[Bug 1541544] Re: ubuntu-installer makes a contradictional statement regarding layer2/layer3

[Dimitri John Ledkov]

Hello,

Ideally we would use heuristics. For example, does the hardware and the
kernel know about layer2 already and e.g. does one need to change
/sys/devices/qeth/0.0.0600/layer2 at all? Ideally layer2 would be set to
the correct value by the kernel, and we simply lower the priority of
this question, and thus stop asking users about it by default. I'm now
digging into the kernel code and it looks like qeth_core_main loads
layer2 by default (unless I'm missing something, I'm not a kernel
developer).

I'm happy to adjust statement to a more technically correct one.
"""
Use this device in layer2 mode?
The qeth network driver is used for OSA-Express cards, HiperSockets and similar devices. Using the card in layer2 mode will make it keep the MAC addresses of IPv4 packets. Alternative is to use layer3 mode, in that mode LLC headers are removed from incoming IPv4 packets. Incorrect mode will lead to lack of connectivity.
"""
Comments on the above?


On the desktop installer, we check the connectivity by retrieving and validating check-sum of http://start.ubuntu.com/connectivity-check and thus really validate that one can access things (but i guess most mainframes are fire-walled to prevent such access). I guess in d-i context it's about being able to access the network mirror to continue installation. Not sure how we can validate automatically, given that local mirror information may not be available yet.

Lastly, I've changed the default based on the statistically
insignificant survey of three people ("most mainframes use layer2,
something like 60-80% probably).  And a personal feeling that a bunch of
things require layer2 network. The fact that our mainframe is configured
with layer2 network cards was a factor too =) to ease things for us.
Defaults should be sensible, or what we want the future be like.

1) ideally kernel and/or with udev assistance would do the autodiscovery of the required mode, if possible.
2) does the proposed new wording sound better to you? or how would you like the question to be worded?
3) should I keep layer2 as default? 

Regards,

Dimitri.

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https://bugs.launchpad.net/bugs/1541544

Title:
  ubuntu-installer makes a contradictional statement regarding
  layer2/layer3

Status in debian-installer package in Ubuntu:
  New

Bug description:
  == Comment: #0 - Thorsten Diehl <thorsten.diehl at de.ibm.com> - 2016-02-03 12:05:19 ==
  When I configure a qeth OSA device, the installer asks for device type, device and protocol layer:

  Please choose the type of your primary network interface that you will need for 
   
  installing the Debian system (via NFS or HTTP). Only the listed devices are   
  supported.  
  Network device type:  
    1: ctc: Channel to Channel (CTC) or ESCON connection,      
    2: qeth: OSA-Express in QDIO mode / HiperSockets,      
    3: iucv: Inter-User Communication Vehicle - available for VM guests only,     
   
    4: virtio: KVM VirtIO,      
  Prompt: '?' for help> 2
  2  
    
  Please select the OSA-Express QDIO / HiperSockets device.  
  Device:  
    1: 0.0.f5f0-0.0.f5f1-0.0.f5f2  [*],  
  Prompt: '?' for help, default=1> 1
  1  
    
  By default OSA-Express cards use layer3 mode. In that mode LLC headers are   
  removed from incoming IPv4 packets. Using the card in layer2 mode will make it
  keep the MAC addresses of IPv4 packets.  
  Use this device in layer2 mode?  
    1: Yes [*]  2: No  
  Prompt: '?' for help, default=1> 

  The last question experienced a change according to https://bugs.launchpad.net/ubuntu/+source/s390-netdevice/+bug/1526801
  Layer2 is the default, which is correct, since the qeth driver uses layer2 as default as well.

  However, the introductional text says: "By default OSA-Express cards
  use layer3 mode."

  And this is wrong and needs to be fixed. Correct wording is:

  "By default OSA-Express cards use layer2 mode. In layer3 mode LLC headers are   
  removed from incoming IPv4 packets. Using the card in layer2 mode will make it   
  keep the MAC addresses of IPv4 packets."

  == Comment: #2 - Thorsten Diehl <thorsten.diehl at de.ibm.com> - 2016-02-03 12:08:52 ==
  Although LP 1526801 deals with this subject, it is different.
  LP 1526801 is implemented and closed. Now the documentational part in the installer needs to follow that. Thus I recommend to treat this as a separate bug.

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