P2P: parse network datastream into header/data components in socket thread

Replaces CNode::vRecv buffer with a vector of CNetMessage's.  This simplifies
ProcessMessages() and eliminates several redundant data copies.

Overview:

* socket thread now parses incoming message datastream into
  header/data components, as encapsulated by CNetMessage
* socket thread adds each CNetMessage to a vector inside CNode
* message thread (ProcessMessages) iterates through CNode's CNetMessage vector

Message parsing is made more strict:

* Socket is disconnected, if message larger than MAX_SIZE
  or if CMessageHeader deserialization fails (latter is impossible?).
  Previously, code would simply eat garbage data all day long.
* Socket is disconnected, if we fail to find pchMessageStart.
  We do not search through garbage, to find pchMessageStart.  Each
  message must begin precisely after the last message ends.

ProcessMessages() always processes a complete message, and is more efficient:

* buffer is always precisely sized, using CDataStream::resize(),
  rather than progressively sized in 64k chunks.  More efficient
  for large messages like "block".
* whole-buffer memory copy eliminated (vRecv -> vMsg)
* other buffer-shifting memory copies eliminated (vRecv.insert, vRecv.erase)

src/main.cpp

@@ -3168,7 +3168,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
 
     else if (strCommand == "verack")
     {
-        pfrom->vRecv.SetVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
+        pfrom->SetRecvVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
     }
 
 
@@ -3705,13 +3705,13 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
     return true;
 }
 
+// requires LOCK(cs_vRecvMsg)
 bool ProcessMessages(CNode* pfrom)
 {
-    CDataStream& vRecv = pfrom->vRecv;
-    if (vRecv.empty())
+    if (pfrom->vRecvMsg.empty())
         return true;
     //if (fDebug)
-    //    printf("ProcessMessages(%u bytes)\n", vRecv.size());
+    //    printf("ProcessMessages(%zu messages)\n", pfrom->vRecvMsg.size());
 
     //
     // Message format
@@ -3722,32 +3722,32 @@ bool ProcessMessages(CNode* pfrom)
     //  (x) data
     //
 
-    loop
+    unsigned int nMsgPos = 0;
+    for (; nMsgPos < pfrom->vRecvMsg.size(); nMsgPos++)
     {
         // Don't bother if send buffer is too full to respond anyway
         if (pfrom->vSend.size() >= SendBufferSize())
             break;
 
-        // Scan for message start
-        CDataStream::iterator pstart = search(vRecv.begin(), vRecv.end(), BEGIN(pchMessageStart), END(pchMessageStart));
-        int nHeaderSize = vRecv.GetSerializeSize(CMessageHeader());
-        if (vRecv.end() - pstart < nHeaderSize)
-        {
-            if ((int)vRecv.size() > nHeaderSize)
-            {
-                printf("\n\nPROCESSMESSAGE MESSAGESTART NOT FOUND\n\n");
-                vRecv.erase(vRecv.begin(), vRecv.end() - nHeaderSize);
-            }
+        // get next message; end, if an incomplete message is found
+        CNetMessage& msg = pfrom->vRecvMsg[nMsgPos];
+
+        //if (fDebug)
+        //    printf("ProcessMessages(message %u msgsz, %zu bytes, complete:%s)\n",
+        //            msg.hdr.nMessageSize, msg.vRecv.size(),
+        //            msg.complete() ? "Y" : "N");
+
+        if (!msg.complete())
             break;
+
+        // Scan for message start
+        if (memcmp(msg.hdr.pchMessageStart, pchMessageStart, sizeof(pchMessageStart)) != 0) {
+            printf("\n\nPROCESSMESSAGE: INVALID MESSAGESTART\n\n");
+            return false;
         }
-        if (pstart - vRecv.begin() > 0)
-            printf("\n\nPROCESSMESSAGE SKIPPED %"PRIpdd" BYTES\n\n", pstart - vRecv.begin());
-        vRecv.erase(vRecv.begin(), pstart);
 
