Re: [PATCH v3] net: neighbour: introduce EVICT_NOCARRIER table option

[James Prestwood <prestwoj@gmail.com>]

On Sat, 2021-10-16 at 14:12 +0300, Nikolay Aleksandrov wrote:
> On 15/10/2021 23:06, James Prestwood wrote:
> > This adds an option to ARP/NDISC tables that clears the table on
> > NOCARRIER events. The default option (1) maintains existing
> > behavior.
> > 
> > Clearing the ARP cache on NOCARRIER is relatively new, introduced
> > by:
> [snip]
> > Signed-off-by: James Prestwood <prestwoj@gmail.com>
> > ---
> >  Documentation/networking/ip-sysctl.rst |  9 +++++++++
> >  include/net/neighbour.h                |  3 ++-
> >  include/uapi/linux/neighbour.h         |  1 +
> >  net/core/neighbour.c                   | 18 +++++++++++++-----
> >  net/ipv4/arp.c                         |  1 +
> >  net/ipv6/ndisc.c                       |  1 +
> >  6 files changed, 27 insertions(+), 6 deletions(-)
> > 
> > diff --git a/Documentation/networking/ip-sysctl.rst
> > b/Documentation/networking/ip-sysctl.rst
> > index 16b8bf72feaf..e2aced01905a 100644
> > --- a/Documentation/networking/ip-sysctl.rst
> > +++ b/Documentation/networking/ip-sysctl.rst
> > @@ -200,6 +200,15 @@ neigh/default/unres_qlen - INTEGER
> >  
> >         Default: 101
> >  
> > +neigh/default/evict_nocarrier - BOOLEAN
> > +       Clears the neighbor cache on NOCARRIER events. This option
> > is important
> > +       for wireless devices where the cache should not be cleared
> > when roaming
> > +       between access points on the same network. In most cases
> > this should
> > +       remain as the default (1).
> > +
> > +       - 1 - (default): Clear the neighbor cache on NOCARRIER
> > events
> > +       - 0 - Do not clear neighbor cache on NOCARRIER events
> > +
> >  mtu_expires - INTEGER
> >         Time, in seconds, that cached PMTU information is kept.
> >  
> > diff --git a/include/net/neighbour.h b/include/net/neighbour.h
> > index e8e48be66755..71b28f83c3d3 100644
> > --- a/include/net/neighbour.h
> > +++ b/include/net/neighbour.h
> > @@ -54,7 +54,8 @@ enum {
> >         NEIGH_VAR_ANYCAST_DELAY,
> >         NEIGH_VAR_PROXY_DELAY,
> >         NEIGH_VAR_LOCKTIME,
> > -#define NEIGH_VAR_DATA_MAX (NEIGH_VAR_LOCKTIME + 1)
> > +       NEIGH_VAR_EVICT_NOCARRIER,
> > +#define NEIGH_VAR_DATA_MAX (NEIGH_VAR_EVICT_NOCARRIER + 1)
> >         /* Following are used as a second way to access one of the
> > above */
> >         NEIGH_VAR_QUEUE_LEN, /* same data as
> > NEIGH_VAR_QUEUE_LEN_BYTES */
> >         NEIGH_VAR_RETRANS_TIME_MS, /* same data as
> > NEIGH_VAR_RETRANS_TIME */
> > diff --git a/include/uapi/linux/neighbour.h
> > b/include/uapi/linux/neighbour.h
> > index db05fb55055e..4322e5f42646 100644
> > --- a/include/uapi/linux/neighbour.h
> > +++ b/include/uapi/linux/neighbour.h
> > @@ -151,6 +151,7 @@ enum {
> >         NDTPA_LOCKTIME,                 /* u64, msecs */
> >         NDTPA_QUEUE_LENBYTES,           /* u32 */
> >         NDTPA_MCAST_REPROBES,           /* u32 */
> > +       NDTPA_EVICT_NOCARRIER,          /* u8 */
> >         NDTPA_PAD,
> >         __NDTPA_MAX
> >  };
> 
> I think this should be the last attribute (after PAD).

Sure.

> 
> Since this is a single patch you don't really need a cover letter,
> you can add the version
> changes below ---. Also your cover letter says v2 and the patch says
> v3.

Ok, I'll move it into the patch itself.

Thanks,
James
> 
> Cheers,
>  Nik
>