25 Oct
2012
25 Oct
'12
10:51 a.m.
On 10/25/12 4:33 PM, Alex Hermann wrote:
On Thursday 25 October 2012, Juha Heinanen wrote:
It does not if it is ipv4 and
the target would be an A record, as well
as when it is ipv6 and the target would be an AAAA record.
The thing here relates to disabling ipv6, resulting in only possible
target A record, for which ipv6 does not match an ipv4 format, resulting
in using the ipv6 for querying an A record.
So some extra validation has to be added when one address family is
disabled by config, but such addresses can actually occur.
Perhaps what Juha suggested with detecting an invalid hostname is the
best, avoiding querying for broken dns tokens.
Cheers,
Daniel
an ipv6 address can thus never be a valid domain
name. an ipv4 address,
on the other hand, is syntactically valid domain name and perhaps
someone has populated their local name server with such names.
But the application
(kamailio) should not attempt a DNS lookup if the hostname
is an IP(v4/v6) address, from RFC1123, section 2.1:
========
Whenever a user inputs the identity of an Internet host, it SHOULD
be possible to enter either (1) a host domain name or (2) an IP
address in dotted-decimal ("#.#.#.#") form. The host SHOULD check
the string syntactically for a dotted-decimal number before
looking it up in the Domain Name System.
.
.
.
However, a valid host name can never
have the dotted-decimal form #.#.#.#, since at least the
highest-level component label will be alphabetic.
========
It would be nice if Kamailio refuses to lookup both IPv4 and IPv6 addresses
independent of the address family of listening sockets (see my emails about
dispatcher and IPv6, where DNS lookups on IPv6 addressed are only skipped if
Kamailio is listening on an IPv6 address).
--
Daniel-Constantin Mierla - http://www.asipto.com
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio Advanced Training, Berlin, Nov 5-8, 2012 - http://asipto.com/u/kat
Kamailio Advanced Training, Miami, USA, Nov 12-14, 2012 - http://asipto.com/u/katu