[OpenWrt-Devel] ramips/mt7621 after 5.4 switch

[Bjørn Mork]

Andre Valentin <avalentin at marcant.net> writes:

> Am 07.04.20 um 17:49 schrieb Bjørn Mork:
>> Just remembered an issue on my todo list: There have been some MTU
>> handling changes in the kernel networking API.  This affected the
>> qmi_wwan QMAP handling.  I am not sure about the current status.  Will
>> have to dig a bit more.  But this might be your problem.
>
>
> That made me set MTU of wwan0 to 1600, and the qmimux* to 1500. No more problems anymore.
> This should go into documentation, not that anybody makes the same errors.

Yes, this goes into the list of issues I'd like to fix with the QMAP
implementation. It's also unnecessary hard to configure.  And there is
no way to figure out which qmap netdev belongs to which mux_id.

> How much overhead does qmux create (for correct calculated MTU
> offset)?

Looks like 4 bytes:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/usb/qmi_wwan.c#n66


Bjørn

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