Duplicated connections

[fuzzypixelz]

Describe the bug

The Runtime obtains Endpoints through scouting and user configuration. It tries to connect to both kinds of Endpoints concurrently without coordination. This can lead to duplicated connections.

~~Moreover, more links are created to the same Transport session than transport/unicast/max_links.~~ transport/unicast/max_links only affects the number of incoming links.

Locators obtained through scouting usually can have IP addresses (even if the listener is configured with a domain name), but Endpoints supplied in configuration can use domain names (e.g. "localhost"), this mismatch is another cause for connection duplication.

To reproduce

⚠️ EDIT(5/8/25): The reproduction commands were incorrect, I meant to use the hostname in the peer and the IP address in zenohd, not the other way around.

1. cargo run --bin zenohd -- --cfg 'transport/unicast/max_links:4' --cfg 'plugins_loading/enabled:false' -l 'tcp/127.0.0.1:9000' -l 'tcp/127.0.0.1:9001' --id a
2. cargo run --example z_get -- -s '@/*/session/transport/unicast/a/link/*' -e 'tcp/localhost:9000' -e 'tcp/localhost:9001'

In my experiments, only one of the Endpoints is duplicated.

System info

• ref: 36b97aa7

[fuzzypixelz]

@sashacmc I can still reproduce this as of 07f5d89526e5391b6199cd8de4fd886ae2776249.