Shorten controller ID in exec-root to not hit UNIX_PATH_MAX

[Rid]

Signed-off-by: Grant Millar [email protected]

Use short controller ID in setkey in order to avoid moby/moby#39608 where using a custom exec-root which contains > 27 chars before the controller ID causes the daemon to fail starting with:

failed to start daemon: Error initializing network controller: error obtaining controller instance: listen unix /cylostore/sdj/9598/var/run/docker/libnetwork/b2757cb82eadaaea94aab22529663e38c3bf799369f5b578fe8a5bb4bcefe0f0.sock: bind: invalid argument

This happens due to hitting the UNIX_PATH_MAX limit (which is 108, ours is 115 in the example above). The patch gives us 79 chars to play with vs 27.

[Rid]

@fcrisciani @ctelfer @AkihiroSuda PTAL?

[arkodg]

@Rid can you please retry, the failed test is flaky and will be fixed soon

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/moby/moby/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "shorten-setkey-id" [email protected]:Rid/libnetwork.git somewhere
$ cd somewhere
$ git rebase -i HEAD~842354554968
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Amending updates the existing PR. You DO NOT need to open a new one.

[Rid]

@arkodg done, it's now passed.

[arkodg]

thanks @Rid
cc @euanh @selansen

[selansen]

Thanks @Rid