Looking for DNS/Operational experience

[Chris Caputo]

On Fri, 8 May 2009, Steve Bertrand wrote:
> - any UNIX command-line tool to convert a compressed v6 addr into a
> reverse DNS entry

Not a complete command-line tool, but one could easily be made using this 
function I wrote...  (below)

(Have your main() function call inet_pton() and then call this function 
with the result, along with the appropriate nibblecount.)

Let me know if it would be helpful to the community for me to write the 
command-line tool for this.  (You'll have to suggest the clever name for 
it though.)

Chris

/*
  Takes a in6_addr and returns a string in reverse DNS zone file format,
  for the number of nibbles needed for the DNS zone.

  So "2001:0DB8::1" in an in6_addr with a nibble count of 20 will return:

    "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0"
*/
char *
myV6rDNS(struct in6_addr *in6,
         int nibblecount)
{
  static char buf[32 * 2 + 1];  // 32 nibbles, 32 '.'s, 1 terminator
  char hex[] = "0123456789abcdef";
  int i = 0;
  int nibble = 0;

  memset(buf, 0, sizeof(buf));

  while (nibble < nibblecount)
    {
      if (0 != i)
        buf[i++] = '.';

      if (nibble % 2)
        buf[i++] = hex[in6->s6_addr[15 - nibble / 2] / 16];
      else
        buf[i++] = hex[in6->s6_addr[15 - nibble / 2] % 16];

      nibble++;
    }

  return buf;
}