In this commit, we fix a bug introduced with the recent bug fix for SCB
state+fail combination. On windwos a rename operation will fail is the
fail one is attempting to rename is still open. Therefore we need to
close the file after we read the contents, to ensure the follow up
rename operations once the channel state changes will succeed. We do
this by using `ioutil.ReadFile`, which will always clsoe the file after
reading.
Fixes#4450.
It has been reported that on Windows, the current file swap process
doesn't properly work since we still have the file open when we try to
rename it. In order to fix this, we'll now close the file _before_ we
rename it.
In this commit, we extend the prior Single format to include the entire
channel config, other than the constraints, but including the CSV delay
for both sides. We do this as we'll need more of the keying information
in order to properly execute the DLP protocol. Additionally, in the
future, if warranted, this would allow channels to be resumed if deemed
safe.
In this commit, we modify the sub-swapper to update the set of backups
files time it's tarted. We do this to ensure that each time we start,
we're up to sync with the current set of open channels. This also ensure
that we'll create a new back up file if this is the first time we're
starting up with this new feature.
In this commit, we add a new MultiFile struct. We'll use this struct in
store the latest multi-channel backup on disk, swap it out atomically,
and finally extract+unpack the contents of the multi-file. The format
that's written to disk is the same as a regular Packed multi. The
contents of this new file are meant to be used to safely implement an
always up to date multi file on disk as a way for users to easily rsync
or fsnotiy (when it changes) the backup state of their channels.
We implement an atomic update and swap in the UpdateAndSwap. The method
uses relies on the underlying file system supporting an atomic rename
syscall. We first make a temporary backup file, write the latest
contents to that, then swap the temp file with the main file using
rename(2). This way, we ensure that we always have a single up to date
file, if the protocol aborts before the rename, then we can detect this,
remove the temp file, and attempt another swap.
