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

5 files changed, 40 insertions, 12 deletions

diff --git a/doc/release-notes-18309.md b/doc/release-notes-18309.md
new file mode 100644
index 0000000000..b31f85eb6e
--- /dev/null
+++ b/doc/release-notes-18309.md
@@ -0,0 +1,4 @@
+Command-line options
+-----------------------------
+
+The same ZeroMQ notification (e.g. `-zmqpubhashtx=address`) can now be specified multiple times to publish the same notification to different ZeroMQ sockets.
\ No newline at end of file
diff --git a/doc/zmq.md b/doc/zmq.md
index f003c90d3a..85f3370130 100644
--- a/doc/zmq.md
+++ b/doc/zmq.md
@@ -67,6 +67,7 @@ Currently, the following notifications are supported:
 
 The socket type is PUB and the address must be a valid ZeroMQ socket
 address. The same address can be used in more than one notification.
+The same notification can be specified more than once.
 
 The option to set the PUB socket's outbound message high water mark
 (SNDHWM) may be set individually for each notification:
@@ -82,6 +83,7 @@ The high water mark value must be an integer greater than or equal to 0.
 For instance:
 
     $ bitcoind -zmqpubhashtx=tcp://127.0.0.1:28332 \
+               -zmqpubhashtx=tcp://192.168.1.2:28332 \
                -zmqpubrawtx=ipc:///tmp/bitcoind.tx.raw \
                -zmqpubhashtxhwm=10000
 
diff --git a/src/zmq/zmqnotificationinterface.cpp b/src/zmq/zmqnotificationinterface.cpp
index a7e9a34269..a2f994d7df 100644
--- a/src/zmq/zmqnotificationinterface.cpp
+++ b/src/zmq/zmqnotificationinterface.cpp
@@ -42,10 +42,8 @@ CZMQNotificationInterface* CZMQNotificationInterface::Create()
     for (const auto& entry : factories)
     {
         std::string arg("-zmq" + entry.first);
-        if (gArgs.IsArgSet(arg))
-        {
-            const auto& factory = entry.second;
-            const std::string address = gArgs.GetArg(arg, "");
+        const auto& factory = entry.second;
+        for (const std::string& address : gArgs.GetArgs(arg)) {
             std::unique_ptr<CZMQAbstractNotifier> notifier = factory();
             notifier->SetType(entry.first);
             notifier->SetAddress(address);
diff --git a/src/zmq/zmqpublishnotifier.cpp b/src/zmq/zmqpublishnotifier.cpp
index a0e7a0a600..c0207f9dd6 100644
--- a/src/zmq/zmqpublishnotifier.cpp
+++ b/src/zmq/zmqpublishnotifier.cpp
@@ -180,7 +180,7 @@ bool CZMQAbstractPublishNotifier::SendZmqMessage(const char *command, const void
 bool CZMQPublishHashBlockNotifier::NotifyBlock(const CBlockIndex *pindex)
 {
     uint256 hash = pindex->GetBlockHash();
-    LogPrint(BCLog::ZMQ, "zmq: Publish hashblock %s\n", hash.GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish hashblock %s to %s\n", hash.GetHex(), this->address);
     char data[32];
     for (unsigned int i = 0; i < 32; i++)
         data[31 - i] = hash.begin()[i];
@@ -190,7 +190,7 @@ bool CZMQPublishHashBlockNotifier::NotifyBlock(const CBlockIndex *pindex)
 bool CZMQPublishHashTransactionNotifier::NotifyTransaction(const CTransaction &transaction)
 {
     uint256 hash = transaction.GetHash();
-    LogPrint(BCLog::ZMQ, "zmq: Publish hashtx %s\n", hash.GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish hashtx %s to %s\n", hash.GetHex(), this->address);
     char data[32];
     for (unsigned int i = 0; i < 32; i++)
         data[31 - i] = hash.begin()[i];
@@ -199,7 +199,7 @@ bool CZMQPublishHashTransactionNotifier::NotifyTransaction(const CTransaction &t
 
