From 41c868f47e671dc5009cd47496c39c13ae36306b Mon Sep 17 00:00:00 2001
From: Ross Nicoll <jrn@jrn.me.uk>
Date: Sun, 22 Apr 2018 17:19:03 +0100
Subject: Re-introduce alert functionality (#1470)

Re-introduce alert functionality removed from Bitcoin upstream
---
 src/net_processing.cpp | 65 ++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 58 insertions(+), 7 deletions(-)

(limited to 'src/net_processing.cpp')

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 706b4c68f..924fc5eb8 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -6,6 +6,7 @@
 #include "net_processing.h"
 
 #include "addrman.h"
+#include "alert.h"
 #include "arith_uint256.h"
 #include "blockencodings.h"
 #include "chainparams.h"
@@ -1366,13 +1367,12 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         pfrom->nTimeOffset = nTimeOffset;
         AddTimeData(pfrom->addr, nTimeOffset);
 
-        // If the peer is old enough to have the old alert system, send it the final alert.
-        /* if (pfrom->nVersion <= 70012) {
-            // TODO: Replace this with a valid Dogecoin alert
-            // Disabled meantime as the remote client considers the nonsense alert a hack and drops the connection
-            CDataStream finalAlert(ParseHex("60010000000000000000000000ffffff7f00000000ffffff7ffeffff7f01ffffff7f00000000ffffff7f00ffffff7f002f555247454e543a20416c657274206b657920636f6d70726f6d697365642c2075706772616465207265717569726564004630440220653febd6410f470f6bae11cad19c48413becb1ac2c17f908fd0fd53bdc3abd5202206d0e9c96fe88d4a0f01ed9dedae2b6f9e00da94cad0fecaae66ecf689bf71b50"), SER_NETWORK, PROTOCOL_VERSION);
-            connman.PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make("alert", finalAlert));
-        } */
+        // Relay alerts
+        {
+            LOCK(cs_mapAlerts);
+            BOOST_FOREACH(PAIRTYPE(const uint256, CAlert)& item, mapAlerts)
+                pfrom->PushAlert(item.second);
+        }
 
         // Feeler connections exist only to verify if address is online.
         if (pfrom->fFeeler) {
@@ -2523,6 +2523,38 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         }
     }
 
+    else if (fAlerts && strCommand == NetMsgType::ALERT)
+    {
+        CAlert alert;
+        vRecv >> alert;
+
+        uint256 alertHash = alert.GetHash();
+        if (pfrom->setKnown.count(alertHash) == 0)
+        {
+            if (alert.ProcessAlert(chainparams.AlertKey()))
+            {
+                // Relay
+                pfrom->setKnown.insert(alertHash);
+                {
+                    
+                    connman.ForEachNode([&alert](CNode* pnode)
+                    {
+                        pnode->PushAlert(alert);
+                    });
+                }
+            }
+            else {
+                // Small DoS penalty so peers that send us lots of
+                // duplicate/expired/invalid-signature/whatever alerts
+                // eventually get banned.
+                // This isn't a Misbehaving(100) (immediate ban) because the
+                // peer might be an older or different implementation with
+                // a different signature key, etc.
+                Misbehaving(pfrom->GetId(), 10);
+            }
+        }
+    }
+
 
     else if (strCommand == NetMsgType::FILTERLOAD)
     {
@@ -3267,6 +3299,25 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                 pto->nextSendTimeFeeFilter = timeNow + GetRandInt(MAX_FEEFILTER_CHANGE_DELAY) * 1000000;
             }
         }
+
+        //
+        // Message: alert
+        //
+        BOOST_FOREACH(const CAlert &alert, pto->vAlertToSend) {
+            // returns true if wasn't already contained in the set
+            if (pto->setKnown.insert(alert.GetHash()).second)
+            {
+                if (alert.AppliesTo(pto->nVersion, pto->strSubVer) ||
+                    alert.AppliesToMe() ||
+                    GetAdjustedTime() < alert.nRelayUntil)
+                {
+                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::ALERT, alert));
+                    return true;
+                }
+            }
+        }
+        pto->vAlertToSend.clear();
+
     }
     return true;
 }
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