p2p: isolate regtest from mainnet bootstrap state

diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index 7ea5689..2964875 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -98,16 +98,18 @@ namespace cryptonote
   , "Fixed difficulty used for testing."
   , 0
   };
-  const command_line::arg_descriptor<std::string, false, true, 2> arg_data_dir = {
+  const command_line::arg_descriptor<std::string, false, true, 3> arg_data_dir = {
     "data-dir"
   , "Specify data directory"
   , tools::get_default_data_dir()
-  , {{ &arg_testnet_on, &arg_stagenet_on }}
-  , [](std::array<bool, 2> testnet_stagenet, bool defaulted, std::string val)->std::string {
-      if (testnet_stagenet[0])
+  , {{ &arg_testnet_on, &arg_stagenet_on, &arg_regtest_on }}
+  , [](std::array<bool, 3> nets, bool defaulted, std::string val)->std::string {
+      if (nets[0])
         return (boost::filesystem::path(val) / "testnet").string();
-      else if (testnet_stagenet[1])
+      else if (nets[1])
         return (boost::filesystem::path(val) / "stagenet").string();
+      else if (nets[2])
+        return (boost::filesystem::path(val) / "fake").string();
       return val;
     }
   };
@@ -479,8 +481,6 @@ namespace cryptonote
     bool keep_fakechain = command_line::get_arg(vm, arg_keep_fakechain);
 
     boost::filesystem::path folder(m_config_folder);
-    if (m_nettype == FAKECHAIN)
-      folder /= "fake";
 
     // make sure the data directory exists, and try to lock it
     CHECK_AND_ASSERT_MES (boost::filesystem::exists(folder) || boost::filesystem::create_directories(folder), false,
diff --git a/src/cryptonote_core/cryptonote_core.h b/src/cryptonote_core/cryptonote_core.h
index d9a97e5..d57c6cc 100644
--- a/src/cryptonote_core/cryptonote_core.h
+++ b/src/cryptonote_core/cryptonote_core.h
@@ -62,7 +62,7 @@ namespace cryptonote
      const size_t long_term_block_weight_window;
    };
 
-  extern const command_line::arg_descriptor<std::string, false, true, 2> arg_data_dir;
+  extern const command_line::arg_descriptor<std::string, false, true, 3> arg_data_dir;
   extern const command_line::arg_descriptor<bool, false> arg_testnet_on;
   extern const command_line::arg_descriptor<bool, false> arg_stagenet_on;
   extern const command_line::arg_descriptor<bool, false> arg_regtest_on;
diff --git a/src/p2p/net_node.inl b/src/p2p/net_node.inl
index c48af62..776bb34 100644
--- a/src/p2p/net_node.inl
+++ b/src/p2p/net_node.inl
@@ -428,8 +428,9 @@ namespace nodetool
   {
     bool testnet = command_line::get_arg(vm, cryptonote::arg_testnet_on);
     bool stagenet = command_line::get_arg(vm, cryptonote::arg_stagenet_on);
+    bool regtest = command_line::get_arg(vm, cryptonote::arg_regtest_on);
     const bool pad_txs = command_line::get_arg(vm, arg_pad_transactions);
-    m_nettype = testnet ? cryptonote::TESTNET : stagenet ? cryptonote::STAGENET : cryptonote::MAINNET;
+    m_nettype = testnet ? cryptonote::TESTNET : stagenet ? cryptonote::STAGENET : regtest ? cryptonote::FAKECHAIN : cryptonote::MAINNET;
 
     network_zone& public_zone = m_network_zones[epee::net_utils::zone::public_];
     public_zone.m_connect = &public_connect;
@@ -774,6 +775,10 @@ namespace nodetool
     {
       return get_ip_seed_nodes();
     }
+    if (m_nettype == cryptonote::FAKECHAIN)
+    {
+      return {};
+    }
     if (!m_enable_dns_seed_nodes)
     {
       // TODO: a domain can be set through socks, so that the remote side does the lookup for the DNS seed nodes.
diff --git a/tests/unit_tests/node_server.cpp b/tests/unit_tests/node_server.cpp
index b5c0fa1..f455ca1 100644
--- a/tests/unit_tests/node_server.cpp
+++ b/tests/unit_tests/node_server.cpp
@@ -133,6 +133,69 @@ static bool is_blocked(Server &server, const epee::net_utils::network_address &a
   return false;
 }
 
+namespace
+{
+  using path_t = boost::filesystem::path;
+  using ec_t = boost::system::error_code;
+
+  path_t create_temp_dir(const char* pattern)
+  {
+    ec_t ec;
+    path_t path = boost::filesystem::temp_directory_path() / boost::filesystem::unique_path(pattern, ec);
+    if (ec)
+      return path_t{};
+
+    const bool success = boost::filesystem::create_directory(path, ec);
+    if (!ec && success)
+      return path;
+
+    return path_t{};
+  }
+
+  void remove_tree(const path_t& path)
+  {
+    ec_t ec;
+    boost::filesystem::remove_all(path, ec);
+  }
+
+  boost::program_options::variables_map make_regtest_options(const path_t& dir)
+  {
+    boost::program_options::options_description desc;
+    cryptonote::core::init_options(desc);
+    Server::init_options(desc);
+
+    std::vector<std::string> args{
+      "--regtest",
+      "--p2p-bind-ip=127.0.0.1",
+      "--no-igd",
+      "--out-peers=0",
+      "--in-peers=0",
+      "--data-dir",
+      dir.string(),
+      "--check-updates=disabled",
+      "--disable-dns-checkpoints",
+      "--offline",
+    };
+
+    boost::program_options::variables_map vm;
+    boost::program_options::store(
+      boost::program_options::command_line_parser(args).options(desc).run(),
+      vm
+    );
+    boost::program_options::notify(vm);
+    return vm;
+  }
+
+  nodetool::peerlist_entry make_peer(const epee::net_utils::network_address& address, const nodetool::peerid_type id, const int64_t last_seen)
+  {
+    nodetool::peerlist_entry peer = AUTO_VAL_INIT(peer);
+    peer.adr = address;
+    peer.id = id;
+    peer.last_seen = last_seen;
+    return peer;
+  }
+}
+
 TEST(ban, add)
 {
   test_core pr_core;
@@ -1270,5 +1333,47 @@ TEST(node_server, race_condition)
   remove_tree(dir);
 }
 
+TEST(regtest, isolates_p2p_state_from_mainnet_data_dir)
+{
+  const path_t dir = create_temp_dir("regtest-%%%%%%%%%%%%%%%%");
+  ASSERT_TRUE(!dir.empty());
+  auto cleanup = epee::misc_utils::create_scope_leave_handler([&dir]{
+    remove_tree(dir);
+  });
+
+  nodetool::peerlist_types peers{};
+  peers.white.push_back(make_peer(MAKE_IPV4_ADDRESS_PORT(11, 22, 33, 44, 18080), 1, 100));
+  peers.gray.push_back(make_peer(MAKE_IPV4_ADDRESS_PORT(55, 66, 77, 88, 18080), 2, 200));
+
+  const path_t mainnet_state = dir / P2P_NET_DATA_FILENAME;
+  ASSERT_TRUE(nodetool::peerlist_storage{}.store(mainnet_state.string(), peers));
+
+  test_core pr_core;
+  cryptonote::t_cryptonote_protocol_handler<test_core> cprotocol(pr_core, NULL);
+  Server server(cprotocol);
+  cprotocol.set_p2p_endpoint(&server);
+
+  const auto vm = make_regtest_options(dir);
+  ASSERT_TRUE(server.init(vm));
+  ASSERT_EQ(0u, server.get_public_white_peers_count());
+  ASSERT_EQ(0u, server.get_public_gray_peers_count());
+  ASSERT_TRUE(server.deinit());
+
+  const path_t regtest_state = dir / "fake" / P2P_NET_DATA_FILENAME;
+  ASSERT_TRUE(boost::filesystem::exists(regtest_state));
+
+  auto base_storage = nodetool::peerlist_storage::open(mainnet_state.string());
+  ASSERT_TRUE(bool(base_storage));
+  nodetool::peerlist_types base_public = base_storage->take_zone(epee::net_utils::zone::public_);
+  EXPECT_EQ(1u, base_public.white.size());
+  EXPECT_EQ(1u, base_public.gray.size());
+
+  auto regtest_storage = nodetool::peerlist_storage::open(regtest_state.string());
+  ASSERT_TRUE(bool(regtest_storage));
+  nodetool::peerlist_types regtest_public = regtest_storage->take_zone(epee::net_utils::zone::public_);
+  EXPECT_TRUE(regtest_public.white.empty());
+  EXPECT_TRUE(regtest_public.gray.empty());
+}
+
 namespace nodetool { template class node_server<cryptonote::t_cryptonote_protocol_handler<test_core>>; }
 namespace cryptonote { template class t_cryptonote_protocol_handler<test_core>; }