[net processing] Warn user if the median outbound time offset is larg…

…er than 70min

src/net_processing.cpp

@@ -43,6 +43,7 @@
 #include <util/strencodings.h>
 #include <util/trace.h>
 #include <validation.h>
+#include <warnings.h>
 
 #include <algorithm>
 #include <atomic>
@@ -3615,6 +3616,12 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
             AddTimeData(pfrom.addr, peer->m_time_offset);
 
             m_outbound_time_offsets.Add(peer->m_time_offset);
+
+            auto median = m_outbound_time_offsets.Median();
+            if (median > m_opts.time_offset_warn_threshold.count() ||
+                median < -m_opts.time_offset_warn_threshold.count()) {
+                SetMedianTimeOffsetWarning();
+            }
         }
 
         // If the peer is old enough to have the old alert system, send it the final alert.

src/net_processing.h

@@ -27,6 +27,7 @@ static const bool DEFAULT_PEERBLOCKFILTERS = false;
 static const int DISCOURAGEMENT_THRESHOLD{100};
 /** Maximum number of outstanding CMPCTBLOCK requests for the same block. */
 static const unsigned int MAX_CMPCTBLOCKS_INFLIGHT_PER_BLOCK = 3;
+static constexpr std::chrono::seconds DEFAULT_TIME_OFFSET_WARN_THRESHOLD{70min};
 
 struct CNodeStateStats {
     int nSyncHeight = -1;
@@ -67,6 +68,8 @@ class PeerManager : public CValidationInterface, public NetEventsInterface
         //! Whether or not the internal RNG behaves deterministically (this is
         //! a test-only option).
         bool deterministic_rng{false};
+        //! Threshold for the network adjusted time offset warning.
+        std::chrono::seconds time_offset_warn_threshold{DEFAULT_TIME_OFFSET_WARN_THRESHOLD};
     };
 
     static std::unique_ptr<PeerManager> make(CConnman& connman, AddrMan& addrman,

src/node/peerman_args.cpp

@@ -23,6 +23,8 @@ void ApplyArgsManOptions(const ArgsManager& argsman, PeerManager::Options& optio
     if (auto value{argsman.GetBoolArg("-capturemessages")}) options.capture_messages = *value;
 
     if (auto value{argsman.GetBoolArg("-blocksonly")}) options.ignore_incoming_txs = *value;
+
+    if (auto value{argsman.GetIntArg("-maxtimeadjustment")}) options.time_offset_warn_threshold = std::chrono::seconds{*value};
 }
 
 } // namespace node

src/warnings.cpp

@@ -15,6 +15,7 @@
 static GlobalMutex g_warnings_mutex;
 static bilingual_str g_misc_warnings GUARDED_BY(g_warnings_mutex);
 static bool fLargeWorkInvalidChainFound GUARDED_BY(g_warnings_mutex) = false;
+static bool g_timeoffset_warning GUARDED_BY(g_warnings_mutex){};
 
 void SetMiscWarning(const bilingual_str& warning)
 {
@@ -28,6 +29,12 @@ void SetfLargeWorkInvalidChainFound(bool flag)
     fLargeWorkInvalidChainFound = flag;
 }
 
+void SetMedianTimeOffsetWarning()
+{
+    LOCK(g_warnings_mutex);
+    g_timeoffset_warning = true;
+}
+
 bilingual_str GetWarnings(bool verbose)
 {
     bilingual_str warnings_concise;
@@ -52,6 +59,11 @@ bilingual_str GetWarnings(bool verbose)
         warnings_verbose.emplace_back(warnings_concise);
     }
 
+    if (g_timeoffset_warning) {
+        warnings_concise = Untranslated("Please check that your computer's date and time are correct");
+        warnings_verbose.emplace_back(warnings_concise);
+    }
+
     if (verbose) {
         return Join(warnings_verbose, Untranslated("<hr />"));
     }

src/warnings.h

@@ -12,6 +12,7 @@ struct bilingual_str;
 
 void SetMiscWarning(const bilingual_str& warning);
 void SetfLargeWorkInvalidChainFound(bool flag);
+void SetMedianTimeOffsetWarning();
 /** Format a string that describes several potential problems detected by the core.
  * @param[in] verbose bool
  * - if true, get all warnings separated by <hr />