How to add support to strongSwan IPsec

[MarkHaysHarris777]

So, how to insert these modules or should I recompile the kernel from the beginning.

First, to answer the question you didn't ask;  Yes, you can use VPN without using strongswan.

...  you may need the IPsec-based VPN solution;  but I would try to avoid it.   On the other hand, if you need the modules you listed then you will have to compile them in;  good thing strongswan is open source.

I tried ppp VPN before, but failed. I figure that the ppp ports are screened by the ISP. I have not tried L2TP.
How should I compile the module for PINE64?
Besides, should the modules complied from kernel source or strongswan source?

Yes.  ISP's and often cafe(s) will block ports ( preventing VPN from working by default ).

VPN normally uses port 1194 UDP which is often blocked by city ISP(s) and coffee houses , etc.  I have discovered a series of public locations that do not block the ports;  otherwise, I use alternate ports that are typically not blocked but can be used for other purposes ( remember a port is just a number ).

For instance port 431  443 ( the https port ) can be used for ssh tunneling;  because customers need to use https ( 431  443 is typically not blocked )  431  443 can be used instead for ssh;  because ssh traffic is very very similar to https  traffic and ISP(s) and cafe(s) are typically not sophisticated enough to separate and block the one vs the other.   Sometimes when VPN does not work, ssh on 431  443 does.

note:  thanks Pete:  443 is the https port...   oops.