Optimizations for qmi_wwan.c

[Fabian Schörghofer]

Life gets easier if they are, or at least behave that way. Most
"bridge" requests come from people who want to use their existing
(expensive?) firewall, gateway ... device with a WWAN modem and the
external IP at one of the interfaces.
So if you have an ethernet behaving device you just bridge two
interfaces and your shiny device can continue, at least if you have a
DHCP server on the modem.


Am Mi., 25. Sept. 2019 um 04:05 Uhr schrieb Dan Williams <dcbw at redhat.com>:
>
> But... WWAN modems aren't ethernet devices. Bridging is inherently L2
> and these devices just don't operate on that level.
>
> That all said, the kernel interface that qmi_wwan exposes even for
> raw_ip mode does have a fake ethernet address so it's not like you
> can't put them into a bridge. Where does the current raw_ip
> implementation fall down when it's in a bridge? The fact that it's
> IFF_NOARP or something?
>
> Dan
>
> On Tue, 2019-09-24 at 22:37 +0200, Markus Gothe wrote:
> > As soon as you want to bridge the devices it won't work very well.
> > And that's a pretty common thing to do.
> >
> > //M
> >
> > Sent from my BlackBerry — the most secure mobile device
> >
> >
> >         Original Message
> >
> >
> >
> > From: dcbw at redhat.com
> > Sent: 24 September 2019 21:17
> > To: nietzsche at lysator.liu.se; libqmi-devel at lists.freedesktop.org
> > Cc: bjorn at mork.no
> > Subject: Re: Optimizations for qmi_wwan.c
> >
> >
> > On Tue, 2019-09-24 at 20:38 +0200, Markus Gothe wrote:
> > > I doubt it is the correct list, but I am giving it a try. At least
> > > it
> > > is related.
> > >
> > > Today I realized the "raw ip" mode got merged a few years ago.
> > > Geesh,
> > > I am getting old.
> > >
> > > However there are some drawbacks with the implementation 1) a
> > > boolean
> > > mode of operation (instead of a tristate with fake MAC layer) 2)
> > > branching in the rx_fixup.
> > >
> > > Since one cannot change the mode of operation when the device is up
> > > and running (at least I couldn't), this seems to be the perfect
> > > place
> > > to use "static keys" a.k.a. "jump labels" a.k.a. memory patching
> > > code
> > > as outlined here
> > > https://www.kernel.org/doc/Documentation/static-keys.txt
> > >
> > > Pros? Speed ofc... Cons? If the architecture doesn't implement it
> > > correctly things might fail.
> > >
> > > To address the 1) is easy and I sent a separate driver that did
> > > fake
> > > the MAC layer here some years ago.
> >
> > Do you mean keep the device in raw_ip mode (since most recent devices
> > don't support the old 802.3 mode), but have the driver fake the MAC
> > and
> > operate like the old "802.3" as Linux/userspace sees it?
> >
> > What applications actually care about L2 Ethernet MAC addresses and
> > don't work with raw-ip mode?
> >
> > Dan
> >
> > _______________________________________________
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> > libqmi-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/libqmi-devel
>
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