Optimizations for qmi_wwan.c

[Dan Williams]

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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