# gnrc_border_router using automatic configuration
This setup uses a single serial interface, ethos (Ethernet Over Serial)
and UHCP (micro Host Configuration Protocol) (using DHCPv6 alternatively is also
possible).
Ethos multiplexes serial data to separate ethernet packets from shell commands.
UHCP is in charge of configuring the wireless interface prefix
and routes on the BR.

The script `start_network.sh` enables a *ready-to-use* BR in only one command.

## Uplink

The border router will route packets between a 6Lo network (PAN) and a 'normal'
IPv6 network (i.e. the Internet).

This requires the border router to have two interfaces: A downstream interface
to run 6LoWPAN on and an IPv6 uplink.

This example comes with support for three uplink types pre-configured:

 - [`ethos`](https://doc.riot-os.org/group__drivers__ethos.html) (default)
 - [`slip`](https://tools.ietf.org/html/rfc1055)
 - `wifi`

For `native` the host-facing [`netdev_tap`](https://doc.riot-os.org/netdev__tap_8h.html) device
is configured, providing connectivity via a TAP interface to the RIOT instance.
On the node-facing side [`socket_zep`](https://doc.riot-os.org/group__drivers__socket__zep.html)
is used to simulate a IEEE 802.15.4 network.

To select an uplink, set the UPLINK environment variable. For instance, use `UPLINK=slip`
for a SLIP uplink.

`ethos` and `slip` will make use of the existing serial interface that is used for the
RIOT shell to provide an upstream interface. Your computer will act as the upstream
router, stdio is multiplexed over the same line.

The `wifi` uplink will connect to an existing WiFi (IEEE 802.11) network.
The network must provide a DHCPv6 server that supports prefix delegation (IA_PD) when
`PREFIX_CONF=dhcpv6` is set (default).

Use `WIFI_SSID="SSID" WIFI_PASS="password"` in your `make` command to set your WiFi's
credentials. You can alternatively edit the `Makefile`.

Currently, `wifi` requires an esp8266 or esp32 for the border router and will default
to using `esp_now` for the downstream interface.

### Connection sharing with host

If the host (Linux) computer has an IPv6 uplink that can be shard with the RIOT border
router to provide it with an uplink.

This requires the host network to be bridged with the TAP network by connecting it to
the TAP bridge:

    sudo dist/tools/tapsetup/tapsetup -u eno1

where `eno1` is the host's uplink interface.

Then specify `REUSE_TAP=1` when building / running the border router application.
This works with both `native` and the `ethos` uplink.

## Requirements
This functionality works only on Linux machines.

If you want to use DHCPv6, you also need a DHCPv6 server configured for prefix
delegation from the interface facing the border router. With the [KEA] DHCPv6
server e.g. you can use the following configuration:

```json
"Dhcp6":
{
  "interfaces-config": {
    "interfaces": [ "tap0" ]
  },
  ...
  "subnet6": [
  {    "interface": "tap0",
       "subnet": "2001:db8::/16",
       "pd-pools": [ { "prefix": "2001:db8::",
                       "prefix-len": 16,
                       "delegated-len": 64 } ] }
  ]
  ...
}
```

Note that when working with TAP interfaces you might need to restart your DHCPv6
server once *after* you started the border router application (see below), since
Linux might not recognize the interface as connected.

[KEA]: https://kea.isc.org/

## Setup

To compile and flash `gnrc_border_router` to your board:

```bash
make clean all flash
```

If you want to use DHCPv6 instead of UHCP compile with the environment variable
`PREFIX_CONF` set to dhcpv6

```bash
PREFIX_CONF=dhcpv6 make clean all flash
```

## Usage
The `start_network.sh` script needed for `ethos` and `slip` is automatically run
if you type

```bash
make term
```

This will execute the needed commands to setup a `tap` (`ethos`) or `tun` (`slip`)
interface and configure the BR.
Notice that this will also configure `2001:db8::/64` as a prefix.
This prefix should be announced to other motes through the wireless interface.

As said previously, `ethos` and `slipdev` allow to send IP packets and shell commands.
This is done through the same serial interface.
By typing `help` you will get the list of available shell commands.

At this point you should be able to ping motes using their global address.
For instance, if you use the [`gnrc_networking`](https://github.com/RIOT-OS/RIOT/tree/master/examples/gnrc_networking) example on the mote, you can
ping it from your machine with:

```
> ping 2001:db8:0:1234:0:567:8:1
```

Just replace this address by your mote's address.
Using `ifconfig` on the shell of your mote shows you the addresses of your
mote, for instance:

```
Iface  7   HWaddr: 59:72  Channel: 26  Page: 0  NID: 0x23
            Long HWaddr: 5a:46:10:6e:f2:f5:d9:72
            TX-Power: 0dBm  State: IDLE  max. Retrans.: 3  CSMA Retries: 4
            AUTOACK  CSMA  MTU:1280  HL:64  6LO  RTR  RTR_ADV  IPHC
            Source address length: 8
            Link type: wireless
            inet6 addr: ff02::1/128  scope: local [multicast]
            inet6 addr: fe80::5846:106e:f2f5:d972/64  scope: local
            inet6 addr: ff02::1:fff5:d972/128  scope: local [multicast]
            inet6 addr: 2001:db8::5846:106e:f2f5:d972/64  scope: global
            inet6 addr: ff02::2/128  scope: local [multicast]
```

The script also sets up a ULA (Unique Local Address) address on your
Linux `tap0` network interface.
You can check your ULA on your PC with `ifconfig` Linux command.
On this example, such address can be pinged from 6lo motes:

```
> ping fd00:dead:beef::1
```

Thus far, IPv6 communication with between your PC and your motes is enabled.

