I did a quick and dirty check with the latest version of libimobiledevice, usbmuxd and ipheth using an iPhone connected by usb cable:
$ sudo modprobe ipheth
$ sudo usbmuxd -f
[15:20:43.642] usbmuxd v1.0.7 starting up
[15:20:43.655] Connecting to new device on location 0x20006 as ID 1
[15:20:43.655] Initialization complete
[15:20:43.656] Connected to v1.0 device 1 on location 0x20006 with serial number 7d873f0ce2c59d19897f1c49f61dbeee64086a1d
$ idevicepair pair
SUCCESS: Paired with device 7d873f0ce2c59d19897f1c49f61dbeee64086a1d
usb 2-1.3: new high speed USB device number 6 using ehci_hcd
usbcore: registered new interface driver ipheth
ipheth 2-1.3:4.2: Apple iPhone USB Ethernet device attached
I realise this is not a Galaxy Gio, but it would seem that things are in place for internet tethering to work?
I'll try to post the updated libimobiledevice extension in the next day or two.