libreswan: uci configuration support

[jempatel]

Maintainer: @lucize @feckert
Run tested: x86-64, aarch64, virtual box, marvell_armada-3720-db

Description:
Add libreswan UCI configuration and hotplug support

packaged uci config (/etc/config/libreswan) file provides examples/details with commented sections.

Continuation from #19079

@feckert

• handled iptables and nftables based firewall rules from hotplug
• added all files to be copied to packages in a Makefile
• changed hotplug hook to libreswan
• removed default config of uci-defaults

[feckert]

The fw4 has recently added a new feature where other packages can add additional rules.
https://git.openwrt.org/?p=project/firewall4.git;a=commit;

Adding the rules to fw4 directly has certain advantages.

• the rules are still there after a firewall reload
• you don't have to work with the command handle from the nftables

I have already prepared the strongswan to use this new feature.
https://github.com/openwrt/packages/pull/18559/files

[jempatel]

@feckert All comments have been addressed, Pls comment If anything else is there to consider.

[feckert]

It will be difficult to test this in my setup. I am not useing libreswan. I'll have to see if I have time to test it.

[lucize]

Good stuff!
LGTM
Tested in conjunction with luci interface

[lucize]

@feckert ping about this

[feckert]

Unfortunately I still don't have a setup for libreswan, but from what I've seen it looks good. I think we can give it a try after you have answered my comments.

[feckert]

Now you have to increment the PKG_RELEASE by one. Then we can merge and give the pullrequest a chance.

[jempatel]

Now you have to increment the PKG_RELEASE by one. Then we can merge and give the pullrequest a chance.

Updated.

[feckert]

Thank you for your patience.
Merged! 👏