wallet2: check wallet compatibility with daemon's hard fork version

src/cryptonote_basic/hardfork.h

@@ -231,6 +231,11 @@ namespace cryptonote
      */
     uint64_t get_window_size() const { return window_size; }
 
+    /**
+     * @brief returns info for all known hard forks
+     */
+    const std::vector<hardfork_t>& get_hardforks() const { return heights; }
+
   private:
 
     uint8_t get_block_version(uint64_t height) const;

src/cryptonote_core/blockchain.h

@@ -899,6 +899,13 @@ namespace cryptonote
      */
     uint64_t get_earliest_ideal_height_for_version(uint8_t version) const { return m_hardfork->get_earliest_ideal_height_for_version(version); }
 
+    /**
+     * @brief returns info for all known hard forks
+     *
+     * @return the hardforks
+     */
+    const std::vector<hardfork_t>& get_hardforks() const { return m_hardfork->get_hardforks(); }
+
     /**
      * @brief get information about hardfork voting for a version
      *

src/rpc/core_rpc_server.cpp

@@ -2861,6 +2861,10 @@ namespace cryptonote
 
     res.version = CORE_RPC_VERSION;
     res.release = MONERO_VERSION_IS_RELEASE;
+    res.current_height = m_core.get_current_blockchain_height();
+    res.target_height = m_p2p.get_payload_object().is_synchronized() ? 0 : m_core.get_target_blockchain_height();
+    for (const auto &hf : m_core.get_blockchain_storage().get_hardforks())
+       res.hard_forks.push_back({hf.version, hf.height});
     res.status = CORE_RPC_STATUS_OK;
     return true;
   }

src/rpc/core_rpc_server_commands_defs.h

@@ -88,7 +88,7 @@ namespace cryptonote
 // advance which version they will stop working with
 // Don't go over 32767 for any of these
 #define CORE_RPC_VERSION_MAJOR 3
-#define CORE_RPC_VERSION_MINOR 10
+#define CORE_RPC_VERSION_MINOR 11
 #define MAKE_CORE_RPC_VERSION(major,minor) (((major)<<16)|(minor))
 #define CORE_RPC_VERSION MAKE_CORE_RPC_VERSION(CORE_RPC_VERSION_MAJOR, CORE_RPC_VERSION_MINOR)
 
@@ -2123,15 +2123,34 @@ namespace cryptonote
     };
     typedef epee::misc_utils::struct_init<request_t> request;
 
+    struct hf_entry
+    {
+      uint8_t hf_version;
+      uint64_t height;
+
+      bool operator==(const hf_entry& hfe) const { return hf_version == hfe.hf_version && height == hfe.height; }
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(hf_version)
+        KV_SERIALIZE(height)
+      END_KV_SERIALIZE_MAP()
+    };
+
     struct response_t: public rpc_response_base
     {
       uint32_t version;
       bool release;
+      uint64_t current_height;
+      uint64_t target_height;
+      std::vector<hf_entry> hard_forks;
 
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE_PARENT(rpc_response_base)
         KV_SERIALIZE(version)
         KV_SERIALIZE(release)
+        KV_SERIALIZE_OPT(current_height, (uint64_t)0)
+        KV_SERIALIZE_OPT(target_height, (uint64_t)0)
+        KV_SERIALIZE_OPT(hard_forks, std::vector<hf_entry>())
       END_KV_SERIALIZE_MAP()
     };
     typedef epee::misc_utils::struct_init<response_t> response;

src/simplewallet/simplewallet.cpp

@@ -181,7 +181,6 @@ namespace
   const command_line::arg_descriptor<bool> arg_restore_from_seed = {"restore-from-seed", sw::tr("alias for --restore-deterministic-wallet"), false};
   const command_line::arg_descriptor<bool> arg_restore_multisig_wallet = {"restore-multisig-wallet", sw::tr("Recover multisig wallet using Electrum-style mnemonic seed"), false};
   const command_line::arg_descriptor<bool> arg_non_deterministic = {"non-deterministic", sw::tr("Generate non-deterministic view and spend keys"), false};
-  const command_line::arg_descriptor<bool> arg_allow_mismatched_daemon_version = {"allow-mismatched-daemon-version", sw::tr("Allow communicating with a daemon that uses a different RPC version"), false};
   const command_line::arg_descriptor<uint64_t> arg_restore_height = {"restore-height", sw::tr("Restore from specific blockchain height"), 0};
   const command_line::arg_descriptor<std::string> arg_restore_date = {"restore-date", sw::tr("Restore from estimated blockchain height on specified date"), ""};
   const command_line::arg_descriptor<bool> arg_do_not_relay = {"do-not-relay", sw::tr("The newly created transaction will not be relayed to the monero network"), false};
@@ -3233,8 +3232,7 @@ bool simple_wallet::scan_tx(const std::vector<std::string> &args)
 }
 
