Make Root nameserver more flexible for plugins

[pinheadmz]

Closes #541

TODO: Include example plugins to close...

• dns/server: blacklist rfc2606 domains in the resolver dns/server: blacklist rfc2606 domains in the resolver #544
• Handshake TLDs .0 and .1 ... .255 confusion with IPv4 Namespace Handshake TLDs .0 and .1 ... .255 confusion with IPv4 Namespace #455
• Blacklist should include homographs of ICANN TLDs Blacklist should include homographs of ICANN TLDs #255
• On Resolving Alternative DNS Systems On Resolving Alternative DNS Systems #208

[coveralls]

Pull Request Test Coverage Report for Build 622382144

• 11 of 17 (64.71%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 59.578%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/dns/server.js	11	13	84.62%
lib/node/node.js	0	4	0.0%

Files with Coverage Reduction	New Missed Lines	%
lib/protocol/consensus.js	1	82.79%

Totals
Change from base Build 615190829:	0.2%
Covered Lines:	19616
Relevant Lines:	30652

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💛 - Coveralls

[pinheadmz]

All of the use cases for this modification are exemplified in this WIP hsd plugin: https://github.com/pinheadmz/holdmyhand

The one exception might be "alternative DNS systems" but the plugin can force lookup of certain names to ICANN (before checking the HNS root zone) and it should be clear to developers that the same method can be used to redirect queries to other systems resolvers like ENS, IPFS, Sia, Footnote, etc. They will just have to return a Message object the same way ns.icann.lookup() does.

[pinheadmz]

Moving the guide to hsd-dev.org, stay tuned for PR over there...

[pinheadmz]

Converted to draft while working on more plugin implementations and ensure everything is properly covered.

[pinheadmz]

Okay I think this one is ready. It should be a total NO-OP unless a user has a plugin installed, examples include https://github.com/imperviousinc/handover and https://github.com/pinheadmz/holdmyhand.

Docs will be updated when merged, working on that here: handshake-org/handshake-org.github.io#113

[buffrr]

Nice! I tried holdmyhand and handover. Having the ability to customize how the root nameserver works with plugins is going to be very useful.

[nodech]

Maybe hook or resolveHook would be more intuitive name?

[pinheadmz]

Hmmm, appreciate the feedback. I've already written two plugins using this and documented the middle() property here: https://hsd-dev.org/guides/plugins.html 🤷‍♂️