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|description=How to refactor the firewall script while being sure there are no iptables or nftables changes
}}
{{intro|
How to refactor the firewall script while being sure there are no iptables or nftables changes
}}
= Instructions =

1) Store current iptables rules to file a.

<pre>
sudo iptables-save-deterministic > a
</pre>

2) Refactor the {{project_name_long}} firewall code.

3) {{Reload_Firewall}}

4) Store current iptables rules to file b.

<pre>
sudo iptables-save-deterministic > b
</pre>

5) Compare files a and b.

Use console diff viewer or...

<pre>
diff a b
</pre>

Use a graphical diff viewer.

<pre>
meld a b
</pre>

6) There should be no diff.

= nftables =

{{CodeSelect|code=
sudo nft --stateless list ruleset > nftables-old
}}

{{CodeSelect|code=
sudo nft --stateless list ruleset > nftables-new
}}

= systemcheck iptables test =
Does not exist yet.

* "''systemcheck (which is somewhat a replacement for the lack of test suite) could indeed be useful to check if the loaded iptables rules match a hardcoded iptables dump. Yes, with additional firewalll add-ons that would be hard. Then these firewall add-ons could ship a dump that also gets verified. (iptables-dumps.d folder checked by systemcheck or so.) But then multiple firewall add-ons gets hard. Mutliple firewall add-ons and dumping, that kind of flexibility might be stretching what the {{project_name_short}} project may be able to implement.''" (From [https://forums.whonix.org/t/bolt-on-for-whonix-firewall-best-place-to-put-files/2222 (Forum)  Bolt on for whonix_firewall - best place to put files?] )
** systemcheck could use this iptables diff facility to warn the user of non-standard / unexpected rules present. And, just like unwanted packages, could ask the user to run ''e.g. iptables-save-whonix'' to establish a new baseline. systemcheck would then pass, unless something else had changed things user unexpectedly, at which point systemcheck would again warn.

= Split {{project_name_short}} Firewall Script for better readability =
''From Patrick:''<br>
" I have been wondering for some time now if the firewall script should be split. A lot sections are being used by multiple packages, the firewall and vpn-firewall. Eventually further in future (corridor-gateway to be created one day)...

* error_handler
* source config folder
* IPv4 DEFAULTS
* IPv4 PREPARATIONS
* IPv4 DROP INVALID INCOMING PACKAGES
* IPv4 FORWARD
* IPv6
* more minor stuff (iptables_cmd, ip6tables_cmd)
<br>
Converted to shell functions. And added to helper-scripts.

The risk of changing firewall rules while refactoring is minimal because it can be verified:

However, the goal is to make the firewall scripts easier to read. Not more difficult to audit. I am not sure which style (all in one file vs split) makes it simpler at this point. "
<br>
* Early files in firewall config foleder could contain bash scripting of the form:
<pre>
function ScriptFuncPreloadElement1() { script lines, e.g. $iptables_cmd ''blah''}
</pre>
** Optionally followed, for inline / immediate execution rather than hooking in later within firewall script, with:
<pre>
ScriptFuncPreloadElement1
# (Within the same file == calling main().)
</pre>
** This separates code definition from code execution.
* "''The other question with firewall code injection, pre/post hooks is when to dispatch them? When you want to dispatch them depends on what you actually want to implement.''"
* e.g.
<pre>
if [ "$(type -t firewall_input_hook_end)" = "function" ]; then
   firewall_input_hook_end
fi
</pre>
** However, such would only allow a single call per hook. (User would have to chain all calls within whonix_firewall.d) Perhaps array variables instead. Code would then be something like ScriptFuncPreloadElement1() as above, then
<pre>
firewall_input_hook_end[${#firewall_input_hook_end[@]}]=ScriptFuncPreloadElement1
</pre>
*** ''It would be up to the user to appropriately manage the array ordering.''
** Hooks within the firewall would then walk the appropriate array at the appropriate time.
<hr>
'''<u>Reference</u>: [https://forums.whonix.org/t/whonix-torrents-and-being-a-good-tor-citizen/1766 (Forum)  torrents, and being a good tor citizen]'''
<br>
<u>''Solution, part b''</u> demonstrates an example sample set of iptables rules that could be injected, within the firewall. (''Proof of concept, only.'')
<hr>
'''<u>Reference</u>: [https://forums.whonix.org/t/favourite-whonix-bash-script-boilerplate-template/2235/2 (Forum)  Favourite (whonix?) bash script boilerplate template?]'''
<br>
* (begins) a corralling of a standard scripting framework.

= See Also =
* [https://www.whonix.org/wiki/Dev/Firewall_Unload Firewall Unloading]

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