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<base href="https://bugzilla.netfilter.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Consider eliding empty variables if expanded within an element list"
href="https://bugzilla.netfilter.org/show_bug.cgi?id=1456">1456</a>
</td>
</tr>
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<th>Summary</th>
<td>Consider eliding empty variables if expanded within an element list
</td>
</tr>
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<th>Product</th>
<td>nftables
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P5
</td>
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<th>Component</th>
<td>nft
</td>
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<th>Assignee</th>
<td>pablo@netfilter.org
</td>
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<th>Reporter</th>
<td>kfm@plushkava.net
</td>
</tr></table>
<p>
<div>
<pre>This concerns a minor usability issue that I noticed after evaluting some of
the criticism in the GitHub issue referenced by <a class="bz_bug_link
bz_status_NEW "
title="NEW - Usability improvements, enabling creation of complex firewalls"
href="show_bug.cgi?id=1434">bug 1434</a>. In the GitHub issue,
one critic complains that this sample ruleset does not work as expected:
define BASE_ALLOWED_INCOMING_TCP_PORTS = {22, 80, 443}
define EXTRA_ALLOWED_INCOMING_TCP_PORTS = {}
table inet filter {
chain input {
type filter hook input priority 0; policy drop;
tcp dport {$BASE_ALLOWED_INCOMING_TCP_PORTS,
$EXTRA_ALLOWED_INCOMING_TCP_PORTS} ct state new counter accept
}
}
Currently, this is not permitted by nft's parser. My first thought was that the
intended outcome could be achieved by instead declaring:
define EXTRA_ALLOWED_INCOMING_TCP_PORTS = ""
However, doing so causes the value to be coerced to 0, resulting in:
tcp dport { 0, 22, 80, 443 } ct state new counter packets 0 bytes 0 accept
Notwithstanding that this isn't a particularly idiomatic way of writing an nft
ruleset, it seems plausible that other new users might try using internal
variables in this way. Perhaps it would be worth supporting.</pre>
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</p>
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