 simple_wallet::simple_wallet()
-  : m_allow_mismatched_daemon_version(false)
+  : m_refresh_progress_reporter(*this)
-  , m_refresh_progress_reporter(*this)
   , m_idle_run(true)
   , m_auto_refresh_enabled(false)
   , m_auto_refresh_refreshing(false)
@@ -4755,7 +4753,6 @@ bool simple_wallet::handle_command_line(const boost::program_options::variables_
   m_restore_deterministic_wallet  = command_line::get_arg(vm, arg_restore_deterministic_wallet) || command_line::get_arg(vm, arg_restore_from_seed);
   m_restore_multisig_wallet       = command_line::get_arg(vm, arg_restore_multisig_wallet);
   m_non_deterministic             = command_line::get_arg(vm, arg_non_deterministic);
-  m_allow_mismatched_daemon_version = command_line::get_arg(vm, arg_allow_mismatched_daemon_version);
   m_restore_height                = command_line::get_arg(vm, arg_restore_height);
   m_restore_date                  = command_line::get_arg(vm, arg_restore_date);
   m_do_not_relay                  = command_line::get_arg(vm, arg_do_not_relay);
@@ -4786,12 +4783,20 @@ bool simple_wallet::try_connect_to_daemon(bool silent, uint32_t* version)
   uint32_t version_ = 0;
   if (!version)
     version = &version_;
-  if (!m_wallet->check_connection(version))
+  bool wallet_is_outdated, daemon_is_outdated = false;
+  if (!m_wallet->check_connection(version, NULL, 200000, &wallet_is_outdated, &daemon_is_outdated))
   {
     if (!silent)
     {
       if (m_wallet->is_offline())
         fail_msg_writer() << tr("wallet failed to connect to daemon, because it is set to offline mode");
+      else if (wallet_is_outdated)
+        fail_msg_writer() << tr("wallet failed to connect to daemon, because it is not up to date. ") <<
+          tr("Please make sure you are running the latest wallet.");
+      else if (daemon_is_outdated)
+        fail_msg_writer() << tr("wallet failed to connect to daemon: ") << m_wallet->get_daemon_address() << ". " <<
+          tr("Daemon is not up to date. "
+          "Please make sure the daemon is running the latest version or change the daemon address using the 'set_daemon' command.");
       else
         fail_msg_writer() << tr("wallet failed to connect to daemon: ") << m_wallet->get_daemon_address() << ". " <<
           tr("Daemon either is not started or wrong port was passed. "
@@ -4799,7 +4804,7 @@ bool simple_wallet::try_connect_to_daemon(bool silent, uint32_t* version)
     }
     return false;
   }
-  if (!m_allow_mismatched_daemon_version && ((*version >> 16) != CORE_RPC_VERSION_MAJOR))
+  if (!m_wallet->is_mismatched_daemon_version_allowed() && ((*version >> 16) != CORE_RPC_VERSION_MAJOR))
   {
     if (!silent)
       fail_msg_writer() << boost::format(tr("Daemon uses a different RPC major version (%u) than the wallet (%u): %s. Either update one of them, or use --allow-mismatched-daemon-version.")) % (*version>>16) % CORE_RPC_VERSION_MAJOR % m_wallet->get_daemon_address();
@@ -10629,7 +10634,6 @@ int main(int argc, char* argv[])
   command_line::add_arg(desc_params, arg_restore_multisig_wallet );
   command_line::add_arg(desc_params, arg_non_deterministic );
   command_line::add_arg(desc_params, arg_electrum_seed );
-  command_line::add_arg(desc_params, arg_allow_mismatched_daemon_version);
   command_line::add_arg(desc_params, arg_restore_height);
   command_line::add_arg(desc_params, arg_restore_date);
   command_line::add_arg(desc_params, arg_do_not_relay);

