diff --git a/test/functional/p2p_invalid_messages.py b/test/functional/p2p_invalid_messages.py
index dd632bfbc..2618d7667 100755
--- a/test/functional/p2p_invalid_messages.py
+++ b/test/functional/p2p_invalid_messages.py
@@ -1,399 +1,296 @@
 #!/usr/bin/env python3
 # Copyright (c) 2015-2019 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test node responses to invalid network messages."""
 import asyncio
 import struct
 import time
 
 from test_framework.messages import (
     CBlockHeader,
     CInv,
     msg_avahello,
     msg_avapoll,
     msg_avaresponse,
     msg_getdata,
     msg_headers,
     msg_inv,
     msg_ping,
     MSG_TX,
     ser_string,
 )
 from test_framework.mininode import (
     NetworkThread,
     P2PDataStore,
     P2PInterface,
 )
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import hex_str_to_bytes
 
+MSG_LIMIT = 2 * 1024 * 1024  # 2MB, per MAX_PROTOCOL_MESSAGE_LENGTH
+VALID_DATA_LIMIT = MSG_LIMIT - 5  # Account for the 5-byte length prefix
+
 
 class msg_unrecognized:
     """Nonsensical message. Modeled after similar types in test_framework.messages."""
 
     msgtype = b'badmsg'
 
     def __init__(self, *, str_data):
         self.str_data = str_data.encode() if not isinstance(str_data, bytes) else str_data
 
     def serialize(self):
         return ser_string(self.str_data)
 
     def __repr__(self):
         return "{}(data={})".format(self.msgtype, self.str_data)
 
 
 class SenderOfAddrV2(P2PInterface):
     def wait_for_sendaddrv2(self):
         self.wait_until(lambda: 'sendaddrv2' in self.last_message)
 
 
 class InvalidMessagesTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
         self.setup_clean_chain = True
 
