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[Rafael Lopez <1930203@xxxxxxxxxxxxxxxxxx>]

Have verified that the -proposed package fixes the bug, details below.

### launch focal vm, install tang
lxc launch ubuntu:focal tangtest --vm
(ssh to vm)
sudo apt update
sudo apt upgrade
sudo apt install tang
systemctl status tangd.socket (active, enabled)


### confirm issue - rebooted vm until tang did not start, check logs for systemd job deleted messages
ubuntu@tangtest:~$ sudo systemctl status tangd.socket
● tangd.socket - Tang Server socket
     Loaded: loaded (/lib/systemd/system/tangd.socket; enabled; vendor preset: enabled)
     Active: inactive (dead)
     Listen: [::]:80 (Stream)
   Accepted: 0; Connected: 0;
ubuntu@tangtest:~$
ubuntu@tangtest:~$ grep 'Job' /var/log/syslog
Jun  5 00:53:24 tangtest kernel: systemd[1]: sockets.target: Job tangd.socket/start deleted to break ordering cycle starting with sockets.target/start
ubuntu@tangtest:~$ 


### added focal-proposed repository, install proposed tang
ubuntu@tangtest:~$ sudo apt-cache policy tang
tang:
  Installed: 7-1build1
  Candidate: 7-1ubuntu0.1
  Version table:
     7-1ubuntu0.1 500
        500 http://archive.ubuntu.com/ubuntu focal-proposed/universe amd64 Packages
 *** 7-1build1 500
        500 http://archive.ubuntu.com/ubuntu focal/universe amd64 Packages
        100 /var/lib/dpkg/status


### tested upgrade from pre-enabled state (result - unit is active, enabled and symlinks correct)
ubuntu@tangtest:~$ sudo apt install tang
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be upgraded:
  tang
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 15.5 kB of archives.
After this operation, 1024 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu focal-proposed/universe amd64 tang amd64 7-1ubuntu0.1 [15.5 kB]
Fetched 15.5 kB in 1s (11.8 kB/s)                     
(Reading database ... 76087 files and directories currently installed.)
Preparing to unpack .../tang_7-1ubuntu0.1_amd64.deb ...
Unpacking tang (7-1ubuntu0.1) over (7-1build1) ...
Setting up tang (7-1ubuntu0.1) ...
Created symlink /etc/systemd/system/sockets.target.wants/tangd.socket → /lib/systemd/system/tangd.socket.
tangd-keygen.service is a disabled or a static unit not running, not starting it.
tangd-update.service is a disabled or a static unit not running, not starting it.
Processing triggers for man-db (2.9.1-1) ...
ubuntu@tangtest:~$ sudo systemctl status tangd.socket
● tangd.socket - Tang Server socket
     Loaded: loaded (/lib/systemd/system/tangd.socket; enabled; vendor preset: enabled)
     Active: active (listening) since Mon 2023-06-05 00:58:19 UTC; 15s ago
   Triggers: ● tangd@0.service
     Listen: [::]:80 (Stream)
   Accepted: 0; Connected: 0;
      Tasks: 0 (limit: 1153)
     Memory: 0B
     CGroup: /system.slice/tangd.socket

Jun 05 00:58:19 tangtest systemd[1]: Listening on Tang Server socket.
ubuntu@tangtest:~$ ls -l /etc/systemd/system/multi-user.target.wants/tangd.socket
ls: cannot access '/etc/systemd/system/multi-user.target.wants/tangd.socket': No such file or directory
ubuntu@tangtest:~$ ls -l /etc/systemd/system/sockets.target.wants/tangd.socket 
lrwxrwxrwx 1 root root 32 Jun  5 00:58 /etc/systemd/system/sockets.target.wants/tangd.socket -> /lib/systemd/system/tangd.socket
ubuntu@tangtest:~$ 


### reboot, checked unit status and logs (result - unit active, enabled and no job cancelled entries)
ubuntu@tangtest:~$ systemctl status tangd.socket
● tangd.socket - Tang Server socket
     Loaded: loaded (/lib/systemd/system/tangd.socket; enabled; vendor preset: enabled)
     Active: active (listening) since Mon 2023-06-05 01:07:26 UTC; 2min 1s ago
   Triggers: ● tangd@0.service
     Listen: [::]:80 (Stream)
   Accepted: 0; Connected: 0;
      Tasks: 0 (limit: 1153)
     Memory: 0B
     CGroup: /system.slice/tangd.socket

Jun 05 01:07:26 tangtest systemd[1]: Listening on Tang Server socket.
ubuntu@tangtest:~$
ubuntu@tangtest:~$ grep 'Job' /var/log/syslog
Jun  5 00:53:24 tangtest kernel: systemd[1]: sockets.target: Job tangd.socket/start deleted to break ordering cycle starting with sockets.target/start
ubuntu@tangtest:~$ 
(only old job deleted entry from pre-upgrade version)