src/simplewallet/simplewallet.h

@@ -429,7 +429,6 @@ namespace cryptonote
     bool m_restore_deterministic_wallet;  // recover flag
     bool m_restore_multisig_wallet;  // recover flag
     bool m_non_deterministic;  // old 2-random generation
-    bool m_allow_mismatched_daemon_version;
     bool m_restoring;           // are we restoring, by whatever method?
     uint64_t m_restore_height;  // optional
     bool m_do_not_relay;

src/wallet/api/wallet.cpp

@@ -2173,9 +2173,15 @@ bool WalletImpl::connectToDaemon()
 Wallet::ConnectionStatus WalletImpl::connected() const
 {
     uint32_t version = 0;
-    m_is_connected = m_wallet->check_connection(&version, NULL, DEFAULT_CONNECTION_TIMEOUT_MILLIS);
+    bool wallet_is_outdated, daemon_is_outdated = false;
+    m_is_connected = m_wallet->check_connection(&version, NULL, DEFAULT_CONNECTION_TIMEOUT_MILLIS, &wallet_is_outdated, &daemon_is_outdated);
     if (!m_is_connected)
+    {
+        if (!m_wallet->light_wallet() && (wallet_is_outdated || daemon_is_outdated))
+            return Wallet::ConnectionStatus_WrongVersion;
+        else
             return Wallet::ConnectionStatus_Disconnected;
+    }
     // Version check is not implemented in light wallets nodes/wallets
     if (!m_wallet->light_wallet() && (version >> 16) != CORE_RPC_VERSION_MAJOR)
         return Wallet::ConnectionStatus_WrongVersion;

src/wallet/node_rpc_proxy.cpp

@@ -82,18 +82,21 @@ void NodeRPCProxy::invalidate()
   m_rpc_payment_seed_hash = crypto::null_hash;
   m_rpc_payment_next_seed_hash = crypto::null_hash;
   m_height_time = 0;
+  m_target_height_time = 0;
   m_rpc_payment_diff = 0;
   m_rpc_payment_credits_per_hash_found = 0;
   m_rpc_payment_height = 0;
   m_rpc_payment_cookie = 0;
+  m_daemon_hard_forks.clear();
 }
 
-boost::optional<std::string> NodeRPCProxy::get_rpc_version(uint32_t &rpc_version)
+boost::optional<std::string> NodeRPCProxy::get_rpc_version(uint32_t &rpc_version, std::vector<std::pair<uint8_t, uint64_t>> &daemon_hard_forks, uint64_t &height, uint64_t &target_height)
 {
   if (m_offline)
     return boost::optional<std::string>("offline");
   if (m_rpc_version == 0)
   {
+    const time_t now = time(NULL);
     cryptonote::COMMAND_RPC_GET_VERSION::request req_t = AUTO_VAL_INIT(req_t);
     cryptonote::COMMAND_RPC_GET_VERSION::response resp_t = AUTO_VAL_INIT(resp_t);
     {
@@ -101,9 +104,28 @@ boost::optional<std::string> NodeRPCProxy::get_rpc_version(uint32_t &rpc_version
       bool r = net_utils::invoke_http_json_rpc("/json_rpc", "get_version", req_t, resp_t, m_http_client, rpc_timeout);
       RETURN_ON_RPC_RESPONSE_ERROR(r, epee::json_rpc::error{}, resp_t, "get_version");
     }
+
     m_rpc_version = resp_t.version;
+    m_daemon_hard_forks.clear();
+    for (const auto &hf : resp_t.hard_forks)
+      m_daemon_hard_forks.push_back(std::make_pair(hf.hf_version, hf.height));
+    if (resp_t.current_height > 0 || resp_t.target_height > 0)
+    {
+      m_height = resp_t.current_height;
+      m_target_height = resp_t.target_height;
+      m_height_time = now;
+      m_target_height_time = now;
     }
+  }
+
   rpc_version = m_rpc_version;
+  daemon_hard_forks = m_daemon_hard_forks;
+  boost::optional<std::string> result = get_height(height);
+  if (result)
+    return result;
+  result = get_target_height(target_height);
+  if (result)
+    return result;
   return boost::optional<std::string>();
 }
 
