# Issue Description Between two systems (different OSs) both with rsync 3.1.3, copies fail with an unhelpful error when they use different ACL formats: rsync: [sender] write error: Broken pipe (32) rsync: connection unexpectedly closed (56591 bytes received so far) [generator] rsync error: error in rsync protocol data stream (code 12) at io.c(820) [sender=3.1.3] This is a nondescript error that sends the user down a rabbit hole debugging the wrong issue (are my rsync versions mismatched? why is there a protocol-level error? is my ssh connection failing? is my disk full?). It doesn't help that by default logs or increasing sender-side verbose produces no further hints; it's only by increasing receiver-side verbosity with -M-vvv that I got to the bottom of it -- incompatible ACL systems: recv_acl_access: "value out of range": 129a000 Once it became clear that it was an ACL issue, per the man page '-M--fake-super' fixes the issue. # Repro steps rsync -aAX macos-timemachine-backups-folder user@linuxhost:/path/to/dst # Actual Results rsync produces a bogus error about protocol failure, when in reality the protocol communication itself is just fine (receiver just has an unsupported ACL error) # Expected Results rsync produces a more appropriate error message, along the lines of "ACL unsupported by receiver"