Add 'mempool' P2P command, and extend 'getdata' behavior

to permit downloading of mempool transactions from the remote peer.

src/main.cpp

@@ -2562,7 +2562,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
     {
         vector<CInv> vInv;
         vRecv >> vInv;
-        if (vInv.size() > 50000)
+        if (vInv.size() > MAX_INV_SZ)
         {
             pfrom->Misbehaving(20);
             return error("message inv size() = %d", vInv.size());
@@ -2613,7 +2613,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
     {
         vector<CInv> vInv;
         vRecv >> vInv;
-        if (vInv.size() > 50000)
+        if (vInv.size() > MAX_INV_SZ)
         {
             pfrom->Misbehaving(20);
             return error("message getdata size() = %d", vInv.size());
@@ -2655,11 +2655,24 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
             else if (inv.IsKnownType())
             {
                 // Send stream from relay memory
+                bool pushed = false;
                 {
                     LOCK(cs_mapRelay);
                     map<CInv, CDataStream>::iterator mi = mapRelay.find(inv);
-                    if (mi != mapRelay.end())
+                    if (mi != mapRelay.end()) {
                         pfrom->PushMessage(inv.GetCommand(), (*mi).second);
+                        pushed = true;
+                    }
+                }
+                if (!pushed && inv.type == MSG_TX) {
+                    LOCK(mempool.cs);
+                    if (mempool.exists(inv.hash)) {
+                        CTransaction tx = mempool.lookup(inv.hash);
+                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
+                        ss.reserve(1000);
+                        ss << tx;
+                        pfrom->PushMessage("tx", ss);
+                    }
                 }
             }
 
@@ -2834,6 +2847,22 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
     }
 
 
+    else if (strCommand == "mempool")
+    {
+        std::vector<uint256> vtxid;
+        mempool.queryHashes(vtxid);
+        vector<CInv> vInv;
+        for (unsigned int i = 0; i < vtxid.size(); i++) {
+            CInv inv(MSG_TX, vtxid[i]);
+            vInv.push_back(inv);
+            if (i == (MAX_INV_SZ - 1))
+                    break;
+        }
+        if (vInv.size() > 0)
+            pfrom->PushMessage("inv", vInv);
+    }
+
+
     else if (strCommand == "checkorder")
     {
         uint256 hashReply;

src/main.h

@@ -27,6 +27,7 @@ static const unsigned int MAX_BLOCK_SIZE = 1000000;
 static const unsigned int MAX_BLOCK_SIZE_GEN = MAX_BLOCK_SIZE/2;
 static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
 static const unsigned int MAX_ORPHAN_TRANSACTIONS = MAX_BLOCK_SIZE/100;
+static const unsigned int MAX_INV_SZ = 50000;
 static const int64 MIN_TX_FEE = 50000;
 static const int64 MIN_RELAY_TX_FEE = 10000;
 static const int64 MAX_MONEY = 21000000 * COIN;

src/version.h

@@ -30,7 +30,7 @@ extern const std::string CLIENT_DATE;
 // network protocol versioning
 //
 
-static const int PROTOCOL_VERSION = 60001;
+static const int PROTOCOL_VERSION = 60002;
 
 // earlier versions not supported as of Feb 2012, and are disconnected
 static const int MIN_PROTO_VERSION = 209;
@@ -46,4 +46,7 @@ static const int NOBLKS_VERSION_END = 32400;
 // BIP 0031, pong message, is enabled for all versions AFTER this one
 static const int BIP0031_VERSION = 60000;
 
+// "mempool" command, enhanced "getdata" behavior starts with this version:
+static const int MEMPOOL_GD_VERSION = 60002;
+
 #endif