Freebsd IP Forwarding performance (question, and some info) [7-stable, current, em, smp]

Paul paul at
Tue Jul 1 02:38:21 UTC 2008

Well it's supposed to, but it doesn't seem to do it as well as it should :>
How about copying header direct DMA from NIC into cache, then copy from 
cache into output NIC after applying whatever filters/changes/etc?

Ingo Flaschberger wrote:
> Dear Alex,
>>    >OK, I setup 2 boxes on either end of a RELENG_7 box from about May
>>    >7th just now, to see with 2 boxes blasting across it how it would
>>    >work.  *However*, this is with no firewall loaded and, I must enable
>>    >ip fast forwarding. Without that enabled, the box just falls over.
>> What is "ip fast forwarding" ?
> instead of copying the while ip packet into system memory, only the ip 
> header is copyied and then in a "fast" path determined if it could be 
> fast forwarded.
> if possible, a ned header is created at the other network-cards-buffer
> and the ip-data is copied from network-card-buffer to 
> network-card-buffer directly.
> Kind regards,
>    Ingo Flaschberger
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