[B.A.T.M.A.N.] Issue with mesh network on different RTL chipsets

[B.A.T.M.A.N.] Issue with mesh network on different RTL chipsets

[Francesco Salvatore [fabbricadigitale]]

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Hi,
we are trying to build a mesh network on Raspberry Pi boards with some USB
Wi-Fi adapters that have different Realtek chipsets and, consequently,
different drivers. Specifically we have:
	Gateway => driver rtl8812au  (probably the chipset is rtl8811a)
	Client => driver rtl8821cu  (probably the chipset is rtl8811u)

We are using Raspbian with kernel 4.14.34-v7+ and we tried using built-in
kernel version of batman-adv (2017.3) and then with latest stable (2018.2),
built with all compile flags active, less than network coding option.

The problem is (seems to be) related to client > gateway communication,
specifically in receive capability of the gateway if we use the scenario
described above.
The client is able to join the network because gateway recognises it as an
originator and the client correctly recognises the gateway, but even so no
client network traffic is visible on the gateway. 
For example, the client is unable to obtain an IP address from DHCP server;
we can see DHCPOFFER packet on the client (dumping with tcpdump) but we
cannot see the same packet transit through the gateway.
The client is also unable to ping or traceroute other neighbours or even the
gateway.
We also tried to disable, one by one, multicast optimization, bridge loop
avoidance, fragmentation and so forth, but unfortunately without success.

All test were made using batctl tools (ping, traceroute, tcpdump etc.).

In other cases, i.e. if we swap the roles (using rtl8812au as client and
rtl8821cu as gateway) or if we use same chipset both for client and gateway,
we have no issue at all.

Do you know if there's any issue related to listed hardware chipsets? If
yes, you know of some action I can take to fix that problem?

Thank you, have a nice day!

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Re: [B.A.T.M.A.N.] Issue with mesh network on different RTL chipsets

[Sven Eckelmann]

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On Donnerstag, 19. Juli 2018 09:53:26 CEST Francesco Salvatore [fabbricadigitale] wrote:
[...]
> Do you know if there's any issue related to listed hardware chipsets? If
> yes, you know of some action I can take to fix that problem?

Yes, nearly all [0] wifi USB sticks are problematic. Please get in contact 
with the driver developers [1] because this (beside the symptoms) has nothing 
to do with batman-adv. If broadcast or unicast tx/rx is broken for a specific 
hardware in a specific mode, the mesh will look broken - nothing we can do 
here.

Kind regards,
	Sven

[0] no usb stick comes to my mind at the moment which is without flaws
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/MAINTAINERS?id=024ddc0ce1049298bd3cae60ae45d9c5f0fb8b9c

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