feat: add ipv4/ipv6 dual stack support

[juwon8891]

What type of PR is this?

feat: add ipv4/ipv6 dual stack support

What this PR does / why we need it: This PR adds IPv4/IPv6 dual stack support to Envoy Gateway. It implements test cases for routing to IPv6-only, dual-stack, and IPv4-only services using HTTPRoute resources. This enhancement is crucial for supporting modern network environments and ensuring compatibility with both IPv4 and IPv6 infrastructures.

Key changes include:

1. New test file backend_dualstack.go for testing IPv6 and dual-stack backends
2. New test file httproute_dualstack.go for testing HTTPRoute support with various IP versions
3. New manifest files for defining resources used in dual-stack tests
4. Implementation of getDnsLookupFamily function to control DNS lookup behavior

Which issue(s) this PR fixes:

Fixes #184

Additional Notes:

• Tests are skipped in IPv4-only environments (IP_FAMILY=ipv4)
• All tests run in IPv6 or dual-stack environments (IP_FAMILY=ipv6 or IP_FAMILY=dual)

[arkodg]

hey @juwon8891 we probably also need to add some logic in https://github.com/envoyproxy/gateway/blob/4b8c2f56dc45534c42b6513b126082f49a009658/internal/gatewayapi/route.go#L1328 which selects specific endpoints based on the ipFamilyPolicy field

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 61.11111% with 7 lines in your changes missing coverage. Please review.

Project coverage is 65.80%. Comparing base (7188dad) to head (faa584b).

Files with missing lines	Patch %	Lines
internal/gatewayapi/helpers.go	36.36%	7 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4375      +/-   ##
==========================================
+ Coverage   65.78%   65.80%   +0.02%     
==========================================
  Files         210      210              
  Lines       31516    31557      +41     
==========================================
+ Hits        20732    20766      +34     
- Misses       9588     9594       +6     
- Partials     1196     1197       +1     

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[arkodg]

hey @juwon8891 lint is failing

internal/xds/translator/testdata/in/xds-ir/tcp-listener-ipfamily.yaml
  Error: 7:5 [indentation] wrong indentation: expected 6 but found 4
  Error: 11:9 [indentation] wrong indentation: expected 10 but found 8
  Error: 12:11 [indentation] wrong indentation: expected 12 but found 10
  Error: 13:32 [new-line-at-end-of-file] no new line character at the end of file

[arkodg]

hey @juwon8891 looks like some gateway api tests got wiped out, can you add them back ?

[zhaohuabing]

@juwon8891 Do you have time to address the comments this week? We want to ensure dual stack support is ready to be included in the coming v1.2.

[juwon8891]

Yes, I'm working on it. I'll answer as soon as possible

[arkodg]

hey @juwon8891, added some minor comments, but overall LGTM !

[zirain]

@juwon8891 please run make gen-check to pass the gen-check CI.

[arkodg]

@juwon8891 DCO is failing, can you sign your commits

[guydc]

/retest