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dns: make dns.setServers support customized port #13723

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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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36 changes: 30 additions & 6 deletions doc/api/dns.md
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Original file line number Diff line number Diff line change
Expand Up @@ -59,8 +59,21 @@ the [Implementation considerations section][] for more information.
added: v0.11.3
-->

Returns an array of IP address strings that are being used for name
resolution.
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',
'2001:4860:4860::8888',
'4.4.4.4:1053',
'[2001:4860:4860::8888]:1053'
]
```

## dns.lookup(hostname[, options], callback)
<!-- YAML
Expand Down Expand Up @@ -482,12 +495,22 @@ one of the [DNS error codes][].
<!-- YAML
added: v0.11.3
-->
- `servers` {string[]}
- `servers` {string[]} array of [rfc3986][] formatted addresses

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.

Sets the IP addresses of the servers to be used when resolving. The `servers`
argument is an array of IPv4 or IPv6 addresses.
eg.

If a port is specified on the address, it will be removed.
```js
dns.setServers([
'4.4.4.4',
'[2001:4860:4860::8888]',
'4.4.4.4:1053',
'[2001:4860:4860::8888]:1053'
]);
```

An error will be thrown if an invalid address is provided.

Expand Down Expand Up @@ -583,3 +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
28 changes: 20 additions & 8 deletions lib/dns.js
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,7 @@ function errnoException(err, syscall, hostname) {
return ex;
}

const IANA_DNS_PORT = 53;
const digits = [
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0-15
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16-31
Expand Down Expand Up @@ -301,7 +302,13 @@ function resolve(hostname, rrtype, callback) {


function getServers() {
return cares.getServers();
const ret = cares.getServers();
return ret.map((val) => {
if (!val[1] || val[1] === IANA_DNS_PORT) return val[0];

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


Expand All @@ -311,26 +318,31 @@ function setServers(servers) {
const orig = cares.getServers();
const newSet = [];
const IPv6RE = /\[(.*)\]/;
const addrSplitRE = /:\d+$/;
const addrSplitRE = /(^.+?)(?::(\d+))?$/;
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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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I'm +1 since this is a "cold-spot"

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

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three options:

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

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@XadillaX XadillaX Jun 19, 2017 •
edited
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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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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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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);
if (ipVersion !== 0)
return newSet.push([ipVersion, serv]);
return newSet.push([ipVersion, serv, IANA_DNS_PORT]);

const match = serv.match(IPv6RE);
// we have an IPv6 in brackets
if (match) {
ipVersion = isIP(match[1]);
if (ipVersion !== 0)
return newSet.push([ipVersion, match[1]]);
if (ipVersion !== 0) {
const port =
parseInt(serv.replace(addrSplitRE, '$2')) ||
IANA_DNS_PORT;
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]);
if (ipVersion !== 0) {
return newSet.push([ipVersion, s, parseInt(p)]);
}

throw new Error(`IP address is not properly formatted: ${serv}`);
});
Expand Down
32 changes: 20 additions & 12 deletions src/cares_wrap.cc