         // Read header
-        vector<char> vHeaderSave(vRecv.begin(), vRecv.begin() + nHeaderSize);
-        CMessageHeader hdr;
-        vRecv >> hdr;
+        CMessageHeader& hdr = msg.hdr;
         if (!hdr.IsValid())
         {
             printf("\n\nPROCESSMESSAGE: ERRORS IN HEADER %s\n\n\n", hdr.GetCommand().c_str());
@@ -3757,19 +3757,9 @@ bool ProcessMessages(CNode* pfrom)
 
         // Message size
         unsigned int nMessageSize = hdr.nMessageSize;
-        if (nMessageSize > MAX_SIZE)
-        {
-            printf("ProcessMessages(%s, %u bytes) : nMessageSize > MAX_SIZE\n", strCommand.c_str(), nMessageSize);
-            continue;
-        }
-        if (nMessageSize > vRecv.size())
-        {
-            // Rewind and wait for rest of message
-            vRecv.insert(vRecv.begin(), vHeaderSave.begin(), vHeaderSave.end());
-            break;
-        }
 
         // Checksum
+        CDataStream& vRecv = msg.vRecv;
         uint256 hash = Hash(vRecv.begin(), vRecv.begin() + nMessageSize);
         unsigned int nChecksum = 0;
         memcpy(&nChecksum, &hash, sizeof(nChecksum));
@@ -3780,17 +3770,13 @@ bool ProcessMessages(CNode* pfrom)
             continue;
         }
 
-        // Copy message to its own buffer
-        CDataStream vMsg(vRecv.begin(), vRecv.begin() + nMessageSize, vRecv.nType, vRecv.nVersion);
-        vRecv.ignore(nMessageSize);
-
         // Process message
         bool fRet = false;
         try
         {
             {
                 LOCK(cs_main);
-                fRet = ProcessMessage(pfrom, strCommand, vMsg);
+                fRet = ProcessMessage(pfrom, strCommand, vRecv);
             }
             if (fShutdown)
                 return true;
@@ -3822,7 +3808,10 @@ bool ProcessMessages(CNode* pfrom)
             printf("ProcessMessage(%s, %u bytes) FAILED\n", strCommand.c_str(), nMessageSize);
     }
 
-    vRecv.Compact();
+    // remove processed messages; one incomplete message may remain
+    if (nMsgPos > 0)
+        pfrom->vRecvMsg.erase(pfrom->vRecvMsg.begin(),
+                              pfrom->vRecvMsg.begin() + nMsgPos);
     return true;
 }
 

src/net.cpp

@@ -536,7 +536,7 @@ void CNode::CloseSocketDisconnect()
         printf("disconnecting node %s\n", addrName.c_str());
         closesocket(hSocket);
         hSocket = INVALID_SOCKET;
-        vRecv.clear();
+        vRecvMsg.clear();
     }
 }
 
@@ -628,6 +628,78 @@ void CNode::copyStats(CNodeStats &stats)
 }
 #undef X
 
+// requires LOCK(cs_vRecvMsg)
+bool CNode::ReceiveMsgBytes(const char *pch, unsigned int nBytes)
+{
+    while (nBytes > 0) {
+
+        // get current incomplete message, or create a new one
+        if (vRecvMsg.size() == 0 ||
+            vRecvMsg.back().complete())
+            vRecvMsg.push_back(CNetMessage(SER_NETWORK, nRecvVersion));
+
+        CNetMessage& msg = vRecvMsg.back();
+
+        // absorb network data
+        int handled;
+        if (!msg.in_data)
+            handled = msg.readHeader(pch, nBytes);
+        else
+            handled = msg.readData(pch, nBytes);
+
+        if (handled < 0)
+                return false;
+
+        pch += handled;
+        nBytes -= handled;
+    }
+
+    return true;
+}
+
+int CNetMessage::readHeader(const char *pch, unsigned int nBytes)
+{
+    // copy data to temporary parsing buffer
+    unsigned int nRemaining = 24 - nHdrPos;
+    unsigned int nCopy = std::min(nRemaining, nBytes);
+
+    memcpy(&hdrbuf[nHdrPos], pch, nCopy);
+    nHdrPos += nCopy;
+
+    // if header incomplete, exit
+    if (nHdrPos < 24)
+        return nCopy;
+
+    // deserialize to CMessageHeader
+    try {
+        hdrbuf >> hdr;
+    }
+    catch (std::exception &e) {
+        return -1;
+    }
+
+    // reject messages larger than MAX_SIZE
+    if (hdr.nMessageSize > MAX_SIZE)
+            return -1;
+
+    // switch state to reading message data
+    in_data = true;
+    vRecv.resize(hdr.nMessageSize);
+
+    return nCopy;
+}
+
+int CNetMessage::readData(const char *pch, unsigned int nBytes)
+{
+    unsigned int nRemaining = hdr.nMessageSize - nDataPos;
+    unsigned int nCopy = std::min(nRemaining, nBytes);
+
+    memcpy(&vRecv[nDataPos], pch, nCopy);
+    nDataPos += nCopy;
+
+    return nCopy;
+}
+
 
