To try to understand better, I started to dig into Modem Manager. Modem Manager has a Wiki article about troubleshooting. To prevent modem-manager from being restarted each time it was killed, I simply renamed the /usr/bin program and then started the program manually by using the –debug flag. After numerous tries of watching the modem get disconnected, I noticed that this state change seemed to occur quite a bit. During the disconnection process, the modem would suddenly jump back to the connected state:
Nov 12 08:49:37 my-laptop modem-manager:ModemManager 0.6.0 appears to fix these issues, as well as introduce a new approach for writing plugins for the package.
Modem /org/freedesktop/ModemManager/Modems/0: state changed (connected -> disconnecting) Nov 12 08:49:37 my-laptop NetworkManager: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0) Nov 12 08:49:37 my-laptop modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (disconnecting -> connected)
Currently Ubuntu 12.04 don't have the latest packages for ModemManager, and the issue was severe enough to compel me to try to compile the latest version myself (http://ftp.gnome.org/pub/gnome/sources/ModemManager/):
sudo apt-get install libdbus-glib-1-dev sudo apt-get install libgudev-1.0-dev wgetI've been running with the latest 0.6.4 version and the problem doesn't happen anymore. If the connection drops, the modem will eventually be made available again in the Network Manager applet.
./configure make sudo apt-get uninstall modem-manager make install
Another problem I've noticed is that the Network Manager applet often has blank entries for VPN connections, which appears to be a reported bug. I've also encountered issues with the Gigabit Ethernet port not reliably connecting with a longer cable, so finally decided to take the hit to try to install the latest versions of Network Manager and the Network Manager applet. There is also the issue that the Network Manager applet fails to respond to any mouse clicks, though typing "nmcli nm wwan on" enables the Mobile Broadband option.
These issues all seemed to necessitate upgrading Network Manager from the standard Ubuntu 12.04 packages. Be forewarned: if you attempt this process, you could easily disable your ability to access the Internet. Without the magic that NetworkManager does to handle all your wired and wireless connections, you will then have to resort to using ifconfig to setup a static IP address (i.e. ifconfig eth0 192.168.1.xxx), setting up a static default gateway (route add default gw 192.168.1.1), and adding a nameserver entry in /etc/resolv.conf (nameserver x.x.x.x). So I'd strongly suggest you try this process out on a local network unless you're adept at also connecting to wireless LAN's via the command line.
Download the latest version of Network Manager from this address:
Unpack the files and make sure you have these dev libraries installed:
sudo apt-get install intltool sudo apt-get install libnl-dev sudo apt-get install uuid-dev sudo apt-get install libnss3-dev sudo apt-get install ppp-dev ./configure --sysconfdir=/etc --libexecdir=/usr/lib/NetworkManager --localstatedir=/var make
At this point, you should avoid doing any make installs. You want to make sure both Network Manager and the Network Manager applet compiles without any issues before removing them. See http://projects.gnome.org/NetworkManager/developers/ since there are also different compile options in the instructions.
Note: The -sysconfdir is set to /etc, which will allow the compiled version of NetworkManager to find your current configuration (in /etc/NetworkManager). This way, you can re-use all your wired, wireless, and mobile broadband connections. The -libexecdir is needed since default Ubuntu installs dump the DHCP/PPTP scripts inside this directory, which are whitelisted by AppArmor. If you start seeing Permission Denied errors, chances are your paths are being blocked by AppArmor. You also need the -localstatedir option for this same reason, since this directory speicifies where the DHCP client will try to write the PID data.
The Network Manager can be downloaded from this location:
tar xvfp network-manager-applet-0.9.6.4.tar.xz sudo apt-get install libgconf2-dev sudo apt-get install libgnome-keyring-dev sudo apt-get install libnotify-dev sudo apt-get install libgtk-3-dev ./configure --sysconfdir=/etc --libexecdir=/usr/lib/NetworkManager makeNote: if you try to compile with libgtk2.0-dev, chances are that the compile will fail. Network Manager needs GTK 2.0+ to compile, but on Ubuntu 12.04 it seems that the libgtk-3-dev library is really what is needed.
If the compiles were successful, now is the time to remove Network Manager. Be forewarned that at this point you could easily block your ability to access the Internet. So only proceed to this point if you're confident enough to recover.
sudo apt-get remove network-manager sudo apt-get purge network-manager-gnome && sudo apt-get install network-manager-gnome
The --libexecdir for the Network Manager is needed for invoking other plugins, such as VPN. Also, if you intend to use VPN, you'll also need to git clone the repo you need to use (in this case, we're cloning the PPTP module).
git clone git://git.gnome.org/network-manager-pptp cd network-manager-pptp/ ./autogen.sh --sysconfdir=/etc --libexecdir=/usr/lib/NetworkManager --localstatedir=/var make sudo make installYou can then do make installs in both project directories and attempt to start Network Manager (or logging out and logging back in)
Note: if you don't see the nm-applet at the top, here are a few places to check. The first requires using the dconf-editor, which needs to be apt-get installed:
apt-get install dconf-tools dconf-editor
The instructions to use dconf-editor are listed here, which is basically to make sure that notifications are not disabled in the nm-applet namespace: http://askubuntu.com/questions/150406/how-do-i-re-enable-disabled-network-notifications-in-gnome-shell
You also want to make sure using dconf-editor that the com.canonical.Unity.Panel systray-whitelist is set toto "['all'] (or at least to include nm-applet). I found that my system tray was not set to this value and therefore prevented nm-applet from being rendered:
Normally I wouldn't recommend trying to compile and install Modem Manager and Network Manager, but the current packaged versions supplied in Ubuntu 12.04 appear to be so buggy and unstable that this approach appears to help deal with many of the issues that have been reported.