TDA4VM: ARP communication is not standard ?

jingang zhang

Part Number: TDA4VM

Hi TI expert,
I use sdk8.2 QNX+RTOS, TDA4 connect to PC via cpsw9g,RGMII, Now I find a issue:
I set IP 192.168.1.90 in QNX of TDA4 and the same segment IP192.168.1.20 in PC. I ping TDA4 from PC.
By wireshark, I find that, although ping is OK. the ARP communication is not standard.

From above picture, we can see that firstly PC sends ARP broadcast, as it doesn't know the MAC address of TDA4.
and TDA4 get the message and do a ARP reply to PC. According to the protocol, now TDA4 has already get the MAC address of PC.
So when PC sends ICMP request, TDA4 should directly do a ICMP reply.
But, from picture we see that TDA4 again sends a ARP broadcast, and get ARP reply from PC, until now TDA4 start doing a ICMP reply.

According protocol, TDA4 should not send ARP broadcast request again, as it has already known the MAC address of PC.
Is this the TI SDK issue ? Does TI SDK not support the standard ARP? How to fix it ?

over 2 years ago

0 Doredla Sudheer Kumar over 2 years ago

TI__Guru 63310 points

Hi Zhang,

I see two way ARP communication in attached Wireshark Image.
It is expected behavior, as per below sequence.

QNX is a Virtual Switch port, It will register IP address with Ethfw.
Ethfw will register an ALE entry for QNX with MAC address of QNX client.
As we are pining from PC. ARP will be sent from PC to CPSW, which is a Broadcast message and will be forwarded to Ethfw.
ARP proxy running on top of Ethfw will respond to ARP request on behalf of QNX client.
As PC side ARP is resolved, it will send ICMP (Ping) frame to CPSW with QNX client MAC address, It will be forwarded to QNX directly because of ALE entry corresponding to QNX MAC address.
QNX side, Network will not have a ARP table corresponding to incoming ICMP frame so, it will send ARP request to the IP received in ICMP frame.
Now, PC will respond back to the ARP request of QNX Network stack so, QNX side ARP entry will be added.
After above ping (ICMP) request and response will be followed.

Summary:
Above behavior is because of Broadcast packets will be routed to Ethfw and ARP response will sent by "Proxy ARP" on top of Ethfw on behalf of client cores.

We have support for Inter-core Virtual Ethernet communication from 8.2 SDK onwards, If we enable this feature it will forward broadcast packets to all client cores from Ethfw.
In this case QNX will directly respond for ARP request from PC.
Note: We need to disable "Proxy ARP" and Enable "Inter-core Ethernet communication" for this.

Refer to below User Guide for more details.

https://software-dl.ti.com/jacinto7/esd/processor-sdk-rtos-jacinto7/08_02_00_05/exports/docs/ethfw/docs/user_guide/ethfw_c_ug_top.html#ethfw_intercore_eth

https://software-dl.ti.com/jacinto7/esd/processor-sdk-rtos-jacinto7/08_02_00_05/exports/docs/ethfw/docs/user_guide/demo_ethfw_combined_top.html#ethfw_intercore_communication

Best Regards,
Sudheer

0 jingang zhang over 2 years ago in reply to Doredla Sudheer Kumar

Prodigy 160 points

Hi Sudheer,

Thank you very much for your reply. For your explanation, I know why.

But, what I research from TI DOC or E2E，I can't see that it support QNX client about Inter-core feature.
(1), In the User Guide you provide, it just describe LINUX and RTOS client, and no QNX.
(2), In SDK8.2, I see the configurate in file ethfw/ethfw_build_flags.mak as follow:

It shows that if QNX_A72, it will config ETHFW_INTERCORE_ETH_SUPPORT?=no, which I think that inter-core ethernet not support QNX.
(3), From E2E, I see another TI expert said in the page(https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1091464/dra821u-cpsw5g-vlan-configuration):

If it really supports QNX Inter-core virtual Ethernet communicate, Could you please tell me:
(1), How to modify it? Can you provide a patch or modify location ?
(2), Whether this change has any other effect on the network?

Please help to confirm it , Thank you very much.

0 Doredla Sudheer Kumar over 2 years ago in reply to jingang zhang

TI__Guru 63310 points

Hi Zhang,

Sorry, Inter-core Virtual Ethernet not supported in QNX and AUTOSAR clients, and It supported only on Linux and RTOS clients.

Best Regards,
Sudheer

0 jingang zhang over 2 years ago in reply to Doredla Sudheer Kumar

Prodigy 160 points

Hi Sudheer，

Does TI have plan to realize inter-core feature in QNX system？
Or could you please provide ideas such as ALE or other method to realize broadcast forwarding to A72 ?

Thanks.

0 Doredla Sudheer Kumar over 2 years ago in reply to jingang zhang

TI__Guru 63310 points

Hi Zhang,

jingang zhang said:
Does TI have plan to realize inter-core feature in QNX system？

Not sure, will check with development team.

jingang zhang said:
Or could you please provide ideas such as ALE or other method to realize broadcast forwarding to A72 ?

Yes, We can add ALE entry to forward broadcast packets to A72.
But, if we add above broadcast packets will not be forwarded to other clients cores & Ethfw.

If two way ARP is not a problem in customer environment, it is recommend to use as is. If not, can forward broadcast to A72 and use.

Please refer to E2E thread supported for above.

Best Regards,
Sudheer

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TDA4VM: ARP communication is not standard ?