Add systemd-resolved mDNS advertiser support

[elyscape]

♻️ Current situation

Homebridge currently supports three different mDNS advertisers, two that run in-process and one that uses Avahi over D-Bus. For a while now, systemd-resolved has supported acting as an mDNS advertiser and resolver. If Homebridge is run on a system that uses systemd-resolved for mDNS, this can cause conflicts similar to homebridge/homebridge#3077.

💡 Proposed solution

systemd-resolved, like Avahi, exposes a D-Bus interface for managing mDNS services. This pull request adds a systemd-resolved mDNS advertiser that makes use of this interface. The code was heavily based on that of the Avahi advertiser.

⚙️ Release Notes

• Added a new mDNS advertiser named resolved that uses systemd-resolved via D-Bus.

➕ Additional Information

In order for homebridge to have the permission to use this interface, a .pkla file with the following contents will need to be installed to /etc/polkit-1/localauthority/10-vendor.d/:

[Homebridge RegisterService]
Identity=unix-user:homebridge
Action=org.freedesktop.resolve1.register-service
ResultAny=yes

[Homebridge UnregisterService]
Identity=unix-user:homebridge
Action=org.freedesktop.resolve1.unregister-service
ResultAny=yes

Testing

Seems to work for me!

See: homebridge/homebridge#3224

[coveralls]

Pull Request Test Coverage Report for Build 3358831774

• 16 of 76 (21.05%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 51.988%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/lib/Accessory.ts	5	7	71.43%
src/lib/Advertiser.ts	11	69	15.94%

Files with Coverage Reduction	New Missed Lines	%
src/lib/Accessory.ts	1	43.01%

Totals
Change from base Build 3313107827:	-0.2%
Covered Lines:	5812
Relevant Lines:	10223

---

💛 - Coveralls

[elyscape]

Dealt with conflicts from master and ESLint warning. This should be ready whenever.

[Supereg]

Thanks for your contribution 🚀
Had only a few comments on certain places ☺️

You mentioned, that there is some initial setup required to set permissions for homebridge/hap-nodejs. Can we please add this to the in-code documentation so users can easily find that.
Further, can programatically detect, if we are missing the permission for systemd-resolved such that we can issue an according warning (maybe with a link to a Wiki documentation page illustration how to configure permissions)?

[elyscape]

Can we please add this to the in-code documentation so users can easily find that.

Sure. Where should I put it?

Further, can programatically detect, if we are missing the permission for systemd-resolved such that we can issue an according warning (maybe with a link to a Wiki documentation page illustration how to configure permissions)?

If we're missing the appropriate permissions, there are a number of different errors that can occur as a result. Rather than try to figure out what they all are, how do you feel about making the error handler always issue that warning in response to failures?

[elyscape]

@Supereg Any thoughts on what else I should do to get this in a mergable state?

[elyscape]

Tests should work now, btw.

[donavanbecker]

@Supereg, I have opened this Pull Request on the UI to add resolved: homebridge/homebridge-config-ui-x#1427