firewalld problems
I updated from Fedora 34 to 36 on my gateway machine.
Computers on the LAN could no longer access the POP3 server.
Somehow some service settings got lost.
What else got lost in the transition?
NAT/forwarding no longer works. This didn't matter because there is a
second gateway with a much faster internet connection. Except it
mattered today because Rogers Communications internet and phone
service went out, across their service area in Canada. When I tried
to use the gateway with F36, it would not work.
Just as a simple example, from the LAN
ping external-site
generated a "Packet filtered" response returned by the gateway.
On the other hand this worked fine:
ping gw-LAN-address
and so did
ping gw-public-address
This looks like a problem with forwarding.
googling got me this:
<https://www.it-hure.de/2021/12/firewalld-fedora-34-35-masquerade-between-...
It proposed this:
firewall-cmd --permanent --new-policy policy_int_to_ext
firewall-cmd --permanent --policy policy_int_to_ext --add-ingress-zone public
firewall-cmd --permanent --policy policy_int_to_ext --add-egress-zone external
firewall-cmd --permanent --policy policy_int_to_ext --set-priority 100
firewall-cmd --permanent --policy policy_int_to_ext --set-target ACCEPT
firewall-cmd --permanent --zone=external --add-masquerade
systemctl restart firewalld
firewall-cmd --info-policy policy_int_to_ext
I tried this (replacing "public" with the right zone for my setup).
This isn't quite working. tcpdumping the gateways external port, I
can see the ICMP Echo Request makes it out and an ICMP Echo Reply
comes back, but it never make it into the LAN.
Ditto for ssh.
Can anyone see what I've missed?
Where can I see "policy" stuff in the firewall GUI? I haven't found
it.
Another oddity. After I did the proposed firewall changes listed
above, I dumped the netfilter rules "nft -l" and compared them with
the previous dump. There seemed to be a certain amount of
refactoring: there were separate functions for virbr0. Why?
I no longer have confidence in the migrated firewall config.
Is there a way to start over, as if this were a fresh installation of
Fedora 36.
I think the "policy" feature is just what I need for other problems, so it
is great to see this addition. It seems too sparsely documented for me to
completely understand it. Boy is "policly" an overused term in
networking.