RE: [PATCH 4.14 03/35] neighbor: Call __ipv4_neigh_lookup_noref in neigh_xmit

[nobuhiro1.iwamatsu]

Hi again.

> -----Original Message-----
> From: stable-owner@xxxxxxxxxxxxxxx
> [mailto:stable-owner@xxxxxxxxxxxxxxx] On Behalf Of Nobuhiro Iwamatsu
> Sent: Monday, June 10, 2019 10:10 AM
> To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; Alan Maguire
> <alan.maguire@xxxxxxxxxx>; David Ahern <dsahern@xxxxxxxxx>; David S.
> Miller <davem@xxxxxxxxxxxxx>
> 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@xxxxxxxxx>
> >
> > [ 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@xxxxxxxxxx>
> > Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
> > Tested-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> > Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> 
> This commit also requires the following commit:
> 
> commit 9b3040a6aafd7898ece7fc7efcbca71e42aa8069
> Author: David Ahern <dsahern@xxxxxxxxx>
> 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@xxxxxxxxx>
>     Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
>     Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> 
> And this is also necessary for 4.4.y, 4.14.y, 4.19.y and 5.1.y.

4.4.y, 4.9.y, 4.19.y and 5.1.y.

> Please apply this commit.
> 
Best regards,
  Nobuhiro