linux-kernel - Re: [PATCH V2] netfilter: nf_conntrack: table full detailed log

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Message-ID: <aINUlqscselprHTd@calendula>
Date: Fri, 25 Jul 2025 11:55:34 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: Florian Westphal <fw@...len.de>
Cc: lvxiafei <xiafei_xupt@....com>, coreteam@...filter.org,
	davem@...emloft.net, edumazet@...gle.com, horms@...nel.org,
	kadlec@...filter.org, kuba@...nel.org, linux-kernel@...r.kernel.org,
	lvxiafei@...setime.com, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, pabeni@...hat.com
Subject: Re: [PATCH V2] netfilter: nf_conntrack: table full detailed log

On Fri, Jul 25, 2025 at 01:55:33AM +0200, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@...filter.org> wrote:
> > I was thinking, does the packet logging exposes already the
> > net->ns.inum? IIUC the goal is to find what netns is dropping what
> > packet and the reason for the packet drop, not only in this case but
> > in every case, to ease finding the needle in the stack. If so, then it
> > probably makes sense to consolidate this around nf_log()
> > infrastructure.
> 
> No, it doesn't.  It also depends on the backend:
> for syslog, nothing will be logged unless nf_log_all_netns sysctl is
> enabled.
> 
> For nflog, it is logged, to the relevant namespaces ulogd, or not in
> case that netns doesn't have ulogd running.
> 
> For syslog one could extend nf_log_dump_packet_common() but I'm not sure
> how forgiving existing log parsers are when this gets additional
> field.
> 
> Also, would (in case we use this for the "table full" condition), should
> this log unconditionally or does it need a new sysctl?
> 
> Does it need auto-ratelimit (probably yes, its called during packet
> flood so we dont want to flood syslog/ulog)?

Yes, such extension would need to answer these questions.

> > Anyway, maybe I'm overdoing, I'll be fine with this approach if you
> > consider it good enough to improve the situation.
> 
> I think its better than current state of affairs since it at least
> allows to figure out which netns is experiencing this.

Thanks for explaining, let's take this patch as is then.