RNDIS USB tethering stuck on 169.x IP

62626368616e · n00b Joined: 23 May 2020 Posts: 30

Hi,
I'm trying to set up USB tethering between my Rockpro64 dev board (gentoo, systemd) and my Gentoo PC (openrc) I have successfully been able to connect the board to my laptop, enumerating it as an RNDIS device. It seems like connectivity is working locally, between my laptop and the device, as I am still able to maintain SSH and start sftp.
I have tried running dhcpcd and I also have an appropriate entry in /etc/conf.d/net for the device.

Here's what my dmesg looks like on the PC:

NeddySeagoon · Posted: Wed Oct 21, 2020 4:59 pm Post subject:

62626368616e,

How are you setting up the Ethernet over USB link at both ends?

There are two ways, PPP, in which case your Rockpro64 uses the PC as a gateway to the wider network.
That OK for a single device

The second way is to make your PC a router for connected devices. That's a lot of work for one device. There is a wiki guide.
Going with PPP, you need a script like this on your PC and ppp support in your kernel both ends ...

62626368616e · n00b Joined: 23 May 2020 Posts: 30

NeddySeagoon · Posted: Wed Oct 21, 2020 6:39 pm Post subject:

62626368616e,

Explain the wider problem you are trying to solve. I'm concerned we have an [XY Problem in the making here.
That link is unkind but its a good explanation.

You cannot bridge a ppp link because ppp0 will not exist until its started, then both ends get an IP address.
Once you have configured the interface, you may not donate it to a bridge.

On Android, the Android device runs as a router.

So to baby steps. Make the link work from your PC to Rockpro64 and nowhere else.
The rest of the world can come along later.

Manage both ends of the link by hand. Say allocate 10.0.0.1/24 to one end and 10.0.0.2/24 to the other end.
That should get you 10.0.0.0/24 in the routing table both ends for free.
You should be able to run ssh, ping and so on over the link.

I'm not sure that donating the Rockpro64 interfaces to a bridge is part of the solution to your problem.
If it is, creating the bridge is the step after all the interfaces work on their own.

In this context 'work' means ping the next hop out of each interface separately.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

62626368616e · n00b Joined: 23 May 2020 Posts: 30

NeddySeagoon · Posted: Wed Oct 21, 2020 7:14 pm Post subject:

62626368616e,

That's it.

A network 'bridge' is where you donate interfaces to a software construct called a bridge.
The bridge then behaves as a single interface which gets configured as any other interface.
Any packets sent on received by the bridge are available an all the interfaces.

Its like the software version of a network hub.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

62626368616e · n00b Joined: 23 May 2020 Posts: 30

NeddySeagoon · Posted: Thu Oct 22, 2020 9:36 am Post subject:

62626368616e,

No problem with the terminology. I suspected we may have a communications issue, which is why I asked aboud the wider problem.

Your 169 ... IP address may well work for a link to your PC. Its not routable, so its confined to the network segment that it appears on.
To test, on your PC, try ifconfig <ifname> <link-local-ip>
Where <link-local-ip> is choosen from 169.254.0.0/16 but not the same as the IP at the other end.
This manually allocates an IPv4 address to your usb interface.

If you have IPv6 each end, then you will have auto allocated IPv6 link local addresses too. They will be in the range fe80::/10
They will work too. ping -6 fe80.... its a lot more typing.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.