DNS mystery: NetworkManager vs SELinux

[D. Hugh Redelmeier]

My netbook has a rather vanilla installation of F15.

I tried a new desktop.  Wireless didn't work (long story, not relevant) so 
I manually ran network manager (didn't help).  Then I rebooted back to 
Gnome.

Wired networking seemed to no longer work.  Actually, networking worked 
but no domain names could be resolved.

After a lot of ineffective poking about (based on my deep understanding of 
how things worked in the good old days before NM), I discovered (with 
help) the problem.

NM creates a new /etc/resolv.conf.tmp whenever it learns (through DHCP or 
whatever) what the name servers are.  On my system, it could not manage to 
replace /etc/resolv.conf.  /var/log/messages showed:
	<warn> could not commit DNS changes: (0) Could not replace /etc/resolv.conf: permission denied

"ls -l /etc/resolv.conf*" showed nothing scary.  But "ls -lZ" did.

Something had labeled /etc/resolv.conf unconfined_u:object_r:etc_t:s0
instead of system_u:object_r:net_conf_t:s0

Fix: "restorecon /etc/resolv.conf"

How the heck is an ordinary user supposed to figure this out?