net.createConnection seems to assume IPv4 localhost address when no host given

[misterdjules]

It seems that Socket.prototype.connect assumes an IPv4 localhost address when no host is given. Here's the code in lib/net.js:

} else if (!options.host) {
    debug('connect: missing host');
    self._host = '127.0.0.1';
    connect(self, self._host, options.port, 4);

Should we instead set options.host to 'localhost' and fall through so that both use cases (host set in options or not) resolve to the same IP address?

There are other places where it seems IPv4 addresses are assumed:

1. In Socket.prototype.listen, when no IP is passed, IPv4 is hardcoded:

} else if (util.isUndefined(arguments[1]) ||
             util.isFunction(arguments[1]) ||
             util.isNumber(arguments[1])) {
    // The first argument is the port, no IP given.
    listen(self, null, port, 4, backlog);

2. There's another case in Socket.prototype.connect when we hard-code IPv4, I'm not sure what use case it covers:

} else {
        timers._unrefActive(self);

        addressType = addressType || 4;

        // node_net.cc handles null host names graciously but user land
        // expects remoteAddress to have a meaningful value
        ip = ip || (addressType === 4 ? '127.0.0.1' : '0:0:0:0:0:0:0:1');

        connect(self,
                ip,
                options.port,
                addressType,
                options.localAddress,
                options.localPort);
      }

/cc @cjihrig

[cjihrig]

@misterdjules thanks for pointing this out. I'll look into removing hard coded IP addresses.

[misterdjules]

@cjihrig Thanks!

[indutny]

@cjihrig ping ;)

[cjihrig]

Closed in b636ba8