From d738a88bc70de6a8e530c617a3671ec7b8d454c7 Mon Sep 17 00:00:00 2001
From: nebularazer <nebularazer@gmail.com>
Date: Fri, 24 May 2019 12:27:42 +0200
Subject: [PATCH] removed transfer-encoding header from ws #3798

---
 CHANGES/3798.feature    |  1 +
 CONTRIBUTORS.txt        |  1 +
 aiohttp/web_response.py | 14 ++++++++++++--
 aiohttp/web_ws.py       |  1 -
 4 files changed, 14 insertions(+), 3 deletions(-)
 create mode 100644 CHANGES/3798.feature

diff --git a/CHANGES/3798.feature b/CHANGES/3798.feature
new file mode 100644
index 00000000000..175ce49fe05
--- /dev/null
+++ b/CHANGES/3798.feature
@@ -0,0 +1 @@
+Removed `Transfer-Encoding: chunked` header from websocket responses to be compatible with more http proxy servers.
diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index f580fa78db4..ee7dc299058 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -90,6 +90,7 @@ Eugene Naydenov
 Eugene Tolmachev
 Evert Lammerts
 FichteFoll
+Florian Scheffler
 Frederik Gladhorn
 Frederik Peter Aalund
 Gabriel Tremblay
diff --git a/aiohttp/web_response.py b/aiohttp/web_response.py
index 750e040afbc..d83f87d43c5 100644
--- a/aiohttp/web_response.py
+++ b/aiohttp/web_response.py
@@ -371,13 +371,22 @@ async def _start(self, request: 'BaseRequest') -> AbstractStreamWriter:
         if self._compression:
             await self._start_compression(request)
 
+        if all([
+            'websocket' == headers.get(hdrs.UPGRADE, '').lower().strip(),
+            'upgrade' == headers.get(hdrs.CONNECTION, '').lower()
+        ]):
+            websocket_response = True
+        else:
+            websocket_response = False
+
         if self._chunked:
             if version != HttpVersion11:
                 raise RuntimeError(
                     "Using chunked encoding is forbidden "
                     "for HTTP/{0.major}.{0.minor}".format(request.version))
             writer.enable_chunking()
-            headers[hdrs.TRANSFER_ENCODING] = 'chunked'
+            if websocket_response is False:
+                headers[hdrs.TRANSFER_ENCODING] = 'chunked'
             if hdrs.CONTENT_LENGTH in headers:
                 del headers[hdrs.CONTENT_LENGTH]
         elif self._length_check:
@@ -385,7 +394,8 @@ async def _start(self, request: 'BaseRequest') -> AbstractStreamWriter:
             if writer.length is None:
                 if version >= HttpVersion11:
                     writer.enable_chunking()
-                    headers[hdrs.TRANSFER_ENCODING] = 'chunked'
+                    if websocket_response is False:
+                        headers[hdrs.TRANSFER_ENCODING] = 'chunked'
                     if hdrs.CONTENT_LENGTH in headers:
                         del headers[hdrs.CONTENT_LENGTH]
                 else:
diff --git a/aiohttp/web_ws.py b/aiohttp/web_ws.py
index faa05ab3e5a..a0795366ca3 100644
--- a/aiohttp/web_ws.py
+++ b/aiohttp/web_ws.py
@@ -179,7 +179,6 @@ def _handshake(self, request: BaseRequest) -> Tuple['CIMultiDict[str]',
         response_headers = CIMultiDict(  # type: ignore
             {hdrs.UPGRADE: 'websocket',
              hdrs.CONNECTION: 'upgrade',
-             hdrs.TRANSFER_ENCODING: 'chunked',
              hdrs.SEC_WEBSOCKET_ACCEPT: accept_val})
 
         notakeover = False