On 11/20/2013 4:44 AM, Rob wrote:
Brian Utterback <[email protected]> wrote:
On 11/19/2013 3:40 PM, Danny Mayer wrote:
You should not be using literal IP addresses of either flavor without
also setting the AI_NUMERICHOST flag otherwise it tries to do a DNS
lookup. That's poorly written code otherwise.
Danny
Not so. The getaddrinfo function will recognize literal addresses and
merely convert them. The point is that for something like ssh or any
other network utility, the user is supposed to give a hostname, but in
virtually all cases you can give a literal address and the application
does not have to treat it differently. If you read the ipng mailing
list, you will see that they were trying to make the whole process of
writing a network application simpler, with getaddrinfo doing the heavy
lifting for all of the major cases. At the same time they were trying to
allow applications to work on either IPv4 or IPv6 systems without
changing them, or dual stack or any combination. But no matter what they
did there were edge cases that needed to work differently.
Brian Utterback
Well most of it was successfull, I converted an application from the
old functions to getaddrinfo/getnameinfo etc, and it really is more
convenient to program for.
However, what I don't understand is why an IPv6 address does not fit
into a struct sockaddr, and why this fact is so badly documented.
It took me a lot of time to find why my queried IPv6 addresses were
truncated.
It is a little tricky to be sure. Part of it was backwards compatibility
and history, part of it was providing the proper abstractions. The root
cause of course is that IPv6 addresses are longer than IPv4 addresses.
If you use them properly, you should never have a problem with
truncation though. You would have to be trying to put a IPv6 address
into a IPv4 sockaddr for that to happen.
Brian Utterback
_______________________________________________
questions mailing list
[email protected]
http://lists.ntp.org/listinfo/questions
