RFR: 8270553: Tests should not use (real, in-use, routable) 1.1.1.1 as dummy IP value

[Aleksey Shipilev]

On Fri, 16 Jul 2021 09:16:23 GMT, Jonathan Dowland <jdowland at openjdk.org> wrote:

> The tests `test/jdk/java/net/HttpURLConnection/HttpURLConWithProxy.java` uses the IP address "1.1.1.1" as a value. I think at the time the address was picked, the assumption was the address was not valid / not routable. Since April 2018 the address is part of CloudFlare's "Free" DNS product: <https://en.wikipedia.org/wiki/1.1.1.1>. (this test was originally written in 2016, before the service was launched)
> 
> I've verified using local packet captures that running the test does result in IP traffic being sent to 1.1.1.1. (Several other tests in JDK use 1.1.1.1 as a placeholder IP. I've checked them all and none of the others connect out to the IP like this one)
>  
> This PR substitutes that IP address value (and two others) for ones from a reserved IP range (240.0.0.0/4 according to RFC 6761) which will not result in runners of the test suit inadvertently sending IP packets to the CloudFlare service. 
> 
> This could be invalidated again if that address range is allocated at some point in the future. A more future-proof fix would be to bind to random ports on localhost for each dummy proxy (as done for the target HTTP server in the test already). I can do that if preferred.
> 
> <https://bugs.openjdk.java.net/browse/JDK-8270553>

I had to read up if this would work, and I am somewhat convinced it would. [IANA Database](https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml ) mentions these addresses are Reserved-by-Protocol, and refers to [RFC 1112, Section 4](https://www.rfc-editor.org/rfc/rfc1112.html) which mentions these are reserved for future addressing modes.

But this rabbit hole excursion makes me think it would be better to just use the local loopback in these tests.

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PR: https://git.openjdk.java.net/jdk/pull/4806