[strongSwan] Interface can't be the loopback interface (lo). Sorry. - problem

[Tobias Brunner]

Hi,

> I found this: https://wiki.strongswan.org/issues/294
> 
> Both ends of my tunnel are Fedora29, so version of Strongswan should be 
> that-bug-free, it's: Linux strongSwan U5.7.1/K4.19.10-300.fc29.x86_64

Why would you think that issue has anything to do with your problem?

> But still when up my tunnel, it's successful with that one problem:

Which is nowhere mentioned in that issue.

> installing DNS server 10.3.1.99 via resolvconf
> resolvconf: Interface can't be the loopback interface (lo). Sorry.
> removing DNS server 10.3.1.99 via resolvconf

Apparently resolvconf on your system has problems with the interface
prefix that the resolve plugin plugin uses to install DNS servers via
resolvconf.  The default value is lo.inet.ipsec. (to which the DNS
server address is added).  The prefix can be changed with the
charon.plugins.resolve.resolvconf.iface_prefix option, so perhaps try a
different prefix/interface (make sure to consider and possibly change
/etc/resolvconf/interface-order so the installed DNS servers have a high
priority).

Regards,
Tobias