This adds support for syncing extended attributes on supported
filesystem on Linux, macOS, FreeBSD and NetBSD. Windows is currently
excluded because the APIs seem onerous and annoying and frankly the uses
cases seem few and far between. On Unixes this also covers ACLs as those
are stored as extended attributes.
Similar to ownership syncing this will optional & opt-in, which two
settings controlling the main behavior: one to "sync" xattrs (read &
write) and another one to "scan" xattrs (only read them so other devices
can "sync" them, but not apply any locally).
Co-authored-by: Tomasz Wilczyński <twilczynski@naver.com>
This adds support for syncing ownership on Unixes and on Windows. The
scanner always picks up ownership information, but it is not applied
unless the new folder option "Sync Ownership" is set.
Ownership data is stored in a new FileInfo field called "platform data". This
is intended to hold further platform-specific data in the future
(specifically, extended attributes), which is why the whole design is a
bit overkill for just ownership.
* lib/fs, lib/model: Add error channel to Watch to avoid panics (fixes#5697)
* forgot unsupported watch
* and more non(-standard)-unixy fixes
* and windows test
* review
This adds a folder option "CopyOwnershipFromParent" which, when set,
makes Syncthing attempt to retain the owner/group information when
syncing files. Specifically, at the finisher stage we look at the parent
dir to get owner/group and then attempt a Lchown call on the temp file.
For this to succeed Syncthing must be running with the appropriate
permissions. On Linux this is CAP_FOWNER, which can be granted by the
service manager on startup or set on the binary in the filesystem. Other
operating systems do other things, but often it's not required to run as
full "root". On Windows this patch does nothing - ownership works
differently there and is generally less of a deal, as permissions are
inherited as ACLs anyway.
There are unit tests on the Lchown functionality, which requires the
above permissions to run. There is also a unit test on the folder which
uses the fake filesystem and hence does not need special permissions.
It turns out that ZFS doesn't do any normalization when storing files,
but does do normalization "as part of any comparison process".
In practice, this seems to mean that if you LStat a normalized filename,
ZFS will return the FileInfo for the un-normalized version of that
filename.
This meant that our test to see whether a separate file with a
normalized version of the filename already exists was failing, as we
were detecting the same file.
The fix is to use os.SameFile, to see whether we're getting the same
FileInfo from the normalized and un-normalized versions of the same
filename.
One complication is that ZFS also seems to apply its magic to os.Rename,
meaning that we can't use it to rename an un-normalized file to its
normalized filename. Instead we have to move via a temporary object. If
the move to the temporary object fails, that's OK, we can skip it and
move on. If the move from the temporary object fails however, I'm not
sure of the best approach: the current one is to leave the temporary
file name as-is, and get Syncthing to syncronize it, so at least we
don't lose the file. I'm not sure if there are any implications of this
however.
As part of reworking normalizePath, I spotted that it appeared to be
returning the wrong thing: the doc and the surrounding code expecting it
to return the normalized filename, but it was returning the
un-normalized one. I fixed this, but it seems suspicious that, if the
previous behaviour was incorrect, noone ever ran afoul of it. Maybe all
filesystems will do some searching and give you a normalized filename if
you request an unnormalized one.
As part of this, I found that TestNormalization was broken: it was
passing, when in fact one of the files it should have verified was
present was missing. Maybe this was related to the above issue with
normalizePath's return value, I'm not sure. Fixed en route.
Kindly tested by @khinsen on the forum, and it appears to work.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4646
