* Add --delay-symlinks to create symlinks after all files are in place
The generator creates a symlink as soon as it reaches it in the file
list, while regular files arrive later through the sender and receiver
(and, with --delay-updates, are only renamed into place at the end).
For the rest of the transfer a new symlink can point at a file that
isn't there yet, so anything reading the destination during the sync --
e.g. a loader resolving libfoo.so -> libfoo.so.2 -- can fail.
The new --delay-symlinks option makes the generator defer new and
changed symlinks and create them once the receiver reports that every
file, including any --delay-updates renames, is in place. Each link is
itemized and logged after it has been created, before the generator
ends the delay-updates phase, and the deletion stats are sent after any
directory that a deferred link replaces.
The option implies --no-inc-recursive on the receiving side and is
passed to a remote receiver, which must also support it. It is an
error to combine it with --remove-source-files, --hard-links,
--compare-dest, --copy-dest, or --link-dest, or to use it with a
protocol older than 29. support/rrsync accepts the option and refuses
it under -no-overwrite, as it does --delay-updates.
Add delay-symlinks_test.py, which holds a push partway through the
link's target to check that new and changed links aren't created early,
and rrsync-no-overwrite-delay-symlinks_test.py.
* Document --delay-symlinks limits and test how it is passed to the server
The man page now says the option narrows the inconsistency window rather
than making the update atomic, that an interrupted transfer leaves new
symlinks missing and changed ones at their old targets, and that
--delete-before can also remove an old target early.
Add delay-symlinks-remote_test.py. Through a remote shell that records
the server command, it checks that the option is passed to a remote
receiver on a push but not to a remote sender on a pull, and that
incremental recursion is off in both directions. It also checks that
--protocol=28 fails with the protocol error, and that a push to an older
rsync (old_versions/rsync_3.4.1) is refused before anything is
transferred while a pull from it works.
* testsuite: seed delay-symlinks fixture with rsync
* NEWS: document --delay-symlinks
---------
Co-authored-by: Zen Dodd <mail@steadytao.com>
--ignore-existing protects the live transfer destination, but three
peer-selectable options reach other existing objects inside the
restricted directory: --log-file appends to one, --partial-dir consumes
and then renames or unlinks one, and --delay-updates does the same
through its implicit .~tmp~ directory. Refuse all three under
-no-overwrite.
Refusal rather than confinement, because confining these paths does not
help: keeping the --log-file append inside the tree still appends to an
existing file, and for the partial directories the peer controls both
the directory and the transferred basename, so a collision is always
reachable. A pre-exec emptiness check would be raceable. The cost is
that a push naming --partial-dir on the remote receiver, or using
--delay-updates, is now refused for a -no-overwrite account.
Each regression drives the option through a wrapper WITHOUT
-no-overwrite as well, and requires that to be accepted. Without that
control the tests cannot tell "refused under -no-overwrite" from
"refused always", and would still pass if the options were disabled for
every rrsync deployment -- verified by making the refusal unconditional,
which the controls then catch.
The wrapper is handed a shim rather than RSYNC directly: RSYNC is a
multi-word command whenever the runner forces --protocol=N, and rrsync
execlp()s its RSYNC as a single executable name, so every one of these
tests died before reaching the policy under test. A fleet run caught it
on the protocol columns of three targets.
Backup mode belongs in the same set. Publishing a backup onto a name
that already exists deletes what is there (backup.c make_backup()), and
deleting a file backs it up first (delete.c), so a --delete of an
unrelated file can land on a protected name -- overwriting a file that
--ignore-existing was holding, with rc=0 and no diagnostic. Disable -b
and --backup-dir. --suffix is left enabled: with both of those refused
nothing can turn backups on, so it is inert.
The short option must be disabled before short_no_arg_re is built, since
a stock client sends b inside the remote short-option bundle and the
regex is snapshotted there; the whole -no-overwrite block therefore
moves up beside the other policy gates rather than sitting after the
chdir. Its regression drives the collision through a wrapper without
-no-overwrite, passing --ignore-existing by hand, which both proves the
refusal is conditional and shows the primitive defeating the very
protection -no-overwrite forces.
rrsync.1.md now states what -no-overwrite costs: no explicit
--partial-dir, no --delay-updates, no server-side --log-file, no backups.
- Add link targets for all option choices, not just the first one.
- Tweak cross-link arg format.
- Add more links, including some in the latest NEWS.
- Split out a few numbered lists.
- Convert rrsync to python.
- Enhance security of arg & option checking.
- Reject `-L` (`--copy-links`) by default.
- Add `-munge` and `-no-del` options.
- Tweak the logfile line format.
- Created an rrsync man page.
- Use `configure --with-rrsync` if you want `make install` to install
rrsync and its man page.
- Give lsh more rrsync testing support.
