Register a invalid IPv6 address

[steverao]

Which Component
eg. Nacos Discovery

Describe the bug
A clear and concise description of what the bug is.
If I use spring.cloud.inetutils.preferred-networks=00 to filter the invalid IPv6 address, it will return [127.0.0.1], that is a invalid IPv6 address.

If I call the service by [127.0.0.1], it will print error information like below:

java.net.URISyntaxException: Malformed IPv6 address at index 8: http://[127.0.0.1]:20003/c
	at java.net.URI$Parser.fail(URI.java:2845) ~[na:1.8.0_291]
	at java.net.URI$Parser.parseIPv6Reference(URI.java:3466) ~[na:1.8.0_291]
	at java.net.URI$Parser.parseServer(URI.java:3216) ~[na:1.8.0_291]
	at java.net.URI$Parser.parseAuthority(URI.java:3152) ~[na:1.8.0_291]
	at java.net.URI$Parser.parseHierarchical(URI.java:3094) ~[na:1.8.0_291]
	at java.net.URI$Parser.parse(URI.java:3050) ~[na:1.8.0_291]
	at java.net.URI.<init>(URI.java:673) ~[na:1.8.0_291]

So, I think if we can't find a valid IPv6 address, we should register a valid IPv4.

[pandaapo]

I agree with you on "if we can't find a valid IPv6 address, we should register a valid IPv4". I intend to modify code according to your opinion.

Additionally, I think method findIPv6Address() should not return IPv4, which means method findFirstNonLoopbackHostInfo()(in class InetIPv6Util) should not. Otherwise, the result may contradict the method name and confuse developers.