tests/multi_net/tcp_client_rst.py: Improve and extend test.

These changes test a few more things related to TCP RST:
- add a second iteration to drain incoming data after TCP RST
- read data after closing socket

Signed-off-by: Damien George <damien@micropython.org>

tests/multi_net/tcp_client_rst.py

@@ -2,6 +2,12 @@
 
 import struct, time, socket, select
 
+try:
+    import errno
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
 PORT = 8000
 
 
@@ -18,27 +24,49 @@ def instance0():
     s.bind(socket.getaddrinfo("0.0.0.0", PORT)[0][-1])
     s.listen(1)
     multitest.next()
-    s2, _ = s.accept()
-    s2.setblocking(False)
-    poll = select.poll()
-    poll.register(s2, select.POLLIN)
-    time.sleep(0.4)
-    print(convert_poll_list(poll.poll(1000)))
-    # TODO: the following recv don't work with lwip, it abandons data upon TCP RST
-    try:
-        print(s2.recv(10))
+
+    for iteration in range(2):
+        print("server iteration", iteration)
+
+        # Accept a connection from the client.
+        s2, _ = s.accept()
+        s2.setblocking(False)
+
+        # Create a poller for the connected socket.
+        poll = select.poll()
+        poll.register(s2, select.POLLIN)
+
+        # Wait for the client to send data and issue a TCP RST.
+        for _ in range(10):
+            if select.POLLIN | select.POLLERR | select.POLLHUP in convert_poll_list(
+                poll.poll(1000)
+            ):
+                break
+            time.sleep(0.1)
         print(convert_poll_list(poll.poll(1000)))
-        print(s2.recv(10))
+
+        # On the second test, drain the incoming data.
+        if iteration == 1:
+            for _ in range(5):
+                try:
+                    print(s2.recv(10))
+                except OSError as er:
+                    # This error should only happen on the 3rd recv.
+                    print("ECONNRESET:", er.errno == errno.ECONNRESET)
+                print(convert_poll_list(poll.poll(1000)))
+
+        # Close the connection to the client.
+        s2.close()
         print(convert_poll_list(poll.poll(1000)))
-        print(s2.recv(10))
+
+        # Try to read more data from the closed socket, to make sure the error code is correct.
+        try:
+            print(s2.recv(10))
+        except OSError as er:
+            print("EBADF:", er.errno == errno.EBADF)
         print(convert_poll_list(poll.poll(1000)))
-    except OSError as er:
-        print(er.errno)
-    print(convert_poll_list(poll.poll(1000)))
-    # TODO lwip raises here but apparently it shouldn't
-    print(s2.recv(10))
-    print(convert_poll_list(poll.poll(1000)))
-    s2.close()
+
+    # Close the listening socket.
     s.close()
 
 
@@ -47,11 +75,13 @@ def instance1():
     if not hasattr(socket, "SO_LINGER"):
         multitest.skip()
     multitest.next()
-    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
-    s.connect(socket.getaddrinfo(IP, PORT)[0][-1])
-    lgr_onoff = 1
-    lgr_linger = 0
-    s.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER, struct.pack("ii", lgr_onoff, lgr_linger))
-    s.send(b"GET / HTTP/1.0\r\n\r\n")
-    time.sleep(0.2)
-    s.close()  # This issues a TCP RST since we've set the linger option
+    for iteration in range(2):
+        print("client iteration", iteration)
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
+        s.connect(socket.getaddrinfo(IP, PORT)[0][-1])
+        lgr_onoff = 1
+        lgr_linger = 0
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER, struct.pack("ii", lgr_onoff, lgr_linger))
+        s.send(b"GET / HTTP/1.0\r\n\r\n")
+        time.sleep(0.2)
+        s.close()  # This issues a TCP RST since we've set the linger option