proxy_redirect is missing feature for HTTP header "Link"

[jochenwezel@…]

PLEASE NOTE: please ignore space chars in urls in following ticket (I had to remove all external links to be able to post this ticket, here: "Maximum number of external links per post exceeded")

Used configuration

Given is a reverse proxy configuration like

location / {
    proxy_pass     https :// upstream/;
    proxy_redirect https :// upstream/ /;
}

As the documentation at https :// nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_redirect explains, proxy_redirect will change Location headers redirect. This is required and good.

HTTP Response of upstream server

My wordpress 6 system now starts to send HTTP responses like:

HTTP/1.1 200 OK
Server: nginx/1.18.0 (Ubuntu)
Date: Wed, 29 Mar 2023 15:31:02 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Link: <https :// upstream/index.php/wp-json/>; rel="https://api.w.org/"
Link: <https :// upstream/index.php/wp-json/wp/v2/pages/69>; rel="alternate"; type="application/json"
Link: <https :// upstream/>; rel=shortlink
Vary: Accept-Encoding
Content-Encoding: gzip

HTTP protocol standard

Since I've never seen this type of 'link' header before, this was a real surprise to me. But it seems that it's a feature which exists for many years, now: https :// www.w3.org/wiki/LinkHeader

Problem description

The problem is, that the many Link headers remain unchanged and are delivered (as they are) to the client. Of course, the client machine doesn't know anything about my upstream server and can't access it to load these linked urls.

The result is, that my nginx reverse proxy response to the client contains unchanged Link headers

Link: <https :// upstream/index.php/wp-json/>; rel="https://api.w.org/"
Link: <https :// upstream/index.php/wp-json/wp/v2/pages/69>; rel="alternate"; type="application/json"
Link: <https :// upstream/>; rel=shortlink

Feature request

So, proxy_redirect should (by default) substitute in headers

• Location
• Link [array]

Optionally, the substitution of Link headers could be configured with another switch (e.g. proxy_redirect_links) to on|off|default