drbd udev rule with multiple symlinks fails

[Dan Streetman]

The drbd udev rule creates multiple symlinks with a single udev rule, by space-separating them inside an env var. However, recent udev changes no longer allow doing that:
https://github.com/systemd/systemd/issues/4833

Now, recent versions of udev will, by default, replace any whitespace introduced into SYMLINK values by variable substitution, so the drbd udev rule that does this breaks:

ENV{SYMLINK}!="", SYMLINK="$env{SYMLINK}", GOTO="have_symlink"

when that SYMLINK env variable contains multiple symlinks, they are combined into a single symlink with an underscore joining them. Instead, since it's desired to leave all spaces in the env var in order to create multiple symlinks, the rule needs to use the "string_escape=none" option which prevents whitespace replacement:

ENV{SYMLINK}!="", SYMLINK="$env{SYMLINK}", OPTIONS+="string_escape=none", GOTO="have_symlink"

Related ubuntu bug that introduced the new udev default whitespace replacement behavior:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1647485

[Dan Streetman (ddstreet)]

Alternately, the drbd udev rule could be refactored, so it didn't place multiple symlinks into an env variable; for example, it could do this:

PROGRAM="/usr/sbin/drbdadm sh-udev minor-%m", SYMLINK="$result",
GOTO="have_symlink"

however, it would need to:

1) make the program return return success (0) if the symlink should be
created, and return failure (!0) if not
2) return only the plain-text symlinks strings; no "SYMLINK="
assignment

However, that would require updating the drbdadm program output as well as the udev rule.

[Dan Streetman (ddstreet)]

No fix needed in trusty; the drbd rules file is different in that older version and will not be affected by the udev behavior change (the rules file contains the space directly in its string value, not in a substituted variable, so udev will process the space correctly and the behavior change only affects whitespace inside substituted variables inside SYMLINK assignment in rules files).

[Dan Streetman (ddstreet)]

upstream commit is
https://github.com/LINBIT/drbd-utils/commit/05c0797248af6f4e3b5b04545fe068dba41e3d81

[Eric Desrochers (slashd)]

Sponsored for Cosmic, please keep an eye at the "excuses..." page to make sure the package is not stuck in cosmic-proposed.

Thanks !

[Launchpad Janitor (janitor)]

This bug was fixed in the package drbd-utils - 8.9.10-2ubuntu1

---------------
drbd-utils (8.9.10-2ubuntu1) cosmic; urgency=medium

  * Fix creation of drbd symlinks with newer udev.
    (LP: #1673255)

 -- Dan Streetman <email address hidden> Fri, 25 May 2018 11:17:50 -0400