Mininet 2.2.2 Release Notes

Mininet 2.2.2 is primarily a bug fix and compatibility release for Mininet 2.2.1.

Security Fix/Advisory!

• The Mininet VM image no longer includes the same, identical ssh key for everyone, and should instead generate new ones the first time it is booted(!!) [In my opinion, the .ovf spec should include an option (and the OS should include a mechanism) to regenerate ssh keys and MAC addresses, since the issue is likely to occur in any VM image with ssh installed!]

• We recommend that you regenerate any default keys in use in Mininet (or derived) VMs:

  sudo rm -f /etc/ssh/*key*
  sudo /usr/sbin/dpkg-reconfigure openssh-server
  sudo service ssh restart                              
  

• We recommend that you use the Mininet 2.2.2 or newer VM images.

Ubuntu 16.04 LTS (Xenial) Compatibility

• Kernel Bug Returns! :( Unfortunately, the annoying kernel bug that causes unshare() to hang (and Mininet to stop working until you reboot) has returned. You may see a message like unregister_netdevice: waiting for lo to become free. Usage count = 1 in the console or kernel log. Until this is fixed, we don't recommend using 16.04 (or the Linux 3.16 kernel.)

• We no longer attempt to delete a nonexistent root qdisc if one is not present (thanks to Olivier Tilmans)

• xenial VMs can now be created using build.py

Ubuntu 15 (Utopic) Compatibility

• We support openvswitch-testcontroller in Ubuntu 15. Note this controller is deprecated and not present in Ubuntu 16.

Code Check and Continuous Integration

• We now run public CI builds via Travis
• The builds include a code check using pylint on Ubuntu 14.04 LTS

Notable Bug Fixes or Workarounds

• We've been seeing a variety of performance test failures running under kvm, so the constraints on some performance tests have been relaxed slightly.

• A race condition that could cause Mininet.iperf() to fail has been addressed. (#589)

• We have forked the Stanford OpenFlow 1.0 reference controller and oflops and use our own versions in the Mininet VM image. Note these are somewhat obsolete.

• install.sh has basic support for RHEL.

• mnexec explicitly recursively marks mounts as private; this should fix compatibility with systemd based systems which inexplicably require the default mount namespace behavior to be shared. ;-( (#565)

• The default OpenFlow port is now the official port of 6653 rather than the classic port of 6633, which was nastily co-opted by Cisco.

• NAT can use all interfaces.

• ip_forward is restored to its original state after NAT shuts down

• An option has been added to the NAT element, and iptables are not flushed by default.

• The NAT element now correctly attaches to the switch that is specified in its parameters.

• A number of tests have been revised to make them more reliable.

Bugs and gotchas

• Ryu installation with install.sh -y is still broken

• The --tests option is slightly different from mainline, accepting multiple test names rather than parameters for the test. Please do not depend on this functionality in 2.2.2, or update to mainline if you require the new functionality.

• As noted, Ubuntu 16.04+/Linux 4.4 includes a kernel regression which breaks container systems with the waiting for lo to become free error. Until this is fixed, we don't recommend those OS/kernel versions. If you run into the problem, Mininet will stop working until you reboot.

Acknowledgments

Thanks to all of the contributors of fixes and enhancements for this release, including Olivier Tilmans, Jono Hart, Tomasz Buchert, Rahman Pujianto, Roan Huang, M S Vishwanath Bhat, Brian O'Connor, and others.