Failed to set multicast interface: no such interface

[kirollosnct]

Hello :)

The following console logs are sent infinitely when a network interface being multicased on has been disconnected, since the zeroconf stack continuously attempts to send multicast packets on a static set of interfaces configured on instantiation with no check whether the interface is alive.

2025/01/13 20:53:51 [WARN] mdns: Failed to set multicast interface: no such interface
2025/01/13 20:53:53 [WARN] mdns: Failed to set multicast interface: no such interface
2025/01/13 20:53:56 [WARN] mdns: Failed to set multicast interface: setsockopt: The requested address is not valid in its context.
2025/01/13 20:53:58 [WARN] mdns: Failed to set multicast interface: setsockopt: The requested address is not valid in its context.
2025/01/13 20:54:02 [WARN] mdns: Failed to set multicast interface: setsockopt: The requested address is not valid in its context.
2025/01/13 20:54:05 [WARN] mdns: Failed to set multicast interface: setsockopt: The requested address is not valid in its context.
2025/01/13 20:54:20 [WARN] mdns: Failed to set multicast interface: setsockopt: The requested address is not valid in its context.
2025/01/13 20:54:21 [WARN] mdns: Failed to set multicast interface: setsockopt: The requested address is not valid in its context.

These messages are triggered from both client.go and server.go.

Steps to reproduce:

1. Start a zeroconf service with selecting at least one connected network interface
2. Intentionally disconnect from a network interface
3. Observe console logs