fix: restore x-forwarded headers

forwarding.go

@@ -0,0 +1,80 @@
+package traefik_umami_feeder
+
+// Copied source from
+// https://github.com/kzmake/traefik-plugin-forward-request/blob/master/util.go
+
+import (
+	"net"
+	"net/http"
+	"strings"
+)
+
+const (
+	xForwardedProto  = "x-forwarded-proto"
+	xForwardedFor    = "x-forwarded-for"
+	xForwardedHost   = "x-forwarded-host"
+	xForwardedPort   = "x-forwarded-port"
+	xForwardedURI    = "x-forwarded-uri"
+	xForwardedMethod = "x-forwarded-method"
+)
+
+func copyHeaders(dst, src http.Header, headersToCopy []string) {
+	for _, key := range headersToCopy {
+		if values := src.Values(key); len(values) > 0 {
+			dst[key] = values
+		}
+	}
+}
+
+func writeXForwardedHeaders(dst http.Header, req *http.Request) {
+	if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
+		if values := req.Header.Values(xForwardedFor); len(values) > 0 {
+			clientIP = strings.Join(values, ", ") + ", " + clientIP
+		}
+		dst.Set(xForwardedFor, clientIP)
+	}
+
+	xfm := req.Header.Get(xForwardedMethod)
+	switch {
+	case xfm != "":
+		dst.Set(xForwardedMethod, xfm)
+	case req.Method != "":
+		dst.Set(xForwardedMethod, req.Method)
+	default:
+		dst.Del(xForwardedMethod)
+	}
+
+	xfp := req.Header.Get(xForwardedProto)
+	switch {
+	case xfp != "":
+		dst.Set(xForwardedProto, xfp)
+	case req.TLS != nil:
+		dst.Set(xForwardedProto, "https")
+	default:
+		dst.Set(xForwardedProto, "http")
+	}
+
+	if xfp := req.Header.Get(xForwardedPort); xfp != "" {
+		dst.Set(xForwardedPort, xfp)
+	}
+
+	xfh := req.Header.Get(xForwardedHost)
+	switch {
+	case xfh != "":
+		dst.Set(xForwardedHost, xfh)
+	case req.Host != "":
+		dst.Set(xForwardedHost, req.Host)
+	default:
+		dst.Del(xForwardedHost)
+	}
+
+	xfu := req.Header.Get(xForwardedURI)
+	switch {
+	case xfu != "":
+		dst.Set(xForwardedURI, xfu)
+	case req.URL.RequestURI() != "":
+		dst.Set(xForwardedURI, req.URL.RequestURI())
+	default:
+		dst.Del(xForwardedURI)
+	}
+}