Re: ARP interfering with Etherboot TFTP?
[email protected] (Geert Stappers) Fri, 3 Mar 2006 20:49:08 +0100
| Newsgroups | gmane.network.etherboot.devel |
|---|---|
| Message-ID | <[email protected]> |
On Fri, Mar 03, 2006 at 05:14:06PM +0000, John Connett/ENG/UK/Plasmon wrote:
> Has anyone experienced problems with ARP interfering with TFTP from
> Etherboot?
>
> I am attempting to load a FreeBSD kernel and all appears to be going
> well with alternate TFTP Data Packet; TFTP Acknowledgement exchanges.
> Then the TFTP server host sends an ARP Who has and it all falls down!
>
> It appears that the server end attempts to receive the first TFTP
> Acknowledgement for Block 10873 but receives ECONNREFUSED and gives
> up.
>
> Attached below are details of the datagrams exchanged around the time
> of the problem and the screen output on the Etherboot client system.
>
> Any thoughts as to the cause of the problem?
Read further for inline comment.
> Thanks in anticipation
> --
> John Connett
>
>
> ----------------------------------------------------------------------
>
> No Time Source Destination Prot Info
> -- ---- ------ ----------- ---- ----
> 54 15.457 10.4.2.152 10.4.2.46 TFTP Data Packet, Block: 10871
Server to Client Data Block n+0
> 55 15.457 10.4.2.46 10.4.2.152 TFTP Acknowledgement, Block: 10871
Client to Server Ack for Data Block n+0
> 56 15.457 10.4.2.152 10.4.2.46 TFTP Data Packet, Block: 10872
Server to Client Data Block n+1
> 57 15.458 10.4.2.46 10.4.2.152 TFTP Acknowledgement, Block: 10872
Client to Server Ack for Data Block n+1
> 58 15.458 10.4.2.152 10.4.2.46 TFTP Data Packet, Block: 10873
Server to Client Data Block n+2
> 59 15.458 skylon.devel 10.4.2.46 ARP Who has 10.4.2.46? Tell 10.4.2.152
Intruder to Client Who has Client? Reply to Server
> 60 15.458 10.4.2.46 10.4.2.152 TFTP Acknowledgement, Block: 10873
Client to Server Ack for Data Block n+2
> 61 15.458 10.4.2.46 skylon.devel ARP 10.4.2.46 is at 00:30:05:83:54:c5
Client to Intruder Client is at my MAC-address
> 62 18.810 10.4.2.46 10.4.2.152 TFTP Acknowledgement, Block: 10873
Client to Server Ack for Data Block n+2
> 63 25.730 10.4.2.46 10.4.2.152 TFTP Acknowledgement, Block: 10873
Client to Server Ack for Data Block n+2
> 64 38.417 10.4.2.46 10.4.2.152 TFTP Acknowledgement, Block: 10873
Client to Server Ack for Data Block n+2
> ----------------------------------------------------------------------
The strange packet is packet #59 where "Intruder" appears the first time.
.... some thinking time ....
I think Server and Intruder are the same computer. I call that computer "Beiden"
Beiden is busy with being TFTP server at the Server address
and for some reason Beiden asks on the Intruder address the MAC-address
of Client and to reply to Server. In #61 Client answers to Intruder, yes
it should have sent the answer to Server.
In packet #60 acknowledges Client the data from #58, but Beiden doesn't answer.
Packet #62 comes after 3 seconds nothing heared from Beiden about #60.
The packets #63 and #64 are also saying "Hey Server, let's continue".
But Server Beiden does not answer.
I don't think it is the Client, Etherboot, that goes bzerk.
About ARP:
> 59 15.458 skylon.devel 10.4.2.46 ARP Who has 10.4.2.46? Tell 10.4.2.152
Intruder to Client Who has Client? Reply to Server
> 61 15.458 10.4.2.46 skylon.devel ARP 10.4.2.46 is at 00:30:05:83:54:c5
Client to Intruder Client is at my MAC-address
I think it is a valid 'Address Resolution Protocol' session.
Hope this helps,
Geert Stappers
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