Merge #13946: p2p: Clarify control flow in ProcessMessage

fa6c3dea42 p2p: Clarify control flow in ProcessMessage() (MarcoFalke)

Pull request description:

  `ProcessMessage` is effectively a massive switch case construct. In the past there were attempts to clarify the control flow in `ProcessMessage()` by moving each case into a separate static function (see #9608). It was closed because it wasn't clear if moving each case into a function was the right approach.
  Though, we can quasi treat each case as a function by adding a return statement to each case. (Can be seen as a continuation of bugfix #13162)

  This patch does exactly that.

  Also note that this patch is a subset of previous approaches such as #9608 and #10145.

  Review suggestion: `git diff HEAD~ --function-context`

Tree-SHA512: 91f6106840de2f29bb4f10d27bae0616b03a91126e6c6013479e1dd79bee53f22a78902b631fe85517dd5dc0fa7239939b4fefc231851a13c819458559f6c201

src/net_processing.cpp

@@ -1618,8 +1618,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         return true;
     }
 
-    else if (strCommand == NetMsgType::VERSION)
+    if (strCommand == NetMsgType::VERSION) {
-    {
         // Each connection can only send one version message
         if (pfrom->nVersion != 0)
         {
@@ -1793,9 +1792,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         return true;
     }
 
-
+    if (pfrom->nVersion == 0) {
-    else if (pfrom->nVersion == 0)
-    {
         // Must have a version message before anything else
         LOCK(cs_main);
         Misbehaving(pfrom->GetId(), 1);
@@ -1839,18 +1836,17 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
         }
         pfrom->fSuccessfullyConnected = true;
+        return true;
     }
 
-    else if (!pfrom->fSuccessfullyConnected)
+    if (!pfrom->fSuccessfullyConnected) {
-    {
         // Must have a verack message before anything else
         LOCK(cs_main);
         Misbehaving(pfrom->GetId(), 1);
         return false;
     }
 
-    else if (strCommand == NetMsgType::ADDR)
+    if (strCommand == NetMsgType::ADDR) {
-    {
         std::vector<CAddress> vAddr;
         vRecv >> vAddr;
 
@@ -1897,16 +1893,16 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             pfrom->fGetAddr = false;
         if (pfrom->fOneShot)
             pfrom->fDisconnect = true;
+        return true;
     }
 
-    else if (strCommand == NetMsgType::SENDHEADERS)
+    if (strCommand == NetMsgType::SENDHEADERS) {
-    {
         LOCK(cs_main);
         State(pfrom->GetId())->fPreferHeaders = true;
+        return true;
     }
 
-    else if (strCommand == NetMsgType::SENDCMPCT)
+    if (strCommand == NetMsgType::SENDCMPCT) {
-    {
         bool fAnnounceUsingCMPCTBLOCK = false;
         uint64_t nCMPCTBLOCKVersion = 0;
         vRecv >> fAnnounceUsingCMPCTBLOCK >> nCMPCTBLOCKVersion;
@@ -1926,11 +1922,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                     State(pfrom->GetId())->fSupportsDesiredCmpctVersion = (nCMPCTBLOCKVersion == 1);
             }
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::INV) {
-    else if (strCommand == NetMsgType::INV)
-    {
         std::vector<CInv> vInv;
         vRecv >> vInv;
         if (vInv.size() > MAX_INV_SZ)
@@ -1984,11 +1979,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 }
             }
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::GETDATA) {
-    else if (strCommand == NetMsgType::GETDATA)
-    {
         std::vector<CInv> vInv;
         vRecv >> vInv;
         if (vInv.size() > MAX_INV_SZ)
@@ -2006,11 +2000,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
 
         pfrom->vRecvGetData.insert(pfrom->vRecvGetData.end(), vInv.begin(), vInv.end());
         ProcessGetData(pfrom, chainparams, connman, interruptMsgProc);
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::GETBLOCKS) {
-    else if (strCommand == NetMsgType::GETBLOCKS)
-    {
         CBlockLocator locator;
         uint256 hashStop;
         vRecv >> locator >> hashStop;
@@ -2075,11 +2068,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 break;
             }
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::GETBLOCKTXN) {
-    else if (strCommand == NetMsgType::GETBLOCKTXN)
-    {
         BlockTransactionsRequest req;
         vRecv >> req;
 
@@ -2125,11 +2117,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         assert(ret);
 
         SendBlockTransactions(block, req, pfrom, connman);
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::GETHEADERS) {
-    else if (strCommand == NetMsgType::GETHEADERS)
-    {
         CBlockLocator locator;
         uint256 hashStop;
         vRecv >> locator >> hashStop;
@@ -2193,11 +2184,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         // in the SendMessages logic.
         nodestate->pindexBestHeaderSent = pindex ? pindex : chainActive.Tip();
         connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::TX) {
-    else if (strCommand == NetMsgType::TX)
-    {
         // Stop processing the transaction early if
         // We are in blocks only mode and peer is either not whitelisted or whitelistrelay is off
         if (!fRelayTxes && (!pfrom->fWhitelisted || !gArgs.GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY)))
@@ -2381,10 +2371,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 Misbehaving(pfrom->GetId(), nDoS);
             }
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::CMPCTBLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
-    else if (strCommand == NetMsgType::CMPCTBLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
     {
         CBlockHeaderAndShortTxIDs cmpctblock;
         vRecv >> cmpctblock;
@@ -2602,10 +2592,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 MarkBlockAsReceived(pblock->GetHash());
             }
         }
-
+        return true;
     }
 
