[lwip-users] Applications to TCP/IP offload

[Curt McDowell]

Hi,

I'm looking into using lwIP as the basis for a TOE (TCP/IP offload engine).  If I understand correctly, the lwIP environment is implemented as one thread for the IP stack, and one thread for each application:

    APPLICATION THREAD                            IP STACK THREAD
App <-> Sockets <-> API-mux <------------> API-demux <-> Stack <-> netif
                            mbox transport

This architecture appears to lend itself fairly well to the following TOE implementation (actually, SOE, as it would be a full sockets offload):

         HOST PROCESSOR                     TOE ADAPTER W/ EMBEDDED CPU
+-------------+   +--------------+            +-------+   +----------+
| App using   |---| lwIP library |------------| lwIP  |---| Network  |--->
| sockets API |   | Sockets API  |  Hardware  | stack |   | hardware |
+-------------+   +--------------+    bus     +-------+   +----------+

- Does this assessment sound correct?
- Could a significant performance improvement be realized, compared to using a host-native IP stack?
- Is anyone else interested in this type of application?

The only problems that I see are with the mbox transport mechanism, in that it assumes a shared address space.

-  It would need to send the data, instead of pointers to the data.
-  It would need to send messages for event notifications instead of using callbacks.
- Message reception on either side of the hardware bus would be signaled through interrupts.

Thanks,
Curt McDowell
Broadcom Corp.