Date: Thu, 16 Feb 2012 22:42:58 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: net@freebsd.org Subject: Re: Abstracting struct ifnet Message-ID: <CAJ-VmomZZkZc4SvfuiKSuL_XC=4mx5BVmCphQrRnZXwbcvL06A@mail.gmail.com> In-Reply-To: <338757D1-6B1E-49CF-983F-5D5851066FD3@xcllnt.net> References: <338757D1-6B1E-49CF-983F-5D5851066FD3@xcllnt.net>
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Hi,
I honestly quite like this idea.
Adrian
On 16 February 2012 20:16, Marcel Moolenaar <marcel@xcllnt.net> wrote:
> All,
>
> Juniper is in the final phases of creating a clean separation
> between FreeBSD and Junos, so as to make upgrades of FreeBSD
> easier. This also allows Juniper to track -current and be more
> active FreeBSD contributors.
>
> To that end, we have a short-term and hopefully short-lived
> problem to solve, which is the ability to use FreeBSD's network
> drivers against the Junos network stack. As some may know, the
> Junos network stack has split up struct ifnet into a physical
> and logical component, called ifdev and iflogical.
>
> We've tried a few approaches to bridge the gap between ifnet
> on the one hand and ifdev and iflogical on the other and found
> that abstracting ifnet and using accessor functions is the
> best way to allow us to use FreeBSD drivers with the Junos
> network stack, while retaining the ability to use them with
> the FreeBSD stack.
>
> FreeBSD is also looking at breaking up ifnet and with that in
> mind, I was wondering if there would be any resistance to
> changing network drivers to use accessor functions or macros
> instead of direct pointer dereferences?
>
> For example, do something like:
>
> Index: if_fxp.c
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- if_fxp.c =A0 =A0(revision 231178)
> +++ if_fxp.c =A0 =A0(working copy)
> @@ -823,13 +823,14 @@
> =A0 =A0 =A0 =A0}
>
> =A0 =A0 =A0 =A0if_initname(ifp, device_get_name(dev), device_get_unit(dev=
));
> - =A0 =A0 =A0 ifp->if_init =3D fxp_init;
> - =A0 =A0 =A0 ifp->if_softc =3D sc;
> - =A0 =A0 =A0 ifp->if_flags =3D IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICA=
ST;
> - =A0 =A0 =A0 ifp->if_ioctl =3D fxp_ioctl;
> - =A0 =A0 =A0 ifp->if_start =3D fxp_start;
> + =A0 =A0 =A0 if_set_init(ifp, fxp_init);
> + =A0 =A0 =A0 if_set_softc(ifp, sc);
> + =A0 =A0 =A0 if_set_flags(ifp, IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICA=
ST, 0);
> + =A0 =A0 =A0 if_set_ioctl(ifp, fxp_ioctl);
> + =A0 =A0 =A0 if_set_start(ifp, fxp_start);
>
> - =A0 =A0 =A0 ifp->if_capabilities =3D ifp->if_capenable =3D 0;
> + =A0 =A0 =A0 if_set_capabilities(ifp, 0);
> + =A0 =A0 =A0 if_set_capenable(ifp, 0);
>
> =A0 =A0 =A0 =A0/* Enable checksum offload/TSO for 82550 or better chips *=
/
> =A0 =A0 =A0 =A0if (sc->flags & FXP_FLAG_EXT_RFA) {
>
> Such a scheme, while initially touching a lot of driver,
> would make it easier to break up ifnet *and* also make it
> easier to hide ABI/API changes from driver vendors (esp.
> when the accessor functions are non-inlined functions and
> not macros or inlines). This is particularly useful for
> Juniper, where we have worked towards network stacks as
> (pre-)loadable modules so as to help with migration and
> validation.
>
> Thoughts, feedback and suggestion are welcome,
>
> --
> Marcel Moolenaar
> marcel@xcllnt.net
>
>
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