     def run_test(self):
-        """
-         . Test msg header
-        0. Send a bunch of large (2MB) messages of an unrecognized type. Check to see
-           that it isn't an effective DoS against the node.
-
-        1. Send an oversized (2MB+) message and check that we're disconnected.
-
-        2. Send a few messages with an incorrect data size in the header, ensure the
-           messages are ignored.
-        """
         self.test_magic_bytes()
         self.test_checksum()
         self.test_size()
         self.test_msgtype()
         self.test_addrv2_empty()
         self.test_addrv2_no_addresses()
         self.test_addrv2_too_long_address()
         self.test_addrv2_unrecognized_network()
         self.test_large_inv()
         self.test_unsolicited_ava_messages()
-
-        node = self.nodes[0]
-        self.node = node
-        node.add_p2p_connection(P2PDataStore())
-        conn2 = node.add_p2p_connection(P2PDataStore())
-
-        # 2MB, per MAX_PROTOCOL_MESSAGE_LENGTH
-        msg_limit = 2 * 1024 * 1024
-        # Account for the 4-byte length prefix
-        valid_data_limit = msg_limit - 5
-
-        #
-        # 0.
-        #
-        # Send as large a message as is valid, ensure we aren't disconnected but
-        # also can't exhaust resources.
-        #
-        msg_at_size = msg_unrecognized(str_data="b" * valid_data_limit)
-        assert len(msg_at_size.serialize()) == msg_limit
-
-        self.log.info(
-            "Sending a bunch of large, junk messages to test memory exhaustion. May take a bit...")
-
-        # Run a bunch of times to test for memory exhaustion.
-        for _ in range(80):
-            node.p2p.send_message(msg_at_size)
-
-        # Check that, even though the node is being hammered by nonsense from one
-        # connection, it can still service other peers in a timely way.
-        for _ in range(20):
-            conn2.sync_with_ping(timeout=2)
-
-        # Peer 1, despite serving up a bunch of nonsense, should still be
-        # connected.
-        self.log.info("Waiting for node to drop junk messages.")
-        node.p2p.sync_with_ping(timeout=320)
-        assert node.p2p.is_connected
-
-        #
-        # 1.
-        #
-        # Send an oversized message, ensure we're disconnected.
-        #
-        msg_over_size = msg_unrecognized(str_data="b" * (valid_data_limit + 1))
-        assert len(msg_over_size.serialize()) == (msg_limit + 1)
-
-        with node.assert_debug_log(["Oversized header detected"]):
-            # An unknown message type (or *any* message type) over
-            # MAX_PROTOCOL_MESSAGE_LENGTH should result in a disconnect.
-            node.p2p.send_message(msg_over_size)
-            node.p2p.wait_for_disconnect(timeout=4)
-
-        node.disconnect_p2ps()
-        conn = node.add_p2p_connection(P2PDataStore())
-        conn.wait_for_verack()
-
-        #
-        # 2.
-        #
-        # Send messages with an incorrect data size in the header.
-        #
-        actual_size = 100
-        msg = msg_unrecognized(str_data="b" * actual_size)
-
-        # TODO: handle larger-than cases. I haven't been able to pin down what
-        # behavior to expect.
-        for wrong_size in (2, 77, 78, 79):
-            self.log.info(
-                "Sending a message with incorrect size of {}".format(wrong_size))
-
-            # Unmodified message should submit okay.
-            node.p2p.send_and_ping(msg)
-
-            # A message lying about its data size results in a disconnect when the incorrect
-            # data size is less than the actual size.
-            #
-            # TODO: why does behavior change at 78 bytes?
-            #
-            node.p2p.send_raw_message(
-                self._tweak_msg_data_size(
-                    msg, wrong_size))
-
-            # For some reason unknown to me, we sometimes have to push additional data to the
-            # peer in order for it to realize a disconnect.
-            try:
-                node.p2p.send_message(msg_ping(nonce=123123))
-            except IOError:
-                pass
-
-            node.p2p.wait_for_disconnect(timeout=10)
-            node.disconnect_p2ps()
-            node.add_p2p_connection(P2PDataStore())
-
-        # Node is still up.
-        conn = node.add_p2p_connection(P2PDataStore())
+        self.test_resource_exhaustion()
 
     def test_magic_bytes(self):
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())
 
         async def swap_magic_bytes():
             # Need to ignore all incoming messages from now, since they come
             # with "invalid" magic bytes
             conn._on_data = lambda: None
             conn.magic_bytes = b'\x00\x11\x22\x32'
 
         # Call .result() to block until the atomic swap is complete, otherwise
         # we might run into races later on
         asyncio.run_coroutine_threadsafe(
             swap_magic_bytes(),
             NetworkThread.network_event_loop).result()
 
         with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: INVALID MESSAGESTART ping']):
             conn.send_message(msg_ping(nonce=0xff))
             conn.wait_for_disconnect(timeout=1)
             self.nodes[0].disconnect_p2ps()
 
     def test_checksum(self):
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())
         with self.nodes[0].assert_debug_log(['CHECKSUM ERROR (badmsg, 2 bytes), expected 78df0a04 was ffffffff']):
             msg = conn.build_message(msg_unrecognized(str_data="d"))
             cut_len = (
                 # magic
                 4 +
                 # msgtype
                 12 +
                 # len
                 4
             )
             # modify checksum
             msg = msg[:cut_len] + b'\xff' * 4 + msg[cut_len + 4:]
             self.nodes[0].p2p.send_raw_message(msg)
             conn.wait_for_disconnect()
             self.nodes[0].disconnect_p2ps()
 
