The opposite direction is described in usb.reverse.tethering
USB tethering is used to connect your OpenWrt-Router over your Smartphone with the Internet. Follow:
This can also be completly done by using the LuCI web UI.
Install USB Basic Support if not already installed by default on your OpenWrt router.
After you finished with USB Basic Support you have to install some Kernel packages to get USB tethering support.
opkg update opkg install kmod-usb-net kmod-usb-net-rndis kmod-usb-net-cdc-ether usbutils udev
usbutils and udev packages may be required to reconnect the phone correctly to the router. These are fairly large packages, and at least the Nexus 5 connects fine without them. Actually, kmod-usb-net-rndis would be sufficient since it depends on kmod-usb-net and kmod-usb-net-cdc-ether.
Enable USB Tethering on your Smartphone and connect it with the USB cable to your routers USB port.
Use the new
usb0 network device as WAN connection and set the protocol to DHCP client mode.
uci del network.wan uci set network.wan=interface uci set network.wan.ifname=usb0 uci set network.wan.proto=dhcp uci commit network
After commiting the changes to the network configuration bring up the WAN interface to obtain an IP, gateway and DNS address from your Smartphones DHCP server.
Login to the OpenWrt router with SSH at 192.168.1.1.
ifconfig $(uci get network.wan.ifname)
ping -c 4 www.google.com