On 08/08/2017 02:42 PM, Dan Williams wrote:
On Tue, 2017-08-08 at 13:07 -0600, James Feeney wrote:
Hello All

Would you please look at kernel bug report "Since 4.12 - bonding
module not
working with wireless drivers", and tell me if you know why the
kernel ethtool
does not receive a speed report from the wireless drivers?

 https://bugzilla.kernel.org/show_bug.cgi?id=196547

It seems that Mahesh Bandewar became annoyed that some network
drivers do not
report speed and duplex to the bonding module properly, so that it
becomes
impossible to make "best connection" decisions.  A patch was applied
to the
bonding module in linux 4.12 which now disables any network interface
that does
not successfully report its speed and duplex.  In practice, this
seems to
include every wireless network driver I've tried, the ath5k, ath9k,
the
rtl8192ce and RTL8188CUS.  Of course, this new behavior breaks
wireless bonding!

Do you know if there is some general reason why the wireless drivers
do not work
with the kernel ethtool?  Is this something that can be fixed?  Can
you tell if
this reporting failure would be the fault of the kernel ethtool?  Or
the
wireless driver?  Or the bonding module?

Because the "speed" (whatever that means) can and sometimes does change
with every packet.  The driver dynamically adjusts the link rate based
on all kinds of things.  But mainly the current radio environment; how
many other APs are around, how much interference there is, how many
other clients are trying to talk, that kind of thing.

So one second the wifi might be the "best" link and then when somebody
turns on a microwave oven or a baby monitor, it may be the "worst"
until the microwave's duty cycle completes a few seconds later then
it'll become the "best" again for a couple seconds then "worst" again,
repeat until your Easy Mac is nice and warm and creamy.

Furthermore, for some drivers IIRC when there isn't any traffic, they
might drop the link rate very low because there's no reason keep
powering blocks when you're not transmitting/receiving any data.  IIRC
the Intel drivers used to do that a couple years ago.

Also, "duplex" doesn't mean anything in wireless land.  So no clue what
bonding is expecting them to say here.  I would say the modifications
to the bonding core made assumptions that simply aren't applicable to
mediums other than wired ones.

Well, wifi acts half-duplex in that only one side can transmit
at once.

But, no argument with the rest!

Thanks,
Ben


Dan



--
Ben Greear <gree...@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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