new: macos connection share script now autodetects the usb interface and uses en0 as default upstream (closes #597)

scripts/macos_connection_share.sh

@@ -1,9 +1,20 @@
 #!/usr/bin/env bash
 
-# name of the ethernet gadget interface on the host
-USB_IFACE=${1:-en8}
-# host interface to use for upstream connection
-UPSTREAM_IFACE=${2:-en7}
+UPSTREAM_IFACE=${1:-en0}
+USB_IFACE=''
+USB_IP=${2:-10.0.0.1}
+
+for i in $(ifconfig -lu); do
+  if ifconfig $i | grep -q "${USB_IP}" ; then USB_IFACE=$i; fi;
+done
+
+if [ -z "$USB_IFACE" ]
+then
+  echo "can't find usb interface with ip $USB_IP"
+  exit 1
+fi
+
+echo "sharing connecting from upstream interface $UPSTREAM_IFACE to usb interface $USB_IFACE ..."
 
 sysctl -w net.inet.ip.forwarding=1
 pfctl -e