From: Tom Herbert <t...@herbertland.com> Date: Thu, 31 Mar 2016 17:18:48 -0400
> On Tue, Mar 29, 2016 at 6:40 PM, Guus Sliepen <g...@tinc-vpn.org> wrote: >> I'm trying to reduce system call overhead when reading/writing to/from a >> tun device in userspace. For sockets, one can use sendmmsg()/recvmmsg(), >> but a tun fd is not a socket fd, so this doesn't work. I'm see several >> options to allow userspace to read/write multiple packets with one >> syscall: >> >> - Implement a TX/RX ring buffer that is mmap()ed, like with AF_PACKET >> sockets. >> >> - Implement a ioctl() to emulate sendmmsg()/recvmmsg(). >> >> - Add a flag that can be set using TUNSETIFF that makes regular >> read()/write() calls handle multiple packets in one go. >> >> - Expose a socket fd to userspace, so regular sendmmsg()/recvmmsg() can >> be used. There is tun_get_socket() which is used internally in the >> kernel, but this is not exposed to userspace, and doesn't look trivial >> to do either. >> >> What would be the right way to do this? >> > Personally I think tun could benefit greatly if it were implemented as > a socket instead of character interface. One thing that could be much > better is sending/receiving of meta data attached to skbuf. For > instance GSO data could be in ancillary data in a socket instead of > inline with packet data as tun seems to be doing now. Agreed.
