From 288ce65d73551a13c818733c78689206110e9ef1 Mon Sep 17 00:00:00 2001
From: Thomas Kriechbaumer <thomas@kriechbaumer.name>
Date: Fri, 3 Jul 2020 12:49:31 +0200
Subject: [PATCH] add h2 trailers example and fix sending

---
 examples/addons/http-trailers.py  | 26 ++++++++++++++++++++++++++
 mitmproxy/proxy/protocol/http2.py |  6 +++---
 2 files changed, 29 insertions(+), 3 deletions(-)
 create mode 100644 examples/addons/http-trailers.py

diff --git a/examples/addons/http-trailers.py b/examples/addons/http-trailers.py
new file mode 100644
index 000000000..77b9d1a40
--- /dev/null
+++ b/examples/addons/http-trailers.py
@@ -0,0 +1,26 @@
+"""
+This script simply prints all received HTTP Trailers.
+
+HTTP requests and responses can container trailing headers which are sent after
+the body is fully transmitted. Such trailers need to be announced in the initial
+headers by name, so the receiving endpoint can wait and read them after the
+body.
+"""
+
+from mitmproxy import http
+from mitmproxy.net.http import Headers
+
+def request(flow: http.HTTPFlow):
+    if flow.request.trailers:
+        print("HTTP Trailers detected! Request contains:", flow.request.trailers)
+
+def response(flow: http.HTTPFlow):
+    if flow.response.trailers:
+        print("HTTP Trailers detected! Response contains:", flow.response.trailers)
+
+    if flow.request.path == "/inject_trailers":
+        flow.response.headers["trailer"] = "x-my-injected-trailer-header"
+        flow.response.trailers = Headers([
+            (b"x-my-injected-trailer-header", b"foobar")
+        ])
+        print("Injected a new trailer...", flow.response.headers["trailer"])
diff --git a/mitmproxy/proxy/protocol/http2.py b/mitmproxy/proxy/protocol/http2.py
index 9275e6bdb..602946f65 100644
--- a/mitmproxy/proxy/protocol/http2.py
+++ b/mitmproxy/proxy/protocol/http2.py
@@ -615,7 +615,7 @@ class Http2SingleStreamLayer(httpbase._HttpTransmissionLayer, basethread.BaseThr
 
     @detect_zombie_stream
     def send_request_trailers(self, request):
-        self._send_trailers(self.server_conn, self.request_trailers)
+        self._send_trailers(self.server_conn, request.trailers)
 
     @detect_zombie_stream
     def send_request(self, request):
@@ -686,8 +686,8 @@ class Http2SingleStreamLayer(httpbase._HttpTransmissionLayer, basethread.BaseThr
         )
 
     @detect_zombie_stream
-    def send_response_trailers(self, _response):
-        self._send_trailers(self.client_conn, self.response_trailers)
+    def send_response_trailers(self, response):
+        self._send_trailers(self.client_conn, response.trailers)
 
     def _send_trailers(self, conn, trailers):
         if not trailers: