Daemon should now exit on conflicting checkpoints

If the "enforce DNS checkpoints" flag is not enabled, it should not exit
if DNS checkpoints conflict with the others, but should still print a
warning to the user.

src/cryptonote_core/cryptonote_core.cpp

@@ -41,6 +41,7 @@ using namespace epee;
 #include "cryptonote_config.h"
 #include "cryptonote_format_utils.h"
 #include "misc_language.h"
+#include <csignal>
 
 DISABLE_VS_WARNINGS(4355)
 
@@ -98,6 +99,12 @@ namespace cryptonote
       res = m_blockchain_storage.update_checkpoints(m_checkpoints_path, false);
       m_last_json_checkpoints_update = time(NULL);
     }
+
+    // if anything fishy happened getting new checkpoints, bring down the house
+    if (!res)
+    {
+      graceful_exit();
+    }
     return res;
   }
   //-----------------------------------------------------------------------------------
@@ -583,4 +590,9 @@ namespace cryptonote
   uint64_t core::get_target_blockchain_height() const {
     return m_target_blockchain_height;
   }
+  //-----------------------------------------------------------------------------------------------
+  void core::graceful_exit()
+  {
+    raise(SIGTERM);
+  }
 }

src/cryptonote_core/cryptonote_core.h

@@ -145,6 +145,7 @@ namespace cryptonote
      bool handle_command_line(const boost::program_options::variables_map& vm, bool testnet);
      bool on_update_blocktemplate_interval();
      bool check_tx_inputs_keyimages_diff(const transaction& tx);
+     void graceful_exit();
 
 
      tx_memory_pool m_mempool;