[FEATURE] Allow for domain participants to be configured for ipv6 and allow for SPDP multicast address configuration

[dtjones190]

Cyclone DDS allows this with a configuration file like this:

<?xml version="1.0" encoding="utf-8"?>
<CycloneDDS
  xmlns="https://cdds.io/config"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://cdds.io/config https://raw.githubusercontent.com/eclipse-cyclonedds/cyclonedds/master/etc/cyclonedds.xsd"
>
  <Domain Id="any">
    <General>
      <Interfaces>
        <NetworkInterface autodetermine="false" priority="default" name="br0"
        multicast="default" />
      </Interfaces>
      <Transport>udp6</Transport>
      <AllowMulticast>default</AllowMulticast>
    </General>
    <Discovery>
      <SPDPMulticastAddress>
        ff03::efff:1
      </SPDPMulticastAddress>
    </Discovery>
  </Domain>
</CycloneDDS>

Ideally HDDS would allow these to be configured with the Participant builder.

[hdds-team]

Hi @dtjones190, thanks for the feature request!

We have partial support for this today:

• Interface selection: HDDS_INTERFACE env var lets you force a specific interface (by IP or name)
• IPv6 locators: supported at the protocol level (RTPS locator encoding)

What's missing:

• Builder API for interface/multicast configuration (currently env var only)
• IPv6 transport (UDP6)
• Custom SPDP multicast address (currently hardcoded to 239.255.0.1)

We'll keep this open to track it. Builder API for interface selection is the most likely near-term addition.