Enable CONFIG_IPV6_OPTIMISTIC_DAD

[Matt Nordhoff]

Feature request: Please enable CONFIG_IPV6_OPTIMISTIC_DAD.

config IPV6_OPTIMISTIC_DAD
 bool "IPv6: Enable RFC 4429 Optimistic DAD"
 ---help---
   This is experimental support for optimistic Duplicate
   Address Detection. It allows for autoconfigured addresses
   to be used more quickly.

   If unsure, say N.

It's no longer marked EXPERIMENTAL, but as you can see the description still calls it "experimental". I don't know its real status.

<https://tools.ietf.org/html/rfc4429>

It might make booting faster and/or more reliable, depending on how init handles waiting for DAD before starting services. I haven't actually used it, and don't know if it really will help anything.

This was previously requested as part of bug #447905, which went nowhere and was automatically closed in 2010. (That bug also requested a second, seemingly unrelated feature which is now enabled.)

I want it for the amd64 virtual and ec2 kernels in Xenial and Bionic, but I can wait until next decade too.

The relevant sysctls remain off by default, keeping the risk low for users who don't choose to enable it. (I think.)

Backporting 35e015e1f5773417952fe91ce8790baf9b4237a2 from 4.14-rc2 would be necessary for the net.ipv6.conf.all.optimistic_dad sysctl to work, but net.ipv6.conf.eth0.optimistic_dad and so forth should work without it. (I think...)

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1728366

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.