Syslinux - Jul 2009 - tftp-hpa fails after lost data packet

Hello,
I am using the tftp-hpa 0.48 as delivered in Linux Fedora Core 9 as a 
client to send a file to another server on an unreliable network.
The transaction is sometimes timing out.

I have monitored the the TFTP packets to see what is missing.

It seems a DATA packet is being lost. The server is repeating the ACKs 
for the previous packet every three seconds. I think these repeated ACKs 
are preventing the receive packet operation in the tftp-hpa client from 
timing out, so that the client never resends the missing DATA
packet. And ultimately the whole transaction fails.

In contrast, if I suddenly turn off the power of the server, then I
do see repeated data packets sent by tftp-hpa, as expected.

Is this a minor bug, or have I mis-understood the TFTP specs?

John

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John Smith wrote:
> Hello,
> I am using the tftp-hpa 0.48 as delivered in Linux Fedora Core 9 as a
> client to send a file to another server on an unreliable network.
> The transaction is sometimes timing out.
> 
> I have monitored the the TFTP packets to see what is missing.
> 
> It seems a DATA packet is being lost. The server is repeating the ACKs
> for the previous packet every three seconds. I think these repeated ACKs
> are preventing the receive packet operation in the tftp-hpa client from
> timing out, so that the client never resends the missing DATA
> packet. And ultimately the whole transaction fails.
> 
> In contrast, if I suddenly turn off the power of the server, then I
> do see repeated data packets sent by tftp-hpa, as expected.
> 
> Is this a minor bug, or have I mis-understood the TFTP specs?
> 
No, you're correct.  tftp-hpa really hasn't had too much attention spent
on the client, but the reset behavior is incorrect.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.