[Click] Strange buffer_length() value for packets of more than 1500 bytes

[Manel.Bourguiba at lip6.fr]

Hi all,

I am using linuxmodule click-1.7 over linux-2.6.24.7 (but this is also  
the case with linux-2.6.18.2)
If I send packets of 1480 bytes and with the default mtu of 1500, the  
the buffer size allocated at the receiver is of 1664,  
(p->buffer_length()= 1664 ) which is fine.
However, when I send large packets of more than 1500 bytes, and set  
the mtu to a value > 1500,  the buffer allocated at the reception is  
always of 256 ((p->buffer_length()= 256)) whatever the packet size is.
So, if I want to access to the data stored beyond the 256 bytes in  
that packet, the data I get is erroneous.
So i am wondering if there is a limitation on the maximum buffers  
size? where this limitation is hard-coded? and why does it change with  
the mtu?

Thanks for helping


Ps: Click scripts are roughly :

Sender :
RatedSource ->UDPIPEncap -> EtherEncap -> ToDevice(eth0)
Receiver:
FromDevice(eth0) -> Myelement -> Discard

In Myelement, I only get p->buffer_length() and p-> data() and p->end_data()


Manel BOURGUIBA
PhD Candidate
PHARE - LIP6 - UPMC - Sorbonne Universités
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