Re: AODVv2 implementation

I think that further exploration of AODVv2 and any AODV
implementation problems would be useful topics for the MNET WG and that we
should consider adding that to the Charter.

Thanks,
Donald
===============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 2386 Panoramic Circle, Apopka, FL 32703 USA
 [email protected]

On Mon, Dec 4, 2023 at 8:42 AM Adamson, Robert B CIV USN NRL (5592)
Washington DC (USA) <[email protected]> wrote:

> As Justin Dean mentioned, our nrlsmf code can act as tun/tap user-space
> forwarding engine (and works on Linux (including Android ... although newer
> Android policies have locked out use of some the the netlink APIs and I
> haven't tested that in a while), OSX/BSD, and even Windows with use of
> WinTAP (or whatever it's called).  We have done some stuff with that using
> our own forwarding tables or with the OS tables but not yet for AODV.  For
> AODV some sort of extra packet caching could be useful or do something
> similar with what we do with the Elastic Multicast implementation to flood
> until the "on demand" route is established.  Related to that the "nrlsmf"
> code has support for some hybrid policies that can be set related to
> flooding/forwarding such as token bucket limited forwarding rate until a
> route is established or flooding a small number (e.g, burst) of packets
> initially upon a new flow until a route is established.  With a little
> tweaking, these could be extended a little bit to support other caching
> strategies if desired.
>
> Also, with the code, I have _slowly_ been refactoring code to keep the
> forwarding plane aspects of the the nrlsmf "engine" distinct and separate
> from the control plane aspects with the idea in mind to eventually have the
> forwarding plane code be used independently in a kernel module (or
> elsewhere) with the various forwarding plane features we see needed for
> these sorts of protocols including duplicate packet detection, control
> plane updates like mentioned for AODV2 below, per-flow forwarding state,
> etc.  It's been _slow_ since my time to work on it is quite limited these
> days.  Meanwhile, we do get pretty good performance with it in user space,
> and I know there's improvements that could be made.
>
> If the kernel forwarding table is used, there are ways (not pretty) to
> update by using a pcap socket to monitor packets and do that independently
> of the actual forwarding.  Again, not pretty or efficient, but a work
> around until such features are resident in the forwarding engine.  That's
> one of the things I see needed, including for the Elastic Multicast
> protocol operation, to have the forwarding plane notify the control plane,
> at least periodically and/or on an event-driven basis (e.g., new flow
> detected).  On Linux, I think that ideally would be through a netlink
> interface and my thought on encapsulating a forwarding mechanism like what
> "nrlsmf" provides into a kernel module would include that interface.  For
> example, to support the "per flow" packet processing and such
> notifications, I created a "Flow Description" data structure that's also
> used as an index on a modified Patricia Trie prefix-based radix tree (with
> field wildcarding support) to detect, identify, and classify packet flows
> for such purposes.
>
> Cheers,
>
> Brian
>
> On 12/4/23, 9:04 AM, "manet on behalf of Henning Rogge" <
> [email protected] <mailto:[email protected]> on behalf of
> [email protected] <mailto:[email protected]>> wrote:
>
>
> Hi,
>
>
> I was thinking about how to implement AODV2 on a TUN but hit an
> interesting issue when reading through the "Interaction with the
> Forwarding Plane" chapter of AODVv2...
>
>
> Chapter 6.4:
> "AODVv2 needs to update the record of when a route was last used to
> forward a packet".
>
>
> Does this mean AODV cannot use the kernel routing forwarding system
> and is expected to do everything in user space? I ask because the
> "routing cache" (and its statistics for each route) were removed from
> Linux in version 3.6.
>
>
> Henning Rogge
>
>
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