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kohler / click

The Click modular router: fast modular packet processing and analysis
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KernelTun: Use IFF_NO_PI on Linux, remove LINUX_ETHERTAP mode #397

Open piotrjurkiewicz opened 6 years ago

piotrjurkiewicz commented 6 years ago

This commit adds flag IFF_NO_PI to tun/tap interface settings on Linux. It changes frame format in order not to include protocol information header. That is, with this flag, frames received/send from tun/tap fd consist solely of raw underlying protocol (Ethernet/IP) frames.

Protocol information header is not used by the element in any way, but its presence adds a requirement for pulling packet data on receive and pushing it before writing packet to the fd. Such a push becomes an expensive push when there is is no enough headroom in packet, for example when using native netmap buffers, which do not have any headroom.

Adding IFF_NO_PI flag eliminates the need for pulling and pushing packet data completely.

Moreover, this commit removes support for LINUX_ETHERTAP mode. Ethertap driver was removed from the kernel more than 15 years ago. Removal of this mode significantly simplifies the logic within the element.

ahenning commented 6 years ago

Tom, does the multi-threading that you are working on add kerneltap multiqueue support?

tbarbette commented 6 years ago

Yes it's the idea. Following the FastClick's FromDPDKDevice idea, the element spawns one task per threads that reads from the TAP device. I'll finish it now.