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dns: add resolvePtr to query plain DNS PTR records

Resolving plain PTR records is used beyond reverse DNS, most
prominently with DNS-SD (RFC6763). This adds dns.resolvePtr(),
and uses it (instead of dns.reverse()) in dns.resolve().

PR-URL: #4921
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Brian White <mscdex@mscdex.net>
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dturing authored and silverwind committed Feb 8, 2016
1 parent c4ab861 commit dbdbdd4998e163deecefbb1d34cda84f749844a4
Showing with 86 additions and 3 deletions.
  1. +7 −1 doc/api/dns.markdown
  2. +2 −1 lib/dns.js
  3. +44 −0 src/cares_wrap.cc
  4. +31 −0 test/internet/test-dns.js
  5. +1 −1 test/parallel/test-c-ares.js
  6. +1 −0 test/parallel/test-dns-cares-domains.js
@@ -155,7 +155,7 @@ Valid values for `rrtype` are:
* `'MX'` - mail exchange records
* `'TXT'` - text records
* `'SRV'` - SRV records
* `'PTR'` - used for reverse IP lookups
* `'PTR'` - PTR records
* `'NS'` - name server records
* `'CNAME'` - canonical name records
* `'SOA'` - start of authority record
@@ -248,6 +248,12 @@ be an array of objects with the following properties:
}
```

## dns.resolvePtr(hostname, callback)

Uses the DNS protocol to resolve pointer records (`PTR` records) for the
`hostname`. The `addresses` argument passed to the `callback` function will
be an array of strings containing the reply records.

## dns.resolveTxt(hostname, callback)

Uses the DNS protocol to resolve text queries (`TXT` records) for the
@@ -251,9 +251,10 @@ exports.resolveMx = resolveMap.MX = resolver('queryMx');
exports.resolveNs = resolveMap.NS = resolver('queryNs');
exports.resolveTxt = resolveMap.TXT = resolver('queryTxt');
exports.resolveSrv = resolveMap.SRV = resolver('querySrv');
exports.resolvePtr = resolveMap.PTR = resolver('queryPtr');
exports.resolveNaptr = resolveMap.NAPTR = resolver('queryNaptr');
exports.resolveSoa = resolveMap.SOA = resolver('querySoa');
exports.reverse = resolveMap.PTR = resolver('getHostByAddr');
exports.reverse = resolver('getHostByAddr');


exports.resolve = function(hostname, type_, callback_) {
@@ -698,6 +698,49 @@ class QuerySrvWrap: public QueryWrap {
}
};

class QueryPtrWrap: public QueryWrap {
public:
explicit QueryPtrWrap(Environment* env, Local<Object> req_wrap_obj)
: QueryWrap(env, req_wrap_obj) {
}

int Send(const char* name) override {
ares_query(env()->cares_channel(),
name,
ns_c_in,
ns_t_ptr,
Callback,
GetQueryArg());
return 0;
}

size_t self_size() const override { return sizeof(*this); }

protected:
void Parse(unsigned char* buf, int len) override {
HandleScope handle_scope(env()->isolate());
Context::Scope context_scope(env()->context());

struct hostent* host;

int status = ares_parse_ptr_reply(buf, len, NULL, 0, AF_INET, &host);
if (status != ARES_SUCCESS) {
ParseError(status);
return;
}

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

for (uint32_t i = 0; host->h_aliases[i] != NULL; i++) {
aliases->Set(i, OneByteString(env()->isolate(), host->h_aliases[i]));
}

ares_free_hostent(host);

this->CallOnComplete(aliases);
}
};

class QueryNaptrWrap: public QueryWrap {
public:
explicit QueryNaptrWrap(Environment* env, Local<Object> req_wrap_obj)
@@ -1276,6 +1319,7 @@ static void Initialize(Local<Object> target,
env->SetMethod(target, "queryNs", Query<QueryNsWrap>);
env->SetMethod(target, "queryTxt", Query<QueryTxtWrap>);
env->SetMethod(target, "querySrv", Query<QuerySrvWrap>);
env->SetMethod(target, "queryPtr", Query<QueryPtrWrap>);
env->SetMethod(target, "queryNaptr", Query<QueryNaptrWrap>);
env->SetMethod(target, "querySoa", Query<QuerySoaWrap>);
env->SetMethod(target, "getHostByAddr", Query<GetHostByAddrWrap>);
@@ -166,6 +166,37 @@ TEST(function test_resolveSrv_failure(done) {
checkWrap(req);
});

TEST(function test_resolvePtr(done) {
var req = dns.resolvePtr('8.8.8.8.in-addr.arpa', function(err, result) {
if (err) throw err;

assert.ok(result.length > 0);

for (var i = 0; i < result.length; i++) {
var item = result[i];
assert.ok(item);
assert.ok(typeof item === 'string');
}

done();
});

checkWrap(req);
});

TEST(function test_resolvePtr_failure(done) {
var req = dns.resolvePtr('something.invalid', function(err, result) {
assert.ok(err instanceof Error);
assert.strictEqual(err.errno, 'ENOTFOUND');

assert.ok(result == undefined);

done();
});

checkWrap(req);
});

TEST(function test_resolveNaptr(done) {
var req = dns.resolveNaptr('sip2sip.info', function(err, result) {
if (err) throw err;
@@ -31,7 +31,7 @@ assert.throws(function() {
// C:\Windows\System32\drivers\etc\hosts
// so we disable this test on Windows.
if (!common.isWindows) {
dns.resolve('127.0.0.1', 'PTR', function(error, domains) {
dns.reverse('127.0.0.1', function(error, domains) {
if (error) throw error;
assert.ok(Array.isArray(domains));
});
@@ -12,6 +12,7 @@ var methods = [
'resolveNs',
'resolveTxt',
'resolveSrv',
'resolvePtr',
'resolveNaptr',
'resolveSoa'
];

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