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Expand Up @@ -442,9 +442,9 @@ void AresEnsureServers(Environment* env) {
}

ares_channel channel = env->cares_channel();
ares_addr_node* servers = nullptr;
ares_addr_port_node* servers = nullptr;

ares_get_servers(channel, &servers);
ares_get_servers_ports(channel, &servers);

/* if no server or multi-servers, ignore */
if (servers == nullptr) return;
Expand All @@ -456,7 +456,9 @@ void AresEnsureServers(Environment* env) {

/* if the only server is not 127.0.0.1, ignore */
if (servers[0].family != AF_INET ||
servers[0].addr.addr4.s_addr != htonl(INADDR_LOOPBACK)) {
servers[0].addr.addr4.s_addr != htonl(INADDR_LOOPBACK) ||
servers[0].tcp_port != 0 ||
servers[0].udp_port != 0) {
ares_free_data(servers);
env->set_cares_is_servers_default(false);
return;
Expand Down Expand Up @@ -1924,12 +1926,12 @@ void GetServers(const FunctionCallbackInfo<Value>& args) {

Local<Array> server_array = Array::New(env->isolate());

ares_addr_node* servers;
ares_addr_port_node* servers;

int r = ares_get_servers(env->cares_channel(), &servers);
int r = ares_get_servers_ports(env->cares_channel(), &servers);
CHECK_EQ(r, ARES_SUCCESS);

ares_addr_node* cur = servers;
ares_addr_port_node* cur = servers;

for (uint32_t i = 0; cur != nullptr; ++i, cur = cur->next) {
char ip[INET6_ADDRSTRLEN];
Expand All @@ -1938,8 +1940,11 @@ void GetServers(const FunctionCallbackInfo<Value>& args) {
int err = uv_inet_ntop(cur->family, caddr, ip, sizeof(ip));
CHECK_EQ(err, 0);

Local<String> addr = OneByteString(env->isolate(), ip);
server_array->Set(i, addr);
Local<Array> ret = Array::New(env->isolate(), 2);
ret->Set(0, OneByteString(env->isolate(), ip));
ret->Set(1, Integer::New(env->isolate(), cur->udp_port));

server_array->Set(i, ret);
}

ares_free_data(servers);
Expand All @@ -1962,8 +1967,8 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
return args.GetReturnValue().Set(rv);
}

ares_addr_node* servers = new ares_addr_node[len];
ares_addr_node* last = nullptr;
ares_addr_port_node* servers = new ares_addr_port_node[len];
ares_addr_port_node* last = nullptr;

int err;

Expand All @@ -1974,12 +1979,15 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {

CHECK(elm->Get(0)->Int32Value());
CHECK(elm->Get(1)->IsString());
CHECK(elm->Get(2)->Int32Value());

int fam = elm->Get(0)->Int32Value();
node::Utf8Value ip(env->isolate(), elm->Get(1));
int port = elm->Get(2)->Int32Value();

ares_addr_node* cur = &servers[i];
ares_addr_port_node* cur = &servers[i];

cur->tcp_port = cur->udp_port = port;
switch (fam) {
case 4:
cur->family = AF_INET;
Expand All @@ -2005,7 +2013,7 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
}

if (err == 0)
err = ares_set_servers(env->cares_channel(), &servers[0]);
err = ares_set_servers_ports(env->cares_channel(), &servers[0]);
else
err = ARES_EBADSTR;

Expand Down
13 changes: 13 additions & 0 deletions test/parallel/test-dns.js
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Expand Up @@ -35,6 +35,8 @@ assert.doesNotThrow(() => {
servers[0] = '127.0.0.1';
servers[2] = '0.0.0.0';
dns.setServers(servers);

assert.deepStrictEqual(dns.getServers(), ['127.0.0.1', '0.0.0.0']);
});

assert.doesNotThrow(() => {
Expand All @@ -53,6 +55,11 @@ assert.doesNotThrow(() => {
});

dns.setServers(servers);
assert.deepStrictEqual(dns.getServers(), [
'127.0.0.1',
'192.168.1.1',
'0.0.0.0'
]);
});

const goog = [
Expand All @@ -63,6 +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 All @@ -79,10 +88,14 @@ assert.deepStrictEqual(dns.getServers(), goog6);
const ports = [
'4.4.4.4:53',
'[2001:4860:4860::8888]:53',
'103.238.225.181:666',
'[fe80::483a:5aff:fee6:1f04]:666'
];
const portsExpected = [
'4.4.4.4',
'2001:4860:4860::8888',
'103.238.225.181:666',
'[fe80::483a:5aff:fee6:1f04]:666'
];
dns.setServers(ports);
assert.deepStrictEqual(dns.getServers(), portsExpected);
Expand Down