Re: [RESEND PATCH v7 2/3] net: ndisc: introduce ndisc_evict_nocarrier sysctl parameter

[David Ahern <dsahern@gmail.com>]

On 10/25/21 10:45 AM, James Prestwood wrote:
> In most situations the neighbor discovery cache should be cleared on a
> NOCARRIER event which is currently done unconditionally. But for wireless
> roams the neighbor discovery cache can and should remain intact since
> the underlying network has not changed.
> 
> This patch introduces a sysctl option ndisc_evict_nocarrier which can
> be disabled by a wireless supplicant during a roam. This allows packets
> to be sent after a roam immediately without having to wait for
> neighbor discovery.
> 
> A user reported roughly a 1 second delay after a roam before packets
> could be sent out (note, on IPv4). This delay was due to the ARP
> cache being cleared. During testing of this same scenario using IPv6
> no delay was noticed, but regardless there is no reason to clear
> the ndisc cache for wireless roams.
> 
> Signed-off-by: James Prestwood <prestwoj@gmail.com>
> ---
>  Documentation/networking/ip-sysctl.rst |  9 +++++++++
>  include/linux/ipv6.h                   |  1 +
>  include/uapi/linux/ipv6.h              |  1 +
>  net/ipv6/addrconf.c                    | 12 ++++++++++++
>  net/ipv6/ndisc.c                       | 12 +++++++++++-
>  5 files changed, 34 insertions(+), 1 deletion(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>