### test upgrade from pre-disabled state (result - unit active, disabled and symlinks correctly missing)
ubuntu@tangtest:~$ sudo systemctl status tangd.socket
● tangd.socket - Tang Server socket
     Loaded: loaded (/lib/systemd/system/tangd.socket; disabled; vendor preset: enabled)
     Active: active (listening) since Mon 2023-06-05 01:13:12 UTC; 25s ago
     Listen: [::]:80 (Stream)
   Accepted: 0; Connected: 0;
      Tasks: 0 (limit: 1153)
     Memory: 52.0K
     CGroup: /system.slice/tangd.socket

Jun 05 01:13:12 tangtest systemd[1]: Listening on Tang Server socket.
ubuntu@tangtest:~$ sudo apt install tang
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be upgraded:
  tang
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 15.5 kB of archives.
After this operation, 1024 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu focal-proposed/universe amd64 tang amd64 7-1ubuntu0.1 [15.5 kB]
Fetched 15.5 kB in 1s (14.0 kB/s)
(Reading database ... 76087 files and directories currently installed.)
Preparing to unpack .../tang_7-1ubuntu0.1_amd64.deb ...
Unpacking tang (7-1ubuntu0.1) over (7-1build1) ...
Setting up tang (7-1ubuntu0.1) ...
tangd-keygen.service is a disabled or a static unit not running, not starting it.
tangd-update.service is a disabled or a static unit not running, not starting it.
Processing triggers for man-db (2.9.1-1) ...
ubuntu@tangtest:~$ sudo systemctl status tangd.socket
● tangd.socket - Tang Server socket
     Loaded: loaded (/lib/systemd/system/tangd.socket; disabled; vendor preset: enabled)
     Active: active (listening) since Mon 2023-06-05 01:14:03 UTC; 6s ago
   Triggers: ● tangd@0.service
     Listen: [::]:80 (Stream)
   Accepted: 0; Connected: 0;
      Tasks: 0 (limit: 1153)
     Memory: 0B
     CGroup: /system.slice/tangd.socket

Jun 05 01:14:03 tangtest systemd[1]: Listening on Tang Server socket.
ubuntu@tangtest:~$ ls -l /etc/systemd/system/multi-user.target.wants/tangd.socket
ls: cannot access '/etc/systemd/system/multi-user.target.wants/tangd.socket': No such file or directory
ubuntu@tangtest:~$ ls -l /etc/systemd/system/sockets.target.wants/tangd.socket 
ls: cannot access '/etc/systemd/system/sockets.target.wants/tangd.socket': No such file or directory
ubuntu@tangtest:~$ 


### reboot, check unit does not start when disabled
ubuntu@tangtest:~$ sudo systemctl status tangd.socket
● tangd.socket - Tang Server socket
     Loaded: loaded (/lib/systemd/system/tangd.socket; disabled; vendor preset: enabled)
     Active: inactive (dead)
     Listen: [::]:80 (Stream)
   Accepted: 0; Connected: 0;
ubuntu@tangtest:~$ 

### install tang fresh from -proposed (result - unit active, enabled, symlinks correct)
ubuntu@tangtest:~$ sudo apt install tang
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  tang
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 15.5 kB of archives.
After this operation, 67.6 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu focal-proposed/universe amd64 tang amd64 7-1ubuntu0.1 [15.5 kB]
Fetched 15.5 kB in 1s (18.1 kB/s)
Selecting previously unselected package tang.
(Reading database ... 76073 files and directories currently installed.)
Preparing to unpack .../tang_7-1ubuntu0.1_amd64.deb ...
Unpacking tang (7-1ubuntu0.1) ...
Setting up tang (7-1ubuntu0.1) ...
Created symlink /etc/systemd/system/sockets.target.wants/tangd.socket → /lib/systemd/system/tangd.socket.
tangd-keygen.service is a disabled or a static unit, not starting it.
tangd-update.path is a disabled or a static unit, not starting it.
tangd-update.service is a disabled or a static unit, not starting it.
Processing triggers for man-db (2.9.1-1) ...
ubuntu@tangtest:~$ sudo systemctl status tang
Unit tang.service could not be found.
ubuntu@tangtest:~$ sudo systemctl status tangd.socket
● tangd.socket - Tang Server socket
     Loaded: loaded (/lib/systemd/system/tangd.socket; enabled; vendor preset: enabled)
     Active: active (listening) since Mon 2023-06-05 02:04:00 UTC; 6s ago
   Triggers: ● tangd@0.service
     Listen: [::]:80 (Stream)
   Accepted: 0; Connected: 0;
      Tasks: 0 (limit: 1153)
     Memory: 0B
     CGroup: /system.slice/tangd.socket