 bool CZMQPublishRawBlockNotifier::NotifyBlock(const CBlockIndex *pindex)
 {
-    LogPrint(BCLog::ZMQ, "zmq: Publish rawblock %s\n", pindex->GetBlockHash().GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish rawblock %s to %s\n", pindex->GetBlockHash().GetHex(), this->address);
 
     const Consensus::Params& consensusParams = Params().GetConsensus();
     CDataStream ss(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
@@ -221,7 +221,7 @@ bool CZMQPublishRawBlockNotifier::NotifyBlock(const CBlockIndex *pindex)
 bool CZMQPublishRawTransactionNotifier::NotifyTransaction(const CTransaction &transaction)
 {
     uint256 hash = transaction.GetHash();
-    LogPrint(BCLog::ZMQ, "zmq: Publish rawtx %s\n", hash.GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish rawtx %s to %s\n", hash.GetHex(), this->address);
     CDataStream ss(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
     ss << transaction;
     return SendZmqMessage(MSG_RAWTX, &(*ss.begin()), ss.size());
@@ -232,7 +232,7 @@ bool CZMQPublishRawTransactionNotifier::NotifyTransaction(const CTransaction &tr
 bool CZMQPublishSequenceNotifier::NotifyBlockConnect(const CBlockIndex *pindex)
 {
     uint256 hash = pindex->GetBlockHash();
-    LogPrint(BCLog::ZMQ, "zmq: Publish sequence block connect %s\n", hash.GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish sequence block connect %s to %s\n", hash.GetHex(), this->address);
     char data[sizeof(uint256)+1];
     for (unsigned int i = 0; i < sizeof(uint256); i++)
         data[sizeof(uint256) - 1 - i] = hash.begin()[i];
@@ -243,7 +243,7 @@ bool CZMQPublishSequenceNotifier::NotifyBlockConnect(const CBlockIndex *pindex)
 bool CZMQPublishSequenceNotifier::NotifyBlockDisconnect(const CBlockIndex *pindex)
 {
     uint256 hash = pindex->GetBlockHash();
-    LogPrint(BCLog::ZMQ, "zmq: Publish sequence block disconnect %s\n", hash.GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish sequence block disconnect %s to %s\n", hash.GetHex(), this->address);
     char data[sizeof(uint256)+1];
     for (unsigned int i = 0; i < sizeof(uint256); i++)
         data[sizeof(uint256) - 1 - i] = hash.begin()[i];
@@ -254,7 +254,7 @@ bool CZMQPublishSequenceNotifier::NotifyBlockDisconnect(const CBlockIndex *pinde
 bool CZMQPublishSequenceNotifier::NotifyTransactionAcceptance(const CTransaction &transaction, uint64_t mempool_sequence)
 {
     uint256 hash = transaction.GetHash();
-    LogPrint(BCLog::ZMQ, "zmq: Publish hashtx mempool acceptance %s\n", hash.GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish hashtx mempool acceptance %s to %s\n", hash.GetHex(), this->address);
     unsigned char data[sizeof(uint256)+sizeof(mempool_sequence)+1];
     for (unsigned int i = 0; i < sizeof(uint256); i++)
         data[sizeof(uint256) - 1 - i] = hash.begin()[i];
@@ -266,7 +266,7 @@ bool CZMQPublishSequenceNotifier::NotifyTransactionAcceptance(const CTransaction
 bool CZMQPublishSequenceNotifier::NotifyTransactionRemoval(const CTransaction &transaction, uint64_t mempool_sequence)
 {
     uint256 hash = transaction.GetHash();
-    LogPrint(BCLog::ZMQ, "zmq: Publish hashtx mempool removal %s\n", hash.GetHex());
+    LogPrint(BCLog::ZMQ, "zmq: Publish hashtx mempool removal %s to %s\n", hash.GetHex(), this->address);
     unsigned char data[sizeof(uint256)+sizeof(mempool_sequence)+1];
     for (unsigned int i = 0; i < sizeof(uint256); i++)
         data[sizeof(uint256) - 1 - i] = hash.begin()[i];
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()