http3: sniff Content-Type when flushing the ResponseWriter (#4412)

* try to sniff content-type as long as the data is not written to the client * only write when body is allowed * fix tests * fix tests * fix header count * fix lint * merge from upstream * merge updates from master * Update http3/response_writer.go Co-authored-by: Marten Seemann <martenseemann@gmail.com> --------- Co-authored-by: Marten Seemann <martenseemann@gmail.com>
quic-go · Apr 27, 2024 · 93c4785 · 93c4785
1 parent c0250ce
commit 93c4785
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Showing 3 changed files with 38 additions and 15 deletions.
diff --git a/http3/response_writer.go b/http3/response_writer.go
@@ -112,23 +112,24 @@ func (w *responseWriter) WriteHeader(status int) {
 	}
 }
 
+func (w *responseWriter) sniffContentType(p []byte) {
+	// If no content type, apply sniffing algorithm to body.
+	// We can't use `w.header.Get` here since if the Content-Type was set to nil, we shouldn't do sniffing.
+	_, haveType := w.header["Content-Type"]
+
+	// If the Transfer-Encoding or Content-Encoding was set and is non-blank,
+	// we shouldn't sniff the body.
+	hasTE := w.header.Get("Transfer-Encoding") != ""
+	hasCE := w.header.Get("Content-Encoding") != ""
+	if !hasCE && !haveType && !hasTE && len(p) > 0 {
+		w.header.Set("Content-Type", http.DetectContentType(p))
+	}
+}
+
 func (w *responseWriter) Write(p []byte) (int, error) {
 	bodyAllowed := bodyAllowedForStatus(w.status)
 	if !w.headerComplete {
-		// If body is not allowed, we don't need to (and we can't) sniff the content type.
-		if bodyAllowed {
-			// If no content type, apply sniffing algorithm to body.
-			// We can't use `w.header.Get` here since if the Content-Type was set to nil, we shoundn't do sniffing.
-			_, haveType := w.header["Content-Type"]
-
-			// If the Transfer-Encoding or Content-Encoding was set and is non-blank,
-			// we shouldn't sniff the body.
-			hasTE := w.header.Get("Transfer-Encoding") != ""
-			hasCE := w.header.Get("Content-Encoding") != ""
-			if !hasCE && !haveType && !hasTE && len(p) > 0 {
-				w.header.Set("Content-Type", http.DetectContentType(p))
-			}
-		}
+		w.sniffContentType(p)
 		w.WriteHeader(http.StatusOK)
 		bodyAllowed = true
 	}
@@ -158,6 +159,7 @@ func (w *responseWriter) Write(p []byte) (int, error) {
 
 func (w *responseWriter) doWrite(p []byte) (int, error) {
 	if !w.headerWritten {
+		w.sniffContentType(w.smallResponseBuf)
 		if err := w.writeHeader(w.status); err != nil {
 			return 0, maybeReplaceError(err)
 		}

diff --git a/http3/response_writer_test.go b/http3/response_writer_test.go
@@ -137,9 +137,10 @@ var _ = Describe("Response Writer", func() {
 
 		// According to the spec, headers sent in the informational response must also be included in the final response
 		fields = decodeHeader(strBuf)
-		Expect(fields).To(HaveLen(3))
+		Expect(fields).To(HaveLen(4))
 		Expect(fields).To(HaveKeyWithValue(":status", []string{"200"}))
 		Expect(fields).To(HaveKey("date"))
+		Expect(fields).To(HaveKey("content-type"))
 		Expect(fields).To(HaveKeyWithValue("link", []string{"</style.css>; rel=preload; as=style", "</script.js>; rel=preload; as=script"}))
 
 		Expect(getData(strBuf)).To(Equal([]byte("foobar")))

diff --git a/http3/server_test.go b/http3/server_test.go
@@ -207,6 +207,26 @@ var _ = Describe("Server", func() {
 			Expect(hfs).To(HaveLen(4))
 		})
 
+		It("sets Content-Type when WriteHeader is called but response is not flushed", func() {
+			s.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusNotFound)
+				w.Write([]byte("<html></html>"))
+			})
+
+			responseBuf := &bytes.Buffer{}
+			setRequest(encodeRequest(exampleGetRequest))
+			str.EXPECT().Context().Return(reqContext)
+			str.EXPECT().Write(gomock.Any()).DoAndReturn(responseBuf.Write).AnyTimes()
+			str.EXPECT().CancelRead(gomock.Any())
+			str.EXPECT().Close()
+
+			s.handleRequest(conn, str, nil, qpackDecoder)
+			hfs := decodeHeader(responseBuf)
+			Expect(hfs).To(HaveKeyWithValue(":status", []string{"404"}))
+			Expect(hfs).To(HaveKeyWithValue("content-length", []string{"13"}))
+			Expect(hfs).To(HaveKeyWithValue("content-type", []string{"text/html; charset=utf-8"}))
+		})
+
 		It("not sets Content-Length when the handler flushes to the client", func() {
 			s.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				w.Write([]byte("foobar"))