 
 
@@ -676,7 +748,7 @@ void ThreadSocketHandler2(void* parg)
             BOOST_FOREACH(CNode* pnode, vNodesCopy)
             {
                 if (pnode->fDisconnect ||
-                    (pnode->GetRefCount() <= 0 && pnode->vRecv.empty() && pnode->vSend.empty()))
+                    (pnode->GetRefCount() <= 0 && pnode->vRecvMsg.empty() && pnode->vSend.empty()))
                 {
                     // remove from vNodes
                     vNodes.erase(remove(vNodes.begin(), vNodes.end(), pnode), vNodes.end());
@@ -708,7 +780,7 @@ void ThreadSocketHandler2(void* parg)
                         TRY_LOCK(pnode->cs_vSend, lockSend);
                         if (lockSend)
                         {
-                            TRY_LOCK(pnode->cs_vRecv, lockRecv);
+                            TRY_LOCK(pnode->cs_vRecvMsg, lockRecv);
                             if (lockRecv)
                             {
                                 TRY_LOCK(pnode->cs_inventory, lockInv);
@@ -873,15 +945,12 @@ void ThreadSocketHandler2(void* parg)
                 continue;
             if (FD_ISSET(pnode->hSocket, &fdsetRecv) || FD_ISSET(pnode->hSocket, &fdsetError))
             {
-                TRY_LOCK(pnode->cs_vRecv, lockRecv);
+                TRY_LOCK(pnode->cs_vRecvMsg, lockRecv);
                 if (lockRecv)
                 {
-                    CDataStream& vRecv = pnode->vRecv;
-                    unsigned int nPos = vRecv.size();
-
-                    if (nPos > ReceiveBufferSize()) {
+                    if (pnode->GetTotalRecvSize() > ReceiveFloodSize()) {
                         if (!pnode->fDisconnect)
-                            printf("socket recv flood control disconnect (%"PRIszu" bytes)\n", vRecv.size());
+                            printf("socket recv flood control disconnect (%u bytes)\n", pnode->GetTotalRecvSize());
                         pnode->CloseSocketDisconnect();
                     }
                     else {
@@ -890,8 +959,8 @@ void ThreadSocketHandler2(void* parg)
                         int nBytes = recv(pnode->hSocket, pchBuf, sizeof(pchBuf), MSG_DONTWAIT);
                         if (nBytes > 0)
                         {
-                            vRecv.resize(nPos + nBytes);
-                            memcpy(&vRecv[nPos], pchBuf, nBytes);
+                            if (!pnode->ReceiveMsgBytes(pchBuf, nBytes))
+                                pnode->CloseSocketDisconnect();
                             pnode->nLastRecv = GetTime();
                         }
                         else if (nBytes == 0)
@@ -1693,9 +1762,10 @@ void ThreadMessageHandler2(void* parg)
         {
             // Receive messages
             {
-                TRY_LOCK(pnode->cs_vRecv, lockRecv);
+                TRY_LOCK(pnode->cs_vRecvMsg, lockRecv);
                 if (lockRecv)
-                    ProcessMessages(pnode);
+                    if (!ProcessMessages(pnode))
+                        pnode->CloseSocketDisconnect();
             }
             if (fShutdown)
                 return;

src/net.h

@@ -27,7 +27,7 @@ extern int nBestHeight;
 
