ENETUNREACH not handled for http.request in 7.10.0

[cyrus-and]

• Version: 7.10.0
• Platform: Linux
• Subsystem: http

As the title says that error is not delivered via the returned event emitter, an exception is thrown instead. Other errors are properly handled, e.g., using {port: 0} which causes ECONNREFUSED. Also the net subsystem doesn't seem to be affected when I try with net.connect using the same options.

Here is the snippet to reproduce it:

const http = require('http');
const request = http.request({host: '255.255.255.255'});
request.on('error', console.error);

Incorrect behavior

$ nvm use 7.10.0
Now using node v7.10.0
$ node issue.js
events.js:163
      throw er; // Unhandled 'error' event
      ^

Error: connect ENETUNREACH 255.255.255.255:80 - Local (0.0.0.0:0)
    at Object.exports._errnoException (util.js:1050:11)
    at exports._exceptionWithHostPort (util.js:1073:20)
    at internalConnect (net.js:889:16)
    at lookupAndConnect (net.js:977:5)
    at Socket.realConnect (net.js:945:5)
    at Agent.connect [as createConnection] (net.js:77:22)
    at Agent.createSocket (_http_agent.js:195:26)
    at Agent.addRequest (_http_agent.js:157:10)
    at new ClientRequest (_http_client.js:212:16)
    at Object.request (http.js:26:10)

Expected behavior

$ nvm use 7.9.0
Now using node v7.9.0
$ node issue.js
{ Error: connect ENETUNREACH 255.255.255.255:80 - Local (0.0.0.0:0)
    at Object.exports._errnoException (util.js:1050:11)
    at exports._exceptionWithHostPort (util.js:1073:20)
    at internalConnect (net.js:894:16)
    at net.js:980:9
    at _combinedTickCallback (internal/process/next_tick.js:73:7)
    at process._tickCallback (internal/process/next_tick.js:104:9)
    at Module.runMain (module.js:607:11)
    at run (bootstrap_node.js:423:7)
    at startup (bootstrap_node.js:147:9)
    at bootstrap_node.js:538:3
  code: 'ENETUNREACH',
  errno: 'ENETUNREACH',
  syscall: 'connect',
  address: '255.255.255.255',
  port: 80 }

[mscdex]

Works fine in v7.9.0. Looks like a regression somewhere...

[mscdex]

Bisecting reveals d0b1be1 is the culprit.

FWIW this is also happening in master.

/cc @bnoordhuis