convert the core filter RequestRedirect to the proper Kong plugin

[mlavacca]

Is there an existing issue for this?

• I have searched the existing issues

Problem Statement

We should support the core HTTPRoute filter RequestRedirect to be compliant with Gateway API. The core filter RequestHeaderModifier has already been supported in KIC by means of a kong plugin, and we should do the same for this filter.

Proposed Solution

Extend the function generatePluginsFromHTTPRouteRuleFilters to support the filter RequestRedirect

Additional information

#2793 (comment)
#2793 (comment)

Acceptance Criteria

• the core filter RequestRedirect is translated to the proper Kong plugin

[randmonkey]

Searched for all free plugins in plugin hub, there was no plugins that fully satisfy the requirements of RequestRedirect. According to the comments in #2793 (comment) and some investigation, the possible implementation of this feature would be :

• Run a server to return such redirect responses, and use request transformer to set fixed fields in request header.
• Use serverless functions to write our own code to return redirect response
• Similar to above, use request transformer to set fixed fields in request header, and use a custom plugin to fill in the fields from request and return the response.

[randmonkey]

After investigation, currently the RequestRedirect feature could NOT be implemented using one or combination of existing free plugins of kong gateway (except for the serverless functions, but this allows running custom lua code, which is insecure). So, we decided not to include this feature in the upcoming 2.6.0 release of KIC.

[mflendrich]

not blocked anymore - @randmonkey has a solution proposal (can you please post it here?)

[randmonkey]

One possible method to implement RequestRedirect filter: Run a server from KIC to return redirect responses, and use RequestModifier plugin to carry the specifications to the redirect server.
When a rule uses RequestRedirect, we generate a route sending traffic to KIC redirect server, and carry the settings of filter using RequestModifier plugin to add headers (if the corresponding field presents. When the fields are configured, they remain unchanged until HTTPRoute resource modified):

• X-Kic-Redirect-Scheme for Scheme field
• X-Kic-Redirect-Hostname for Hostname
• X-Kic-Redirect-Path-Modifier-Type for Path.Type
• X-Kic-Redirect-Path-Replace-Fullpath for Path.ReplaceFullPath
• X-Kic-Redirect-Path-Replace-Prefixmatch for Path.ReplacePrefixMatch
• X-Kic-Redirect-Port for Port
• X-Kic-Redirect-Statuscode for StatusCode
  When a request to that path came to Kong, it first go through the RequestModifier plugin to add the header carrying the settings. Then the request with added headers is proxied to KIC redirect server, then KIC server use the header and original request to generate and return the redirect response.

[mheap]

@mlavacca Is this core or extended conformance?

[mlavacca]

This is core and has already been fixed by ##3702. We can close it 🎉