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[209.85.219.178]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e638b936e94sm1411680276.5.2025.03.11.00.12.59 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Mar 2025 00:12:59 -0700 (PDT) Received: by mail-yb1-f178.google.com with SMTP id 3f1490d57ef6-e5dcc411189so4713684276.0 for ; Tue, 11 Mar 2025 00:12:59 -0700 (PDT) X-Received: by 2002:a05:6902:340c:b0:e5d:d9f6:d804 with SMTP id 3f1490d57ef6-e635c1e35d2mr16531670276.38.1741677179075; Tue, 11 Mar 2025 00:12:59 -0700 (PDT) List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@FreeBSD.org MIME-Version: 1.0 References: In-Reply-To: From: Gleb Popov Date: Tue, 11 Mar 2025 10:12:33 +0300 X-Gmail-Original-Message-ID: X-Gm-Features: AQ5f1Jrxd1q8FMMbZRKi42SSQyNXJVs2w6-94SMurPnwLCfJGW-DFxysUa-ao0E Message-ID: Subject: Re: Would we want pidfd_open(2) & SO_PEERPIDFD? To: Konstantin Belousov Cc: freebsd-hackers Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spamd-Result: default: False [1.03 / 15.00]; RBL_SENDERSCORE_REPUT_9(-1.00)[209.85.219.182:from]; SUBJECT_ENDS_QUESTION(1.00)[]; NEURAL_HAM_SHORT(-0.99)[-0.987]; NEURAL_SPAM_LONG(0.98)[0.975]; NEURAL_SPAM_MEDIUM(0.95)[0.946]; FORGED_SENDER(0.30)[arrowd@freebsd.org,6yearold@gmail.com]; R_SPF_ALLOW(-0.20)[+ip4:209.85.128.0/17]; MIME_GOOD(-0.10)[text/plain]; DMARC_POLICY_SOFTFAIL(0.10)[freebsd.org : SPF not aligned (relaxed), No valid DKIM,none]; RCVD_TLS_LAST(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; RCPT_COUNT_TWO(0.00)[2]; ARC_NA(0.00)[]; FREEMAIL_TO(0.00)[gmail.com]; FREEMAIL_ENVFROM(0.00)[gmail.com]; MIME_TRACE(0.00)[0:+]; TO_DN_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; ASN(0.00)[asn:15169, ipnet:209.85.128.0/17, country:US]; PREVIOUSLY_DELIVERED(0.00)[freebsd-hackers@freebsd.org]; TO_MATCH_ENVRCPT_SOME(0.00)[]; FROM_NEQ_ENVFROM(0.00)[arrowd@freebsd.org,6yearold@gmail.com]; RCVD_IN_DNSWL_NONE(0.00)[209.85.219.182:from,209.85.219.178:received]; MLMMJ_DEST(0.00)[freebsd-hackers@freebsd.org]; RWL_MAILSPIKE_POSSIBLE(0.00)[209.85.219.182:from]; R_DKIM_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[] X-Rspamd-Queue-Id: 4ZBlMx13rSz3GkL X-Spamd-Bar: + On Wed, Feb 12, 2025 at 8:17=E2=80=AFAM Konstantin Belousov wrote: > > On Wed, Feb 12, 2025 at 07:10:25AM +0300, Gleb Popov wrote: > > On Tue, Feb 11, 2025 at 9:57=E2=80=AFPM Konstantin Belousov wrote: > > > > > > > > > The semantic of the Linux' fd returned by pidfd_open() is not compati= ble > > > with our pidfd. > > > > What's the difference, exactly? > > I mean, it is still a descriptor and the only thing I need to do with > > it is check if it is still open. We even have pdgetpid() to go from > > the fd to a PID. This all looks like a perfect match to me. > > Read the man page for Linux pidfd_open(), and compare with our procdesc(4= ). > The one feature _you plan to use_ might be almost identical, but everythi= ng > else is different. When I started this thread the only use case I had was my own D-Bus service I'm writing. Now it turned out that a new version of xdg-desktop-portal [1] also started to rely on pidfd's passed by callers. I agree that our procdesc is indeed different compared to Linux pidfd, but not having a compatibility shim of some sort would mean a lot of non-upstreamable patching for dbus and xdg-desktop-portal. I'm not skilled enough to determine what parts of this API can be emulated in a userland library a-la libepoll-shim or libudev-dev. At the bare minimum I need a way to obtain a procdesc from a connected unix socket via getsockopt(LOCAL_PEERCRED) or something like that. [1] https://github.com/flatpak/xdg-desktop-portal/