 
 
-inline unsigned int ReceiveBufferSize() { return 1000*GetArg("-maxreceivebuffer", 5*1000); }
+inline unsigned int ReceiveFloodSize() { return 1000*GetArg("-maxreceivebuffer", 5*1000); }
 inline unsigned int SendBufferSize() { return 1000*GetArg("-maxsendbuffer", 1*1000); }
 
 void AddOneShot(std::string strDest);
@@ -126,6 +126,44 @@ public:
 
 
 
+class CNetMessage {
+public:
+    bool in_data;                   // parsing header (false) or data (true)
+
+    CDataStream hdrbuf;             // partially received header
+    CMessageHeader hdr;             // complete header
+    unsigned int nHdrPos;
+
+    CDataStream vRecv;              // received message data
+    unsigned int nDataPos;
+
+    CNetMessage(int nTypeIn, int nVersionIn) : hdrbuf(nTypeIn, nVersionIn), vRecv(nTypeIn, nVersionIn) {
+        hdrbuf.resize(24);
+        in_data = false;
+        nHdrPos = 0;
+        nDataPos = 0;
+    }
+
+    bool complete() const
+    {
+        if (!in_data)
+            return false;
+        return (hdr.nMessageSize == nDataPos);
+    }
+
+    void SetVersion(int nVersionIn)
+    {
+        hdrbuf.SetVersion(nVersionIn);
+        vRecv.SetVersion(nVersionIn);
+    }
+
+    int readHeader(const char *pch, unsigned int nBytes);
+    int readData(const char *pch, unsigned int nBytes);
+};
+
+
+
+
 
 /** Information about a peer */
 class CNode
@@ -135,9 +173,12 @@ public:
     uint64 nServices;
     SOCKET hSocket;
     CDataStream vSend;
-    CDataStream vRecv;
     CCriticalSection cs_vSend;
-    CCriticalSection cs_vRecv;
+
+    std::vector<CNetMessage> vRecvMsg;
+    CCriticalSection cs_vRecvMsg;
+    int nRecvVersion;
+
     int64 nLastSend;
     int64 nLastRecv;
     int64 nLastSendEmpty;
@@ -191,10 +232,11 @@ public:
     CCriticalSection cs_inventory;
     std::multimap<int64, CInv> mapAskFor;
 
-    CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn = "", bool fInboundIn=false) : vSend(SER_NETWORK, MIN_PROTO_VERSION), vRecv(SER_NETWORK, MIN_PROTO_VERSION)
+    CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn = "", bool fInboundIn=false) : vSend(SER_NETWORK, MIN_PROTO_VERSION)
     {
         nServices = 0;
         hSocket = hSocketIn;
+        nRecvVersion = MIN_PROTO_VERSION;
         nLastSend = 0;
         nLastRecv = 0;
         nLastSendEmpty = GetTime();
@@ -250,6 +292,26 @@ public:
         return std::max(nRefCount, 0) + (GetTime() < nReleaseTime ? 1 : 0);
     }
 
+    // requires LOCK(cs_vRecvMsg)
+    unsigned int GetTotalRecvSize()
+    {
+        unsigned int total = 0;
+        for (unsigned int i = 0; i < vRecvMsg.size(); i++)
+            total += vRecvMsg[i].vRecv.size();
+        return total;
+    }
+
+    // requires LOCK(cs_vRecvMsg)
+    bool ReceiveMsgBytes(const char *pch, unsigned int nBytes);
+
+    // requires LOCK(cs_vRecvMsg)
+    void SetRecvVersion(int nVersionIn)
+    {
+        nRecvVersion = nVersionIn;
+        for (unsigned int i = 0; i < vRecvMsg.size(); i++)
+            vRecvMsg[i].SetVersion(nVersionIn);
+    }
+
     CNode* AddRef(int64 nTimeout=0)
     {
         if (nTimeout != 0)