non operational question related to IP

Mon Nov 22 22:22:04 UTC 2010

On Mon, Nov 22, 2010 at 12:56:00PM -0700, Matlock, Kenneth L wrote:
> 'Octal' (Base-8) :)
> 
> The leading '0' is telling the box to interpret it as octal instead of
> decimal or hex.

My guess you're seeing an interface that uses inet_addr() instead
of inet_pton(); the latter is used more nowadays at it supports
both IPv4 and IPv6 addressing schemes.

Whereas I've seen this behavior with a lot of vendors, I'm tempted
to call it a bug:

  The Open Group Base Specifications Issue 6
  IEEE Std 1003.1, 2004 Edition

  http://www.opengroup.org/onlinepubs/009695399/functions/inet_ntop.html

  inet_pton():

  If the af argument of inet_pton() is AF_INET, the src string shall be in
  the standard IPv4 dotted-decimal form:

  ddd.ddd.ddd.ddd

  where "ddd" is a one to three digit decimal number between 0 and 255 (see
  inet_addr()).

No mention of dotted quad being anything other than 'decimal', much
less getting cute about guessing the radix.

The *BSD manpages for inet_pton() call out a similar constraint:

  http://www.freebsd.org/cgi/man.cgi?query=inet_aton&apropos=0&sektion=0&manpath=FreeBSD+8.1-RELEASE&format=html

  STANDARDS
     The inet_ntop() and inet_pton() functions conform to X/Open
     Networking Services Issue 5.2 (``XNS5.2'').  Note that inet_pton()
     does not accept 1-, 2-, or 3-part dotted addresses; all four
     parts must be specified and are interpreted only as decimal
     values.  This is a narrower input set than that accepted by
     inet_aton().

As does Linux():

  http://www.kernel.org/doc/man-pages/online/pages/man3/inet_pton.3.html

  AF_INET
      src points to a character string containing an IPv4 network
      address in dotted-decimal format, "ddd.ddd.ddd.ddd", ...

RFC 2553 also calls out the non-decimal interpretation as being
'non-standard':

  http://www.ietf.org/rfc/rfc2553.txt

  If the af argument is AF_INET, the function accepts a string in
  the standard IPv4 dotted-decimal form:

      ddd.ddd.ddd.ddd

   where ddd is a one to three digit decimal number between 0 and 255.
   Note that many implementations of the existing inet_addr() and
   inet_aton() functions accept nonstandard input: octal numbers,
   hexadecimal numbers, and fewer than four numbers.  inet_pton() does
   not accept these formats.

Etc.

I've never been happy with inconsistencies in serializing data structures...

> Ken Matlock
> Network Analyst
> Exempla Healthcare
> (303) 467-4671
> matlockk at exempla.org

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