How to expand the udp_sendspace

Chris Johns chrisj at
Wed Mar 18 00:36:22 UTC 2009

Busalski, Wilfried wrote:
> I need to send more than the 9216 Bytes in a udp packet.

The data passed into a send call will be broken up (fragmentation) into MTU 
size packets for the physical transporting. If you send more than the MTU you 
will not have a 1:1 relationship with the packets on the physical interface.

> How do I expand the size of the udp_sendspace without changing the 
> source of  udp_usrreq.c ?

Did you try the setsockopt [1] and SO_SNDBUF ?

> Any Ideas ?

Take a look at the ttcp code in:

I think it sends large UDP packets to get the highest line rate possible.


[1] FreeBSD Man page for getsockopt

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