linux-kernel - Re: [EXTERNAL] Re: [PATCH] neighbour: guarantee the localhost connections be established successfully even the ARP table is full

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Date: Tue, 19 Mar 2024 17:42:34 +0800
From: James Lee <lizheng043@...il.com>
To: Ratheesh Kannoth <rkannoth@...vell.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "nhorman@...driver.com" <nhorman@...driver.com>, 
	"davem@...emloft.net" <davem@...emloft.net>, "jmorris@...ei.org" <jmorris@...ei.org>, 
	"James.Z.Li@...l.com" <James.Z.Li@...l.com>
Subject: Re: [EXTERNAL] Re: [PATCH] neighbour: guarantee the localhost
 connections be established successfully even the ARP table is full

It's not an issue, the loopback device can only be created by kernel
itself, loopback neigh entry also can only be created by kernel, one
loopback neigh for ipv4 ,one for ipv6, impossible that the num of
loopback neigh entries exceeds 2.

Ratheesh Kannoth <rkannoth@...vell.com> 于2024年3月18日周一 23:36写道：
>
> > From: James Lee <lizheng043@...il.com>
> > Sent: Monday, March 18, 2024 2:09 PM
> > To: Ratheesh Kannoth <rkannoth@...vell.com>
> > Cc: linux-kernel@...r.kernel.org; netdev@...r.kernel.org;
> > nhorman@...driver.com; davem@...emloft.net; jmorris@...ei.org;
> > James.Z.Li@...l.com
> > Subject: [EXTERNAL] Re: [PATCH] neighbour: guarantee the localhost
> > connections be established successfully even the ARP table is full
> >
> > Prioritize security for external emails: Confirm sender and content safety
> > before clicking links or opening attachments
> >
> > ----------------------------------------------------------------------
> > loopback neigh is a special device in the neighbour system which is used by all
> > local communications and state is NUD_NOARP.
> > Any setting value of gc_thresh3 might encounter arp table be full, manually
> > increasing gc_thresh3 can resolve this issue for every time, but we hope this
> > issue automatically be resolved in Linux kernel for all local communications
> > whenever ARP table is full, rather than manually operation as a workaround.
>
> Issue is , these are dynamic entries which cannot be removed by gc.  And there is no
> Threshold applicable on it.  I feel like, this may be exploited.
>