Multinode setups with CentOS 8 block won't work due to traffic being blocked

[Daniel Alvarez]

Right now, if we deploy a multinode setup with devstack, we'll see that the traffic between nodes it's going to be dropped.

The reason is default iptables rules added by iptables-service who's enabled here [0].

After we do this, the following rules are installed in the INPUT chain:

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target prot opt in out source destination
   10 664 ACCEPT all -- any any anywhere anywhere state RELATED,ESTABLISHED
    0 0 ACCEPT icmp -- any any anywhere anywhere
    0 0 ACCEPT all -- lo any anywhere anywhere
    0 0 ACCEPT tcp -- any any anywhere anywhere state NEW tcp dpt:ssh
    0 0 REJECT all -- any any anywhere anywhere reject-with icmp-host-prohibited

The last REJECT rule will prevent services to communicate across hosts so we must disable this.

For reference, this is the default firewall configuration on a CentOS8 machine:

$ sudo cat /etc/sysconfig/iptables
# sample configuration for iptables service
# you can edit this manually or use system-config-firewall
# please do not ask us to add additional ports/services to this default configuration
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

[0] https://opendev.org/openstack/devstack/src/branch/master/tools/fixup_stuff.sh#L132-L135

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/755554

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Dr. Jens Harbott <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/devstack/+/755554
Reason: Feel free to reopen if you want to continue with this

[Dr. Jens Harbott (j-harbott)]

Patch didn't make progress, feel free to update if this is still relevant.

[Launchpad Janitor (janitor)]

[Expired for devstack because there has been no activity for 60 days.]