Our Networking Story

[Bryan Quigley]

We've had a lot of internal Canonical discussions about our networking
story and before going to a UDS session [1] it was suggested to post to
ubuntu-devel.

*Network Restart*
I'd like to start by asking each of you what you think is the correct way
to restart networking on Ubuntu server?  Feel free to write it down and
include it in any replies :).

It turns out our documentation has been wrong and the following are not
correct and more importantly don't work consistently over 10.04/12.04/14.04
[2]:
sudo /etc/init.d/networking restart
sudo restart networking

The correct way I've been told is to use the ifupdown scripts. It's
important to note that this is different on the desktop due to
network-manager.

I feel we need to publicly discuss if we really want the ifupdown scripts
to be the only supported way to manage/restart networking.  We've been
communicating the opposite for quite some time now..

Related question:
Do we not support giving users the ability to restart networking equivalent
to rebooting the system?  (Upstart is used when booting, not when manually
doing the ifupdown scripts).


*More complicated network setups*
There are many bugs in regards to bonds/vlans/bridging and other more
complex networking setups.  It appears like it might be a limitation to how
ifupdown is designed.

We have had cases where the MTU needs to be set using a pre-up or post-up
option in the interfaces file instead of a plain MTU line.
Bond interfaces can cause significant pausing in boot/network restart
The ifupdown script doesn't actually work on bonded interfaces [3]

race condition updating statefile "sometimes networking interfaces won't
come up" - was fixed [4]-

We are seeing many more of cases involving complicated networking setups
and with more OpenStack deployments this is going to become more of the
norm.

My understanding is that ifupdown was not designed to handle a parallel
boot process like Upstart or systemd.  I'm guessing there are a lot more
bugs lurking due to that, aside from some other issues with the codebase
[5].

*Future Releases*
NetworkManager everywhere?  systemd-networkd?

Thanks for discussing,
Bryan


[1]
https://blueprints.launchpad.net/ubuntu/+spec/servercloud-1403-networking
[2] If you want to see where those actually work see my document here:
https://docs.google.com/document/d/1OBN3efJ1LmA0-0DzD3K0eUkIuQdscxLQ-QO1yi3bHeM/edit
[3] https://bugs.launchpad.net/ubuntu/+source/ifenslave-2.6/+bug/1254120
[4] https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/1160490
[5]
http://pureperl.blogspot.com/2013/01/the-debian-ifupdown-package-and.html
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