Nginx fix Location header on redirects behind reverse proxy

nginx.conf

http {

    map $http_x_forwarded_proto=$http_x_forwarded_port $redirect_port {
        http=80 '';
        https=443 '';
        default :$http_x_forwarded_port;
    }

    server {
        listen 8080;

        location / {
            proxy_pass http://unix:/tmp/nginx.sock;
            proxy_set_header Host $host;
            proxy_buffering off;
            proxy_request_buffering off;
            proxy_redirect http://$host/ $http_x_forwarded_proto://$http_x_forwarded_host$redirect_port/;
        }
    }
  
    server {
        listen unix:/tmp/nginx.sock;
        location / {
            root /data;
            autoindex on;
        }
    }
}

The problem:

• https://www.netexpertise.eu/en/misc/nginx/nginx-behind-reverse-proxy-301-https-to-http-redirect-when-url-has-no-trailing-slash.html
• https://serverfault.com/questions/1155277/nginx-automatically-redirect-to-add-a-trailing-slash

Nginx Lua Module:

header_filter_by_lua_block {
    local location = ngx.header.location
    if location and string.sub(location, 1, 1) == '/' then
        local proto = ngx.var.http_x_forwarded_proto
        local host = ngx.var.http_x_forwarded_host
        local port = ngx.var.http_x_forwarded_port
        if proto == 'http' and port == '80' or proto == 'https' and port == '443' then
            location = string.format('%s://%s%s', proto, host, location)
        else
            location = string.format('%s://%s:%s%s', proto, host, port, location)
        end
        ngx.header.location = location
    end
}

Apparently this is no longer necessary.

RFC 2616 Hypertext Transfer Protocol -- HTTP/1.1, June 1999 requires an absolute URI: 14.30 Location.

RFC 7231 Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content, June 2014, which obsoletes RFC 2616, allows a relative URI: 7.1.2. Location.

RFC 9110 HTTP Semantics, June 2022, which obsoletes RFC 7231, allows a relative URI: 10.2.2. Location.

TL;DR use absolute_redirect off.