netdev - [BISECTED] [4.17.0-rc6] IPv6 link-local address not getting added

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Date:   Wed, 27 Jun 2018 20:35:15 -0400
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     dsahern@...il.com
Cc:     netdev@...r.kernel.org
Subject: [BISECTED] [4.17.0-rc6] IPv6 link-local address not getting added


Hi David,

An IPv6 regression has been introduced in 4.17.0-rc6 by
  8308f3f net/ipv6: Add support for specifying metric of connected routes

The regression is that some interfaces on my test machine come
up with link-local addrs but the fe80 prefix is missing.
After this bug, I cannot send any packets to anyone onlink 
(including my routers). 

Here are the symptoms:

When everything is fine, "ip -6 route|grep eno" shows

2606:b400:400:18c8::/64 dev eno1 proto ra metric 100  pref medium
fe80::5:73ff:fea0:52d dev eno1 proto static metric 100  pref medium
fe80::/64 dev eno1 proto kernel metric 256  pref medium
fe80::/64 dev eno3 proto kernel metric 256  pref medium
fe80::/64 dev eno4 proto kernel metric 256  pref medium
default via fe80::5:73ff:fea0:52d dev eno1 proto static metric 100  pref medium

But after 8308f3f, I only find

# ip -6 route|grep eno
2606:b400:400:18c8::/64 dev eno1 proto ra metric 100  pref medium
fe80::5:73ff:fea0:52d dev eno1 proto static metric 100  pref medium
fe80::/64 dev eno1 proto kernel metric 256  pref medium
default via fe80::5:73ff:fea0:52d dev eno1 proto static metric 100  pref medium

(note that eno2 is not enabled in my config, so its absence is expected)

Please have a look, thanks.
--Sowmini