Network Setup

Hi all, 
I was thinking about the network scripts again and how we can prevent that
changes of 
the hardware affect the network settings for a card. In summary the problem
is this: 
 
Example: 
a laptop with a built in mini-pci nic and a pcmcia nic. The driver for the
pci nic doesnt get 
loaded, because its only installed as an alias. the driver for the pcmcia
nic is going to be 
modprobed. That leads to a situation where the pcmcia nic is eth0 and the
pci nic aliases 
as eth0. Then the user wants to configure the card and configures eth0. on
the next boot, 
the alias will kick in and load the pci nic as eth0 and suddenly the users
pcmcia card will 
stop working, because its eth1 now. 
 
There are many more examples like this thinkable. 
 
So one approach would be to have a value in the ifcfg-ethX file that can
binds it to a 
particular card. on boot up we simply verify that ethX is still the same
card and if not we 
can readjust the device. When the nic was eth1 before and now the nic uses
eth0 we 
simply rename the ifcfg-ethX file.  
 
Possible values are to achieve node/device binding are: 
- A System Id 
The concept of a system ID is to give each device a unique identifier. One
concept uses 
the bustype follwed by the device number: 
PCI:BusNo:DeviceNo:FunctionNo 
USB:BusNo:DeviceNo 
PCMCIA:Socketno 
Serial:DeviceNo 
PS2:DeviceNo 
etc... 
Problem with this is that is very unflexible and only moving a pci card one
slot would 
require reconfiguration of the binding. 
 
 - Mac address.  
Every ethernet nic should have one. plipo has one, dummy0 has one,
usbnet(usbX) has 
one. Token Ring I dont know. Advantage is that even with multiple cards of
the same 
manufacturers this is going to work. 
 
- the vendor/device ID 
We could bind eth0 to a card by using the vendor/device ID. This is very
elegant, because 
the concept can be reused for other cases of numbered system nodes. In case
of multiple 
cards of the same model it should still work, because we only want to know
if ethX uses a 
different card now. If you swap two cards of the same model all is fine. If
you remove one 
we will see it anyway, because an ethX is missing 
 
 
 --- Proposal --- 
 
1) Add two values to the ifcfg-XXX files like: 
VENDOR=<vendor id> 
DEVICE=<device id> 
 
2) Write a tool for nic verification on boot up: networkmgr 
HardwareKit is already capable of being a backend for this. We can evaluate
to make this 
a demon in the future and let it react to hotplug network events (linux2.6) 
 
 
regards, 
Marc 
 
 
 
 
 
 
 
 
 
 
 
 

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