Date: Tue, 25 Mar 2025 08:27:14 +0300 From: Gleb Popov <arrowd@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-hackers <freebsd-hackers@freebsd.org> Subject: Re: Would we want pidfd_open(2) & SO_PEERPIDFD? Message-ID: <CALH631=582=rpqCaR6FQTF_4C88NRf%2BLGnZR3fAynVvuNNWheA@mail.gmail.com> In-Reply-To: <Z-I5Vwb3383R6UZs@kib.kiev.ua> References: <CALH631mgztNmngL1Hffbbcf0n-kLZP-2YmsMLJ8Xi33HV8uuvw@mail.gmail.com> <Z6udhDuj4uBjNUsM@kib.kiev.ua> <CALH631=7MnCAe67yPqG%2BAJfy_CPxf3HUxsfeVvgmiTEXEy27Bg@mail.gmail.com> <Z6wuyS4uBQJbCG-c@kib.kiev.ua> <CALH631m7DZKOLkjn4Z9z7arE9xwfEEjaGVSO=5KyHJ=iZ8o9Qw@mail.gmail.com> <Z9BR90ijwniJr2IJ@kib.kiev.ua> <CALH631mhpv7tzr1vhNgF2Hs6=ynSrMeuP1=NeXU63FEAmfUwRw@mail.gmail.com> <Z-I5Vwb3383R6UZs@kib.kiev.ua>
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On Tue, Mar 25, 2025 at 8:04 AM Konstantin Belousov <kostikbel@gmail.com> wrote: > > Can this be summarized as just a use of pidfd to > - get the pid of the peer > - ensure the peer liveness? > > I do not see much need of pidfd for this functionality. What's the alternative? Tapping into a socket with getsockopt(LOCAL_PEERCRED) to obtain a PID via xucred is not an option because a client is not required to maintain an established connection to a D-Bus socket. The high level code expects a descriptor with some properties, so we either provide it or have to patch large parts of the code using it. Emulating pidfd somehow is also fine to me, but I have no idea how to do that. libinotify-kqueue example shows that emulating a descriptor with certain properties is quite a non-trivial task. > pidfd takes ownership of the parent/child relation. Wait() family of the > functions clean after zombies, but this functionality is subsumed by > the procdesc, so it is 'kind of' contradicts each other. Also, as I > can guess, wait() contradicts the capsicum idea of representing all > access rights as file descriptors, since the special relation with the > child presented yet another special process right. Yes, this is a problem, and I have no experience to have an opinion there.
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