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'use strict';
child_process: fix handle delivery Commit 9352c19 ("child_process: don't emit same handle twice") trades one bug for another. Before said commit, a handle was sometimes delivered with messages it didn't belong to. The bug fix introduced another bug that needs some explaining. On UNIX systems, handles are basically file descriptors that are passed around with the sendmsg() and recvmsg() system calls, using auxiliary data (SCM_RIGHTS) as the transport. node.js and libuv depend on the fact that none of the supported systems ever emit more than one SCM_RIGHTS message from a recvmsg() syscall. That assumption is something we should probably address someday for the sake of portability but that's a separate discussion. So, SCM_RIGHTS messages are never coalesced. SCM_RIGHTS and normal messages however _are_ coalesced. That is, recvmsg() might return this: recvmsg(); // { "message-with-fd", "message", "message" } The operating system implicitly breaks pending messages along SCM_RIGHTS boundaries. Most Unices break before such messages but Linux also breaks _after_ them. When the sender looks like this: sendmsg("message"); sendmsg("message-with-fd"); sendmsg("message"); Then on most Unices the receiver sees messages arriving like this: recvmsg(); // { "message" } recvmsg(); // { "message-with-fd", "message" } The bug fix in commit 9352c19 assumes this behavior. On Linux however, those messages can also come in like this: recvmsg(); // { "message", "message-with-fd" } recvmsg(); // { "message" } In other words, it's incorrect to assume that the file descriptor is always attached to the first message. This commit makes node wise up. Fixes #5330.
12 years ago
// Test that a Linux specific quirk in the handle passing protocol is handled
// correctly. See https://github.com/joyent/node/issues/5330 for details.
var common = require('../common');
var assert = require('assert');
var net = require('net');
var spawn = require('child_process').spawn;
if (process.argv[2] === 'worker')
worker();
else
master();
function master() {
// spawn() can only create one IPC channel so we use stdin/stdout as an
// ad-hoc command channel.
var proc = spawn(process.execPath, [__filename, 'worker'], {
stdio: ['pipe', 'pipe', 'pipe', 'ipc']
});
var handle = null;
proc.on('exit', function() {
handle.close();
});
proc.stdout.on('data', function(data) {
assert.equal(data, 'ok\r\n');
net.createServer(assert.fail).listen(common.PORT, function() {
handle = this._handle;
proc.send('one');
proc.send('two', handle);
proc.send('three');
proc.stdin.write('ok\r\n');
});
});
proc.stderr.pipe(process.stderr);
}
function worker() {
process._channel.readStop(); // Make messages batch up.
process.stdout.ref();
process.stdout.write('ok\r\n');
process.stdin.once('data', function(data) {
assert.equal(data, 'ok\r\n');
process._channel.readStart();
});
var n = 0;
process.on('message', function(msg, handle) {
n += 1;
if (n === 1) {
assert.equal(msg, 'one');
assert.equal(handle, undefined);
}
else if (n === 2) {
assert.equal(msg, 'two');
assert.equal(typeof handle, 'object'); // Also matches null, therefore...
assert.ok(handle); // also check that it's truthy.
handle.close();
}
else if (n === 3) {
assert.equal(msg, 'three');
assert.equal(handle, undefined);
process.exit();
}
});
}