[test] Test that we intentionally select addr relay peers.

This test checks that we only relay addresses with inbound peers who have sent
us an addr related message. Uses a combination of GETADDR and ADDR to verify
when peers are eligible.

test/functional/p2p_addr_relay.py

@@ -19,7 +19,7 @@ from test_framework.p2p import (
     p2p_lock,
 )
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal
+from test_framework.util import assert_equal, assert_greater_than
 import random
 import time
 
@@ -83,6 +83,10 @@ class AddrTest(BitcoinTestFramework):
     def run_test(self):
         self.oversized_addr_test()
         self.relay_tests()
+        self.inbound_blackhole_tests()
+
+        # This test populates the addrman, which can impact the node's behavior
+        # in subsequent tests
         self.getaddr_tests()
         self.blocksonly_mode_tests()
         self.rate_limit_tests()
@@ -195,6 +199,49 @@ class AddrTest(BitcoinTestFramework):
 
         self.nodes[0].disconnect_p2ps()
 
+    def sum_addr_messages(self, msgs_dict):
+        return sum(bytes_received for (msg, bytes_received) in msgs_dict.items() if msg in ['addr', 'addrv2', 'getaddr'])
+
+    def inbound_blackhole_tests(self):
+        self.log.info('Check that we only relay addresses to inbound peers who have previously sent us addr related messages')
+
+        addr_source = self.nodes[0].add_p2p_connection(P2PInterface())
+        receiver_peer = self.nodes[0].add_p2p_connection(AddrReceiver())
+        blackhole_peer = self.nodes[0].add_p2p_connection(AddrReceiver(send_getaddr=False))
+        initial_addrs_received = receiver_peer.num_ipv4_received
+
+        # addr_source sends 2 addresses to node0
+        msg = self.setup_addr_msg(2)
+        addr_source.send_and_ping(msg)
+        self.mocktime += 30 * 60
+        self.nodes[0].setmocktime(self.mocktime)
+        receiver_peer.sync_with_ping()
+        blackhole_peer.sync_with_ping()
+
+        peerinfo = self.nodes[0].getpeerinfo()
+
+        # Confirm node received addr-related messages from receiver peer
+        assert_greater_than(self.sum_addr_messages(peerinfo[1]['bytesrecv_per_msg']), 0)
+        # And that peer received addresses
+        assert_equal(receiver_peer.num_ipv4_received - initial_addrs_received, 2)
+
+        # Confirm node has not received addr-related messages from blackhole peer
+        assert_equal(self.sum_addr_messages(peerinfo[2]['bytesrecv_per_msg']), 0)
+        # And that peer did not receive addresses
+        assert_equal(blackhole_peer.num_ipv4_received, 0)
+
+        self.log.info("After blackhole peer sends addr message, it becomes eligible for addr gossip")
+        blackhole_peer.send_and_ping(msg_addr())
+        msg = self.setup_addr_msg(2)
+        self.send_addr_msg(addr_source, msg, [receiver_peer, blackhole_peer])
+
+        # Confirm node has now received addr-related messages from blackhole peer
+        assert_greater_than(self.sum_addr_messages(peerinfo[1]['bytesrecv_per_msg']), 0)
+        # And that peer received addresses
+        assert_equal(blackhole_peer.num_ipv4_received, 2)
+
+        self.nodes[0].disconnect_p2ps()
+
     def getaddr_tests(self):
         # In the previous tests, the node answered GETADDR requests with an
         # empty addrman. Due to GETADDR response caching (see