@@ -138,6 +160,7 @@ boost::optional<std::string> NodeRPCProxy::get_info()
     m_adjusted_time = resp_t.adjusted_time;
     m_get_info_time = now;
     m_height_time = now;
+    m_target_height_time = now;
   }
   return boost::optional<std::string>();
 }
@@ -160,6 +183,13 @@ boost::optional<std::string> NodeRPCProxy::get_height(uint64_t &height)
 
 boost::optional<std::string> NodeRPCProxy::get_target_height(uint64_t &height)
 {
+  const time_t now = time(NULL);
+  if (now < m_target_height_time + 30) // re-cache every 30 seconds
+  {
+    height = m_target_height;
+    return boost::optional<std::string>();
+  }
+
   auto res = get_info();
   if (res)
     return res;

src/wallet/node_rpc_proxy.h

@@ -48,7 +48,7 @@ public:
   void invalidate();
   void set_offline(bool offline) { m_offline = offline; }
 
-  boost::optional<std::string> get_rpc_version(uint32_t &version);
+  boost::optional<std::string> get_rpc_version(uint32_t &rpc_version, std::vector<std::pair<uint8_t, uint64_t>> &daemon_hard_forks, uint64_t &height, uint64_t &target_height);
   boost::optional<std::string> get_height(uint64_t &height);
   void set_height(uint64_t h);
   boost::optional<std::string> get_target_height(uint64_t &height);
@@ -103,6 +103,8 @@ private:
   crypto::hash m_rpc_payment_next_seed_hash;
   uint32_t m_rpc_payment_cookie;
   time_t m_height_time;
+  time_t m_target_height_time;
+  std::vector<std::pair<uint8_t, uint64_t>> m_daemon_hard_forks;
 };
 
 }

src/wallet/wallet2.cpp

@@ -47,6 +47,7 @@
 using namespace epee;
 
 #include "cryptonote_config.h"
+#include "hardforks/hardforks.h"
 #include "cryptonote_core/tx_sanity_check.h"
 #include "wallet_rpc_helpers.h"
 #include "wallet2.h"
@@ -275,6 +276,7 @@ struct options {
   const command_line::arg_descriptor<bool> no_dns = {"no-dns", tools::wallet2::tr("Do not use DNS"), false};
   const command_line::arg_descriptor<bool> offline = {"offline", tools::wallet2::tr("Do not connect to a daemon, nor use DNS"), false};
   const command_line::arg_descriptor<std::string> extra_entropy = {"extra-entropy", tools::wallet2::tr("File containing extra entropy to initialize the PRNG (any data, aim for 256 bits of entropy to be useful, which typically means more than 256 bits of data)")};
+  const command_line::arg_descriptor<bool> allow_mismatched_daemon_version = {"allow-mismatched-daemon-version", tools::wallet2::tr("Allow communicating with a daemon that uses a different version"), false};
 };
 
 void do_prepare_file_names(const std::string& file_path, std::string& keys_file, std::string& wallet_file, std::string &mms_file)
@@ -484,6 +486,9 @@ std::unique_ptr<tools::wallet2> make_basic(const boost::program_options::variabl
     add_extra_entropy_thread_safe(data.data(), data.size());
   }
 
+  if (command_line::has_arg(vm, opts.allow_mismatched_daemon_version))
+    wallet->allow_mismatched_daemon_version(true);
+
   try
   {
     if (!command_line::is_arg_defaulted(vm, opts.tx_notify))
@@ -1219,7 +1224,8 @@ wallet2::wallet2(network_type nettype, uint64_t kdf_rounds, bool unattended, std
   m_load_deprecated_formats(false),
   m_credits_target(0),
   m_enable_multisig(false),
-  m_has_ever_refreshed_from_node(false)
+  m_has_ever_refreshed_from_node(false),
+  m_allow_mismatched_daemon_version(false)
 {
   set_rpc_client_secret_key(rct::rct2sk(rct::skGen()));
 }
@@ -1279,6 +1285,7 @@ void wallet2::init_options(boost::program_options::options_description& desc_par
   command_line::add_arg(desc_params, opts.no_dns);
   command_line::add_arg(desc_params, opts.offline);
   command_line::add_arg(desc_params, opts.extra_entropy);
+  command_line::add_arg(desc_params, opts.allow_mismatched_daemon_version);
 }
 
