Prepare to drop legacy fields from version message

Early in its life, Gridcoin added some fields to CNode for the legacy
research reward system. The design of the code that used these fields
had security and privacy issues so later changes set the fields to an
empty string. This commit prepares nodes for the removal of fields in
legacy "version" messages in the release that will follow the pending
mandatory version.

Author: cyrossignol

src/main.cpp

@@ -4427,17 +4427,22 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         CAddress addrMe;
         CAddress addrFrom;
         uint64_t nNonce = 1;
-        std::string legacy_dummy;
-
-        vRecv >> pfrom->nVersion
-            >> legacy_dummy      // pfrom->boinchashnonce
-            >> legacy_dummy      // pfrom->boinchashpw
-            >> legacy_dummy      // pfrom->cpid
-            >> legacy_dummy      // pfrom->enccpid
-            >> legacy_dummy      // acid
-            >> pfrom->nServices
-            >> nTime
-            >> addrMe;
+
+        vRecv >> pfrom->nVersion;
+
+        // In the version following 180324 (mandatory v5.0.0 - Fern), we can finally
+        // drop the garbage legacy fields added to the version message:
+        //
+        if (pfrom->nVersion <= 180324) {
+            std::string legacy_dummy;
+            vRecv >> legacy_dummy      // pfrom->boinchashnonce
+                  >> legacy_dummy      // pfrom->boinchashpw
+                  >> legacy_dummy      // pfrom->cpid
+                  >> legacy_dummy      // pfrom->enccpid
+                  >> legacy_dummy;     // acid
+        }
+
+        vRecv >> pfrom->nServices >> nTime >> addrMe;
 
         LogPrint(BCLog::LogFlags::NOISY, "received aries version %i ...", pfrom->nVersion);
 
@@ -4463,15 +4468,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             vRecv >> addrFrom >> nNonce;
         if (!vRecv.empty())
             vRecv >> pfrom->strSubVer;
-
         if (!vRecv.empty())
             vRecv >> pfrom->nStartingHeight;
+
         // 12-5-2015 - Append Trust fields
         pfrom->nTrust = 0;
 
-        if (!vRecv.empty())         vRecv >> legacy_dummy; // pfrom->sGRCAddress;
-
-
         // Allow newbies to connect easily with 0 blocks
         if (GetArgument("autoban","true") == "true")
         {

src/net.cpp

@@ -722,19 +722,39 @@ void CNode::PushVersion()
     LogPrint(BCLog::LogFlags::NOISY, "send version message: version %d, blocks=%d, us=%s, them=%s, peer=%s",
         PROTOCOL_VERSION, nBestHeight, addrMe.ToString(), addrYou.ToString(), addr.ToString());
 
-    std::string sboinchashargs;
-    std::string nonce;
-    std::string pw1;
-    std::string mycpid;
-    std::string acid;
-
-    //TODO: change `PushMessage()` to use ServiceFlags so we don't need to cast nLocalServices
-    PushMessage("aries", PROTOCOL_VERSION, nonce, pw1,
-                mycpid, mycpid, acid, (uint64_t) nLocalServices, nTime, addrYou, addrMe,
-                nLocalHostNonce, FormatSubVersion(CLIENT_NAME, CLIENT_VERSION, std::vector<string>()),
-                nBestHeight);
-
-
+    // In the version following 180324 (mandatory v5.0.0 - Fern), we can finally
+    // drop the garbage legacy fields added to the version message:
+    //
+    if (PROTOCOL_VERSION > 180324) {
+        //TODO: change `PushMessage()` to use ServiceFlags so we don't need to cast nLocalServices
+        PushMessage(
+            "aries",
+            PROTOCOL_VERSION,
+            (uint64_t)nLocalServices,
+            nTime,
+            addrYou,
+            addrMe,
+            nLocalHostNonce,
+            FormatSubVersion(CLIENT_NAME, CLIENT_VERSION, std::vector<string>()),
+            nBestHeight);
+    } else {
+        const std::string legacy_dummy;
+        PushMessage(
+            "aries",
+            PROTOCOL_VERSION,
+            legacy_dummy, // nonce
+            legacy_dummy, // pw1
+            legacy_dummy, // mycpid
+            legacy_dummy, // enccpid
+            legacy_dummy, // acid
+            (uint64_t)nLocalServices,
+            nTime,
+            addrYou,
+            addrMe,
+            nLocalHostNonce,
+            FormatSubVersion(CLIENT_NAME, CLIENT_VERSION, std::vector<string>()),
+            nBestHeight);
+    }
 }
 
 bool CNode::Misbehaving(int howmuch)