[U-Boot-Users] RE: Ethernet loopback command

Jerry Van Baren gerald.vanbaren at smiths-aerospace.com
Tue Mar 8 17:00:35 CET 2005

Thomas Schäfer wrote:
> Hi, 
>>-----Original Message-----
>>From: wd at denx.de [mailto:wd at denx.de] 


>>I also don't understand why specific ethernet packet  types  
>>must  be invented. I don't like such non-standard solutions.
> The PROT_IP part of the NetReceive function examines the complete IP
> header which is not necessary here. I introduced that packet type to
> achieve a proper separtion from all other packet types. Normally the
> generated packet would remain on the board because PHY or EMAC are
> switched into loopback mode, but i agree that those non-standard packets
> could be problematic when sent to a network.

Just a thought... I have not looked at the code, so I don't know how 
practical/reasonable this thought is...

If you sent a "ping" (ICMP echo-request) packet and had your loopback 
responder return a "ping" response (ICMP echo-reply) this will be a 
standard packet and may be useful elsewhere.

* Ping packet (echo-request) generation and parsing (echo-reply) is 
already present in u-boot.  If you can reuse this code, you are that 
much further ahead.

* If you add a handler for echo-request packets, returning echo-reply 
packets, this would potentially be useful for responding to external 
computers "ping" requests (currently not implemented because of limited 
usefulness and implementation issues).


> Best regards,
> Thomas Schäfer


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