From: Mahesh Bandewar <mah...@bandewar.net>
Date: Fri, 6 Jan 2017 16:33:11 -0800
> From: Mahesh Bandewar <mahe...@google.com>
>
> The patch 009146d117b ("ipvlan: assign unique dev-id for each slave
> device.") used ida_simple_get() to generate dev_ids assigned to the
> slave devices. However (Eric has pointed out that) there is a shortcoming
> with that approach as it always uses the first available ID. This
> becomes a problem when a slave gets deleted and a new slave gets added.
> The ID gets reassigned causing the new slave to get the same link-local
> address. This side-effect is undesirable.
>
> This patch replaces IDR logic with a simple per-port variable that keeps
> incrementing and wraps around when the MAX (0xFFFE) is reached. The
> only downside is that this is an inefficient (n^2) search if there are
> 64k (or close to 64k) slaves in the system, the dev-id search takes time.
> However having these many devices in the system has it's own challenges.
>
> Fixes: 009146d117b ("ipvlan: assign unique dev-id for each slave device.")
> Signed-off-by: Mahesh Bandewar <mahe...@google.com>
I kind of cringe when I see yet another implementation of an integer ID
allocator.
I think it's much simpler to keep using ida_simple_alloc(), but alongside
it have start point you maintain based upon previous allocations. Put it
in the ipvl_port, just like dev_id_base, but call it "dev_id_start".
Then your ID allocation sequence becomes:
err = ida_simple_get(&port->ida, port->dev_id_start, 0xFFFE,
GFP_KERNEL);
if (err < 0)
err = ida_simple_get(&port->ida, 0, port->dev_id_start,
GFP_KERNEL);
if (err < 0)
goto destroy_ipvlan_port;
dev->dev_id = err;
port->dev_id_start = err;
if (port->dev_id_start = 0FFFE)
port->dev_id_start = 0;
Something like that.
Alternatively, IDR/IDA can be extended to have this kind of functionality
too.