 std::pair<std::unique_ptr<wallet2>, tools::password_container> wallet2::make_from_json(const boost::program_options::variables_map& vm, bool unattended, const std::string& json_file, const std::function<boost::optional<tools::password_container>(const char *, bool)> &password_prompter)
@@ -2915,6 +2922,26 @@ void wallet2::refresh(bool trusted_daemon, uint64_t start_height, uint64_t & blo
   refresh(trusted_daemon, start_height, blocks_fetched, received_money);
 }
 //----------------------------------------------------------------------------------------------------
+void check_block_hard_fork_version(cryptonote::network_type nettype, uint8_t hf_version, uint64_t height, bool &wallet_is_outdated, bool &daemon_is_outdated)
+{
+  const size_t wallet_num_hard_forks = nettype == TESTNET ? num_testnet_hard_forks
+    : nettype == STAGENET ? num_stagenet_hard_forks : num_mainnet_hard_forks;
+  const hardfork_t *wallet_hard_forks = nettype == TESTNET ? testnet_hard_forks
+    : nettype == STAGENET ? stagenet_hard_forks : mainnet_hard_forks;
+
+  wallet_is_outdated = static_cast<size_t>(hf_version) > wallet_num_hard_forks;
+  if (wallet_is_outdated)
+    return;
+
+  // check block's height falls within wallet's expected range for block's given version
+  uint64_t start_height = hf_version == 1 ? 0 : wallet_hard_forks[hf_version - 1].height;
+  uint64_t end_height = static_cast<size_t>(hf_version) + 1 > wallet_num_hard_forks
+    ? std::numeric_limits<uint64_t>::max()
+    : wallet_hard_forks[hf_version].height;
+
+  daemon_is_outdated = height < start_height || height >= end_height;
+}
+//----------------------------------------------------------------------------------------------------
 void wallet2::pull_and_parse_next_blocks(uint64_t start_height, uint64_t &blocks_start_height, std::list<crypto::hash> &short_chain_history, const std::vector<cryptonote::block_complete_entry> &prev_blocks, const std::vector<parsed_block> &prev_parsed_blocks, std::vector<cryptonote::block_complete_entry> &blocks, std::vector<parsed_block> &parsed_blocks, bool &last, bool &error, std::exception_ptr &exception)
 {
   error = false;
@@ -2956,6 +2983,23 @@ void wallet2::pull_and_parse_next_blocks(uint64_t start_height, uint64_t &blocks
         error = true;
         break;
       }
+
+      if (!m_allow_mismatched_daemon_version)
+      {
+        // make sure block's hard fork version is expected at the block's height
+        uint8_t hf_version = parsed_blocks[i].block.major_version;
+        uint64_t height = blocks_start_height + i;
+        bool wallet_is_outdated = false;
+        bool daemon_is_outdated = false;
+        check_block_hard_fork_version(m_nettype, hf_version, height, wallet_is_outdated, daemon_is_outdated);
+        THROW_WALLET_EXCEPTION_IF(wallet_is_outdated || daemon_is_outdated, error::incorrect_fork_version,
+          "Unexpected hard fork version v" + std::to_string(hf_version) + " at height " + std::to_string(height) + ". " +
+          (wallet_is_outdated
+            ? "Make sure your wallet is up to date"
+            : "Make sure the node you are connected to is running the latest version")
+        );
+      }
+
       parsed_blocks[i].o_indices = std::move(o_indices[i]);
     }
 
@@ -3574,6 +3618,11 @@ void wallet2::refresh(bool trusted_daemon, uint64_t start_height, uint64_t & blo
       THROW_WALLET_EXCEPTION_IF(!waiter.wait(), error::wallet_internal_error, "Exception in thread pool");
       throw;
     }
+    catch (const error::incorrect_fork_version&)
+    {
+      THROW_WALLET_EXCEPTION_IF(!waiter.wait(), error::wallet_internal_error, "Exception in thread pool");
+      throw;
+    }
     catch (const std::exception&)
     {
       blocks_fetched += added_blocks;
@@ -4184,6 +4233,7 @@ bool wallet2::load_keys_buf(const std::string& keys_buf, const epee::wipeable_st
     m_auto_mine_for_rpc_payment_threshold = -1.0f;
     m_credits_target = 0;
     m_enable_multisig = false;
+    m_allow_mismatched_daemon_version = false;
   }
   else if(json.IsObject())
   {
@@ -5327,7 +5377,7 @@ bool wallet2::prepare_file_names(const std::string& file_path)
   return true;
 }
 //----------------------------------------------------------------------------------------------------
-bool wallet2::check_connection(uint32_t *version, bool *ssl, uint32_t timeout)
+bool wallet2::check_connection(uint32_t *version, bool *ssl, uint32_t timeout, bool *wallet_is_outdated, bool *daemon_is_outdated)
 {
   THROW_WALLET_EXCEPTION_IF(!m_is_initialized, error::wallet_not_initialized);
 
