Envoy: Support for X-Forwarded-Prefix header

[shalako]

Title: One line description

Enable applications that support the X-Forwarded-Prefix header to generate working links when an ingress proxy has rewritten the context path to root.

Description:

It is common to have an application responsible for only one context path of a domain; e.g. example.com/foo/* should be routed to myapp. However, myapp serves content on /, not /foo, because the application shouldn't have to know the client-facing context path. So the ingress proxy is configured to rewrite the path from /foo/* to /*. However, since the app doesn't know that this rewrite has occurred, it is unable to generate working self-referential link in responses, e.g. the app would return a link to /products instead of /foo/products.

The X-Forwarded-Prefix header provides the path that was stripped by the proxy.

App devs told me that this header is supported by Spring Boot, which helps with automation of link generation.

[mattklein123]

We do already write the original path in x-envoy-original-path. I assume this is not sufficient?

[shalako]

I was not aware, thank you for your reply.

While X-Envoy-Original-Path may provide the same function, it is not likely to have the same support in Spring or other frameworks as X-Forwarded-Prefix does. I’ll look into it a bit further and post an update or close this issue.

On Jan 7, 2019, at 6:55 PM, Matt Klein [e-mail] wrote:

We do already write the original path in x-envoy-original-path. I assume this is not sufficient?

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[rstoyanchev]

There is a standard HTTP header for this https://tools.ietf.org/html/rfc7239#section-4.

[shalako]

Good call. A standard header will likely be an easier sell with the framework communities, like Spring, than an Envoy-specific one. But, requires changes on both sides.

On Jan 9, 2019, at 5:58 PM, Rossen Stoyanchev [e-mail] wrote:

There is a standard HTTP header for this https://tools.ietf.org/html/rfc7239#section-4.

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[rstoyanchev]

Actually never mind the link to the RFC. The Forwarded header is for the host, port, and protocol. This request is for the path prefix.

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This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or other activity occurs. Thank you for your contributions.

[stale[bot]]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as "help wanted". Thank you for your contributions.

[wicksim]

Are there any plans to support X-Forwarded-Prefix-header in the future?

As far as I can see, it is not possible, to dynamically add this with add_request_headers, because there is no dynamic value for this (like %DOWNSTREAM_REMOTE_ADDRESS_WITHOUT_PORT%)?