contrib/envoyproxy: fix context propagation from envoy tracing (#3144)

Author: e-n-0

contrib/envoyproxy/go-control-plane/envoy_test.go

@@ -23,6 +23,7 @@ import (
 	v3 "github.com/envoyproxy/go-control-plane/envoy/config/core/v3"
 	"github.com/stretchr/testify/require"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
 )
 
 func TestAppSec(t *testing.T) {
@@ -273,6 +274,45 @@ func TestGeneratedSpan(t *testing.T) {
 		require.Equal(t, "server", span.Tag("span.kind"))
 		require.Equal(t, "Mistake Not...", span.Tag("http.useragent"))
 	})
+
+	t.Run("span-with-injected-context", func(t *testing.T) {
+		client, mt, cleanup := setup()
+		defer cleanup()
+
+		ctx := context.Background()
+
+		// add metadata to the context
+		ctx = metadata.AppendToOutgoingContext(ctx,
+			"x-datadog-trace-id", "12345",
+			"x-datadog-parent-id", "67890",
+		)
+
+		stream, err := client.Process(ctx)
+		require.NoError(t, err)
+
+		end2EndStreamRequest(t, stream, "/../../../resource-span/.?id=test", "GET", map[string]string{"user-agent": "Mistake Not...", "test-key": "test-value"}, map[string]string{"response-test-key": "response-test-value"}, false)
+
+		err = stream.CloseSend()
+		require.NoError(t, err)
+		stream.Recv() // to flush the spans
+
+		finished := mt.FinishedSpans()
+		require.Len(t, finished, 1)
+
+		// Check for tags
+		span := finished[0]
+		require.Equal(t, "http.request", span.OperationName())
+		require.Equal(t, "https://datadoghq.com/../../../resource-span/.?id=test", span.Tag("http.url"))
+		require.Equal(t, "GET", span.Tag("http.method"))
+		require.Equal(t, "datadoghq.com", span.Tag("http.host"))
+		require.Equal(t, "GET /resource-span", span.Tag("resource.name"))
+		require.Equal(t, "server", span.Tag("span.kind"))
+		require.Equal(t, "Mistake Not...", span.Tag("http.useragent"))
+
+		// Check for trace context
+		require.Equal(t, uint64(12345), span.Context().TraceID())
+		require.Equal(t, uint64(67890), span.ParentID())
+	})
 }
 
 func TestXForwardedForHeaderClientIp(t *testing.T) {

contrib/envoyproxy/go-control-plane/fakehttp.go

@@ -76,6 +76,28 @@ func splitPseudoHeaders(receivedHeaders []*corev3.HeaderValue) (headers map[stri
 	return headers, pseudoHeaders
 }
 
+// mergeMetadataHeaders merges the metadata headers of the grpc connection into the http headers of the request
+// - Skip pseudo headers and headers that are already set
+// - Set headers keys to be canonical
+func mergeMetadataHeaders(md metadata.MD, headers http.Header) {
+	for k, v := range md {
+		if strings.HasPrefix(k, ":") {
+			continue
+		}
+
+		// Skip the content-type header of the grpc request
+		// Note: all envoy set headers are lower-case
+		if k == "content-type" {
+			continue
+		}
+
+		k = http.CanonicalHeaderKey(k)
+		if _, ok := headers[k]; !ok {
+			headers[k] = v
+		}
+	}
+}
+
 func createFakeResponseWriter(w http.ResponseWriter, res *extproc.ProcessingRequest_ResponseHeaders) error {
 	headers, pseudoHeaders := splitPseudoHeaders(res.ResponseHeaders.GetHeaders().GetHeaders())
 
@@ -103,6 +125,13 @@ func newRequest(ctx context.Context, req *extproc.ProcessingRequest_RequestHeade
 		return nil, err
 	}
 
+	var remoteAddr string
+	md, ok := metadata.FromIncomingContext(ctx)
+	if ok {
+		mergeMetadataHeaders(md, headers)
+		remoteAddr = getRemoteAddr(md)
+	}
+
 	parsedURL, err := url.Parse(fmt.Sprintf("%s://%s%s", pseudoHeaders[":scheme"], pseudoHeaders[":authority"], pseudoHeaders[":path"]))
 	if err != nil {
 		return nil, fmt.Errorf(
@@ -113,12 +142,6 @@ func newRequest(ctx context.Context, req *extproc.ProcessingRequest_RequestHeade
 			err)
 	}
 
-	var remoteAddr string
-	md, ok := metadata.FromIncomingContext(ctx)
-	if ok {
-		remoteAddr = getRemoteAddr(md)
-	}
-
 	var tlsState *tls.ConnectionState
 	if pseudoHeaders[":scheme"] == "https" {
 		tlsState = &tls.ConnectionState{}