OS throws away large packets

Tom Judge tom at tomjudge.com
Mon Apr 28 17:45:06 UTC 2008

Mr Y wrote:
> Hi all,
> I'm trying to implement Large Recieve Offload for an Ethernet driver on
> FreeBSD 6.3, but all my >MTU packets are being thrown by the OS.
> I'm using mbuf chains in this imlpementation, each mbuf is a cluster of
> MCLBYTES bytes. They are linked by the m_next pointer.
> The first packet being thrown away is 2945 bytes long. Wireshark shows the
> packet that is being passed to the OS is correct.
> Do I need to set some OS parameter to make it recieve mbuf chains?
> Please help.

Hi Yony,

I seem to remember some discussion about this list last year see the 
following threads:


 From my limited reading of these threads just now and possibly bad 
memory.  It would seem that the MRU to MTU relationship is defined in 
the nic driver rather than enforced further up the stack or at least 
that seamed to be the case with the bce driver.

Hope this is helpful,


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