[SR-Users] dns queries on ipv6 addresses

[Marius Zbihlei]

On 10/25/2012 05:33 PM, Alex Hermann wrote:
> On Thursday 25 October 2012, Juha Heinanen wrote:
>> 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.
> .
> .
Hello,

Didn't had time to check the RFCs (RFC 1123 is from 1989 so it might be 
updated), but from what I know the rule of the thumb (and inet_pton(3) 
is useful describing several cases where a string is considered an ip 
address):

- if a string can represent a 32-bit number (ipv4), or a 128 bit number 
(ipv6) than it represents and IP address of respective family (ping 
0xdeadbeef in console to see that 0xdeadbeef is a correct ip address).
-quad doted formats (decimal, octal or hexa) are allowed for IPv4 
(010.010.010.010 is actually 8.8.8.8)
-IPv6 addresses have several forms, eight groups or less, or the hybrid 
notation (e.g. ::FFFF:192.168.0.2)

inet_pton(3), inet_aton(3), inet_addr(3) only handle part of these 
types, the new resolver API getaddrinfo(3) handles all + a and quad-a 
DNS request.

I think we should handle all as well...

Cheers,
Marius

> .
> 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).
>
>


-- 
Zbihlei Marius

Head of
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