Give Hush mainnet a dedicated minimum protocol version #345

Hush and DragonX do not have the same requirements for which nodes they
should talk to because they don't necessarily have consensus changes at
the same time. For instance, 3.10.0 was a consensus change for Hush but
not DragonX. This commit changes things so that Hush nodes will no
longer talk to old nodes that are not consensus compatible but leaves
things the same for DragonX mainnet, which has never had a consensus
change.

src/main.cpp

@@ -106,7 +106,7 @@ size_t nCoinCacheUsage = 5000 * 300;
 uint64_t nPruneTarget = 0;
 // If the tip is older than this (in seconds), the node is considered to be in initial block download.
 int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE;
-bool ishush3 = strncmp(SMART_CHAIN_SYMBOL, "HUSH3",5) == 0 ? true : false;
+const bool ishush3 = strncmp(SMART_CHAIN_SYMBOL, "HUSH3",5) == 0 ? true : false;
 int32_t nFirstHalvingHeight = 340000;
 
 unsigned int expiryDelta = DEFAULT_TX_EXPIRY_DELTA;
@@ -6886,7 +6886,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         LogPrintf("dropmessagestest DROPPING RECV MESSAGE\n");
         return true;
     }
-    auto p2pdebug = GetArg("-p2pdebug",0);
+    const bool p2pdebug = GetArg("-p2pdebug",0);
 
     if(p2pdebug)
         fprintf(stderr,"%s: netmsg: %s from %s\n", __func__, strCommand.c_str(), pfrom->addr.ToString().c_str() );
@@ -6913,7 +6913,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         CAddress addrFrom;
         uint64_t nNonce = 1;
         int nVersion;           // use temporary for version, don't set version number until validated as connected
-        int minVersion = MIN_PEER_PROTO_VERSION;
+        const int minVersion = ishush3 ? MIN_HUSH_PEER_PROTO_VERSION : MIN_PEER_PROTO_VERSION;
         vRecv >> nVersion >> pfrom->nServices >> nTime >> addrMe;
         if (nVersion == 10300)
             nVersion = 300;

src/version.h

@@ -26,8 +26,13 @@ static const int PROTOCOL_VERSION = 1987426;
 static const int INIT_PROTO_VERSION = 209;
 //! In this version, 'getheaders' was introduced.
 static const int GETHEADERS_VERSION = 31800;
-//! disconnect from peers older than this proto version
+
+//! disconnect from peers older than this proto version (HUSH mainnet)
+static const int MIN_HUSH_PEER_PROTO_VERSION = 1987426;
+
+//! disconnect from peers older than this proto version (HACs)
 static const int MIN_PEER_PROTO_VERSION = 1987420;
+
 //! nTime field added to CAddress, starting with this version;
 //! if possible, avoid requesting addresses nodes older than this
 static const int CADDR_TIME_VERSION = 31402;