     def test_size(self):
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())
         with self.nodes[0].assert_debug_log(['']):
-            msg = conn.build_message(msg_unrecognized(str_data="d"))
-            cut_len = (
-                # magic
-                4 +
-                # command
-                12
-            )
-            # modify len to MAX_SIZE + 1
-            msg = msg[:cut_len] + \
-                struct.pack("<I", 0x02000000 + 1) + msg[cut_len + 4:]
+            # Create a message with oversized payload
+            msg = msg_unrecognized(str_data="d" * (VALID_DATA_LIMIT + 1))
+            msg = conn.build_message(msg)
             self.nodes[0].p2p.send_raw_message(msg)
             conn.wait_for_disconnect(timeout=1)
             self.nodes[0].disconnect_p2ps()
 
     def test_msgtype(self):
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())
         with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: ERRORS IN HEADER']):
             msg = msg_unrecognized(str_data="d")
             msg.msgtype = b'\xff' * 12
             msg = conn.build_message(msg)
             # Modify msgtype
             msg = msg[:7] + b'\x00' + msg[7 + 1:]
             self.nodes[0].p2p.send_raw_message(msg)
             conn.sync_with_ping(timeout=1)
             self.nodes[0].disconnect_p2ps()
 
     def test_addrv2(self, label, required_log_messages, raw_addrv2):
         node = self.nodes[0]
         conn = node.add_p2p_connection(SenderOfAddrV2())
 
         # Make sure bitcoind signals support for ADDRv2, otherwise this test
         # will bombard an old node with messages it does not recognize which
         # will produce unexpected results.
         conn.wait_for_sendaddrv2()
 
         self.log.info('Test addrv2: ' + label)
 
         msg = msg_unrecognized(str_data=b'')
         msg.msgtype = b'addrv2'
         with node.assert_debug_log(required_log_messages):
             # override serialize() which would include the length of the data
             msg.serialize = lambda: raw_addrv2
             conn.send_raw_message(conn.build_message(msg))
             conn.sync_with_ping()
 
         node.disconnect_p2ps()
 
     def test_addrv2_empty(self):
         self.test_addrv2('empty',
                          [
                              'received: addrv2 (0 bytes)',
                              'ProcessMessages(addrv2, 0 bytes): Exception',
                              'end of data',
                          ],
                          b'')
 
     def test_addrv2_no_addresses(self):
         self.test_addrv2('no addresses',
                          [
                              'received: addrv2 (1 bytes)',
                          ],
                          hex_str_to_bytes('00'))
 
     def test_addrv2_too_long_address(self):
         self.test_addrv2('too long address',
                          [
                              'received: addrv2 (525 bytes)',
                              'ProcessMessages(addrv2, 525 bytes): Exception',
                              'Address too long: 513 > 512',
                          ],
                          hex_str_to_bytes(
                              # number of entries
                              '01' +
                              # time, Fri Jan  9 02:54:25 UTC 2009
                              '61bc6649' +
                              # service flags, COMPACTSIZE(NODE_NONE)
                              '00' +
                              # network type (IPv4)
                              '01' +
                              # address length (COMPACTSIZE(513))
                              'fd0102' +
                              # address
                              'ab' * 513 +
                              # port
                              '208d'))
 
     def test_addrv2_unrecognized_network(self):
         now_hex = struct.pack('<I', int(time.time())).hex()
         self.test_addrv2('unrecognized network',
                          [
                              'received: addrv2 (25 bytes)',
                              'IP 9.9.9.9 mapped',
                              'Added 1 addresses',
                          ],
                          hex_str_to_bytes(
                              # number of entries
                              '02' +
 
                              # this should be ignored without impeding acceptance of
                              # subsequent ones
 
                              # time
                              now_hex +
                              # service flags, COMPACTSIZE(NODE_NETWORK)
                              '01' +
                              # network type (unrecognized)
                              '99' +
                              # address length (COMPACTSIZE(2))
                              '02' +
                              # address
                              'ab' * 2 +
                              # port
                              '208d' +
 
