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Date: Thu, 10 Apr 2025 15:17:17 +0200
From: Florian Westphal <fw@strlen.de>
To: lvxiafei <xiafei_xupt@163.com>
Cc: fw@strlen.de, coreteam@netfilter.org, davem@davemloft.net,
	edumazet@google.com, horms@kernel.org, kadlec@netfilter.org,
	kuba@kernel.org, linux-kernel@vger.kernel.org,
	lvxiafei@sensetime.com, netdev@vger.kernel.org,
	netfilter-devel@vger.kernel.org, pabeni@redhat.com,
	pablo@netfilter.org
Subject: Re: [PATCH V3] netfilter: netns nf_conntrack: per-netns
 net.netfilter.nf_conntrack_max sysctl
Message-ID: <20250410131717.GA14051@breakpoint.cc>
References: <20250409094206.GB17911@breakpoint.cc>
 <20250410130531.17824-1-xiafei_xupt@163.com>
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User-Agent: Mutt/1.10.1 (2018-07-13)

lvxiafei <xiafei_xupt@163.com> wrote:
> Florian Westphal <fw@strlen.de> wrote:
> > I suggest to remove nf_conntrack_max as a global variable,
> > make net.nf_conntrack_max use init_net.nf_conntrack_max too internally,
> > so in the init_net both sysctls remain the same.
> 
> The nf_conntrack_max global variable is a system calculated
> value and should not be removed.
> nf_conntrack_max = max_factor * nf_conntrack_htable_size;

Thats the default calculation for the initial sysctl value:

net/netfilter/nf_conntrack_standalone.c:                .data           = &nf_conntrack_max,
net/netfilter/nf_conntrack_standalone.c:                .data           = &nf_conntrack_max,

You can make an initial patch that replaces all occurences of
nf_conntrack_max with cnet->sysctl_conntrack_max

(adding a 'unsigned int sysctl_conntrack_max' to struct
 nf_conntrack_net).

Then, in a second patch, remove the '0444' readonly and redirect
the child netns to use the copy in its own pernet area rather than the
init_net one.