Date: Sat, 7 Feb 2026 15:50:17 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Dag-Erling =?utf-8?B?U23DuHJncmF2?= <des@freebsd.org> Cc: Lionel Cons <lionelcons1972@gmail.com>, Freebsd hackers list <freebsd-hackers@freebsd.org> Subject: Re: Implementing O_SYMLINK in FreeBSD? Message-ID: <aYdDGdESyONZja4j@kib.kiev.ua> In-Reply-To: <86wm0oagde.fsf@ltc.des.dev> References: <CAPJSo4VDAb5yPh%2BLV9qDgFPUisuTWk1DhB3boGPenrY3GJo2yQ@mail.gmail.com> <aYZuY2th1CXXAULX@kib.kiev.ua> <86wm0oagde.fsf@ltc.des.dev>
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On Sat, Feb 07, 2026 at 01:27:09PM +0100, Dag-Erling Smørgrav wrote: > Konstantin Belousov <kostikbel@gmail.com> writes: > > Lionel Cons <lionelcons1972@gmail.com> writes: > > > Would it be possible to implement O_SYMLINK to open a symlink > > > directly in FreeBSD? > > What is the semantic, exactly? > > You get a file descriptor that represents the symbolic link. You cannot > read(2) from it or write(2) to it but you can fchflags(2), fchmod(2), > fchown(2), f[gs]etxattr(2) (their equivalent of extattr_[gs]et_fd(2)), > fstat(2) etc. and there is an freadlink(2). It can make it easier to > safely copy symbolic links, or safely extract them from an archive. I > would love to see it in FreeBSD. > > Note that O_SYMLINK is not like O_DIRECTORY; it is not an error to use > O_SYMLINK when opening something that is not a symbolic link. It just > means “if the name refers to a link, open the link, not the target”. I remember it was already mentioned O_PATH | O_NOFOLLOW as sort of substitute for the O_SYMLINK. What is the difference with proposed O_SYMLINK? We do not have freadlink(2), but I think it is possible to add the semantic to readlinkat(2) when dirfd is a symlink opened with O_PATH, and path is NULL. Unfortunately readlinkat() does not take flags, with O_EMPTYPATH it would be even natural. Or I can implement freadlink() as ioctl(2) or fcntl(2). Anyway, I think we are almost there with existing facilities. We are short on bits for openat(2) flags, so there is some opposition against adding new flags unless absolutely required.home | help
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