Sounds like the opposite of this bug. GitHub's system represents 0.0.0.0/0 and ::ffff:0.0.0.0/96 as distinct values, when they should be merged/normalized. I

Sounds like the opposite of this bug. GitHub's system represents 0.0.0.0/0 and ::ffff:0.0.0.0/96 as distinct values, when they should be merged/normalized. I think it's best to treat IPv4-mapped addresses as an implementation detail of the socket API, and not leak them into general purpose code. Though things get interesting when an external user provides "::ffff:1.2.3.4" as text.