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Date:   Thu, 13 May 2021 11:40:47 +0200
From:   Pablo Neira Ayuso <pablo@netfilter.org>
To:     Dexuan Cui <decui@microsoft.com>
Cc:     "'netfilter-devel@vger.kernel.org'" <netfilter-devel@vger.kernel.org>,
        "'netdev@vger.kernel.org'" <netdev@vger.kernel.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: Re: netfilter: iptables-restore: setsockopt(3, SOL_IP,
 IPT_SO_SET_REPLACE, "security...", ...) return -EAGAIN
Message-ID: <20210513094047.GA24842@salvia>
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On Thu, May 13, 2021 at 06:19:38AM +0000, Dexuan Cui wrote:
> > From: Dexuan Cui
> > Sent: Wednesday, May 12, 2021 11:02 PM
> 
> BTW, I found a similar report in 2019:
> 
> "
> https://serverfault.com/questions/101022/error-applying-iptables-rules-using-iptables-restore
> I stumbled upon this issue on Ubuntu 18.04. The netfilter-persistent
> service failed randomly on boot while working ok when launched manually.
> Turned out it was conflicting with sshguard service due to systemd trying
> to load everything in parallel. What helped is to setting
> ENABLE_FIREWALL=0 in /etc/default/sshguard and then adding sshguard chain
> and rule manually to /etc/iptables/rules.v4 and /etc/iptables/rules.v6.
> "
> 
> The above report provided a workaround.

There's -w and -W to serialize ruleset updates. You could follow a
similar approach from userspace if you don't use iptables userspace
binary.

> I think we need a real fix.

iptables-nft already fixes this.