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dns: make dns.setServers support customized port #13723

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b5b28e0
dns: make `dns.setServers` support customized port
XadillaX Jun 16, 2017
92f8619
update the test cases and documentation
XadillaX Jun 16, 2017
41da7fa
update after reviewing
XadillaX Jun 16, 2017
b5f8bba
make 53 be const
XadillaX Jun 19, 2017
c8152ac
fix typo
XadillaX Jun 19, 2017
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update after reviewing
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@XadillaX
XadillaX committed Jun 16, 2017
commit 41da7fac40e932bc9a4c95df9fd5f4df797c5e4a
16 changes: 9 additions & 7 deletions doc/api/dns.md
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Expand Up @@ -59,12 +59,13 @@ the [Implementation considerations section][] for more information.
added: v0.11.3
-->

Returns an array of IP address and port strings that are being used for name
resolution, splited with `:`. If a server uses a default DNS server port, the
port part will be ignored in the result.
Returns an array of IP address strings, formatted according to [rfc3986][],
that are currently configured for DNS resolution. A string will include a port
section if a custom port is used.

eg.

<!-- eslint-disable -->
```js
[
'4.4.4.4',
Expand Down Expand Up @@ -494,11 +495,11 @@ one of the [DNS error codes][].
<!-- YAML
added: v0.11.3
-->
- `servers` {string[]}
- `servers` {string[]} array of [rfc3986][] formatted addresses

Sets the IP addresses and port of the servers to be used when resolving. The
`servers` argument is an array of IPv4 or IPv6 addresses. If the port of a
server is the default DNS server port, this part can be ignored in the string.
Sets the IP address and port of servers to be used when performing DNS
resolution. The `servers` argument is an array of [rfc3986][] formatted
addresses. If the port is the IANA default DNS port (53) it can be omitted.

eg.

Expand Down Expand Up @@ -605,3 +606,4 @@ uses. For instance, _they do not use the configuration from `/etc/hosts`_.
[supported `getaddrinfo` flags]: #dns_supported_getaddrinfo_flags
[the official libuv documentation]: http://docs.libuv.org/en/latest/threadpool.html
[`util.promisify()`]: util.html#util_util_promisify_original
[rfc3986]: https://tools.ietf.org/html/rfc3986#section-3.2.2
18 changes: 7 additions & 11 deletions lib/dns.js
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Expand Up @@ -305,8 +305,8 @@ function getServers() {
return ret.map((val) => {
if (!val[1] || val[1] === 53) return val[0];
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@refack refack Jun 19, 2017

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I just noticed this, IMHO we should format IPv6 with [], so need to move the const host up:
e.g.

return ret.map(([host, port]) => {
  if (isIP(host) === 6) host = `[${host}]`;
  return (!port || port === 53) host : `${host}:${port}`;
}

But that will make this semver-major (since till now IPv6 would be represented without [])

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@refack refack Jun 19, 2017 •
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Fix this in a future PR.
Ref: #13795

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@cjihrig cjihrig Jun 19, 2017

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Can you put the 53 into a constant. It's used a few times throughout.

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@refack refack Jun 19, 2017 •
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Suggestion: IANA_DNS_PORT


const ipVersion = isIP(val[0]);
return ipVersion === 6 ? `[${val[0]}]:${val[1]}` : `${val[0]}:${val[1]}`;
const host = isIP(val[0]) === 6 ? `[${val[0]}]` : val[0];
return `${host}:${val[1]}`;
});
}

Expand All @@ -317,7 +317,7 @@ function setServers(servers) {
const orig = cares.getServers();
const newSet = [];
const IPv6RE = /\[(.*)\]/;
const addrSplitRE = /:(\d+)$/;
const addrSplitRE = /(^.+?)(?::(\d+))?$/;
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@jasnell jasnell Jun 19, 2017

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another possible way to handle this that may provide more robust and consistent handling of the address and port would be to leverage the new URL parser. Essentially:

const URL = require('url').URL;
const u = new URL(`dns://${serv}`);

If perf is a concern around creating multiple URL objects, one can be created and reused:

const url = new URL(`dns://${serv}`);
// use it
url.host = nextServ;
// etc

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@refack refack Jun 19, 2017

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I'm +1 since this is a "cold-spot"

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@XadillaX XadillaX Jun 19, 2017

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But how about something like 8.8.8.8:53/abc?foo=bar?

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@refack refack Jun 19, 2017

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three options:

  1. allow
  2. check url.path === ''
  3. keep RegEx

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@XadillaX XadillaX Jun 19, 2017 •
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I think keeping RegEx would be fine because URL does some extra operation in semantics, though URL's performance may be better than RegEx.

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@jasnell jasnell Jun 19, 2017

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Not sure I follow? Just ignore any additional input. The host and the port are the only bits we care about. If you do not think it is appropriate to ignore the rest, then throw if values for the other parts are provided.

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@refack refack Jun 19, 2017

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Not sure I follow? Just ignore any additional input. The host and the port are the only bits we care about. If you do not think it is appropriate to ignore the rest, then throw if values for the other parts are provided.

I think the issue is that this is our only validity check. Now setServers(['8.8.8.8:53/abc?foo=bar']) would throw. If we only use URL it would be accepted with the path ignored (which is a future bug and semverity issue)


servers.forEach((serv) => {
var ipVersion = isIP(serv);
Expand All @@ -329,20 +329,16 @@ function setServers(servers) {
if (match) {
ipVersion = isIP(match[1]);
if (ipVersion !== 0) {
const portMatch = serv.match(addrSplitRE) || [];
return newSet.push([ipVersion, match[1], parseInt(portMatch[1] || 53)]);
const port = parseInt(serv.replace(addrSplitRE, '$2')) || 53;
return newSet.push([ipVersion, match[1], port]);
}
}

const s = serv.split(addrSplitRE)[0];
const [, s, p] = serv.match(addrSplitRE);
ipVersion = isIP(s);

if (ipVersion !== 0) {
return newSet.push([
ipVersion,
s,
parseInt(serv.substr(serv.indexOf(':') + 1))
]);
return newSet.push([ipVersion, s, parseInt(p)]);
}

throw new Error(`IP address is not properly formatted: ${serv}`);
Expand Down
2 changes: 2 additions & 0 deletions test/parallel/test-dns.js
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Expand Up @@ -70,6 +70,8 @@ assert.doesNotThrow(() => dns.setServers(goog));
assert.deepStrictEqual(dns.getServers(), goog);
assert.throws(() => dns.setServers(['foobar']),
/^Error: IP address is not properly formatted: foobar$/);
assert.throws(() => dns.setServers(['127.0.0.1:va']),
/^Error: IP address is not properly formatted: 127\.0\.0\.1:va$/);
assert.deepStrictEqual(dns.getServers(), goog);

const goog6 = [
Expand Down