On Jan 11 15:00, Martin Wege via Cygwin wrote: > On Mon, Jan 8, 2024 at 3:11 PM Corinna Vinschen via Cygwin > <cygwin@cygwin.com> wrote: > so this is IMO OK.
Yeah, but... It's not just an open flag, it requires extending functionality of other APIs and, for full support, tools, see https://docs.oracle.com/cd/E19253-01/816-5175/6mbba7f02/. It's also rather weird to call alternate data streams "extended attributes", because that's just a small part of streams and it's already supported via the Linux functions getxattr(2) and friends, see https://man7.org/linux/man-pages/man2/getxattr.2.html > > Apart from that, this sounds like a nice idea for Cygwin 3.6, > > provided somebody implements it, https://cygwin.com/acronyms/#SHTDI > > > > Assuming we can live without actually having a subdir and just > > allowing to open and create a file with the O_XATTR flag, it might be > > pretty simple to implement. The path handling code would just have to > > drop the colon from the list of characters converted to the private-use > > Unicode area. > > > > Implementing the subdir is a bit more complicated, especially when > > taking opendir/readdir of that virtual subdir into account, but it > > would certainly be doable. > > How do other OSes implement the O_XATTR subdir? IDK. But there are a few points we have to keep in mind from the Solaris man page: - Given fd is an open file descriptor, openat(fd, ".", O_RDONLY|O_XATTR); opens the virtual subdir containing the ADS of a file. It's the only valid way to open the virtual dir. That's a bit of a relief because it simplifies handling this in openat(2). openat(fd, "foo", ...|O_XATTR); allows to create or open an ADS for an open file fd. - unlinkat, renameat, fstatat, fchownat, futimesat and fdopendir need to be made ADS-aware. They only work on ADS if the fd arg already resolves to an ADS, or if fd is the virtual ADS dir of a file and (except in case of fdopendir) the path argument is the name of an existing ADS. - pathconf needs to support a new flag XATTR_ENABLED. This can be made to work given the current fhandler framework in Cygwin, but again, https://cygwin.com/acronyms/#SHTDI FTR, I'm generally not a friend of ADS, because they look like a builtin security problem. They don't show up in standard directory listings, and you can't even see that a file has ADS, except you look for them explicitely. This is a really user-unfriendly interface. Corinna -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
