KernelTun: Use IFF_NO_PI on Linux, remove LINUX_ETHERTAP mode #397
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This commit adds flag IFF_NO_PI to tun/tap interface settings on Linux. It flag 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 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.
tbarbette
approved these changes
May 3, 2018
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Tom, does the multi-threading that you are working on add kerneltap multiqueue support? |
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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. |
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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.