RTOS/MSP432E401Y: Multiple Interfaces on Common Subnet

Mark Swanson

Expert 3520 points

Part Number: MSP432E401Y
Other Parts Discussed in Thread: CC3120

Tool/software: TI-RTOS

Hi!

Tools

CCS v7.3.0.00019
SimpleLink MSP432E4 SDK v1.55.0.21
SimpleLink SDK WiFi Plugin v1.50.0.38
tcpEcho Example

Goal

I would like to include both the Ethernet and WiFi interfaces in the tcpEcho example, with each one obtaining an IP address via DHCP and responding to tcpSendReceive tests from a PC connected to the same AP as a proof-of-concept.

References - E2E post

Question

* The referenced E2E post indicates packets will not be forwarded/routed from one interface to the other - what implication does this have (from a networking standpoint I guess) for my desired use-case of TCP connections over each interface?

* Is it at all possible to support two interfaces being on the same subnet with the NDK assuming the user knows packets will not be forwarded from the one interface over to the other as warned/mentioned in the other post?

* Are there other ways to approach this problem that I am missing?

Background

I am interested in developing an application using the MSP4320E401Y and TI-RTOS' NDK acting as an HTTP server (and other networking tasks) supporting two interfaces - Ethernet and WiFi. Both interfaces will be connected to the same Access Point.

A custom EMAC driver for the CC3120 placed in bypass mode was previously completed by another individual for a previous TI-RTOS version and device which I have ported to the SDK versions noted above. The tcpEcho example has been successfully modified and tested to work with the WiFi interface (IP acquired through DHCPC, TCP packets echoed).

After adding both interfaces to the NIMUDeviceTable each interface is capable of obtaining an IP address, but once one IP address is obtained the other interface never obtains its own IP address. SysMin contains repeated entries of "BindNew: Duplicate bindings ignored". After performing some research on the E2E forums it appears this is expected behavior of the NDK where no two IP addresses can be on the same subnet.

Any guidance is greatly appreciated!

Best Regards,

Mark-

over 7 years ago

0 Bob Landers over 7 years ago

TI__Expert 8510 points

Mark,

Are you asking to work around the NDK restriction on 2 IP addresses on the same subnet? or are you trying to set up your HTTP server to service the WiFi and Ether interfaces on 2 subnets?

-Bob L.

0 Mark Swanson over 7 years ago in reply to Bob Landers

TI__Expert 3520 points

Hi Bob,

I would prefer to work around the NDK restriction on 2 IP addresses on the same subnet as well as understand any ramifications from doing so (as networking is not a strength of mine).

I did add a second-level check within bind.c to check if the bind request is on a different interface index than the current one and to allow it if they are unique, but I could see how this could be an issue with 3 or more interfaces.

The change allows tcpEcho to function on both Ethernet and WiFi, but I am nervous about introducing bugs and other error conditions as a result of the change.

Best Regards,

Mark-

0 Sai Reddy over 7 years ago in reply to Mark Swanson

TI__Mastermind 22640 points

Hello Mark,

Are you still looking for an answer on your question?

Thanks,
Sai

0 Mark Swanson over 7 years ago in reply to Sai Reddy

TI__Expert 3520 points

Hi Sai,

As this was discussed offline, I am no longer looking for any further answer and the thread can be closed.

Thank you!

Mark-

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RTOS/MSP432E401Y: Multiple Interfaces on Common Subnet