SLIP on NRF HW

[pbtgit]

I have successfully used SLIP with QEMU on a Linux host.
Now i want to run SLIP on NRF52840DK HW but it does not work.
The NRF board does not have Ethernet HW so the SLIP driver uses NET_DEVICE_INIT with DUMMY_L2 layer instead of ETH_NET_DEVICE_INIT.

Assuming the DUMMY_L2 interace could have problems with Ethernet frames i changed the tunslip6 setup on linux side to use a tunnel device instead of the default tap device but still no go.

[jukkar]

I have not tested this kind of setup, but there should be no difference in zephyr side whether the slip is running in qemu or in target device. Note the dummy L2 in zephyr side does not add or use any L2 header so in linux side, a TUN device must be used (and not TAP).
Could you for example run a wireshark to your TUN device and see if there is any data transferred?

[ofirshe]

@AndreyDodonov-EH
On the Host side:

1. Install `tunslip6` by cloning and building the net-tools repository:
   git clone https://github.com/zephyrproject-rtos/net-tools.git
   cd net-tools/
   make

2. Create the SLIP interface using:
   ./tunslip6 -s <serial_port> -T <IPv6_prefix>

   For example:
   ./tunslip6 -s /dev/ttyS2 -T 2001:db8::1/64

On zephyr, I set the following SLIP related configurations:

CONFIG_NET_CONFIG_MY_IPV4_ADDR="192.0.2.1"
CONFIG_NET_CONFIG_MY_IPV4_NETMASK="255.255.255.0"
CONFIG_NET_CONFIG_MY_IPV4_GW=""
CONFIG_NET_DRIVERS=y
CONFIG_SLIP=y
CONFIG_SLIP_TAP=y
CONFIG_SLIP_MAC_ADDR="00:00:00:00:00:01"

[AndreyDodonov-EH]

@ofirshe Thanks for a quick response!
I see you are using -T option here and CONFIG_SLIP_TAP=y, meaning that you are effectively using TAP, transferring Ethernet frames via SLIP. Do I understand correctly?
Do you know if it's possible for Zephyr to do TUN, i.e. transfer IP frames over SLIP? Will then DUMMY NET L2 be used?

[ofirshe]

Yes, I transmit Ethernet frames via SLIP. Regarding your second question, I have no answer.

[jukkar]

Since there is no actual NET_L2 SLIP and we land in ethernet_recv and do things like NET_ETH_HDR, I'd expect that it should be Ethernet, but it is not how SLIP is supposed to work, directly encapsulating IP, or am I missing something?

If you want to transfer Ethernet frames, then the TAP interface should be created in the Linux side, and you should select CONFIG_SLIP_TAP=y to enable it (this is the default if SLIP is enabled). If you want to avoid L2 header, then CONFIG_SLIP_TAP=n should be set.

Why is there no actual NET_L2_SLIP, by the way? Same as NET_L2_PPP exists? @jukkar @rlubos would appreaciate your view here

There is no need for such layer as NET_L2_DUMMY exists already and it handles the case where we have no L2 (so when using TUN).

[jukkar]

Do you know if it's possible for Zephyr to do TUN, i.e. transfer IP frames over SLIP? Will then DUMMY NET L2 be used?

It should be possible, you just need to setup the Linux side properly and disable TAP i.e., CONFIG_SLIP_TAP=n