DirecPC Protocols

Fri Nov 15 23:00:10 UTC 2002

Crist,

I am a contributor of RFC3077 and we will have a IETF meeting in 
Atlanta. I will discuss the issue which you wrote below at the UDLR-WG 
meeting. Now we are preparing a updated draft which support the 
operation the network employing RFC3077.

Thank you.

Jun Takei

Crist J. Clark wrote:
> On Fri, Nov 15, 2002 at 04:41:10PM +0100, Jurian van der Knaap wrote:
> 
>>You might get some info out of the Linux DirecPC driver, or maybe the 
>>developers of the driver can help.
>>
>>Find it at http://sourceforge.net/projects/direcpc
>>
>>Hope this is of any help,
> 
> 
> Yeah, this helped. It showed me that their protocol is totally
> broken.
> 
> They do an GRE- or IPIP-like encapsulation, but then set the protocol
> field to that of the encapsulated packet. Or if the encapsulated
> packet is not TCP, UDP, or ICMP, they set the outer protocol to TCP.
> This will totally break behind NAT when the NATing device changes the
> source IP address and then "fixes" the TCP or UDP checksum due to the
> pseudo-header change. Either the NATing device drops the packet when
> the intial checksum is wrong or it mangles the payload, which isn't
> really TCP.
> 
> Who designs these things? And what were they smoking when they did?