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

[Greg KH]

On Mon, Jun 10, 2019 at 01:13:16AM +0000, nobuhiro1.iwamatsu@xxxxxxxxxxxxx wrote:
> 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.

Thanks for the information, now queued up everywhere.

greg k-h