[Olsr-users] OLSR mesh and a PC with ad-hoc link but without OLSR - Options and Issues

Bhat, Ishwara (spam-protected)
Wed Jan 14 17:54:09 CET 2009



I have the following problem and I need your valuable suggestions on


I have a set of embedded wireless devices and one PC. All of these have
only one NIC - a Wi-Fi interface. 


The requirement is that - 


1.	All embedded devices can run OLSR and can form mesh. 
2.	PC is also within 1-hop distance from the mesh (i.e. at least
one OLSR device is within 1-hop from the PC). But it is preferred "not
to have OLSRd running". But it should work as if it is part of the mesh.
i.e. I should be able to send packet from the PC to any of the mesh
nodes. And also, any of the mesh nodes shall be able to send packets to
the PC. PC shall not do mesh control activities
3.	From requirement perspective, there is no constraint on the
subnets. They can be in the same subnet. 
4.	All the embedded nodes are mobile and the devices in 1-hop
distance could dynamically change.


What would work - 


            From my past discussion this this group I understand that
there is no issue in packet from the PC reaching any of the nodes in the


            We can block PC doing mesh control activities such as MPR.


What may not work - 


            But the return path (i.e. a packet originating in any mesh
node reaching the PC) seems to be the problem. Unless that node is
within 1-hop distance from the     PC, it can not reach the PC. 


Is there any solution to this ? 


"Here are some options I am looking at. Please go through and answer my


1.	a. Is there any routing table setting that says that " If the
route is not known, send this packet to a gateway ? " 

            or - if the packet is for a particular IP then send it to a
particular known node's IP (This is not HNA. In HNA we "register" a new
network to this mesh. Here I am talking about just one IP address)?


       Is this possible ?


      1. b. If (1.a.) can I write a plugin which checks whether I am
1-hop away from the PC (I know the IP address) ? My concern is that I
may have to implement my own Hello packet in my plugin as well as in PC.

My second concern is that if there is an established gateway with my own
hello packets, then the packets from every node would reach PC through
the established gateway. So every node might think that they are within
1 hop from the PC and tell every other mesh node that they are the
gateway. There could be infinite loop.. ?



If 1.a and 1.b work, then I can achieve my goal.


2. Some proxy application - 


Is there any way a proxy application/server be used in the node 1-hop
away from the PC ? This application could modify the destination IP


All the nodes shall "note" the "i-am-the-gateway" announcement from a
particular node (if question 1.b works) . Whenever they need to send a
packet to the PC they shall send it this 'gateway'. The application in
this gteway node could modify the packet such that destination IP field
is filled with PC's IP.



3. Virtual IP and HNA:


Can any virtual IP be set (I have only one NIC which is a Wi-fi) and HNA
be used ? 


There was a suggestion from this forum to use NAT for this case. But NAT
needs 2 NICs to be present. 



Considering the requirements please tell me if anything is feasible to
meet the above. (It is about making the PC part of mesh without running
OLSR on it).




Thank you very very much.





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