[Babel-users] Detecting bridges

[Dave Taht]

On Tue, Dec 15, 2015 at 11:00 AM, Henning Rogge <hrogge at gmail.com> wrote:
> On Tue, Dec 15, 2015 at 10:35 AM, Dave Taht <dave.taht at gmail.com> wrote:
>> On Mon, Dec 14, 2015 at 8:44 PM, Juliusz Chroboczek
>>>> Is there a reliable way of determining that an underlying interface is
>>>> a bridge?
>>>
>>> https://github.com/jech/babeld/blob/master/kernel_netlink.c#L723
>>>
>>> However, this only works for the Linux software bridge.  It doesn't work
>>> for the hardware switches built into your favourite router, and of course
>>> it doesn't work for switches connected over Ethernet, which is what the
>>> WLAN-SI people are using.
>>
>> I was basically wondering if there was something like an igmp message that asked
>> if this "wire" was bridged to anything.
>>
>> The default outside of babel towers and the yurtlab is to bridge wifi
>> to ethernet.
>
> Maybe something like this?
>
> https://en.wikipedia.org/wiki/Link_Layer_Discovery_Protocol
>
> Not sure how well it is supported by consumer grade switches.

Well, while I have seen those go by, along with stp, in fiddling with
bridging and unbridging a test openwrt box (linksys ac1200) today I do
not even see BPDUs with wireshark...

https://en.wikipedia.org/wiki/Spanning_Tree_Protocol

deep magic, long hidden. My thought was to put out a query over a
protocol like this, and/or learn something about the bridging
topology, passively, just as the switches do.

> Henning Rogge