Jun 05 02:04:00 tangtest systemd[1]: Listening on Tang Server socket.
ubuntu@tangtest:~$ ls -l /etc/systemd/system/sockets.target.wants/tangd.socket 
lrwxrwxrwx 1 root root 32 Jun  5 02:03 /etc/systemd/system/sockets.target.wants/tangd.socket -> /lib/systemd/system/tangd.socket
ubuntu@tangtest:~$ ls -l /etc/systemd/system/multi-user.target.wants/tangd.socket
ls: cannot access '/etc/systemd/system/multi-user.target.wants/tangd.socket': No such file or directory
ubuntu@tangtest:~$

-- 
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https://bugs.launchpad.net/bugs/1930203

Title:
  ordering cycle after reboot

Status in tang package in Ubuntu:
  Fix Released
Status in tang source package in Focal:
  Fix Committed

Bug description:
  [ Impact ]
  The enabled tangd.socket service starting on boot is unreliable, due to
  the start job being deleted as a result of a systemd ordering cycle.
  Users relying on tangd to be started on boot have to manually
  check that the service started after a reboot, or implement custom
  workarounds to ensure the same.

  The fix removes the opportunity for an ordering cycle to occur in the
  unit by moving dependencies out of the socket unit and changing the
  WantedBy to sockets.target (what it should be for a socket unit).

  [ Test Plan ]
  The bug is reproduced by installing 'tang' (version 7-1build1) on a machine running Focal 20.04.6 or earlier. The unit should be enabled by default.
   `sudo apt install tang`

  After installing the package, ensure the tang service is enabled.
   `systemctl is-enabled tang`

  reboot the server, and check that the tangd.socket service is running
   `systemctl status tangd.socket`

  The service may or may not be running depending how systemd ordered
  the startup jobs for this boot. You can simply repeat rebooting the server
  and eventually at some point the service will not come up after a boot.

  Regardless if the service is started on boot, you can see similar messages
  to these in the system log:
  Apr  5 05:01:05 tangtest-vm-2 kernel: systemd[1]: sockets.target: Found ordering cycle on tangd.socket/start
  Apr  5 05:01:05 tangtest-vm-2 kernel: systemd[1]: sockets.target: Found dependency on tangd-update.service/start
  Apr  5 05:01:05 tangtest-vm-2 kernel: systemd[1]: sockets.target: Found dependency on basic.target/start
  Apr  5 05:01:05 tangtest-vm-2 kernel: systemd[1]: sockets.target: Found dependency on sockets.target/start
  Apr  5 05:01:05 tangtest-vm-2 kernel: systemd[1]: sockets.target: Job tangd.socket/start deleted to break ordering cycle starting with sockets.target/start

  The fix requires modifying the tangd.socket unit WantedBy from multi-
  user.target to sockets.target. This means the 'enabled' status relies
  on links in a different directory before and after upgrade. The
  upgrade ought to remove the old multi-user.target link. So assuming
  the unit is 'enabled', the only links existing should be:

  Before upgrade:
  /etc/systemd/system/multi-user.target.wants/tangd.socket

  After upgrade:
  /etc/systemd/system/sockets.target.wants/tangd.socket

  [ Where problems could occur ]
  The tang service may not start correctly. If it is made to be part of
  a systemd dependency chain with other services, those services may also
  be impacted/fail to start.

  Since the systemd units are altered, even if the service starts it may
  change the way the tang service was originally configured to run. Other
  applications/clients relying on the tang service may experiences issues
  if the service is not running as originally configured in prior release.

  [ Other Info ]
  The proposed fix is derived from an upstream fix:
  https://github.com/latchset/tang/commit/77785125fb56

  There is a minor modification to the diff since the Ubuntu package
  source file for tangd.socket has a '.in' extension, upstream does not.

  Versions starting with v8 already contain the fix:
  $ git describe --contains 77785125fb56
  v8~9

  Since we are updating the WantedBy link from multi-user to socket via
  a change in postinst, a downgrade using `apt install tang={version}`
  will not have a postinst to account for this. The best way to
  downgrade is to remove the package, and then install the desired
  version to add the correct link.

  Original bug text below:
  ----------
  I had the same issue, described here: https://bugzilla.redhat.com/show_bug.cgi?id=1792173
  This issue was found, because tangd didn't provide the advertisement payload anymore, after reboot.

  Ubuntu version: 20.04.2
  Package version of tang: 7-1build1

  The bug could be fixed by the recommended changes from Renaud Métrich 2020-01-17 08:35:08 UTC.
  ----------

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