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Fix managing build-in chain on iptables nft #1261

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@waipeng waipeng commented Apr 29, 2025

iptables-save does not show any build-in chains when they have not been interacted with. This leads to the chain being (re)-created.

#1206 attempted to fix this, by listing the chain instead of creating it, but this method only seems to work on non-nft iptables (#1217 (comment)).

Fix this for nft version of iptables by setting the policy of the chain instead of listing it. This seems to work for both nft and non-nft version of iptables (tested on Ubuntu 20.04 and 24.04).

Fixes #1217

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Checklist

  • 🟢 Spec tests.
  • 🟢 Acceptance tests.
  • Manually verified. (For example puppet apply)

`iptables-save` does not show any build-in chains when they have not
been interacted with. This leads to the chain being (re)-created.

PR#1206 attempted to fix this, by listing the chain instead of creating
it, but this method only seems to work on non-nft iptables[1].

Fix this for nft version of iptables by setting the policy of the chain
instead of listing it. This seems to work for both nft and non-nft
version of iptables (tested on Ubuntu 20.04 and 24.04).

Fixes puppetlabs#1217

[1] puppetlabs#1217 (comment)
@waipeng waipeng marked this pull request as ready for review April 29, 2025 16:16
@waipeng waipeng requested a review from a team as a code owner April 29, 2025 16:16
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Non idempotent logs for empty firewall chains
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