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

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Message-ID: 
 <MWHPR1801MB19185089A3147123D1E877D0D32D2@MWHPR1801MB1918.namprd18.prod.outlook.com>
Date: Mon, 18 Mar 2024 15:36:00 +0000
From: Ratheesh Kannoth <rkannoth@...vell.com>
To: James Lee <lizheng043@...il.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

> 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.