Merge bitcoin/bitcoin#23575: fuzz: Rework FillNode

fa19bab90a3ccc2f76c20aa805292d6a9c5d8071 fuzz: Rework FillNode (MarcoFalke)
fae6e31df7c6df04f41fc8401e2a9781a4d75be7 refactor: Set fSuccessfullyConnected in FillNode (MarcoFalke)
fa3583f856e34b6c6134745da14f5206cf71fa3e fuzz: Avoid negative NodeId in ConsumeNode (MarcoFalke)

Pull request description:

  Currently `FillNode` is a bit clumsy because it directly modifies memory of `CNode`. This gets in the way of moving that memory to `Peer`. Also, it isn't particularly consistent. See for example https://github.com/bitcoin/bitcoin/pull/21160#discussion_r739206139 .

  Fix all issues by sending a `version`/`verack` in `FillNode` and let net_processing figure out the internal details.

ACKs for top commit:
  jnewbery:
    Strong concept ACK and light code review ACK fa19bab90a3ccc2f76c20aa805292d6a9c5d8071

Tree-SHA512: 33261d857c3fa6d5d39d742624009a29178ad5a15eb3fd062da741affa5a4854fd45ed20d59a6bba2fb068cf7b39cad6f95b2910be7cb6afdc27cd7917955b67

4 files changed, 50 insertions, 16 deletions

diff --git a/src/test/fuzz/process_message.cpp b/src/test/fuzz/process_message.cpp
index 94a71859e9..1763cd8af3 100644
--- a/src/test/fuzz/process_message.cpp
+++ b/src/test/fuzz/process_message.cpp
@@ -79,11 +79,9 @@ void fuzz_target(FuzzBufferType buffer, const std::string& LIMIT_TO_MESSAGE_TYPE
     }
     CNode& p2p_node = *ConsumeNodeAsUniquePtr(fuzzed_data_provider).release();
 
-    const bool successfully_connected{fuzzed_data_provider.ConsumeBool()};
-    p2p_node.fSuccessfullyConnected = successfully_connected;
     connman.AddTestNode(p2p_node);
     g_setup->m_node.peerman->InitializeNode(&p2p_node);
-    FillNode(fuzzed_data_provider, p2p_node, /*init_version=*/successfully_connected);
+    FillNode(fuzzed_data_provider, connman, *g_setup->m_node.peerman, p2p_node);
 
     const auto mock_time = ConsumeTime(fuzzed_data_provider);
     SetMockTime(mock_time);
diff --git a/src/test/fuzz/process_messages.cpp b/src/test/fuzz/process_messages.cpp
index 21a959315e..e1c11e1afd 100644
--- a/src/test/fuzz/process_messages.cpp
+++ b/src/test/fuzz/process_messages.cpp
@@ -46,11 +46,8 @@ FUZZ_TARGET_INIT(process_messages, initialize_process_messages)
         peers.push_back(ConsumeNodeAsUniquePtr(fuzzed_data_provider, i).release());
         CNode& p2p_node = *peers.back();
 
-        const bool successfully_connected{fuzzed_data_provider.ConsumeBool()};
-        p2p_node.fSuccessfullyConnected = successfully_connected;
-        p2p_node.fPauseSend = false;
         g_setup->m_node.peerman->InitializeNode(&p2p_node);
-        FillNode(fuzzed_data_provider, p2p_node, /*init_version=*/successfully_connected);
+        FillNode(fuzzed_data_provider, connman, *g_setup->m_node.peerman, p2p_node);
 
         connman.AddTestNode(p2p_node);
     }
diff --git a/src/test/fuzz/util.cpp b/src/test/fuzz/util.cpp
index ae5f7a379e..843b29b911 100644
--- a/src/test/fuzz/util.cpp
+++ b/src/test/fuzz/util.cpp
@@ -3,6 +3,8 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <consensus/amount.h>
+#include <net_processing.h>
+#include <netmessagemaker.h>
 #include <pubkey.h>
 #include <test/fuzz/util.h>
 #include <test/util/script.h>
@@ -200,22 +202,57 @@ bool FuzzedSock::IsConnected(std::string& errmsg) const
     return false;
 }
 