-    else if (strCommand == NetMsgType::BLOCKTXN && !fImporting && !fReindex) // Ignore blocks received while importing
+    if (strCommand == NetMsgType::BLOCKTXN && !fImporting && !fReindex) // Ignore blocks received while importing
     {
         BlockTransactions resp;
         vRecv >> resp;
@@ -2677,10 +2667,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 mapBlockSource.erase(pblock->GetHash());
             }
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::HEADERS && !fImporting && !fReindex) // Ignore headers received while importing
-    else if (strCommand == NetMsgType::HEADERS && !fImporting && !fReindex) // Ignore headers received while importing
     {
         std::vector<CBlockHeader> headers;
 
@@ -2705,7 +2695,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         return ProcessHeadersMessage(pfrom, connman, headers, chainparams, should_punish);
     }
 
-    else if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
+    if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
     {
         std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
         vRecv >> *pblock;
@@ -2731,11 +2721,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             LOCK(cs_main);
             mapBlockSource.erase(pblock->GetHash());
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::GETADDR) {
-    else if (strCommand == NetMsgType::GETADDR)
-    {
         // This asymmetric behavior for inbound and outbound connections was introduced
         // to prevent a fingerprinting attack: an attacker can send specific fake addresses
         // to users' AddrMan and later request them by sending getaddr messages.
@@ -2759,11 +2748,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         FastRandomContext insecure_rand;
         for (const CAddress &addr : vAddr)
             pfrom->PushAddress(addr, insecure_rand);
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::MEMPOOL) {
-    else if (strCommand == NetMsgType::MEMPOOL)
-    {
         if (!(pfrom->GetLocalServices() & NODE_BLOOM) && !pfrom->fWhitelisted)
         {
             LogPrint(BCLog::NET, "mempool request with bloom filters disabled, disconnect peer=%d\n", pfrom->GetId());
@@ -2780,11 +2768,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
 
         LOCK(pfrom->cs_inventory);
         pfrom->fSendMempool = true;
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::PING) {
-    else if (strCommand == NetMsgType::PING)
-    {
         if (pfrom->nVersion > BIP0031_VERSION)
         {
             uint64_t nonce = 0;
@@ -2802,11 +2789,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             // return very quickly.
             connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::PONG, nonce));
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::PONG) {
-    else if (strCommand == NetMsgType::PONG)
-    {
         int64_t pingUsecEnd = nTimeReceived;
         uint64_t nonce = 0;
         size_t nAvail = vRecv.in_avail();
@@ -2859,11 +2845,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         if (bPingFinished) {
             pfrom->nPingNonceSent = 0;
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::FILTERLOAD) {
-    else if (strCommand == NetMsgType::FILTERLOAD)
-    {
         CBloomFilter filter;
         vRecv >> filter;
 
@@ -2880,11 +2865,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             pfrom->pfilter->UpdateEmptyFull();
             pfrom->fRelayTxes = true;
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::FILTERADD) {
-    else if (strCommand == NetMsgType::FILTERADD)
-    {
         std::vector<unsigned char> vData;
         vRecv >> vData;
 
@@ -2905,19 +2889,19 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 100);
         }
+        return true;
     }
 
-
+    if (strCommand == NetMsgType::FILTERCLEAR) {
-    else if (strCommand == NetMsgType::FILTERCLEAR)
-    {
         LOCK(pfrom->cs_filter);
         if (pfrom->GetLocalServices() & NODE_BLOOM) {
             pfrom->pfilter.reset(new CBloomFilter());
         }
         pfrom->fRelayTxes = true;
+        return true;
     }
 
-    else if (strCommand == NetMsgType::FEEFILTER) {
+    if (strCommand == NetMsgType::FEEFILTER) {
         CAmount newFeeFilter = 0;
         vRecv >> newFeeFilter;
         if (MoneyRange(newFeeFilter)) {
@@ -2927,20 +2911,17 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             }
             LogPrint(BCLog::NET, "received: feefilter of %s from peer=%d\n", CFeeRate(newFeeFilter).ToString(), pfrom->GetId());
         }
+        return true;
     }
 
-    else if (strCommand == NetMsgType::NOTFOUND) {
+    if (strCommand == NetMsgType::NOTFOUND) {
         // We do not care about the NOTFOUND message, but logging an Unknown Command
         // message would be undesirable as we transmit it ourselves.
+        return true;
     }
 
-    else {
     // Ignore unknown commands for extensibility
     LogPrint(BCLog::NET, "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->GetId());
-    }
-
-
-
     return true;
 }