Rippled Server Software Upgrade Notification

src/ripple/app/ledger/LedgerMaster.h

@@ -407,6 +407,9 @@ class LedgerMaster : public Stoppable, public AbstractFetchPackContainer
     // without first wiping the database.
     LedgerIndex const max_ledger_difference_{1000000};
 
+    // Time of printing the upgrade warning message previously
+    TimeKeeper::time_point upgradeWarningPrevTime_{};
+
 private:
     struct Stats
     {

src/ripple/app/ledger/impl/LedgerMaster.cpp

@@ -43,6 +43,8 @@
 #include <ripple/nodestore/DatabaseShard.h>
 #include <ripple/overlay/Overlay.h>
 #include <ripple/overlay/Peer.h>
+#include <ripple/protocol/BuildInfo.h>
+#include <ripple/protocol/Feature.h>
 #include <ripple/protocol/HashPrefix.h>
 #include <ripple/protocol/digest.h>
 #include <ripple/resource/Fees.h>
@@ -1037,6 +1039,53 @@ LedgerMaster::checkAccept(std::shared_ptr<Ledger const> const& ledger)
     app_.getFeeTrack().setRemoteFee(fee);
 
     tryAdvance();
+
+    if (ledger->seq() % 256 == 0)
+    {
+        // Check if the majority of validators run a higher version rippled
+        // software. If so print a warning.
+        //
+        // Once the HardenedValidations amendment is enabled, validators include
+        // their rippled software version in the validation messages of every
+        // (flag - 1) ledger. We wait for one ledger time before checking the
+        // version information to accumulate more validation messages.
+
+        auto const& parentHash = ledger->info().parentHash;
+        auto const parentLedger = getLedgerByHash(parentHash);
+        if (parentLedger &&
+            parentLedger->rules().enabled(featureHardenedValidations))
+        {
+            // To throttle the warning messages, instead of printing a warning
+            // every flag ledger, we print every week.
+            auto currentTime = app_.timeKeeper().now();
+            if (currentTime - upgradeWarningPrevTime_ >= weeks{1})
+            {
+                auto const vals =
+                    app_.getValidations().getTrustedForLedger(parentHash);
+                auto higherVersionCount = std::count_if(
+                    vals.begin(), vals.end(), [](auto const& v) -> bool {
+                        if (v->isFieldPresent(sfServerVersion))
+                            return BuildInfo::isNewerVersion(
+                                v->getFieldU64(sfServerVersion));
+                        else
+                            return false;
+                    });
+                // We set the threshold of majority to be 60% of the UNL
+                auto const threshold =
+                    app_.validators().getQuorumKeys().second.size() * 60 / 100;
+                if (higherVersionCount >= threshold)
+                {
+                    upgradeWarningPrevTime_ = currentTime;
+                    auto const upgradeMsg =
+                        "Check for upgrade: "
+                        "A majority of trusted validators are "
+                        "running a newer version.";
+                    std::cerr << upgradeMsg << std::endl;
+                    JLOG(m_journal.error()) << upgradeMsg;
+                }
+            }
+        }
+    }
 }
 
 /** Report that the consensus process built a particular ledger */

src/ripple/protocol/BuildInfo.h

@@ -68,6 +68,19 @@ getFullVersionString();
 std::uint64_t
 getEncodedVersion();
 
+/** Check if the version is newer than the local node's rippled software
+    version.
+
+    @param version another node's rippled software version
+    @return true if the version is newer than the local node's rippled software
+        version, false otherwise.
+
+    @note This function only understands version numbers that are generated by
+        rippled. Please see the getEncodedVersion() function for detail.
+*/
+bool
+isNewerVersion(std::uint64_t version);
+
 }  // namespace BuildInfo
 
 }  // namespace ripple

src/ripple/protocol/impl/BuildInfo.cpp

@@ -148,6 +148,15 @@ getEncodedVersion()
     return cookie;
 }
 
+bool
+isNewerVersion(std::uint64_t version)
+{
+    std::uint64_t constexpr mask = 0x183B000000000000;
+    if ((version & mask) == mask)
+        return version > getEncodedVersion();
+    return false;
+}
+
 }  // namespace BuildInfo
 
 }  // namespace ripple