### Simulated network with native

On native a IEEE 802.15.4 network is simulated by encapsulating 802.15.4 frames
inside UDP packets. For this the `socket_zep` modules is used both on the border
router and on the virtual mote.

The UDP packets are sent to a dispatcher which forwards them to all other nodes.
By default a simple dispatcher is provided that will forward every packet to
every node (perfect broadcast), but it can be replaced by the user with alternative
dispatchers to simulate more advanced topologies.

# gnrc_border_router with manual config
You can use `ethos` as a standalone driver, if you want to setup the BR manually.

## Setup
To select ethos as the serial driver, be sure that the `Makefile`
has the following:

```make
ifeq (,$(filter native native64,$(BOARD)))
USEMODULE += stdio_ethos
CFLAGS += '-DETHOS_UART=UART_DEV(0)' -DETHOS_BAUDRATE=115200
FEATURES_REQUIRED += periph_uart
endif
# include UHCP client
USEMODULE += gnrc_uhcpc
```

You'll need IPv6 access to the nodes attached to the BR from your Linux PC.
To do this, it is necessary to add a `tap` interface.
As an example, you can do it as follows:

```bash
sudo ip tuntap add tap0 mode tap user ${USER}
```

This will setup your `tap` interface.
Then configure it to route the packets coming from your 6lo network:

```bash
sudo ip link set tap0 up
sudo ip a a 2001:db8::1/48 dev tap0
sudo ip r d 2001:db8::/48 dev tap0
sudo ip r a 2001:db8::2 dev tap0
sudo ip r a 2001:db8::/48 via 2001:db8::2 dev tap0
```

Please note that the prefix `2001:db8::` is used as an example.

Then you can flash the `gnrc_border_router` example on your board:

```bash
make clean all flash
```

On this RIOT BR two interfaces are present.
A wired interface represents the serial link between Linux and your mote.
A wireless interface represents the 802.15.4 radio link.
In order to route packets between this two interfaces,
you can do the following:

```
> ifconfig 6 add 2001:db8::2/48
> ifconfig 5 add 2001:db8::3/64
> fibroute add :: via <link-local of tap> dev 6
```

By adding the address to the wireless interface the prefix will be
disseminated.
This prefix will be automatically added by the motes in the radio range.

## Usage
Run ethos by choosing a serial interface according to your board.
For instance `/dev/ttyUSB*` or `/dev/ttyACM*`.

```bash
sudo ./ethos tap0 /dev/ttyACM0
```

Now, you should be able to ping your nodes.
Use the global address starting by your prefix, on our case `2001:db8::`:

```
> ping 2001:db8:0:1234:0:567:8:1
```

# gnrc_networking_border_router with SLIP

## Requirements

In order to setup a 6LoWPAN border router on RIOT, you need either a board that
offers an IPv6 capable network interface (e.g. the `encx24j600` Ethernet chip)
or connect it over the serial interface to a Linux host and use the SLIP
standard [1]. The example application in this folder assumes as a default to be
run on an Atmel SAM R21 Xplained Pro evaluation board using an external UART
adapter for the second serial interface. However, it is feasible to run the
example on any RIOT supported platform that offers either more than one UART or
be equipped with an IPv6 capable network device. In this case only the Makefile.board.dep
of this application has to be slightly modified, e.g. by replacing the line
```
USEMODULE += ethos
```
with something like
```
USEMODULE += encx24j600
```
and specify the target platform as `BOARD = myplatform`.

Be sure that you have replaced on your `Makefile` the lines to use SLIP.
You should have something like this:

```make
UPLINK ?= slip
```

## Configuration

In order to connect a RIOT 6LoWPAN border router over SLIP you run a small
program called tunslip6 (imported from Contiki) [2] on the Linux host. The
program can be found in the `dist/tools/tunslip` folder and has to be compiled
before first use (simple calling `make` should be enough). Now, one can start
the program by calling something like:
```bash
cd dist/tools/tunslip
make
sudo ./tunslip6 2001:db8::1/64 -t tun0 -s /dev/ttyUSB0
```
Assuming that `/dev/ttyUSB0` is the device descriptor for the (additional) UART
interface of your RIOT board.

On the RIOT side you have to configure the SLIP interface by configuring a
corresponding IPv6 address, e.g.
```
ifconfig 6 add 2001:db8::2
```
and adding the SLIP interface to the neighbor cache (because Linux won't
respond to neighbor solicitations on an interface without a link-layer address)
by calling
```
ncache add 6 2001:db8::1
```

Then, to propagate the prefix you should add an address to the wireless interface:

```
ifconfig 5 add 2001:db8::3
```

After this you're basically done and should be able to ping between the border
router and the outside world (assuming that the Linux host is properly
forwarding your traffic).

Additionally, you can configure IPv6 addresses on the 6LoWPAN interface for
communication with other 6LoWPAN nodes. See also the `gnrc_networking` example
for further help.

[1] https://tools.ietf.org/html/rfc1055

[2] https://github.com/contiki-os/contiki/blob/master/tools/tunslip.c