@@ -5364,20 +5414,99 @@ bool wallet2::check_connection(uint32_t *version, bool *ssl, uint32_t timeout)
     }
   }
 
-  if (!m_rpc_version)
+  if (!m_rpc_version && !check_version(version, wallet_is_outdated, daemon_is_outdated))
+    return false;
+  if (version)
+    *version = m_rpc_version;
+
+  return true;
+}
+//----------------------------------------------------------------------------------------------------
+bool wallet2::check_version(uint32_t *version, bool *wallet_is_outdated, bool *daemon_is_outdated)
+{
+  uint32_t rpc_version;
+  std::vector<std::pair<uint8_t, uint64_t>> daemon_hard_forks;
+  uint64_t height;
+  uint64_t target_height;
+  if (m_node_rpc_proxy.get_rpc_version(rpc_version, daemon_hard_forks, height, target_height))
   {
-    cryptonote::COMMAND_RPC_GET_VERSION::request req_t = AUTO_VAL_INIT(req_t);
-    cryptonote::COMMAND_RPC_GET_VERSION::response resp_t = AUTO_VAL_INIT(resp_t);
-    bool r = invoke_http_json_rpc("/json_rpc", "get_version", req_t, resp_t);
-    if(!r || resp_t.status != CORE_RPC_STATUS_OK) {
     if(version)
       *version = 0;
     return false;
   }
-    m_rpc_version = resp_t.version;
+
+  // check wallet compatibility with daemon's hard fork version
+  if (!m_allow_mismatched_daemon_version)
+    if (!check_hard_fork_version(m_nettype, daemon_hard_forks, height, target_height, wallet_is_outdated, daemon_is_outdated))
+      return false;
+
+  m_rpc_version = rpc_version;
+  return true;
+}
+//----------------------------------------------------------------------------------------------------
+bool wallet2::check_hard_fork_version(cryptonote::network_type nettype, const std::vector<std::pair<uint8_t, uint64_t>> &daemon_hard_forks, const uint64_t height, const uint64_t target_height, bool *wallet_is_outdated, bool *daemon_is_outdated)
+{
+  const size_t wallet_num_hard_forks = nettype == TESTNET ? num_testnet_hard_forks
+    : nettype == STAGENET ? num_stagenet_hard_forks : num_mainnet_hard_forks;
+  const hardfork_t *wallet_hard_forks = nettype == TESTNET ? testnet_hard_forks
+    : nettype == STAGENET ? stagenet_hard_forks : mainnet_hard_forks;
+
+  // First check if wallet or daemon is outdated (whether either are unaware of
+  // a hard fork). Then check if fork has passed rendering versions incompatible
+  if (daemon_hard_forks.size() > 0)
+  {
+    bool daemon_outdated = daemon_hard_forks.size() < wallet_num_hard_forks;
+    bool wallet_outdated = daemon_hard_forks.size() > wallet_num_hard_forks;
+
+    if (daemon_is_outdated)
+      *daemon_is_outdated = daemon_outdated;
+    if (wallet_is_outdated)
+      *wallet_is_outdated = wallet_outdated;
+
+    if (daemon_outdated)
+    {
+      uint64_t daemon_missed_fork_height = wallet_hard_forks[daemon_hard_forks.size()].height;
+
+      // If the daemon missed the fork, then technically it is no longer part of
+      // the Monero network. Don't connect.
+      bool daemon_missed_fork = height >= daemon_missed_fork_height || target_height >= daemon_missed_fork_height;
+      if (daemon_missed_fork)
+        return false;
+    }
+    else if (wallet_outdated)
+    {
+      uint64_t wallet_missed_fork_height = daemon_hard_forks[wallet_num_hard_forks].second;
+
+      // If the wallet missed the fork, then technically it is no longer able
+      // to communicate with the Monero network. Don't connect.
+      bool wallet_missed_fork = height >= wallet_missed_fork_height || target_height >= wallet_missed_fork_height;
+      if (wallet_missed_fork)
+        return false;
+    }
+  }
+  else
+  {
+    // Non-updated daemons won't return daemon_hard_forks in response to
+    // get_version. Fall back to extra call to get_hard_fork_info by version.
+    uint64_t daemon_fork_height;
+    get_hard_fork_info(wallet_num_hard_forks-1/* wallet expects "double fork" pattern */, daemon_fork_height);
+    bool daemon_outdated = daemon_fork_height == std::numeric_limits<uint64_t>::max();
+
+    if (daemon_is_outdated)
+      *daemon_is_outdated = daemon_outdated;
+
+    if (daemon_outdated)
+    {
+      uint64_t daemon_missed_fork_height = wallet_hard_forks[wallet_num_hard_forks-2].height;
+      bool daemon_missed_fork = height >= daemon_missed_fork_height || target_height >= daemon_missed_fork_height;
+      if (daemon_missed_fork)
+        return false;
+    }
+
+    // Don't need to check if wallet is outdated here because the daemons updated
+    // for a future hard fork will serve daemon_hard_forks above. The check for
+    // an outdated wallet is done above using daemon_hard_forks.
   }
-  if (version)
-    *version = m_rpc_version;
 