-void FillNode(FuzzedDataProvider& fuzzed_data_provider, CNode& node, bool init_version) noexcept
+void FillNode(FuzzedDataProvider& fuzzed_data_provider, ConnmanTestMsg& connman, PeerManager& peerman, CNode& node) noexcept
 {
+    const bool successfully_connected{fuzzed_data_provider.ConsumeBool()};
     const ServiceFlags remote_services = ConsumeWeakEnum(fuzzed_data_provider, ALL_SERVICE_FLAGS);
     const NetPermissionFlags permission_flags = ConsumeWeakEnum(fuzzed_data_provider, ALL_NET_PERMISSION_FLAGS);
     const int32_t version = fuzzed_data_provider.ConsumeIntegralInRange<int32_t>(MIN_PEER_PROTO_VERSION, std::numeric_limits<int32_t>::max());
     const bool filter_txs = fuzzed_data_provider.ConsumeBool();
 
-    node.nServices = remote_services;
-    node.m_permissionFlags = permission_flags;
-    if (init_version) {
-        node.nVersion = version;
-        node.SetCommonVersion(std::min(version, PROTOCOL_VERSION));
+    const CNetMsgMaker mm{0};
+
+    CSerializedNetMsg msg_version{
+        mm.Make(NetMsgType::VERSION,
+                version,                                        //
+                Using<CustomUintFormatter<8>>(remote_services), //
+                int64_t{},                                      // dummy time
+                int64_t{},                                      // ignored service bits
+                CService{},                                     // dummy
+                int64_t{},                                      // ignored service bits
+                CService{},                                     // ignored
+                uint64_t{1},                                    // dummy nonce
+                std::string{},                                  // dummy subver
+                int32_t{},                                      // dummy starting_height
+                filter_txs),
+    };
+
+    (void)connman.ReceiveMsgFrom(node, msg_version);
+    node.fPauseSend = false;
+    connman.ProcessMessagesOnce(node);
+    {
+        LOCK(node.cs_sendProcessing);
+        peerman.SendMessages(&node);
     }
+    if (node.fDisconnect) return;
+    assert(node.nVersion == version);
+    assert(node.GetCommonVersion() == std::min(version, PROTOCOL_VERSION));
+    assert(node.nServices == remote_services);
     if (node.m_tx_relay != nullptr) {
         LOCK(node.m_tx_relay->cs_filter);
-        node.m_tx_relay->fRelayTxes = filter_txs;
+        assert(node.m_tx_relay->fRelayTxes == filter_txs);
+    }
+    node.m_permissionFlags = permission_flags;
+    if (successfully_connected) {
+        CSerializedNetMsg msg_verack{mm.Make(NetMsgType::VERACK)};
+        (void)connman.ReceiveMsgFrom(node, msg_verack);
+        node.fPauseSend = false;
+        connman.ProcessMessagesOnce(node);
+        {
+            LOCK(node.cs_sendProcessing);
+            peerman.SendMessages(&node);
+        }
+        assert(node.fSuccessfullyConnected == true);
     }
 }
 
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index 40aaeac63f..7937315822 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -36,6 +36,8 @@
 #include <string>
 #include <vector>
 
+class PeerManager;
+
 template <typename... Callables>
 size_t CallOneOf(FuzzedDataProvider& fuzzed_data_provider, Callables... callables)
 {
@@ -257,7 +259,7 @@ inline CAddress ConsumeAddress(FuzzedDataProvider& fuzzed_data_provider) noexcep
 template <bool ReturnUniquePtr = false>
 auto ConsumeNode(FuzzedDataProvider& fuzzed_data_provider, const std::optional<NodeId>& node_id_in = std::nullopt) noexcept
 {
-    const NodeId node_id = node_id_in.value_or(fuzzed_data_provider.ConsumeIntegral<NodeId>());
+    const NodeId node_id = node_id_in.value_or(fuzzed_data_provider.ConsumeIntegralInRange<NodeId>(0, std::numeric_limits<NodeId>::max()));
     const ServiceFlags local_services = ConsumeWeakEnum(fuzzed_data_provider, ALL_SERVICE_FLAGS);
     const SOCKET socket = INVALID_SOCKET;
     const CAddress address = ConsumeAddress(fuzzed_data_provider);
@@ -275,7 +277,7 @@ auto ConsumeNode(FuzzedDataProvider& fuzzed_data_provider, const std::optional<N
 }
 inline std::unique_ptr<CNode> ConsumeNodeAsUniquePtr(FuzzedDataProvider& fdp, const std::optional<NodeId>& node_id_in = std::nullopt) { return ConsumeNode<true>(fdp, node_id_in); }
 
-void FillNode(FuzzedDataProvider& fuzzed_data_provider, CNode& node, bool init_version) noexcept;
+void FillNode(FuzzedDataProvider& fuzzed_data_provider, ConnmanTestMsg& connman, PeerManager& peerman, CNode& node) noexcept;
 
 class FuzzedFileProvider
 {