OTBR on loopback

[om26er]

Is it theoretically possible to run OTBR on loopback instead of WiFi/Ethernet?

I have a setup where OTBR and chip-tool run on the same hardware and any communication to the matter device happens by invoking chip-tool, so I don't really want the devices to be visible on my WAN. How can I do that?

I tried running otbr-agent on loopback, it starts but when I commission a device, the process fails because it cannot be discovered on mDNS

root@SimpleThings-Hub-d8-47-8f-21-7b-04:~# otbr-agent -I wpan0 -B lo 'spinel+spi:///dev/spidev2.0?gpio-int-device=/dev/gpiochip3&gpio-int-line=30&gpio-reset-device=/dev/gpiochip4&gpio-reset-line=3&spi-mode=0&spi-speed=1000000&spi-reset-delay=500&' --rest-listen-port 7000 --debug-level=5 -v
otbr-agent[64251]: [NOTE]-AGENT---: Running 0.3.0-thread-reference-20230710-8-g0761e725a2-dirty
otbr-agent[64251]: [NOTE]-AGENT---: Thread version: 1.3.0
otbr-agent[64251]: [NOTE]-AGENT---: Thread interface: wpan0
otbr-agent[64251]: [NOTE]-AGENT---: Radio URL: spinel+spi:///dev/spidev2.0?gpio-int-device=/dev/gpiochip3&gpio-int-line=30&gpio-reset-device=/dev/gpiochip4&gpio-reset-line=3&spi-mode=0&spi-speed=1000000&spi-reset-delay=500&
otbr-agent[64251]: [NOTE]-ILS-----: Infra link selected: lo
otbr-agent[64251]: 00:00:00.081 [N] RoutingManager: BR ULA prefix: fd89:69f9:3c0e::/48 (loaded)
otbr-agent[64251]: 00:00:00.081 [N] RoutingManager: Local on-link prefix: fd11:1111:1122:2222::/64
otbr-agent[64251]: 00:00:00.164 [N] Mle-----------: Role disabled -> detached
otbr-agent[64251]: 00:00:00.172 [N] Platform------: [netif] Changing interface state to up.
otbr-agent[64251]: 00:00:26.318 [N] Mle-----------: RLOC16 4c00 -> fffe
otbr-agent[64251]: 00:00:26.641 [N] Mle-----------: Attach attempt 1, AnyPartition reattaching with Active Dataset
otbr-agent[64251]: 00:00:33.141 [N] RouterTable---: Allocate router id 19
otbr-agent[64251]: 00:00:33.141 [N] Mle-----------: RLOC16 fffe -> 4c00
otbr-agent[64251]: 00:00:33.144 [N] Mle-----------: Role detached -> leader
otbr-agent[64251]: 00:00:33.144 [N] Mle-----------: Partition ID 0x4665a02f
otbr-agent[64251]: [NOTE]-BBA-----: BackboneAgent: Backbone Router becomes Primary!

[jwhui]

I've never tried running OTBR in this way.

One thing to check is that OTBR would be publishing DNS-SD services on the lo interface, so chip-tool would need to perform DNS-SD queries on the lo interface as well.