netdev - Re: Best way to reduce system call overhead for tun device I/O?

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Message-ID: <20160331222857.GH3771@sliepen.org>
Date:	Fri, 1 Apr 2016 00:28:57 +0200
From:	Guus Sliepen <guus@...c-vpn.org>
To:	David Miller <davem@...emloft.net>
Cc:	tom@...bertland.com, netdev@...r.kernel.org
Subject: Re: Best way to reduce system call overhead for tun device I/O?

On Thu, Mar 31, 2016 at 05:20:50PM -0400, David Miller wrote:

> >> I'm trying to reduce system call overhead when reading/writing to/from a
> >> tun device in userspace. [...] 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.

Ok. So how should the userspace API work? Creating an AF_PACKET socket
and then using a tun ioctl to create a tun interface and bind it to the
socket?

int fd = socket(AF_PACKET, ...)
struct ifreq ifr = {...};
ioctl(fd, TUNSETIFF, &ifr);

-- 
Met vriendelijke groet / with kind regards,
     Guus Sliepen <guus@...c-vpn.org>