common: validate endpoint fields in parseEndpoint

[wenzaee]

What type of PR is this?
/kind bug

What this PR does / why we need it:
This PR implements the TODO in parseEndpoint by adding IP and port validation.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:
NONE

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[kubeedge-bot]

Welcome @wenzaee! It looks like this is your first PR to kubeedge/edgemesh 🎉

[gemini-code-assist]

Code Review

This pull request implements IP and port validation in the parseEndpoint function within pkg/loadbalancer/util.go, replacing a previous TODO. The review feedback suggests refining the validation logic by incorporating a port range check and removing redundant checks, while also highlighting that the current implementation is limited to IPv4 support.

[gemini-code-assist]

The validation logic can be improved by checking the full valid port range (1-65535) and removing redundant checks. Since net.ParseIP already validates that the string is a valid IP address, the host != "" check inside isValidEndpoint is unnecessary here. Combining the port conversion and range check also makes the code more concise.

Additionally, note that the current parsing logic using strings.Split(endpoint, ":") is incompatible with IPv6 addresses as they contain colons. While fixing the parsing logic might be out of scope for this PR, it's worth noting that this function currently only supports IPv4.

Suggested change

	port, err := strconv.Atoi(info[portIndex])
	if err != nil {
	return "", "", "", "", false
	}
	if net.ParseIP(info[ipIndex]) == nil || !isValidEndpoint(info[ipIndex], port) {
	return "", "", "", "", false
	}
	port, err := strconv.Atoi(info[portIndex])
	if err != nil || port <= 0 || port > 65535 {
	return "", "", "", "", false
	}
	if net.ParseIP(info[ipIndex]) == nil {
	return "", "", "", "", false
	}