   return true;
 }

src/wallet/wallet2.h

@@ -1091,7 +1091,9 @@ private:
     bool sign_multisig_tx_to_file(multisig_tx_set &exported_txs, const std::string &filename, std::vector<crypto::hash> &txids);
     std::vector<pending_tx> create_unmixable_sweep_transactions();
     void discard_unmixable_outputs();
-    bool check_connection(uint32_t *version = NULL, bool *ssl = NULL, uint32_t timeout = 200000);
+    bool check_connection(uint32_t *version = NULL, bool *ssl = NULL, uint32_t timeout = 200000, bool *wallet_is_outdated = NULL, bool *daemon_is_outdated = NULL);
+    bool check_version(uint32_t *version, bool *wallet_is_outdated, bool *daemon_is_outdated);
+    bool check_hard_fork_version(cryptonote::network_type nettype, const std::vector<std::pair<uint8_t, uint64_t>> &daemon_hard_forks, const uint64_t height, const uint64_t target_height, bool *wallet_is_outdated, bool *daemon_is_outdated);
     void get_transfers(wallet2::transfer_container& incoming_transfers) const;
     void get_payments(const crypto::hash& payment_id, std::list<wallet2::payment_details>& payments, uint64_t min_height = 0, const boost::optional<uint32_t>& subaddr_account = boost::none, const std::set<uint32_t>& subaddr_indices = {}) const;
     void get_payments(std::list<std::pair<crypto::hash,wallet2::payment_details>>& payments, uint64_t min_height, uint64_t max_height = (uint64_t)-1, const boost::optional<uint32_t>& subaddr_account = boost::none, const std::set<uint32_t>& subaddr_indices = {}) const;
@@ -1358,6 +1360,8 @@ private:
     void credits_target(uint64_t threshold) { m_credits_target = threshold; }
     bool is_multisig_enabled() const { return m_enable_multisig; }
     void enable_multisig(bool enable) { m_enable_multisig = enable; }
+    bool is_mismatched_daemon_version_allowed() const { return m_allow_mismatched_daemon_version; }
+    void allow_mismatched_daemon_version(bool allow_mismatch) { m_allow_mismatched_daemon_version = allow_mismatch; }
 
     bool get_tx_key_cached(const crypto::hash &txid, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys) const;
     void set_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, const boost::optional<cryptonote::account_public_address> &single_destination_subaddress = boost::none);
@@ -1875,6 +1879,7 @@ private:
     rpc_payment_state_t m_rpc_payment_state;
     uint64_t m_credits_target;
     bool m_enable_multisig;
+    bool m_allow_mismatched_daemon_version;
 
