need to parse [mapped addresses] and it's perfectly valid > to reject them as invalid input. No, it's not OK to reject them. You can't just say they are invalid, they are not. > Finally, at this point, if you're feeling like you have to write your own IP address parser, > you're probably doing something wrong. PLEASE PLEASE PLEASE use the standard > libraries whenever possible. Definitely oh very yes! That said, I have had to write my own three times now, because of errors or inadequacies in the existing parsers, and I can confidently say it is slightly tricky, but not hard. The key, the essential and vital thing, is to unit test that sucker until it is gasping and limp. > There are similar library functions for virtually every other language at this point as well. Java's is broken, for a start. I have had to replace it for literals, because it doesn't compress for output, and because it treats a mapped IPv4 address as an IPv4 address! It's also hard to do some operations on InetAddress objects. I still use InetAddress where actual names are concerned, so as not to duplicate the Java DNS functionality. Unfortunately Java appears to not properly prefer IPv6 addresses. There is allegedly a system property to control that, but it is either documented incorrectly or just doesn't work. Regards, K. --=20 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Karl Auer (kauer@biplane.com.au) http://www.biplane.com.au/kauer http://www.biplane.com.au/blog GPG fingerprint: AE1D 4868 6420 AD9A A698 5251 1699 7B78 4EEE 6017 Old fingerprint: DA41 51B1 1481 16E1 F7E2 B2E9 3007 14ED 5736 F687 --=-Sm+N8xUSds63WZ8YzmfP Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iF4EABEIAAYFAlCTCyoACgkQFpl7eE7uYBck4gD/RGqXvyOsW7Ayh35n1kRgOoNp pEAGM/LNMPeiDt7bmL0BAI3kq1SmWHGKGihbsc/hAfJ1zDDco0cTso1EDA6nAc03 =vgP1 -----END PGP SIGNATURE----- --=-Sm+N8xUSds63WZ8YzmfP--
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