On Thu, Mar 28, 2002 at 05:59:20PM +0000, E.B. Dreger wrote:
I like to log interesting packets; I agree with Carl.
Logging interesting packets is easy enough, its logging ALL packets that would be a problem. At any rate, you'd run out of harddrive space pretty quick if you were pushing max performance at any length of time. I can write a linerate FastE's worth of data to a $100 IDE disk on a $100 processor easily enough, so as long as you're buffering it intelligently it shouldn't be an issue.
Or if you're comfortable writing kernel code, I recommend you make a character device for sniffer device control, and use it to pass page-aligned malloc'd memory pointers from userland into the nic driver, which you then pass to the card as the RX ring buffers. This will let you DMA your packets directly into userland. If not, at least unhook ether_input(). :)
Never done this. About how much "capacity" does the zero-copy approach add?
Eliminating the bulk "data" being DMA's across the PCI bus is what adds most of your "capacity". Doing zero copy just lets you spend all your CPU time doing actual analysis instead of copying stuff around unnecessarily. I never did get the opportunity to benchmark it at 1.4million packets/sec, (I spent more time trying to get the 20ft of fiber to reach the lab at the previous employeer than I did writing the code to do this in the first place) but I don't see any reason it shouldn't work, with proper interrupt coalescing of course. -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras PGP Key ID: 0x138EA177 (67 29 D7 BC E8 18 3E DA B2 46 B3 D8 14 36 FE B6)