Re: Issues with IPFW skipto Rule and Whitelisting Logic

From: Christos Chatzaras <chris_at_cretaforce.gr>
Date: Sun, 13 Jul 2025 20:53:25 UTC
> My intended logic is that any IP present in table(3) should always be allowed, even if it or its subnet also appears in table(1).
> 
> For instance, 175.178.167.241 is in table(3), while 175.178.0.0/16 is present in table(1).
> 
> After rebooting the server and populating the tables by running the update script for the first time, access from 175.178.167.241 works correctly. However, after subsequent runs of the update script - which only updates unrelated entries and does not modify 175.178.167.241 or 175.178.0.0/16 - access from 175.178.167.241 is no longer permitted.
> 
> Additionally, when this issue arises, adding 175.178.0.0/16 to table(3) allows access again. Even after removing that entry, as long as 175.178.167.241 remains in table(3) and I wait for any active sessions to clear, access continues to work.

To add more detail:

When this issue occurs, I can resolve it by just removing 175.178.167.241 from table(3) and then immediately re-adding it to table(3).

These commands restores access for the IP:

ipfw table 3 delete 175.178.167.241

ipfw table 3 add 175.178.167.241