[Bug 1949643] Re: iptables-persistent unconditionally drops existing iptables rules

[Brian Murray]

Hello Mauricio, or anyone else affected,

Accepted iptables-persistent into impish-proposed. The package will
build now and be available at
https://launchpad.net/ubuntu/+source/iptables-
persistent/1.0.15ubuntu0.21.10.1 in a few hours, and then in the
-proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
impish to verification-done-impish. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-impish. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: iptables-persistent (Ubuntu Impish)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-impish

** Changed in: iptables-persistent (Ubuntu Hirsute)
       Status: In Progress => Fix Committed

** Tags added: verification-needed-hirsute

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https://bugs.launchpad.net/bugs/1949643

Title:
  iptables-persistent unconditionally drops existing iptables rules

Status in iptables-persistent package in Ubuntu:
  Fix Released
Status in iptables-persistent source package in Bionic:
  Fix Committed
Status in iptables-persistent source package in Focal:
  Fix Committed
Status in iptables-persistent source package in Hirsute:
  Fix Committed
Status in iptables-persistent source package in Impish:
  Fix Committed
Status in iptables-persistent source package in Jammy:
  Fix Released
Status in iptables-persistent package in Debian:
  Fix Released

Bug description:
  [Impact]

  The iptables-persistent plugins/{15-ip4tables,25-ip6tables}
  use ip[6]tables-restore without --noflush unconditionally.

  This doesn't play along well with ufw, which starts before
  netfilter-persistent typically, and gets its rules flushed.

  This makes `ufw status` return that ufw is disabled, which
  is misleading, as `ufw.service` is enabled and ufw actually
  loaded all its rules correctly (but they were flushed later.)

  Some images ship iptables-persistent rules, thus are subject
  to this issue if ufw is used.

  [Workaround]

  Disable the netfilter-persistent.service unit, after rules
  have been migrated to ufw.

  [Fix]

  Add options IP[6]TABLES_RESTORE_NOFLUSH (disabled by default)
  to `/etc/default/netfilter-persistent` to allow not flushing
  existing ip[6]tables rules.

  Proposed in Debian bug #998416 [1], Salsa Merge Request [2].

  [Test Steps]

  See commment #14 (based on the Debian bug.)

  [Regression Potential]

  Regressions would manifest when netfilter-persistent.service
  starts/loads rules, probably in the form  of failures to run
  ip[6]tables-restore or incorrectly (not) flushing rules.

  Note: there is _no_ behavior change is by default, so users
  have to opt-in, which should reduce the chances/numbers of
  potential regressions.

  [Links]

  [1] https://bugs.debian.org/998416
  [2] https://salsa.debian.org/debian/iptables-persistent/-/merge_requests/3

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