linux-kernel - Re: [PATCH 4.14 03/35] neighbor: Call __ipv4_neigh_lookup_noref in neigh

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Date:   Mon, 10 Jun 2019 10:10:25 +0900
From:   Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Alan Maguire <alan.maguire@...cle.com>,
        David Ahern <dsahern@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 4.14 03/35] neighbor: Call __ipv4_neigh_lookup_noref in
 neigh_xmit

Hi,

On Sun, Jun 09, 2019 at 06:42:09PM +0200, Greg Kroah-Hartman wrote:
> From: David Ahern <dsahern@...il.com>
> 
> [ Upstream commit 4b2a2bfeb3f056461a90bd621e8bd7d03fa47f60 ]
> 
> Commit cd9ff4de0107 changed the key for IFF_POINTOPOINT devices to
> INADDR_ANY but neigh_xmit which is used for MPLS encapsulations was not
> updated to use the altered key. The result is that every packet Tx does
> a lookup on the gateway address which does not find an entry, a new one
> is created only to find the existing one in the table right before the
> insert since arp_constructor was updated to reset the primary key. This
> is seen in the allocs and destroys counters:
>     ip -s -4 ntable show | head -10 | grep alloc
> 
> which increase for each packet showing the unnecessary overhread.
> 
> Fix by having neigh_xmit use __ipv4_neigh_lookup_noref for NEIGH_ARP_TABLE.
> 
> Fixes: cd9ff4de0107 ("ipv4: Make neigh lookup keys for loopback/point-to-point devices be INADDR_ANY")
> Reported-by: Alan Maguire <alan.maguire@...cle.com>
> Signed-off-by: David Ahern <dsahern@...il.com>
> Tested-by: Alan Maguire <alan.maguire@...cle.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---

This commit also requires the following commit:

commit 9b3040a6aafd7898ece7fc7efcbca71e42aa8069
Author: David Ahern <dsahern@...il.com>
Date:   Sun May 5 11:16:20 2019 -0700

    ipv4: Define __ipv4_neigh_lookup_noref when CONFIG_INET is disabled

    Define __ipv4_neigh_lookup_noref to return NULL when CONFIG_INET is disabled.

    Fixes: 4b2a2bfeb3f0 ("neighbor: Call __ipv4_neigh_lookup_noref in neigh_xmit")
    Reported-by: kbuild test robot <lkp@...el.com>
    Signed-off-by: David Ahern <dsahern@...il.com>
    Signed-off-by: David S. Miller <davem@...emloft.net>

And this is also necessary for 4.4.y, 4.14.y, 4.19.y and 5.1.y.
Please apply this commit.

Best regards,
  Nobuhiro