Hi Fabrice,

Thank you for reporting this problem.  Comments inline.

On Mon, Dec 5, 2011 at 11:27 AM, Fabrice Deyber
<[email protected]> wrote:
> Hi Javier, Thomas
> I 'm running some tests on a secured mesh setup and found an issue. My setup
> has four nodes. One of the node, node 4,  is used as a mesh portal and is
> connected to PC. All the nodes (including the portal) send traffic
> constantly to the PC (FTP, iperf...).
> When I bring the secured mesh up, everything works fine. All the nodes are
> within reach of each other so the all the paths (routes) point to the mesh
> portal (one hop).
>
> node 1 <----->
> node 2 <-----> node 4 <====> PC
> node 3 <----->
>
> <=>: Ethernet link
> <-->: mesh link
>
> Now if I bring down one node 1, I can see that I loose traffic for that node
> (which is expected).
>
> node 1 <--X-->
> node 2 <-----> node 4 <====> PC
> node 3 <----->
>
> If I bring node 1 back into the mesh something strange happens. All the
> paths(routes) for all the nodes will point to node 1. All the traffic is
> restored (even if now we have multi-hop routes). The paths should not be
> updated this way.
>
> node 2 <-----> node 1 <----> node 4 <====> PC
> node 3 <----->
>
> Now if I bring back down the node 1, I loose all the traffic from all the
> nodes but the portal (node 4 is Ethernet connected to the PC). Node 2 and
> Node 3 paths still point to node 1.
>
> node 2 <--X--> node 1 <-X--> node 4 <====> PC
> node 3 <--X-->

Your explanation is very good, but I'm afraid I would need wireshark
captures to get to the bottom of this.
Unfortunately at this point all I have is questions:

1. Path selection is identical in secure and open mesh networks.  The
only difference between the two is how peer links are created.  But
once a peer link is created, the paths are discovered in exactly the
same way.  Of course in the secure case, if there are mismatched keys,
path selection will fail.  But this is not what you are seeing.  How
do you bring up/down node 1?  Are you temporarily moving it out of
range?  I'm interested in knowing whether node 1 needs to
re-authenticate when it re-joins the mesh or if it will continue using
the keys from the previous authentication.

> If I wait long enough, several minutes, the nodes seem to recover. This is a
> problem, the mesh should self heal when nodes come and go from the mesh.
>
> This behavior does not happen in an open mesh setup. I'm using
> open80211s-0.5.

2. Just to make sure I understand the problem... In the open mesh
setup, I understand your network just transitions between the two
states below, is that right?

# node 1 up
node 1 <--X-->
node 2 <-----> node 4 <====> PC
node 3 <----->

# node 1 down
node 1 <----->
node 2 <-----> node 4 <====> PC
node 3 <----->

3. When node 1 is down, what is the state of the peer link between
nodes 1 and 4 @node 4?  Is it different in secure vs. open?

4. Is this behavior specific to proxying?  In other words, if you
replace PC for a mesh node (e.g. node 5) and you force the same
topology (by blacklisting nodes 1-3 on node 5 and vice versa), do you
see the same problem?

Cheers,

Javier


-- 
Javier Cardona
cozybit Inc.
http://www.cozybit.com
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