Preserve chunked flag when re-calling urlopen() in retry loop

dummyserver/testcase.py

@@ -15,8 +15,13 @@
 
 
 def consume_socket(sock, chunks=65536):
-    while not sock.recv(chunks).endswith(b"\r\n\r\n"):
-        pass
+    consumed = bytearray()
+    while True:
+        b = sock.recv(chunks)
+        consumed += b
+        if b.endswith(b"\r\n\r\n"):
+            break
+    return consumed
 
 
 class SocketDummyServerTestCase(object):

src/urllib3/connectionpool.py

@@ -839,6 +839,7 @@ def drain_and_release_conn(response):
                 timeout=timeout,
                 pool_timeout=pool_timeout,
                 release_conn=release_conn,
+                chunked=chunked,
                 body_pos=body_pos,
                 **response_kw
             )

test/with_dummyserver/test_chunked_transfer.py

@@ -1,7 +1,8 @@
 # -*- coding: utf-8 -*-
 
 from urllib3 import HTTPConnectionPool
-from dummyserver.testcase import SocketDummyServerTestCase
+from urllib3.util.retry import Retry
+from dummyserver.testcase import SocketDummyServerTestCase, consume_socket
 
 
 class TestChunkedTransfer(SocketDummyServerTestCase):
@@ -100,3 +101,24 @@ def test_provides_default_host_header(self):
 
             host_headers = [x for x in header_lines if x.startswith(b"host")]
             assert len(host_headers) == 1
+
+    def test_preserve_chunked_on_retry(self):
+        self.chunked_requests = 0
+
+        def socket_handler(listener):
+            for _ in range(2):
+                sock = listener.accept()[0]
+                request = consume_socket(sock)
+                if b"Transfer-Encoding: chunked" in request.split(b"\r\n"):
+                    self.chunked_requests += 1
+
+                sock.send(b"HTTP/1.1 404 Not Found\r\n\r\n")
+                sock.close()
+
+        self._start_server(socket_handler)
+        with HTTPConnectionPool(self.host, self.port) as pool:
+            retries = Retry(total=1, raise_on_status=False, status_forcelist=[404])
+            pool.urlopen(
+                "GET", "/", chunked=True, preload_content=False, retries=retries
+            )
+        assert self.chunked_requests == 2