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

On Sat, 2021-10-16 at 14:12 +0300, Nikolay Aleksandrov wrote:

On 15/10/2021 23:06, James Prestwood wrote:

quoted

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]

quoted

Signed-off-by: James Prestwood <redacted>
---
 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