Van Jacobson's network channels and Netfilter

Van Jacobson's network channels and Netfilter

Posted Jan 31, 2006 22:29 UTC (Tue) by csamuel (subscriber, #2624)
In reply to: Van Jacobson's network channels by ernest
Parent article: Van Jacobson's network channels

I was fortunate enough to be both at the original presentation and when he repeated it for the "best of" stream at the end of LCA2006 and got to ask him about what the situation was with netfilter.

His comment was that there was no reason why netfilter couldn't become just another consumer of packets, and my take on that is that whilst that would require patching to the netfilter code that too could be a good thing if it eliminates the use of double-linked lists (the use of which would cause you to fail CS 101 under VJ according to him :-)) but would probably be a lot of code.

Of course this is only necessary if you go further than chanellising the drivers themselves as one of the really elegant things is that this change of thinking is that its very modular - you can convert drivers one at a time until they're all done, then start on looking at channelising the socket layer and then start on the consumers of the socket layer.

There are 2 nice things about having the TCP stack running in user space, one is that it allows you to easily experiment and debug TCP issues and have custom behaviour for different applications based on need, and the second is that VJ explained the only reason it had to go into the kernel in Multics in the first place was that if a user process got pages out there it could take 2 minutes to get paged in, which TCP/IP doesn't like.. :-)

Chris

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