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Wladimir J. van der Laan 0ebae26c05 linux: Optimize binaries for size
2020-02-22 14:37:06 +00:00
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.gitignore Add k210 linux utilities 2020-02-21 15:42:04 +00:00
esptun.c linux: Optimize binaries for size 2020-02-22 14:37:06 +00:00
Makefile linux: Optimize binaries for size 2020-02-22 14:37:06 +00:00
README.md linux: Mention mtu setting in esptun doc 2020-02-22 14:26:29 +00:00
term.c linux: Set timeout argument on poll() properly 2020-02-22 12:22:25 +00:00

README.md

esptun

A tool to tunnel IP packets over UDP over WIFI through an UART connected to a ESP8285 with the standard AT firmware.

Usage

esptun <ifname> <uart> <ssid> <passwd> <host> <port>

This will create tun interface ifname. Then, with the with the ESP WIFI device on uart it connects to the AP ssid with password passwd. It creates a UDP over IP tunnel with the other endpoint host:port.

The new tun device will not be configured, use the ip utility to assign an IP address and switch the interface on.

For example:

/root/esptun tun0 /dev/ttyS1 "accesspointname" "secretpassword" 192.168.122.21 23232
/sbin/ip link set dev tun0 mtu 1472
/sbin/ip addr add 10.0.1.2/24 dev tun0
/sbin/ip link set tun0 up
/sbin/ip route add default via 10.0.1.1 dev tun0

(setting the MTU to 1500-20-8 the typical network MTU minus IP and UDP header overhead, because otherwise the ESP's network stack will drop the oversized packets)

Host side

On the other endpoint the tunnel is expected to be a host running socat or similar to unwrap the tunnel. For example:

sudo socat UDP:192.168.2.127:23232,bind=192.168.122.21:23232 \
    TUN:10.0.1.1/24,tun-name=tundudp,iff-no-pi,tun-type=tun,su=$USER,iff-up &
sudo ip link set dev tundudp mtu 1472

Optionally, enable forwarding and masquerading:

sudo iptables -t nat -F
sudo iptables -t nat -A POSTROUTING -o ens3 -j MASQUERADE
echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward

Linux kernel

Until there is a proper solution, you can use the following kernel branch to get the UART working on Kendryte K210 under Linux:

https://github.com/laanwj/linux/tree/kendryte-5.6-rc1-wifi

This is a hack that configures the FPIOA and GPIOHS manually, and configures UART1 from the device tree.

To enable TUN/TAP, enable the following kernel settings:

CONFIG_NET=y
CONFIG_INET=y
CONFIG_TUN=y

While building the root filesystem, make sure you enable at least ip and ping (and possibly other network tools) for busybox.

Author

Copyright (c) 2020 W.J. van der Laan Distributed under the MIT software license,