Integrity requirements

• I confirm that I have read the documentation, understand the meaning of all the configuration items I wrote, and did not pile up seemingly useful options or default values.
• I provided the complete config and logs, rather than just providing the truncated parts based on my own judgment.
• I searched issues and did not find any similar issues.
• The problem can be successfully reproduced in the latest Release

Description

As mention at 2dust/v2rayNG#4846 :
If the configuration uses TLS and prefers IPv6, but IPv6 is not reachable or ISP not supported, the connection should gracefully fall back to IPv4. To handle this reliably, the core’s built-in Happy Eyeballs function is used to automatically select the best available address family and avoid connection failures.

So, after checking the UseIPv6v4 and UseIPv4v6 scenarios seems fallback only use when no IPs available, I decided to implement a fallback in case the IPs are not reachable.

Do you think it makes sense to add this to the core, or is there anything should be improved?

hossinasaadi@e96e273

Reproduction Method

UseIPv6v4 | UseIPv4v6 domainStrategy

Client config

Server config

Client log

Server log