I am using OPNSENSE to connect with another network via GRE. The peer side requires GRE to use a tunnel key. After reading the FreeBSD manual, I found that FreeBSD GRE supports tunnel keys, but the GRE implementation in OpnSense does not yet support tunnel keys. Is there any way to temporarily enable tunnel key support for GRE in OpnSense, such as an interim solution? Thank you for your help.