Fixing the DNS resolv.conf issue

[rusty-snake]

A lot network connection issues are caused by /etc/resolv.conf being outdated or wrong in other ways.

Examples:

• ExpressVPN internet issues (resolv.conf) #1889
• web browsers have no internet connection (resolv.conf) #3646
• private-etc=resolv.conf will not update for changed DNS server #3649
• No internet access with whitelist-run-common.inc (OpenSUSE) (resolv.conf) #4954
• firefox: cannot make new connections after switching network connection methods (resolv.conf) #5010
• signal: cannot reconnect if started without internet connection (resolv.conf) #5171
• php-fpm: no internet access (--noprofile) (resolv.conf) #5746

Relates to:

• modif: stop hiding blacklisted files in /etc by default and add a new etc-no-blacklisted option #5591
• private-etc rework broke profiles without resolv.conf in private-etc #5608
• profiles: fix private-etc (add missing resolv.conf) #5609
• [meta] private-etc rework #6400

When using options like private-etc, we bind mount /etc/resolv.conf into the sandbox. This is a problem if programs like NetworkManager/... make changes to /etc/resolv.conf by replacing rather than editing. (How do we handle the symlink case?).

This discussion is to find a concept to always properly propagate /etc/resolv.conf changes to the sandbox.

[e-pirate]

Just saying: came here from [#5010 ] to stay in tune. Currently using 0.9.64.4 cause later versions are not usable in my every day scenario.