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Re: [DNSOP] Re: getaddrinfo() and searching

2007-09-27 17:10:13

On 27-sep-2007, at 3:33, Mark Andrews wrote:

So your issue that the results are inconsistent is certainly real.

I'd say that the best way to avoid this is not having a search domain
at all, or at the very least not several.

    Which is a totally unreasonable suggestion.

It's not. Even without IPv6, having search domains means you can get  
unexpected results. If that's not acceptable, don't complain, but put  
a period behind your FQDNs.

        Please state were in RFC 952 a final period is legal in
        a hostname. 

        Remember applications take HOSTNAMES not DOMAIN NAMES.
        There are HOSTNAMES that you cannot store in the DNS.
        There are DOMAIN NAMES that are not legal HOSTNAMES.

    The problem here is not the search but different stoping
    critera depending apon the address families supported by
    the host or requested by the application.

    We wrote a API that failed to account for the usual use
    senario.  In fact the guidance in there is the direct
    opposite of what should be done with the usual use senario.

I thought the solution would be hard or would be suboptimal in the  
common case, but I think that doesn't have to be so.

In my example, MacOS would go through the search domains and keep  
going until it found AAAA records for IPv6 or IPv4+IPv6 applications  
(and presumably look for A records if there were no AAAA records and  
IPv4 was present/requested also).

So basically, both the "answers = 0, noerror" and "nxdomain"  
responses trigger trying the next search domain. If we change this to  
"answers = 0, noerror" means try the same FQDN again for an A record,  
and "nxdomain" means move on to the next search domain, the results  
for different permutations of IP version availability would all  
result in connecting to the same FQDN = the first one with an address  
that's compatible with current connectivity, rather than the first  
one with an AAAA record if there is IPv6 connectivity.

    I'm saying we should go back and fix the specification for
    getaddrinfo() so that it accounts for searching.

Volunteers...?

        If need be, yes.
 
    We should also add a AI_NOSEARCH flag so that searching is
    controlled directly rather than indirectly.

That's what the period terminating a domain name is for.

        Again you confuse domain names and hostname.
 
    I've set Reply-To to ipv6(_at_)ietf(_dot_)org as this is more approriate
    for 6man.

No, it's a DNS issue, so it should go to dnsop. dnsop people: see  
discussion between Mark, Keith and me that started under the subject  
"renumbering" on the ietf discussion list.

        I chose ipv6(_at_)ietf(_dot_)org (or it predecessor) because 
ipv6(_at_)ietf(_dot_)org
        was where getaddrinfo()s behaviour was spec'd out.  We need to
        at least give the 6man a chance to address it.
 
        Mark

Everyone: feel free to prune some lists when you respond.  :-)

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Mark Andrews, ISC
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