softethervpn_4.21-9613_brcm2708.ipk is for OpenWrt 15.05.1 with RPI2
softethervpn_4.22-9634-1_arm_cortex-a7_neon-vfpv4.ipk is for OpenWrt 17.01.4 with RPI2
softethervpn_4.22-9634-1_arm_cortex-a53_neon-vfpv4.ipk is for OpenWrt 17.01.4 with RPI3