From: Xin Long <lucien.xin@gmail.com>
Date: Fri, 21 Sep 2018 15:55:34 +0800

It's under the protection of the sock lock, I think any other places
that want to access the address also need to acquire this sock lock
first.

Hash table lookups don't even have a socket context yet, so can't hold
the sock lock, but look at the address for comparisons.

Anything visible in a table lookup has to have stable keying
information.