Don't call listen() for systemd-allocated sockets

[Roshan Shariff]

I'm running calibre-server using systemd socket activation on Linux. For security reasons, it is running inside a container restricted with SELinux.

In the function ServerLoop.serve() in calibre/srv/loop.py, the listen() function is called on the socket, regardless of whether it is a pre-allocated socket or not. However, when the socket is passed by systemd, you only need to call accept() on it, not bind() or listen() (see the code example in [1]).

I think the code should be changed so that both bind() and listen() are skipped for pre-allocated sockets, not just bind() as is done currently.

[1] https://0pointer.de/blog/projects/socket-activation.html

[Roshan Shariff (roshan.shariff)]

I've opened a pull request that fixes this issue: https://github.com/kovidgoyal/calibre/pull/2069.

[Kovid Goyal (kovid)]

We can track this on the PR

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.