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git-svn-id: http://svn-archive.gnome.org/svn/NetworkManager/trunk@1109 4912f4e0-d625-0410-9fb7-b9a5a253dbdc
62 lines
3.8 KiB
Text
62 lines
3.8 KiB
Text
THEORY OF OPERATION:
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NetworkManager attempts to keep an active network connection available at all
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times. It is intended only for the desktop use-case, and is not intended for
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usage on servers. The point of NetworkManager is to make networking
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configuration and setup as painless and automatic as possible. If using DHCP,
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NetworkManager is _intended_ to replace default routes, obtain IP addresses
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from a DHCP server, and change nameservers whenever it sees fit. If you have
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special needs, we'd like to hear about them, but understand that NetworkManager
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is not intended to serve the needs of all users.
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From a list of all adapters currently installed on the system, NetworkManager
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will first try a wired and then a wireless adapter. Wireless adapters that
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support wireless scanning are preferred over ones that cannot. NetworkManager
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does not try to keep a connection up as long as possible, meaning that plugging
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into a wired network will switch the connection to the wired network away from
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the wireless one.
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For wireless networking support, NetworkManager keeps two lists of wireless
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networks: a Trusted list, and a Preferred list. The Trusted list contains
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networks the user specifically adds to it, while the preferred list contains
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networks the user forces NetworkManager to connect to. For example, while the
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company's wireless network and WEP/WPA key would be preloaded into the Trusted
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Networks list, if the user wished to use the wireless network in a Starbucks,
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the user would explicitly tell NetworkManager to associate with that network.
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NetworkManager does not try to use _any_ available network in the area (a
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possible security risk), but will associate with any Trusted Network first, and
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Preferred Networks later. Preferred Networks are ones the user has explicitly
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made NetworkManager associate with at some previous time. So if the user walks
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into a Starbucks and explicitly asks NetworkManager to associate with that
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Starbucks network, NetworkManager will remember the Starbucks network
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information from that point on. Upon returning to that Starbucks,
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NetworkManager will attempt to associate _automatically_ with the Starbucks
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network since it is now in the Preferred Networks list. The point of this is to
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ensure that only the user can determine which wireless networks to associate
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with, and that the user is aware which networks are security risks and which
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are not.
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STRUCTURE:
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NetworkManager runs as a root-user system level daemon, since it
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must manipulate hardware directly. It communicates over DBUS with a
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desktop-level per-user process, nm-applet. Since Trusted and Preferred
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Networks are user-specific, there must be some mechanism of getting this
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information per-user. NetworkManager cannot store that information as it is
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user-specific, and therefore communicates over DBUS to the user daemon which
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provides those lists. NetworkManager also provides an API over DBUS for any
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DBUS-aware application to determine the current state of the network, including available wireless networks the computer is aware of and specific details about
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those networks. This API also provides the means for forcing NetworkManager to
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associate with a specific wireless network. Use of DBUS allows separation of
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NetworkManager, which requires no user-interface, and the parts of the user
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interface which might be desktop environment specific.
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The nm-applet provides a DBUS service called NetworkManagerInfo, which should
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provide to NetworkManager the Trusted and Preferred Networks lists upon request.
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It also should be able to display a dialog to retrieve a WEP/WPA key or
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passphrase from the user when NetworkManager requests it. The GNOME version of
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NetworkManagerInfo, for example, stores Trusted and Preferred Networks in
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GConf and WEP/WPA keys in gnome-keyring, and proxies that information to
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NetworkManager upon request.
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