tests: Expand HTTP coverage to assert libevent behavior

Covers:
- http pipelining
- rpcservertimeout

  Testing this requires adding an option to TestNode to force
  the test framework to establish a new HTTP connection for
  every RPC. Otherwise, attempting to reuse a persistent connection
  would cause framework RPCs during startup and shutdown to fail.

- "chunked" Transfer-Encoding

test/functional/interface_http.py

@@ -8,6 +8,7 @@ from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import assert_equal, str_to_b64str
 
 import http.client
+import time
 import urllib.parse
 
 class HTTPBasicsTest (BitcoinTestFramework):
@@ -105,5 +106,136 @@ class HTTPBasicsTest (BitcoinTestFramework):
         assert_equal(out1.status, http.client.BAD_REQUEST)
 
 
+        self.log.info("Check pipelining")
+        # Requests are responded to in order they were received
+        # See https://www.rfc-editor.org/rfc/rfc7230#section-6.3.2
+        tip_height = self.nodes[2].getblockcount()
+
+        req = "POST / HTTP/1.1\r\n"
+        req += f'Authorization: Basic {str_to_b64str(authpair)}\r\n'
+
+        # First request will take a long time to process
+        body1 = f'{{"method": "waitforblockheight", "params": [{tip_height + 1}]}}'
+        req1 = req
+        req1 += f'Content-Length: {len(body1)}\r\n\r\n'
+        req1 += body1
+
+        # Second request will process very fast
+        body2 = '{"method": "getblockcount"}'
+        req2 = req
+        req2 += f'Content-Length: {len(body2)}\r\n\r\n'
+        req2 += body2
+        # Get the underlying socket from HTTP connection so we can send something unusual
+        conn = http.client.HTTPConnection(urlNode2.hostname, urlNode2.port)
+        conn.connect()
+        sock = conn.sock
+        sock.settimeout(5)
+        # Send two requests in a row. The first will block the second indefinitely
+        sock.sendall(req1.encode("utf-8"))
+        sock.sendall(req2.encode("utf-8"))
+        try:
+            # The server should not respond to the fast, second request
+            # until the (very) slow first request has been handled:
+            res = sock.recv(1024)
+            assert False
+        except TimeoutError:
+            pass
+
+        # Use a separate http connection to generate a block
+        self.generate(self.nodes[2], 1, sync_fun=self.no_op)
+
+        # Wait for two responses to be received
+        res = b""
+        while res.count(b"result") != 2:
+            res += sock.recv(1024)
+
+        # waitforblockheight was responded to first, and then getblockcount
+        # which includes the block added after the request was made
+        chunks = res.split(b'"result":')
+        assert chunks[1].startswith(b'{"hash":')
+        assert chunks[2].startswith(bytes(f'{tip_height + 1}', 'utf8'))
+
+
+        self.log.info("Check HTTP request encoded with chunked transfer")
+        headers_chunked = headers.copy()
+        headers_chunked.update({"Transfer-encoding": "chunked"})
+        body_chunked = [
+            b'{"method": "submitblock", "params": ["',
+            b'0' * 1000000,
+            b'1' * 1000000,
+            b'2' * 1000000,
+            b'3' * 1000000,
+            b'"]}'
+        ]
+        conn = http.client.HTTPConnection(urlNode2.hostname, urlNode2.port)
+        conn.connect()
+        conn.request(
+            method='POST',
+            url='/',
+            body=iter(body_chunked),
+            headers=headers_chunked,
+            encode_chunked=True)
+        out1 = conn.getresponse().read()
+        assert_equal(out1, b'{"result":"high-hash","error":null}\n')
+
+
+        self.log.info("Check -rpcservertimeout")
+        # The test framework typically reuses a single persistent HTTP connection
+        # for all RPCs to a TestNode. Because we are setting -rpcservertimeout
+        # so low on this one node, its connection will quickly timeout and get dropped by
+        # the server. Negating this setting will force the AuthServiceProxy
+        # for this node to create a fresh new HTTP connection for every command
+        # called for the remainder of this test.
+        self.nodes[2].reuse_http_connections = False
+
+        self.restart_node(2, extra_args=["-rpcservertimeout=2"])
+        # This is the amount of time the server will wait for a client to
+        # send a complete request. Test it by sending an incomplete but
+        # so-far otherwise well-formed HTTP request, and never finishing it.
+
+        # Copied from http_incomplete_test_() in regress_http.c in libevent.
+        # A complete request would have an additional "\r\n" at the end.
+        http_request = "GET /test1 HTTP/1.1\r\nHost: somehost\r\n"
+
+        # Get the underlying socket from HTTP connection so we can send something unusual
+        conn = http.client.HTTPConnection(urlNode2.hostname, urlNode2.port)
+        conn.connect()
+        sock = conn.sock
+        sock.sendall(http_request.encode("utf-8"))
+        # Wait for response, but expect a timeout disconnection after 1 second
+        start = time.time()
+        res = sock.recv(1024)
+        stop = time.time()
+        # Server disconnected with EOF
+        assert_equal(res, b"")
+        # Server disconnected within an acceptable range of time:
+        # not immediately, and not too far over the configured duration.
+        # This allows for some jitter in the test between client and server.
+        duration = stop - start
+        assert duration <= 4, f"Server disconnected too slow: {duration} > 4"
+        assert duration >= 1, f"Server disconnected too fast: {duration} < 1"
+
+        # The connection is definitely closed.
+        got_expected_error = False
+        try:
+            conn.request('GET', '/')
+            conn.getresponse()
+        #       macos/linux           windows
+        except (ConnectionResetError, ConnectionAbortedError):
+            got_expected_error = True
+        assert got_expected_error
+
+        # Sanity check
+        http_request = "GET /test2 HTTP/1.1\r\nHost: somehost\r\n\r\n"
+        conn = http.client.HTTPConnection(urlNode2.hostname, urlNode2.port)
+        conn.connect()
+        sock = conn.sock
+        sock.sendall(http_request.encode("utf-8"))
+        res = sock.recv(1024)
+        assert res.startswith(b"HTTP/1.1 404 Not Found")
+        # still open
+        conn.request('GET', '/')
+        conn.getresponse()
+
 if __name__ == '__main__':
     HTTPBasicsTest(__file__).main()