Merge #18309: zmq: Add support to listen on multiple interfaces

e66870c5a4c2adbd30dca67d409fd5cd98697587 zmq: Append address to notify log output (nthumann)
241803da211265444e65f254f24dd184f2457fa9 test: Add zmq test to support multiple interfaces (nthumann)
a0b2e5cb6aa8db0563fac7d67a949b9baefe3a25 doc: Add release notes to support multiple interfaces (nthumann)
b1c3f180ecb63f3960506d202feebaa4271058ae doc: Adjust ZMQ usage to support multiple interfaces (nthumann)
347c94f551c3f144c44e00373e4dd61ff6d908b7 zmq: Add support to listen on multiple interfaces (Nicolas Thumann)

Pull request description:

  This PR adds support for ZeroMQ to listen on multiple interfaces, just like the RPC server.
  Currently, if you specify more than one e.g. `zmqpubhashblock` paramter, only the first one will be used. Therefore a user may be forced to listen on all interfaces (e.g. `zmqpubhashblock=0.0.0.0:28332`), which can result in an increased attack surface.
  With this PR a user can specify multiple interfaces to listen on, e.g.
  `-zmqpubhashblock=tcp://127.0.0.1:28332 -zmqpubhashblock=tcp://192.168.1.123:28332`.

ACKs for top commit:
  laanwj:
    Code review ACK e66870c5a4c2adbd30dca67d409fd5cd98697587
  instagibbs:
    reACK https://github.com/bitcoin/bitcoin/pull/18309/commits/e66870c5a4c2adbd30dca67d409fd5cd98697587

Tree-SHA512: f38ab4a6ff00dc821e5f4842508cefadb701e70bb3893992c1b32049be20247c8aa9476a1f886050c5f17fe7f2ce99ee30193ce2c81a7482a5a51f8fc22300c7

1 files changed, 24 insertions, 0 deletions

diff --git a/test/functional/interface_zmq.py b/test/functional/interface_zmq.py
index 17032a3b83..a0bc937f75 100755
--- a/test/functional/interface_zmq.py
+++ b/test/functional/interface_zmq.py
@@ -75,6 +75,7 @@ class ZMQTest (BitcoinTestFramework):
             self.test_sequence()
             self.test_mempool_sync()
             self.test_reorg()
+            self.test_multiple_interfaces()
         finally:
             # Destroy the ZMQ context.
             self.log.debug("Destroying ZMQ context")
@@ -506,5 +507,28 @@ class ZMQTest (BitcoinTestFramework):
 
         self.nodes[0].generatetoaddress(1, ADDRESS_BCRT1_UNSPENDABLE)
 
+    def test_multiple_interfaces(self):
+        # Set up two subscribers with different addresses
+        subscribers = []
+        for i in range(2):
+            address = 'tcp://127.0.0.1:%d' % (28334 + i)
+            socket = self.ctx.socket(zmq.SUB)
+            socket.set(zmq.RCVTIMEO, 60000)
+            hashblock = ZMQSubscriber(socket, b"hashblock")
+            socket.connect(address)
+            subscribers.append({'address': address, 'hashblock': hashblock})
+
+        self.restart_node(0, ['-zmqpub%s=%s' % (subscriber['hashblock'].topic.decode(), subscriber['address']) for subscriber in subscribers])
+
+        # Relax so that the subscriber is ready before publishing zmq messages
+        sleep(0.2)
+
+        # Generate 1 block in nodes[0] and receive all notifications
+        self.nodes[0].generatetoaddress(1, ADDRESS_BCRT1_UNSPENDABLE)
+
+        # Should receive the same block hash on both subscribers
+        assert_equal(self.nodes[0].getbestblockhash(), subscribers[0]['hashblock'].receive().hex())
+        assert_equal(self.nodes[0].getbestblockhash(), subscribers[1]['hashblock'].receive().hex())
+
 if __name__ == '__main__':
     ZMQTest().main()