Which packages are needed to setup AES256GCM IPsec VPN?

I have successfully configured an aes256gcm encrypted strongswan ipsec vpn server on debian, but it failed on OpenWrt, I got an error message saying "function not implemented".
so which packages should be installed? or I need to compile kernel myself?

I have tried to installed strongswan-full, kmod-crypto-aead, kmod-crypto-gcm, but nothing changed.

Fir size reasons, strongswan on OpenWrt is split into many separate subpackages, splitting out functionality and independent plugins - you'll have to check which you might be missing (and it's entirely possible that the plugins you might be needing is currently missing). Checking logread, jacking up the verbosity and other debugging steps might be needed.