                              # this should be added:
 
                              # time
                              now_hex +
                              # service flags, COMPACTSIZE(NODE_NETWORK)
                              '01' +
                              # network type (IPv4)
                              '01' +
                              # address length (COMPACTSIZE(4))
                              '04' +
                              # address
                              '09' * 4 +
                              # port
                              '208d'))
 
     def test_large_inv(self):
         conn = self.nodes[0].add_p2p_connection(P2PInterface())
         with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=8 (0 -> 20): oversized-inv: message inv size() = 50001']):
             msg = msg_inv([CInv(MSG_TX, 1)] * 50001)
             conn.send_and_ping(msg)
         with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=8 (20 -> 40): too-many-inv: message getdata size() = 50001']):
             msg = msg_getdata([CInv(MSG_TX, 1)] * 50001)
             conn.send_and_ping(msg)
         with self.nodes[0].assert_debug_log(['Misbehaving', 'peer=8 (40 -> 60): too-many-headers: headers message size = 2001']):
             msg = msg_headers([CBlockHeader()] * 2001)
             conn.send_and_ping(msg)
         self.nodes[0].disconnect_p2ps()
 
     def test_unsolicited_ava_messages(self):
         """Node 0 has avalanche disabled by default. If a node does not
         advertise the avalanche service flag, it does not expect to receive
         any avalanche related message and should consider it as spam.
         """
         conn = self.nodes[0].add_p2p_connection(P2PInterface())
         with self.nodes[0].assert_debug_log(
                 ['Misbehaving', 'peer=9 (0 -> 20): unsolicited-avahello']):
             msg = msg_avahello()
             conn.send_and_ping(msg)
         with self.nodes[0].assert_debug_log(
                 ['Misbehaving', 'peer=9 (20 -> 40): unsolicited-avapoll']):
             msg = msg_avapoll()
             conn.send_and_ping(msg)
         with self.nodes[0].assert_debug_log(
                 ['Misbehaving', 'peer=9 (40 -> 60): unsolicited-avaresponse']):
             msg = msg_avaresponse()
             conn.send_and_ping(msg)
         self.nodes[0].disconnect_p2ps()
 
-    def _tweak_msg_data_size(self, message, wrong_size):
-        """
-        Return a raw message based on another message but with an incorrect data size in
-        the message header.
-        """
-        raw_msg = self.node.p2p.build_message(message)
+    def test_resource_exhaustion(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        conn2 = self.nodes[0].add_p2p_connection(P2PDataStore())
+        msg_at_size = msg_unrecognized(str_data="b" * VALID_DATA_LIMIT)
+        assert len(msg_at_size.serialize()) == MSG_LIMIT
+
+        self.log.info(
+            "Sending a bunch of large, junk messages to test memory exhaustion. May take a bit...")
 
-        bad_size_bytes = struct.pack("<I", wrong_size)
-        num_header_bytes_before_size = 4 + 12
+        # Run a bunch of times to test for memory exhaustion.
+        for _ in range(80):
+            conn.send_message(msg_at_size)
 
-        # Replace the correct data size in the message with an incorrect one.
-        raw_msg_with_wrong_size = (
-            raw_msg[:num_header_bytes_before_size] +
-            bad_size_bytes +
-            raw_msg[(num_header_bytes_before_size + len(bad_size_bytes)):]
-        )
-        assert len(raw_msg) == len(raw_msg_with_wrong_size)
+        # Check that, even though the node is being hammered by nonsense from one
+        # connection, it can still service other peers in a timely way.
+        for _ in range(20):
+            conn2.sync_with_ping(timeout=2)
 
-        return raw_msg_with_wrong_size
+        # Peer 1, despite being served up a bunch of nonsense, should still be
+        # connected.
+        self.log.info("Waiting for node to drop junk messages.")
+        conn.sync_with_ping(timeout=400)
+        assert conn.is_connected
+        self.nodes[0].disconnect_p2ps()
 
 
 if __name__ == '__main__':
     InvalidMessagesTest().main()