[ -n "$if" ] && grep -qs "^ *$if:" /proc/net/dev && echo "$if"
}
find_6in4_wanip() {
local ip=$(ip -4 a s dev "$1"); ip="${ip#*inet }"
[ -n "$if" ] && grep -qs "^ *$if:" /proc/net/dev && echo "$if"
}
find_6in4_wanip() {
local ip=$(ip -4 a s dev "$1"); ip="${ip#*inet }"