I could reproduce the issue by building git v1.8.5 and the issue was fixed after cherry-picking "iptables-nft: fix basechain policy configuration"
$ git log commit 8d985eb4eb7a23fd98b75d71179af40169144cc5 (HEAD -> bug1898547) Author: Pablo Neira Ayuso <pa...@netfilter.org> Date: Fri Oct 2 13:44:36 2020 +0200 iptables-nft: fix basechain policy configuration Previous to this patch, the basechain policy could not be properly configured if it wasn't explictly set when loading the ruleset, leading to iptables-nft-restore (and ip6tables-nft-restore) trying to send an invalid ruleset to the kernel. Signed-off-by: Arturo Borrero Gonzalez <art...@netfilter.org> Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org> commit 14ac250946289e280fb09ef978a45042871275b0 (tag: v1.8.5) Author: Pablo Neira Ayuso <pa...@netfilter.org> Date: Wed Jun 3 11:37:52 2020 +0200 configure: bump version for 1.8.5 release Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org> ** Also affects: iptables (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to iptables in Ubuntu. https://bugs.launchpad.net/bugs/1898547 Title: neutron-linuxbridge-agent fails to start with iptables 1.8.5 Status in iptables package in Ubuntu: New Status in neutron package in Ubuntu: Invalid Bug description: Ubuntu Groovy (20.10) kernel 5.8.0-20-generic neutron-linuxbridge-agent: 2:17.0.0~git2020091014.215a541bd4-0ubuntu1 iptables: 1.8.5-3ubuntu1 (nf_tables) iptables-restore points to xtables-nft-multi After upgrading iptables from 1.8.4 to 1.8.5 and rebooting the neutron network node, neutron-linuxbridge-agent didn't properly start anymore. The log file shows many errors like: 2020-10-05 10:20:37.998 551 ERROR neutron.plugins.ml2.drivers.agent._common_agent ; Stdout: ; Stderr: iptables-restore: line 29 failed Downgrading iptables to 1.8.4 solves the problem. Trying to do what the linuxbridge agent does: 2020-10-05 10:20:37.998 551 ERROR neutron.plugins.ml2.drivers.agent._common_agent *filter 2020-10-05 10:20:37.998 551 ERROR neutron.plugins.ml2.drivers.agent._common_agent :FORWARD - [0:0] shows that iptables-restore <<EOF *filter :INPUT - [0:0] COMMIT EOF works fine with iptables 1.8.4 but fails with 1.8.5 Workaround It seems neutron-linuxbridge agent tries to create the default chains (like INPUT) with a "-" as policy. By making sure the chains already exist (and are shown with iptables-save) the agent doesn't try to create those default chains and the agent starts fine. So just running: sudo iptables -F OUTPUT sudo iptables -F OUTPUT -t raw sudo ip6tables -F OUTPUT sudo ip6tables -F OUTPUT -t raw is enough to get neutron-linuxbridge-agent working with iptables 1.8.5. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/iptables/+bug/1898547/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp