XForwardedHeadersFilter does not add X-Forwarded-For when remote address is an IPv6

[ZIRAKrezovic]

This is a continuation of the Forwarded headers bug, but this time for XForwardedFilter

After adding property spring.cloud.gateway.forwarded.enabled=false to https://github.com/ZIRAKrezovic/gateway-reproducer, XForwardedFilter check for remote address fails when IPv6 is parsed as remote address

Last conditional will fail, and X-Forwarded-For will not be added to the request.

[bclozel]

If this is a continuation of #3643, the premise in #3643 seems wrong so maybe this should be closed as well?

[ZIRAKrezovic]

There is a valid IPv6 in request.getRemoteAddress(), so the problem still persists. I have updated the test to use "[]" - issue is still the same.

[ZIRAKrezovic]

Note the following in ForwardedHeadersFilter

This seems to be missing in XForwardedHeadersFilter.

Here's the culprit

https://github.com/spring-projects/spring-framework/blob/main/spring-web/src/main/java/org/springframework/web/util/ForwardedHeaderUtils.java#L184

[ZIRAKrezovic]

Created spring-projects/spring-framework#34253 as well.