Upstream network interface: Main upstream regex used to reroute traffic. Leave blank for auto detect system VPN (allow/do not bypass this app to use VPN for it to work). Put none (or a^ or other similarly invalid entries) to suppress tethering VPN.
Fallback upstream: Fallback upstream is used when some VPN leave certain routes fallback to default network interface. Leave blank for auto detect. Put none (or a^ or other similarly invalid entries) to forbid falling back. Put other interface name if you feel like it.
IP Masquerade Mode:
None: Nothing will be done to remap address/port from downstream. I find turning this option off sometimes works better for dummy VPNs like ad-blockers and socksifiers than Simple mode, e.g. Shadowsocks. But you should never use this for real VPNs like OpenVPN, etc.
Simple: Source address/port from downstream packets will be remapped and that's about it.
(since Android 9) Android Netd Service: Let your system handle masquerade. Android system will do a few extra things to make things like FTP and tethering traffic counter work. You should probably not use this if you are trying to hide your tethering activity from your carrier.
Downstream
Disable IPv6 tethering: Turning this option on will disable IPv6 for system tethering. Useful for stopping IPv6 leaks as this app currently doesn't handle IPv6 VPN tethering (see #6).
(since Android 8.1) Tethering hardware acceleration: This is a shortcut to the same setting in system Developer options. Turning this option off is probably a must for making VPN tethering over system tethering work, but it might also decrease your battery life while tethering is enabled.
Enable DHCP workaround: Only used if your device isn't able to get your clients IP addresses with VPN on. This is a global setting, meaning it will only be applied once globally.
Misc
Keep Wi-Fi alive: Acquire Wi-Fi locks when repeater, temporary hotspot or system VPN hotspot is activated.
Choose "System default" (default since Android 10) to save battery life;
(prior to Android 10) Choose "On" (default) if repeater/hotspot turns itself off automatically or stops working after a while;
(prior to Android 10) Choose "High Performance Mode" to minimize packet loss and latency (will consume more power);
(since Android 10) Choose "Disable power save" to decrease packet latency. An example use case is when a voice connection needs to be kept active even after the device screen goes off. Using this mode may improve the call quality. Requires support from the hardware.
(since Android 10) Choose "Low latency mode" to optimize for reduced packet latency, and this might result in:
Reduced battery life.
Reduced throughput.
Reduced frequency of Wi-Fi scanning. This may cause the device not roaming or switching to the AP with highest signal quality, and location accuracy may be reduced. Example use cases are real time gaming or virtual reality applications where low latency is a key factor for user experience. Requires support from the hardware. Note: Requires this app running in foreground with screen on.
Start repeater on boot: Self explanatory.
Repeater safe mode: (Android 10, March 2020 security patch or newer) You might be required to turn this mode off if you want to use short SSID (at most 8 bytes long). Unsafe mode might not work for your device, and there is a small chance you will soft brick your device (recoverable). See #153 for more information.
Network status monitor mode: This option controls how the app monitors connected devices as well as interface changes (when custom upstream is used). Requires restarting the app to take effects. (best way is to go to app info and force stop)
Netlink monitor: Use Linux netlink mechanism, most battery efficient but may not work with SELinux enforcing mode. Sometimes auto fallbacks to Netlink monitor with root and Poll.
Netlink monitor with root: Same as above but runs netlink as root. This option works well with SELinux enforcing mode but might still be bugged on devices heavily modified by OEM and/or carriers. Sometimes auto fallbacks to Poll.
Poll: (default) Update network information manually every second. Least battery efficient but it should work on most devices. Recommended to switch to other modes if possible.
Poll with root: Same as Poll but polling is done using a root shell.