Introduction

On several Linux distributions, the NetworkManager daemon provides user-configurable control of network connections. In KDE, the KNetworkManager (KDE3) and Network Management (KDE4) are the main user interfaces to NetworkManager.

Bugs

Reporting Bugs

To report a useful bug against Network Management, provide the following items of information:

Your distro version
Is NetworkManager in use? On some distributions it is optional, as it is out of place on a static, server-like system. Stop now if it is not.
The version of the Network Management applet (NetworkManager-kde4.rpm on openSUSE, plasma-applet-networkmanager on kubuntu)
The version of the NetworkManager package
Your computer's hardware if not a vanilla x86 compatible. PPC user? I want to know.
Your network hardware (use lshal to find this out)
A system log from NetworkManager during the connection attempt
- for openSUSE: /var/log/NetworkManager
- for kubuntu: /var/log/syslog
- for fedora: /var/log/messages

For wireless networks:
- Is it using a hidden SSID?
- Wireless security type: WEP/WPA-PSK/WPA-EAP?
- Key length
- Key type (passphrase or hex for WEP)
- Ciphers (TKIP/AES)
- Auth mechanisms (TLS/TTLS/PEAP/...)

For mobile broadband:
- hardware
- driver in use (see dmesg when you connect the hardware)
- network in use
- network type (GSM/CDMA/UMTS)
- apn used, if any.

And very importantly: Are you able to connect with another client? For example, nm-applet under GNOME or cnetworkmanager on the console. If so, please try to attach comparative troubleshooting information as described at the end of this article.

Bug handling

Network Management on most Linux desktops sits on top of a large and fragile stack of components. This is necessary to deal with the vast number of different configurations. When a connection fails, it can be for any one of a number of reasons throughout this stack, but the symptoms will usually be something like "Connection got to 28% and then failed". Bugs reported at bugs.kde.org will be triaged to try and find out at what layer the failure occurred, so that it can be fixed by those responsible.

The Stack

The Hardware

Wireless hardware has a surprising number of bugs. These are dealt with at the next layer, if you are lucky.

The Kernel

This is where the actual driver that controls the hardware is located. There are many interesting bugs here too. Since the introduction of a standard wireless MAC layer in the Linux kernel, this situation is improving. Some hardware doesn't have a Linux driver, so people control it using the ndiswrapper tool, which loads Windows drivers and their bugs. You can see its output in the system log, and talk to the drivers using the iwtools set of commands.

WPA Supplicant

wpa_supplicant is a low level tool for talking to the driver, providing authentication and encryption settings. It is open source and generally of high quality. Before the advent of NetworkManager, users had to configure it manually with control files in /etc. This has been known to get people out of a tight spot occasionally. It usually logs to /var/log/wpa_supplicant.log. Nowadays it is mostly controlled remotely by

NetworkManager

NetworkManager is the system daemon at the centre of the networking subsystem on most end user Linux installations. It has root privileges, needed to control the lower layers, and exposes some controls up to clients running in the user session via DBUS. It writes a log in /var/log. NM also controls DHCP clients as needed and rewrites /etc/resolv.conf with DNS servers it has configured. NetworkManager also provides a SystemSettings service, which is responsible for reading your distribution's network configuration files (system wide) and feeding them into NetworkManager.

User Clients

Network Management under KDE 4, KNetworkManager under KDE 3, nm-applet under GNOME, and cnetworkmanager is your last life. These are responsible for

giving feedback on the networking status of ths system,
communicating the user's actions to NetworkManager and for storing
communicating the user's network connection details (policy) to NM.

While they are the most visible part of the system, they are also the least important to making a successful connection. Since they share a standard interface to NetworkManager, they can be exchanged easily.

When Things Go Wrong

Where Does It Hurt?

Simple. Start at the top of the stack and work down. When you find something that works, you found the site of the problem. When you run out of things you can change, hand over to an expert (probably the responsible team at your Linux distribution).

Are you actually using NetworkManager on your system? Mandriva doesn't use it. ArchLinux uses wicd. Moblin uses Connman.
Try a different NetworkManager client. If that helps, continue in the next section to try and further localise the problem in Network Management. Then bugs.kde.org, product 'Network Management' is the place to go.
Try to configure a connection using your distro's system configuration tools, so SystemSettings picks it up. It's unlikely but worth a go.
Try a manually configured connection via wpa_supplicant. The documentation is rather sparse but there are example configurations include in the package. Here is the list of supported hardware. If wpa_supplicant on its own works, NetworkManager is at fault. Talk to your distro or report it at bugs.freedesktop.org.
If that didn't work, reconfigure a wireless router to use a different (weaker) encryption type or none at all. If this works, the problem is either in wpa_supplicant or the driver. Either way, take it to your distro.

It's All KDE's Fault!

If you are reading this, you will have been able to make a connection using a different NetworkManager client.

First, make sure that you are not running another client as well as Network Management. This will lead to unpredictable results. If you were, remove and restart Network Management. You can run it externally to Plasma as 'plasmoidviewer networkmanagement' if you want.

You should now try to figure out how the connection provided by Network Management differs from that provided by the other client. To do this you currently need to build Network Management from source. The tool 'qdbusfornm' is a version of qdbus extended to handle NM's data types. You can use qdbusviewer to introspect the entire system bus, but it cannot call GetSettings. The value 0 below identifies the connection. Change it if you have more than one until you find the relevant connection.

./qdbusfornm --system org.freedesktop.NetworkManagerUserSettings /org/freedesktop/NetworkManagerSettings/0 org.freedesktop.NetworkManagerSettings.Connection.GetSettings

returns here

a{sa{sv}}(==802-11-wireless==
band: bg
mode: infrastructure
security: 802-11-wireless-security
ssid: opensuse-guest
==802-11-wireless-security==
auth-alg: open
key-mgmt: wpa-psk
wep-tx-keyidx: 0
==connection==
autoconnect: true
id: openSUSE
type: 802-11-wireless
uuid: {951cc7d9-1fa0-4525-9ab7-7199849e1b19}
==ipv4==
dns-search:
method: auto
)

Now you should repeat using the other, working client and copy both sets of output, before attaching them securely to a bug report at bugs.kde.org. With this information we will quickly be able to implement a fix.