Adjustments for std examples

I extended the README.md file to extend instructions for the rest of network examples

I modified the tap.sh script to give ownership to the user running it and avoiding running the examples with sudo. This would help someone using a debuger.

examples/std/README.md

@@ -1,19 +1,126 @@
 
 ## Running the `embassy-net` examples
 
-First, create the tap99 interface. (The number was chosen to
+To run `net`, `tcp_accept`, `net_udp` examples you will need a tap interface. Before running any example, create the tap99 interface. (The number was chosen to
 hopefully not collide with anything.) You only need to do
-this once.
+this once every time you reboot your computer.
 
 ```sh
 sudo sh tap.sh
 ```
 
-Second, have something listening there. For example `nc -lp 8000`
+### `net` example
+
+For this example, you need to have something listening in the correct port. For example `nc -lp 8000`.
 
 Then run the example located in the `examples` folder:
 
 ```sh
 cd $EMBASSY_ROOT/examples/std/
-sudo cargo run --bin net -- --tap tap99 --static-ip
+cargo run --bin net -- --tap tap99 --static-ip
+```
+### `tcp_accept` example
+
+This example listen for a tcp connection.
+
+First run the example located in the `examples` folder:
+
+```sh
+cd $EMBASSY_ROOT/examples/std/
+cargo run --bin tcp_accept -- --tap tap99 --static-ip
+```
+
+Then open a connection to the port. For example `nc 192.168.69.2 9999`.
+
+### `net_udp` example
+
+This example listen for a udp connection.
+
+First run the example located in the `examples` folder:
+
+```sh
+cd $EMBASSY_ROOT/examples/std/
+cargo run --bin net_udp -- --tap tap99 --static-ip
+```
+
+Then open a connection to the port. For example `nc -u 192.168.69.2 9400`.
+
+### `net_dns` example
+
+This example queries a `DNS` for the IP address of `www.example.com`.
+
+In order to achieve this, the `tap99` interface requires configuring tap99 as a gateway device temporarily.
+
+For example, in Ubuntu you can do this by:
+
+1. Identifying your default route device. In the next example `eth0`
+
+```sh
+ip r | grep "default"
+default via 192.168.2.1 dev eth0 proto kernel metric 35
+```
+
+2. Enabling temporarily IP Forwarding:
+
+```sh
+sudo sysctl -w net.ipv4.ip_forward=1
+```
+
+3. Configuring NAT to mascarade traffic from `tap99` to `eth0`
+
+```sh
+sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
+sudo iptables -A FORWARD -i tap99 -j ACCEPT
+sudo iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
+```
+
+4. Then you can run the example located in the `examples` folder:
+
+```sh
+cd $EMBASSY_ROOT/examples/std/
+cargo run --bin net_dns -- --tap tap99 --static-ip
+```
+
+### `net_ppp` example
+
+This example establish a Point-to-Point Protocol (PPP) connection that can be used, for example, for connecting to internet through a 4G modem via a serial channel.
+
+The example creates a PPP bridge over a virtual serial channel between `pty1` and `pty2` for the example code and a PPP server running on the same computer. 
+
+To run this example you will need:
+- ppp (pppd server)
+- socat (socket CAT)
+
+To run the examples you may follow the next steps:
+
+1. Save the PPP server configuration:
+```sh
+sudo sh -c 'echo "myuser $(hostname) mypass 192.168.7.10" >> /etc/ppp/pap-secrets'
+```
+
+2. Create a files `pty1` and `pty2` and link them 
+```sh
+cd $EMBASSY_ROOT/examples/std/
+socat -v -x PTY,link=pty1,rawer PTY,link=pty2,rawer
+```
+
+3. open a second terminal and start the PPP server:
+```sh
+cd $EMBASSY_ROOT/examples/std/
+sudo pppd $PWD/pty1 115200 192.168.7.1: ms-dns 8.8.4.4 ms-dns 8.8.8.8 nodetach debug local persist silent
+```
+
+4. Open a third terminal and run the example
+```sh
+cd $EMBASSY_ROOT/examples/std/
+RUST_LOG=trace cargo run --bin net_ppp -- --device pty2
+```
+5. Observe the output in the second and third terminal
+6. Open one last terminal to interact with `net_ppp` example through the PPP connection
+```sh
+# ping the net_ppp client
+ping 192.168.7.10
+# open an tcp connection
+nc 192.168.7.10 1234
+# Type anything and observe the output in the different terminals
 ```

examples/std/tap.sh

@@ -1,4 +1,4 @@
-ip tuntap add name tap99 mode tap user $USER
+ip tuntap add name tap99 mode tap user $SUDO_USER
 ip link set tap99 up
 ip addr add 192.168.69.100/24 dev tap99
 ip -6 addr add fe80::100/64 dev tap99