Systemd Socket Activation - File Descriptor with HTTP Server

[doc987]

How do I start \React\Socket\Server using systemd socket activation? There would need to be a way to accept a file descriptor from systemd, and then use that file descriptor to instantiate \React\Socket\Server.

[clue]

Thank you for bringing this up! Right now, this component does not support listening on existing file descriptors and I think this would be a very useful addition to this package!

PHP does technically support this via the php://fd/n wrapper since PHP 5.3.6 (http://php.net/manual/de/wrappers.php.php#refsect1-wrappers.php-changelog). I recall this was briefly discussed in reactphp/reactphp#252 a while ago, but this never quite made it.

I've just looked into this again and the existing component is pretty much already compatible with this except that this needs to use fopen() instead of stream_socket_server(). Here's a gist of how this can be used in PHP (which suggests that this is apparently broken in PHP 7.1.2 to PHP 7.1.6 and not supported on HHVM at all): https://3v4l.org/PWjMH

Implementing this as part of this package means that we would have to come up with some tests to verify correct execution. PHP does not currently expose a sane way to access the underlying file descriptor for an existing socket or stream resource (https://stackoverflow.com/questions/5600811/fopen-and-getting-system-file-descriptor, reactphp/child-process#51 and maybe https://github.com/YuriyNasretdinov/phprocksyd/blob/master/php-fd.patch). On Linux, we may use /proc/self/fd/ to iterate over all existing file descriptors and on Mac we may be able to use lsof (https://unix.stackexchange.com/questions/235979/how-do-i-find-out-more-about-socket-files-in-proc-fd).

Long story short, here's a gist with a WIP version of a FdServer to show how this could potentially be used with ReactPHP: https://gist.github.com/clue/fa4f1ddf26f2f8727232215a0f700e09

Maybe somebody else feels like giving this a try or looking into this? Any feedback is appreciated 👍

[phpbg]

This would be really nice to improve security when listening privileged ports