net: advertise support for ADDRv2 via new message

Introduce a new message `sendaddrv2` to signal support for ADDRv2.
Send the new message immediately after sending the `VERACK` message.

Add support for receiving and parsing ADDRv2 messages.

Send ADDRv2 messages (instead of ADDR) to a peer if he has
advertised support for it.

Co-authored-by: Carl Dong <contact@carldong.me>

test/functional/p2p_addrv2_relay.py

@@ -0,0 +1,79 @@
+#!/usr/bin/env python3
+# Copyright (c) 2020 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 addrv2 relay
+"""
+
+import time
+
+from test_framework.messages import (
+    CAddress,
+    msg_addrv2,
+    NODE_NETWORK,
+    NODE_WITNESS,
+)
+from test_framework.p2p import P2PInterface
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+ADDRS = []
+for i in range(10):
+    addr = CAddress()
+    addr.time = int(time.time()) + i
+    addr.nServices = NODE_NETWORK | NODE_WITNESS
+    addr.ip = "123.123.123.{}".format(i % 256)
+    addr.port = 8333 + i
+    ADDRS.append(addr)
+
+
+class AddrReceiver(P2PInterface):
+    addrv2_received_and_checked = False
+
+    def __init__(self):
+        super().__init__(support_addrv2 = True)
+
+    def on_addrv2(self, message):
+        for addr in message.addrs:
+            assert_equal(addr.nServices, 9)
+            assert addr.ip.startswith('123.123.123.')
+            assert (8333 <= addr.port < 8343)
+        self.addrv2_received_and_checked = True
+
+    def wait_for_addrv2(self):
+        self.wait_until(lambda: "addrv2" in self.last_message)
+
+
+class AddrTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.num_nodes = 1
+
+    def run_test(self):
+        self.log.info('Create connection that sends addrv2 messages')
+        addr_source = self.nodes[0].add_p2p_connection(P2PInterface())
+        msg = msg_addrv2()
+
+        self.log.info('Send too-large addrv2 message')
+        msg.addrs = ADDRS * 101
+        with self.nodes[0].assert_debug_log(['addrv2 message size = 1010']):
+            addr_source.send_and_ping(msg)
+
+        self.log.info('Check that addrv2 message content is relayed and added to addrman')
+        addr_receiver = self.nodes[0].add_p2p_connection(AddrReceiver())
+        msg.addrs = ADDRS
+        with self.nodes[0].assert_debug_log([
+                'Added 10 addresses from 127.0.0.1: 0 tried',
+                'received: addrv2 (131 bytes) peer=0',
+                'sending addrv2 (131 bytes) peer=1',
+        ]):
+            addr_source.send_and_ping(msg)
+            self.nodes[0].setmocktime(int(time.time()) + 30 * 60)
+            addr_receiver.wait_for_addrv2()
+
+        assert addr_receiver.addrv2_received_and_checked
+
+
+if __name__ == '__main__':
+    AddrTest().main()