verbatim flag for dns resolution does not change order

[asbachb]

• Version: v8.9.3
• Platform: 4.14.5-1-ARCH deps: update openssl to 1.0.1j #1 SMP PREEMPT Sun Dec 10 14:50:30 UTC 2017 x86_64 GNU/Linux
• Subsystem: dns

I currently have some issues with dual stack ipv6 resolution. The nodejs dns module returns ipv4 address instead of expected ipv6.

I saw there was a PR which introduced a verbatim flag: #14731

Based on the test (https://github.com/nodejs/node/pull/14731/files#diff-91621d3f4af56103203147a5cc370565) I tried to do some test code to validate if it's doing what I expect: Order the ipv6 before the ipv4 which was not the case:

const domain = 'google.com'

const cares = process.binding('cares_wrap');
const req1 = new cares.GetAddrInfoReqWrap();

dns(false);
dns(true);

function dns(verbatim) {
  const req = new cares.GetAddrInfoReqWrap();
  cares.getaddrinfo(req, domain, 0, /* hints */ 0, /* verbatim */ verbatim);

  req.oncomplete = function(err, domains) {
    console.log('%s = ', domain, domains);
  };
}

output:

google.com =  [ '172.217.23.142', '2a00:1450:4001:81e::200e' ]
google.com =  [ '172.217.23.142', '2a00:1450:4001:81e::200e' ]

[cjihrig]

My understanding was that verbatim just means that the DNS results are not sorted. That doesn't guarantee that IPv6 will come first.

Side question: Why are you using process.binding() instead of dns.lookup()?

[asbachb]

I also had some windows test system which results in:

google.com =  [ '2a00:1450:4001:806::200e', '216.58.205.238' ]
google.com =  [ '2a00:1450:4001:806::200e', '216.58.205.238' ]

So I don't get when the verbatim flag is doing anything.

@cjihrig, Since dns.lookup didn't returned the expected result I dived a little bit deeper unto dns.js and saw that in my use case only the first result of getaddrinfo is used: https://github.com/nodejs/node/blob/master/lib/dns.js#L95-L104
So I wrote a test case based on process.binding().

[bnoordhuis]

So I don't get when the verbatim flag is doing anything.

verbatim does exactly what it says - when true, it returns the results as it receives them from the resolver. (I'm basically restating what Colin already said...)

If you only want IPv6 results, query for AAAA records. I'll close this out.

[asbachb]

Just to complete this one. I did the mistake to run this on the wrong machine. On a host with correct ipv6 configuration the test code results to:

google.com =  [ '216.58.204.142', '2a00:1450:4007:812::200e' ]
google.com =  [ '2a00:1450:4007:812::200e', '216.58.204.142' ]