Re: USB rndis_host - slow download transfers, RX errors

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Feb 08, 2018 at 10:53:20AM -0500, Tomasz Janowski wrote:
> On Thursday, February 8, 2018 3:43:05 PM EST Greg KH wrote:
> > On Thu, Feb 08, 2018 at 02:16:08PM +0000, Tomasz Janowski, Ph.D. wrote:
> > > Dear USB developers,
> > > 
> > > Based on my google research, the problem I experience seems to happen
> > > with some newer smartphones. My test case is Samsung Galaxy S8 (SM-950U1).
> > > I am trying to use USB tethering and everything seems to work as expected
> > > (modules are loaded, Ethernet devices are up and running, dhcp works
> > > fine). I can connect to the external world using both LTE or wireless
> > > network on the phone.
> > > 
> > > Now, the problem is that the download speeds are terrible, around 64 KB/s,
> > > while uploads are fast, the order of 15 MB/s. These speeds do not depend
> > > on the wireless service provider: the results are similar when I tether
> > > wi-fi. The USB Ethernet interface on the Linux host reports a lot of
> > > receive errors (attached: device_state.txt), while kernel reports bad
> > > rndis messages (attached: kernel.log.txt).
> > > 
> > > Windows 10 works great with the same hardware (same PC and same phone),
> > > with uploads and downloads in the order of 150 Mbit/s, which is probably
> > > as fast as my wireless network can do. But some people reported issues
> > > with older Windows drivers too. Is possible that some newer version of
> > > RNDIS protocol is around and Linux hasn't updated its RNDIS module yet?
> > 
> > Hey, I was _just_ talking to someone at Google about this same issue
> > yesterday, you beat him sending this same type of report to the mailing
> > list, nice job :)
> > 
> > Yes, this is not good, and we should work to resolve this, but first,
> > what kernel version are you using?  I think some fixes for the rndis
> > driver went in recently to 4.15, but it would be good to verify that
> > this isn't already resolved.
> 
> The error messages which I have attached were produced by a precompiled Debian 
> kernel: "Linux version 4.14.0-0.bpo.3-amd64 (debian-kernel@lists.debian.org) 
> (gcc version 6.3.0 20170516 (Debian 6.3.0-18)) #1 SMP Debian 4.14.13-1~bpo9+1 
> (2018-01-14)".
> 
> But I have downloaded the most recent version of the kernel from the official 
> git repository (last commit: Jan 31, 2018) and it had exactly the same 
> problem. Unless a patch was submitted within the last week, the issue is still 
> there.
> 
> Should I get the version as of today and test it again?

If you find a 4.15 tree, that would be great to test, but odds are, the
issues are still there.

I'll try to carve out some time to look at this tomorrow, as I have a
bunch of Android devices to test with, and there's no good reason why
Windows should be slower than Linux for stuff like this.  We should be
able to go as fast as the device lets us.  Most likely we are doing
something "stupid" in the rndis driver somewhere :)

thanks,

greg k-h