intermittent dns name resolution errors - network-manager

[Odysseus]

I'm a relative newbie to Ubuntu, but not Linux. I've been using Gentoo as my primary OS for the last 12 years, and other distros for the 6 years prior.

I've tried 3 versions of Ubuntu/Kubuntu over the last month (14.04, 15.10, and today 16.04) all have had intermittent issues with dns name resolving. The problem appears to be with the network-manger application. My laptop is a Dell Precision M90 with an Intel Corporation PRO/Wireless 4965 AG or AGN [Kedron] Network Connection (rev 61) WiFi network controller. The drivers are properly configured and I have no issues connecting to wireless networks.

The problem is 2/3 of the time when I connect with wifi there is no dns name resolution, so I'm unable to surf the web. Unfortunately, even if dns resolution does work after boot-up, it often fails after long periods of inactivity.

I've tried numerous possible workarounds that have been suggested on the net, as this seems to be a frequent problem. Unfortunately, I can't send a bug report while affected.

The only 100% effective solution that always gives me a usable internet connection was to remove the offending applications network-manager, network-manager-pptp, and plasma-nm. Then replace them with wicd, wicd-daemon, wicd-gtk, and python-wicd. Using these packages I get a usable connection 100% of the time, no matter how long the connection is inactive.

This problem appears to be long standing, as there are hundreds of pages on the net mentioning this and similar issues with network manger. Please resolve, or include a properly functioning equivalent, such as wicd in the default installation. TIA

[Odysseus (robcab666)]

I spent hours sorting through my system logs to see if I could find out on my own what is causing this issue. I found numerous error messages. that appear to be at least partially a timing issue with systemd. Network-manger was trying to establish a connection prior to reaching the desktop environment, then only starting after Kwallet opened. This would make sense if I was on an always wired machine, not so much on a laptop. I also noticed numerous times where whoopsie is trying to send bug reports prior to achieving the connection, failing, then sending immediately after connecting (hogging all of my limited bandwidth in the process). This could account for some DNS resolution issues if there was not enough bandwidth left for queries.

I experimented by purging WICD and its dependencies, then reinstalling Network-manager and its dependencies. I noticed an immediate improvement in dns name resolution from yesterday before I purged it from my system. However, now there is a graphical glitch in Plymouth as X starts, where there are 3 miniature instances still running as SDM launches, which I can deal with, and Kwallet opened upon reaching the desktop prompting for a password before wifi would connect. I resolved that issue by going to the wallet-manager and entering a null password.

Now I'm getting consistent dns resolution, and wifi is connected before I reach the desktop. I can live with no wallet password and the graphical glitches. So consider this now partially resolved.