Merge bitcoin/bitcoin#29009: fuzz: p2p: Detect peer deadlocks

9f265d8825 fuzz: Detect deadlocks in process_message (dergoegge)
fae1e7e012 fuzz: p2p: Detect peer deadlocks (MarcoFalke)

Pull request description:

  It may be possible that a peer connection will deadlock, due to software bugs such as https://github.com/bitcoin/bitcoin/pull/18808.

  Fix this by detecting them in the fuzz target.

  Can be tested by introducing a bug such as:

  ```diff
  diff --git a/src/net_processing.cpp b/src/net_processing.cpp
  index 1067341495..97495a13df 100644
  --- a/src/net_processing.cpp
  +++ b/src/net_processing.cpp
  @@ -2436,3 +2436,3 @@ void PeerManagerImpl::ProcessGetData(CNode& pfrom, Peer& peer, const std::atomic
       if (it != peer.m_getdata_requests.end() && !pfrom.fPauseSend) {
  -        const CInv &inv = *it++;
  +        const CInv& inv = *it;
           if (inv.IsGenBlkMsg()) {
  ```

  Using a fuzz input such as:

  ```
  $ base64 ./timeout-ada0fecaba2b8c46c6e970cf637d9625b01bf7e5
  kNptdNbW1tbWYghvXIpwb25vPQAA////////cwAjLv8AXAB2ZXJhY2sAQW5v/62tra3Pz///////
  //////////////////////9c8GZpbHRlcmxvYWQAAAEAAwAAAABVYwC2XABmaWx0ZXJhZGQAAAAX
  Fxdn/////2V0F861tcqvEmAAACEAAABjYXB0dXJldmUAAH4AgAA1PNfX11x0Z2V0ZGF0YQBDACOw
  AQMAAAAGIm5GERoLWcqvEmBD61u/KMNPOl4zKh/HKLK3PPGIkQ9eE/////////8AAAAAAAAAAFtb
  WyjDTzpeMSofx7K3PNfX11x0Z2V0ZGF0YQBDACMwAQMAAAAGIm5GERoLWcqvEmBD61u/KMNPOl4z
  Kh/Hsrc88YiRD2/Nzc3Nzc3Nzc3NTc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3N
  zWWj1NTUudTU1NTU1P///0j+P/9cdHR4AAAAAAAAy/4AAHR4AAAAAAAAP8v+AAD/+P//////////
  AX55bJl8HWnz/////wAgXGF0YVPxY2RkAAAA
  ```

  And running the fuzz target:

  ```
  $ FUZZ=process_messages ./src/test/fuzz/fuzz -runs=1 -timeout=18 ./timeout-ada0fecaba2b8c46c6e970cf637d9625b01bf7e5
  INFO: Running with entropic power schedule (0xFF, 100).
  INFO: Seed: 3436516708
  INFO: Loaded 1 modules   (390807 inline 8-bit counters): 390807 [0x55d0d6221e80, 0x55d0d6281517),
  INFO: Loaded 1 PC tables (390807 PCs): 390807 [0x55d0d6281518,0x55d0d6877e88),
  ./src/test/fuzz/fuzz: Running 1 inputs 1 time(s) each.
  Running: ./timeout-ada0fecaba2b8c46c6e970cf637d9625b01bf7e5
  ALARM: working on the last Unit for 19 seconds
         and the timeout value is 18 (use -timeout=N to change)
  ==375014== ERROR: libFuzzer: timeout after 19 seconds
  ```

ACKs for top commit:
  naumenkogs:
    ACK 9f265d8825
  dergoegge:
    ACK 9f265d8825
  brunoerg:
    ACK 9f265d8825

Tree-SHA512: da83ff90962bb679aae00e8e9dba639c180b7aaba544e0c4d0978d36e28a9ff1cd7a2e13009d8ab407ef57767656aca1ebc767a7d2f1bc880284f8f57c197a50

src/test/fuzz/process_message.cpp

@@ -79,14 +79,23 @@ FUZZ_TARGET(process_message, .init = initialize_process_message)
     const auto mock_time = ConsumeTime(fuzzed_data_provider);
     SetMockTime(mock_time);
 
+    CSerializedNetMsg net_msg;
+    net_msg.m_type = random_message_type;
     // fuzzed_data_provider is fully consumed after this call, don't use it
-    DataStream random_bytes_data_stream{fuzzed_data_provider.ConsumeRemainingBytes<unsigned char>()};
-    try {
-        g_setup->m_node.peerman->ProcessMessage(p2p_node, random_message_type, random_bytes_data_stream,
-                                                GetTime<std::chrono::microseconds>(), std::atomic<bool>{false});
-    } catch (const std::ios_base::failure&) {
+    net_msg.data = fuzzed_data_provider.ConsumeRemainingBytes<unsigned char>();
+
+    connman.FlushSendBuffer(p2p_node);
+    (void)connman.ReceiveMsgFrom(p2p_node, std::move(net_msg));
+
+    bool more_work{true};
+    while (more_work) {
+        p2p_node.fPauseSend = false;
+        try {
+            more_work = connman.ProcessMessagesOnce(p2p_node);
+        } catch (const std::ios_base::failure&) {
+        }
+        g_setup->m_node.peerman->SendMessages(&p2p_node);
     }
-    g_setup->m_node.peerman->SendMessages(&p2p_node);
     SyncWithValidationInterfaceQueue();
     g_setup->m_node.connman->StopNodes();
 }

src/test/fuzz/process_messages.cpp

@@ -78,13 +78,17 @@ FUZZ_TARGET(process_messages, .init = initialize_process_messages)
 
         connman.FlushSendBuffer(random_node);
         (void)connman.ReceiveMsgFrom(random_node, std::move(net_msg));
-        random_node.fPauseSend = false;
 
-        try {
-            connman.ProcessMessagesOnce(random_node);
-        } catch (const std::ios_base::failure&) {
+        bool more_work{true};
+        while (more_work) { // Ensure that every message is eventually processed in some way or another
+            random_node.fPauseSend = false;
+
+            try {
+                more_work = connman.ProcessMessagesOnce(random_node);
+            } catch (const std::ios_base::failure&) {
+            }
+            g_setup->m_node.peerman->SendMessages(&random_node);
         }
-        g_setup->m_node.peerman->SendMessages(&random_node);
     }
     SyncWithValidationInterfaceQueue();
     g_setup->m_node.connman->StopNodes();

src/test/util/net.h

@@ -70,7 +70,10 @@ struct ConnmanTestMsg : public CConnman {
                    bool relay_txs)
         EXCLUSIVE_LOCKS_REQUIRED(NetEventsInterface::g_msgproc_mutex);
 
-    void ProcessMessagesOnce(CNode& node) EXCLUSIVE_LOCKS_REQUIRED(NetEventsInterface::g_msgproc_mutex) { m_msgproc->ProcessMessages(&node, flagInterruptMsgProc); }
+    bool ProcessMessagesOnce(CNode& node) EXCLUSIVE_LOCKS_REQUIRED(NetEventsInterface::g_msgproc_mutex)
+    {
+        return m_msgproc->ProcessMessages(&node, flagInterruptMsgProc);
+    }
 
     void NodeReceiveMsgBytes(CNode& node, Span<const uint8_t> msg_bytes, bool& complete) const;