[U-Boot-Users] Multicast TFTP problems

[David Updegraff <dave@cray.com>]

Sorry all; I've lost access to my testbed hardware, so for now am out of
the loop.


> Rafal Jaworowski wrote:
>> Dave,
>>
>> I'm having problems with tftp transfer with current U-Boot running on 
>> MPC5121 (FEC controller); since your mcast tftp implementation we first 
>> attempt to transfer using some bigger blocksize:
>> #define TFTP_MTU_BLOCKSIZE 1468, and it seems my problems are related to 
>> this size.
>>
>> When running current code (ET_DEBUG enabled) it fails like the following:
>>
>> => run load
>> Using FEC ETHERNET device
>> TFTP from server 192.168.1.1; our IP address is 192.168.160.77
>> Filename '/tftpboot/ads5121/u-boot.bin'.
>> Load address: 0x100000
>> Loading: send option "timeout 5"
>> Got OACK: timeout 5
>> Blocksize ack: 1468, 1468
>> T T T T T T T T T T
>> Retry count exceeded; starting again
>> Using FEC ETHERNET device
>> TFTP from server 192.168.1.1; our IP address is 192.168.160.77
>> Filename '/tftpboot/ads5121/u-boot.bin'.
>> Load address: 0x100000
>> Loading: send option "timeout 5"
>> Got OACK: timeout 5
>> Blocksize ack: 1468, 1468
>>
>> Abort
>> =>
>>
>> It fails with TFTP_MTU_BLOCKSIZE values above 1454, but it's ok with 
>> anything up to this (including 1454):
>>
>> => run load
>> Using FEC ETHERNET device
>> TFTP from server 192.168.1.1; our IP address is 192.168.160.77
>> Filename '/tftpboot/ads5121/u-boot.bin'.
>> Load address: 0x100000
>> Loading: send option "timeout 5"
>> Got OACK: timeout 5
>> Blocksize ack: 1454, 1454
>> ###########
>> done
>> Bytes transferred = 157720 (26818 hex)
>> =>
>>
>> Any hints on these observations? What might be going wrong here?
>>
>> kind regards,
>> Rafal
>>   
> TFTP packets are structured as follows:
> 
> | Eth header (14 bytes) | IP header (20 bytes) | UDP header (8 bytes) | 
> TFTP message | Eth FCS (4 bytes) |
> 
> You can see that the total overhead is 46 bytes. If your network port's 
> maximum MTU size is 1500 bytes (the default), the math works out for a 
> maximum TFTP PDU size of 1454 bytes.
> 
> However... the Ethernet header/trailer is not supposed to be included in 
> the MTU. I suspect we have a terminology problem here. Let me dig a bit 
> further to find out what's going on.
> 
> regards,
> Ben
> 
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