Merge pull request #7079

ebb25f4 Limit setAskFor and retire requested entries only when a getdata returns. (Gregory Maxwell)
5029698 prevent peer flooding request queue for an inv (kazcw)

Author: laanwj

src/main.cpp

@@ -4675,6 +4675,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         bool fMissingInputs = false;
         CValidationState state;
 
+        pfrom->setAskFor.erase(inv.hash);
         mapAlreadyAskedFor.erase(inv);
 
         if (!AlreadyHave(inv) && AcceptToMemoryPool(mempool, state, tx, true, &fMissingInputs))
@@ -5623,6 +5624,9 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
                     pto->PushMessage("getdata", vGetData);
                     vGetData.clear();
                 }
+            } else {
+                //If we're not going to ask, don't expect a response.
+                pto->setAskFor.erase(inv.hash);
             }
             pto->mapAskFor.erase(pto->mapAskFor.begin());
         }

src/net.cpp

@@ -2407,8 +2407,12 @@ CNode::~CNode()
 
 void CNode::AskFor(const CInv& inv)
 {
-    if (mapAskFor.size() > MAPASKFOR_MAX_SZ)
+    if (mapAskFor.size() > MAPASKFOR_MAX_SZ || setAskFor.size() > SETASKFOR_MAX_SZ)
         return;
+    // a peer may not have multiple non-responded queue positions for a single inv item
+    if (!setAskFor.insert(inv.hash).second)
+        return;
+
     // We're using mapAskFor as a priority queue,
     // the key is the earliest time the request can be sent
     int64_t nRequestTime;

src/net.h

@@ -58,6 +58,8 @@ static const bool DEFAULT_UPNP = false;
 #endif
 /** The maximum number of entries in mapAskFor */
 static const size_t MAPASKFOR_MAX_SZ = MAX_INV_SZ;
+/** The maximum number of entries in setAskFor (larger due to getdata latency)*/
+static const size_t SETASKFOR_MAX_SZ = 2 * MAX_INV_SZ;
 /** The maximum number of peer connections to maintain. */
 static const unsigned int DEFAULT_MAX_PEER_CONNECTIONS = 125;
 /** The default for -maxuploadtarget. 0 = Unlimited */
@@ -389,6 +391,7 @@ class CNode
     mruset<CInv> setInventoryKnown;
     std::vector<CInv> vInventoryToSend;
     CCriticalSection cs_inventory;
+    std::set<uint256> setAskFor;
     std::multimap<int64_t, CInv> mapAskFor;
     // Used for headers announcements - unfiltered blocks to relay
     // Also protected by cs_inventory