no udp response on FreeBSD/arm

Ronald Klop ronald-freebsd8@klop.yi.org
Sun Jun 24 15:58:43 UTC 2012


On Sun, 24 Jun 2012 16:33:43 +0200, Vernon Schryver <vjs@rhyolite.com>  
wrote:

>> From: "Ronald Klop" <ronald-freebsd8@klop.yi.org>
>
>> I am trying to run dccproc/dccifd on FreeBSD-9/arm. I get no response on
>> the UDP request. I suspected firewall issues so I tried it on my desktop
>> FreeBSD-9/amd64 and there everything works well.
>> The output of ngrep looks different on the same e-mail.
>
> The DCC client-server protocol is purely binary and involves no
> text.  Every request and response packet, including retransmissions
> of a request, should have a unique combination of transaction ID
> and other bits.
>
> I think there was once an Ethereal DCC decoder.  A recent Wireshark
> DCC decoder seems to understand at least some DCC requests from
> clients but responses from servers not so much.  I've never used
> either one.
>
>>                                                         I don't know  
>> what
>> to think about that, but maybe the udp packet is 'corrupted' on arm.
>> Is this a known issue?
>
> It's news to me.
>
>>                        What can I provide to debug this?
>
> I would first check for an IPFW firewall on the FreeBSD-9/arm system.
> Then I would try:
>
>    `cdcc info`
>
>     cdcc "host x.dcc-servers.net; rtt"
>
>     see if cdcc and then dccproc can talk to a DCC server running on
>      the local machine.  If that works, then my guess would involve
>      compiler or kernel network bugs.
>
>
> Vernon Schryver    vjs@rhyolite.com
>

Cdcc info works and the network traffic looks ok. So I do not see a  
firewall issue.
Wireshark (1.8) gives some interesting outcome. Here are the dump files.
https://dl.dropbox.com/u/74961258/dump-amd64.pcap
https://dl.dropbox.com/u/74961258/dump-arm.pcap

The first md5 sum is shifted 2 bytes in dump-arm.
amd: 28:49:3c:d1:60:ac:70:13:16:df:e6:a7:d7:0c:4c:e4
arm: 08:20:28:49:3c:d1:60:ac:70:13:16:df:e6:a7:d7:0c

The length field of the checksum says 36 on arm and 18 on amd64. And the  
arm value looks padded with 0's at the end.

Ronald.



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