rohc

About ROHC embedded in Linux kernel world

Asked by Gregory G

Hi,

I have embedded ROHC in Linux kernel.
My purpose is to compress UDP frame on a router and decompress on an other router.

PC1 <-> Linux_Ubuntu_router_1 <----> Linux_Ubuntu_router_2 <----> PC2

So there is a compressor on PC1 and a decompressor on PC2.
So I branch rohc_compress2 and rohc_decompress function into the IP stack source code (Ubuntu 11.04).
And I test it.

On PC1, I use tftp Linux command. Tftp server is installed on PC2.
So UDP frames are send from PC1, compress by Linux_Ubuntu_router_1, decompress by Linux_Ubuntu_router_2 and then send to PC2.
Most of frames are well received by PC2, but sometimes there are malformed frame received by PC2.

I get one malformed frame with wireshark tool. And with scapy script, I send this frame 10 times.
1 per 10, this frame is received malformed. A byte change it is always the same.

Without rohc compression there are no frame mal formed.

Have you any idea about this issue?

Thanks for your help

Best regards

Gregory

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Didier Barvaux (didier-barvaux) said : 		#1

Hello,

Difficult to say without more information. Please answer to the questions hereafter to try to analyze the problem you encounter.

1/ How do you transmit the ROHC packets between Linux_Ubuntu_router_1 and Linux_Ubuntu_router_2? Do you put the ROHC packets directly in Ethernet frames?
2/ You say that one specific frame is malformed. Has that frame some specific characteristics (sorter, larger, specific pattern...) that could explain that only this frames is affected?
3/ You say that one single byte is altered. Which one? The first one, the last one... ?
4/ Just to be sure: with scapy, do you sent the well-formed frame or the malformed one?
5/ What library version do you use?

Regards,
Didier

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Launchpad Janitor (janitor) said : 		#2

This question was expired because it remained in the 'Needs information' state without activity for the last 15 days.