In a nutshell, data going to and from the application is stored in memory (either RAM or Flash). When the packet driver sends a packet, it sends the payload part of the data from the same memory that the application provided to be sent. When the packet driver receives data, the payload is passed to the application in the same memory that it came in to from the MAC. There can be significant improvement of program performance by not copying, especially when sending or receiving lots of data. This is true from both ends of the spectrum - low speed processors which take a lot of time to simply copy memory and very high speed processors where a memory copy is slow because of the relatively slow speed of memory and not because the speed of the processor.
Bill From: [email protected] [mailto:[email protected]] On Behalf Of Francois Bouchard Sent: Friday, February 13, 2009 10:16 AM To: Mailing list for lwIP users Subject: Re: [lwip-users] Hello to mailinglist What exactly is zero-copy rx/tx? ----- Original Message ----- From: Piero 74 <mailto:[email protected]> To: Mailing list <mailto:[email protected]> for lwIP users Sent: Friday, February 13, 2009 9:52 AM Subject: Re: [lwip-users] Hello to mailinglist I suppose I can post it as a patch on savannah. I forgot, I also developed a driver for the on-chip FEC+PHY of FreeScale's MCF5223x. It does zero-copy receive. I'll post it as well, please notify me after post... i want to see your implementation for zero-copy as you know we had some discussions in mailing list regarding zero-copy rx and also zero-copy tx But filtering IP addresses and ports in the driver would be straightforward, wouldn't it? Just match the appropriate fields from IP header against the whitelist. yes, i know... i also suppose is simple... but i wanted to know if other people has developed a similar feature... i know that is not a robust protection against hacking attack, but it could mitagate them, and it could be an interesting feature for the marketing (just label on the box: "built-in firewall") thanks for your reply bye Piero _____ _______________________________________________ lwip-users mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/lwip-users
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