     // Aux transaction data from device
     serializable_unordered_map<crypto::hash, std::string> m_tx_device;

src/wallet/wallet_errors.h

@@ -439,6 +439,16 @@ namespace tools
       std::string to_string() const { return refresh_error::to_string(); }
     };
     //----------------------------------------------------------------------------------------------------
+    struct incorrect_fork_version : public refresh_error
+    {
+      explicit incorrect_fork_version(std::string&& loc, const std::string& message)
+        : refresh_error(std::move(loc), message)
+      {
+      }
+
+      std::string to_string() const { return refresh_error::to_string(); }
+    };
+    //----------------------------------------------------------------------------------------------------
     struct signature_check_failed : public wallet_logic_error
     {
       explicit signature_check_failed(std::string&& loc, const std::string& message)

tests/functional_tests/functional_tests_rpc.py

@@ -55,7 +55,7 @@ monerod_extra = [
   ["--add-exclusive-node", "127.0.0.1:18283"],
   ["--add-exclusive-node", "127.0.0.1:18282"],
 ]
-wallet_base = [builddir + "/bin/monero-wallet-rpc", "--wallet-dir", WALLET_DIRECTORY, "--rpc-bind-port", "wallet_port", "--disable-rpc-login", "--rpc-ssl", "disabled", "--daemon-ssl", "disabled", "--log-level", "1"]
+wallet_base = [builddir + "/bin/monero-wallet-rpc", "--wallet-dir", WALLET_DIRECTORY, "--rpc-bind-port", "wallet_port", "--disable-rpc-login", "--rpc-ssl", "disabled", "--daemon-ssl", "disabled", "--log-level", "1", "--allow-mismatched-daemon-version"]
 wallet_extra = [
   ["--daemon-port", "18180"],
   ["--daemon-port", "18180"],

utils/fish/monero-wallet-cli.fish

@@ -30,6 +30,7 @@ complete -c monero-wallet-cli -l tx-notify -r -d "Run a program for each new inc
 complete -c monero-wallet-cli -l no-dns -d "Do not use DNS"
 complete -c monero-wallet-cli -l offline -d "Do not connect to a daemon, nor use DNS"
 complete -c monero-wallet-cli -l extra-entropy -r -F -d "File containing extra entropy to initialize the PRNG (any data, aim for 256 bits of entropy to be useful, which typically means more than 256 bits of data)"
+complete -c monero-wallet-cli -l allow-mismatched-daemon-version -d "Allow communicating with a daemon that uses a different version"
 complete -c monero-wallet-cli -l wallet-file -r -F -d "Use wallet <arg>"
 complete -c monero-wallet-cli -l generate-new-wallet -r -F -d "Generate new wallet and save it to <arg>"
 complete -c monero-wallet-cli -l generate-from-device -r -F -d "Generate new wallet from device and save it to <arg>"
@@ -45,7 +46,6 @@ complete -c monero-wallet-cli -l restore-from-seed -d "alias for --restore-deter
 complete -c monero-wallet-cli -l restore-multisig-wallet -d "Recover multisig wallet using Electrum-style mnemonic seed"
 complete -c monero-wallet-cli -l non-deterministic -d "Generate non-deterministic view and spend keys"
 complete -c monero-wallet-cli -l electrum-seed -r -d "Specify Electrum seed for wallet recovery/creation"
-complete -c monero-wallet-cli -l allow-mismatched-daemon-version -d "Allow communicating with a daemon that uses a different RPC version"
 complete -c monero-wallet-cli -l restore-height -r -d "Restore from specific blockchain height. Default: 0"
 complete -c monero-wallet-cli -l restore-date -r -d "Restore from estimated blockchain height on specified date"
 complete -c monero-wallet-cli -l do-not-relay -d "The newly created transaction will not be relayed to the monero network"

utils/fish/monero-wallet-rpc.fish

@@ -30,6 +30,7 @@ complete -c monero-wallet-rpc -l tx-notify -r -d "Run a program for each new inc
 complete -c monero-wallet-rpc -l no-dns -d "Do not use DNS"
 complete -c monero-wallet-rpc -l offline -d "Do not connect to a daemon, nor use DNS"
 complete -c monero-wallet-rpc -l extra-entropy -r -F -d "File containing extra entropy to initialize the PRNG (any data, aim for 256 bits of entropy to be useful, which typically means more than 256 bits of data)"
+complete -c monero-wallet-cli -l allow-mismatched-daemon-version -d "Allow communicating with a daemon that uses a different version"
 complete -c monero-wallet-rpc -l rpc-bind-port -r -d "Sets bind port for server"
 complete -c monero-wallet-rpc -l disable-rpc-login -d "Disable HTTP authentication for RPC connections served by this process"
 complete -c monero-wallet-rpc -l restricted-rpc -d "Restricts to view-only commands"