macOS internet connection sharing doesn't show `local scan` devices

[hedss]

• balena CLI version: 11.9.5
• Operating system version: macOS 10.14.5
• 32/64 bit OS and processor: 64-bit Intel processor
• Install method: npm
• If npm install, Node.js and npm version: Node v10.16.0 and npm v6.9.0

When Internet Connection Sharing (ICS) with a device, whilst that device does use the host machines connection for sharing, it doesn't show up via a balena local scan. However, MDNS is working on the device, and records are being passed. From the host machine:

$ dns-sd -B _ssh
Browsing for _ssh._tcp
DATE: ---Thu 12 Sep 2019---
14:01:22.328  ...STARTING...
Timestamp     A/R    Flags  if Domain               Service Type         Instance Name
...
14:01:22.329  Add        3  14 local.               _ssh._tcp.           f2a1f0d
14:01:22.329  Add        3  13 local.               _ssh._tcp.           f2a1f0d
...

Furthermore, this isn't Avahi dropping SRV/A/TXT records (which sometimes it does, given the known bug):

$ dns-sd -G v4 f2a1f0d.local
DATE: ---Thu 12 Sep 2019---
14:02:08.988  ...STARTING...
Timestamp     A/R    Flags if Hostname                               Address                                      TTL
14:02:09.194  Add        3 14 f2a1f0d.local.                         192.168.2.2                                  120
14:02:09.194  Add        2 13 f2a1f0d.local.                         192.168.2.2                                  120

It looks like because the ICS is rebinding to a separate subnet for the passthrough, the MDNS module (https://github.com/balena-io-modules/multicast-dns#listen-on-all-interfaces) isn't picking this up. Need to look into this and see exactly what's going on.

[pdcastro]

Connects to:

• 940 balena scan does not always return all balenaOS development devices

• 542 balena scan requires running as sudo

• 1715 balena scan [Windows]: solve Bonjour situation #1715