Re: Excluding some device types from persistent-net (xen, s390)

[Matthias Schwarzott <zzam@gentoo.org>]

On Donnerstag, 12. April 2007, Matthias Schwarzott wrote:
> Hi there!
>
> I have a change to persistent-net behaviour, to exclude xen-devices, and
> s390-devices.
>

I thought even more about the persistent-net framework.

The problems appear in two different cases:
1. Random MAC addresses (as we for now only use by-mac as method)
This will lead to increasing numbers for the device after each reboot with 
different mac.

2. Devices that are ignored and does not add persistent-rules.

This leads to errors as soon as on a system there are devices which we try to 
get persistent, and devices which we ignore (with the same prefix, e.g. 
eth*).
As udev cannot rename the device as soon as the dest name is already occupied.
(ignored devices being eth1, and udev trying to rename eth2 to eth1 will lead 
to eth?_rename devices ...)

Possible solutions for different devices (restricting me to eth, will add new 
mail about wifi stuff):


xen-devices: 
# udevinfo -a -p /sys/class/net/eth0
 
  looking at device '/class/net/eth0':
    KERNEL="eth0"
    SUBSYSTEM="net"
    DRIVER=""
    ATTR{weight}="64"
    ATTR{tx_queue_len}="1000"
    ATTR{flags}="0x1003"
    ATTR{mtu}="1500"
    ATTR{carrier}="1"
    ATTR{broadcast}="ff:ff:ff:ff:ff:ff"
    ATTR{address}="00:16:3e:08:25:1d"
 
  looking at parent device '/devices/xen/vif-0':
    KERNELS="vif-0"
    SUBSYSTEMS="xen"
    DRIVERS="vif"
    ATTRS{devtype}="vif"
    ATTRS{nodename}="device/vif/0"
 
  looking at parent device '/devices/xen':
    KERNELS="xen"
    SUBSYSTEMS=""
    DRIVERS=""

Perhaps the KERNEL(S) attribute of the parent device can be used for 
persistence (even though I don't know how the rule should look like) but 
perhaps just KERNELS="vif-0" will work. As I think the number refers to the 
(n+1)-th network interface declared in xen-conf for this domain. And that 
should be constant, even if mac changes.
Better solutions for xen-devices?


s390: For s390 I don't know the facts, please others discuss if there is 
something special necessary or not.

eth1394: Some users seem to have problems with eth1394, but the people I asked 
seem to have no problems with it (seem to have macs set and constant).

See this thread: "Problems with udev > 106 and multiple network cards"
Perhaps if just one device of this type appears we can persist it with 
ATTR{type}="24" in case no mac exists, ugly :(

Matthias

-- 
Matthias Schwarzott (zzam)

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