Date: Tue, 11 Feb 2025 21:03:20 +0300 From: Gleb Popov <arrowd@freebsd.org> To: freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Would we want pidfd_open(2) & SO_PEERPIDFD? Message-ID: <CALH631mgztNmngL1Hffbbcf0n-kLZP-2YmsMLJ8Xi33HV8uuvw@mail.gmail.com>
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Hey hackers. D-Bus services can obtain PIDs of their clients via the sendmsg(2) mechanism over unix sockets (or getsockopt(SO_PEERCRED)). But operating on PIDs is racy, so to make sure the process has not been terminated a service would need to call getsockopt(SO_PEERCRED) again. It isn't immediately possible with D-Bus API and would require hacking on its code. However, Linux has a better alternative for this case - getsockopt(SO_PEERPIDFD) [1]. The call returns a pidfd (see procdesc(4)), which is pinned to the caller process. DBus already supports this [2], so if FreeBSD implements SO_PEERPIDFD the feature will work for us out of the box. My question is - would it be possible for FreeBSD to support SO_PEERPIDFD or I'd be better off to hack on D-Bus internals? Thanks in advance. [1] https://blog.sebastianwick.net/posts/so-peerpidfd-usefulness/ [2] https://gitlab.freedesktop.org/dbus/dbus/-/merge_requests/398#b9391b9a8a6c8fb67b48b03b25e8893befbeff87
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