Replace mruset setAddrKnown with CRollingBloomFilter addrKnown

Use a probabilistic bloom filter to keep track of which addresses
we think we have given our peers, instead of a list.

This uses much less memory, at the cost of sometimes failing to
relay an address to a peer-- worst case if the bloom filter happens
to be as full as it gets, 1-in-1,000.

Measured memory usage of a full mruset setAddrKnown: 650Kbytes
Constant memory usage of CRollingBloomFilter addrKnown: 37Kbytes.

This will also help heap fragmentation, because the 37K of storage
is allocated when a CNode is created (when a connection to a peer
is established) and then there is no per-item-remembered memory
allocation.

I plan on testing by restarting a full node with an empty peers.dat,
running a while with -debug=addrman and -debug=net, and making sure
that the 'addr' message traffic out is reasonable.
(suggestions for better tests welcome)

src/main.cpp

@@ -3995,7 +3995,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 {
                     LOCK(cs_vNodes);
                     // Use deterministic randomness to send to the same nodes for 24 hours
-                    // at a time so the setAddrKnowns of the chosen nodes prevent repeats
+                    // at a time so the addrKnowns of the chosen nodes prevent repeats
                     static uint256 hashSalt;
                     if (hashSalt.IsNull())
                         hashSalt = GetRandHash();
@@ -4779,9 +4779,9 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
             LOCK(cs_vNodes);
             BOOST_FOREACH(CNode* pnode, vNodes)
             {
-                // Periodically clear setAddrKnown to allow refresh broadcasts
+                // Periodically clear addrKnown to allow refresh broadcasts
                 if (nLastRebroadcast)
-                    pnode->setAddrKnown.clear();
+                    pnode->addrKnown.clear();
 
                 // Rebroadcast our address
                 AdvertizeLocal(pnode);
@@ -4799,9 +4799,9 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
             vAddr.reserve(pto->vAddrToSend.size());
             BOOST_FOREACH(const CAddress& addr, pto->vAddrToSend)
             {
-                // returns true if wasn't already contained in the set
-                if (pto->setAddrKnown.insert(addr).second)
+                if (!pto->addrKnown.contains(addr.GetKey()))
                 {
+                    pto->addrKnown.insert(addr.GetKey());
                     vAddr.push_back(addr);
                     // receiver rejects addr messages larger than 1000
                     if (vAddr.size() >= 1000)

src/net.cpp

@@ -1905,7 +1905,7 @@ bool CAddrDB::Read(CAddrMan& addr)
 unsigned int ReceiveFloodSize() { return 1000*GetArg("-maxreceivebuffer", 5*1000); }
 unsigned int SendBufferSize() { return 1000*GetArg("-maxsendbuffer", 1*1000); }
 
-CNode::CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn, bool fInboundIn) : ssSend(SER_NETWORK, INIT_PROTO_VERSION), setAddrKnown(5000)
+CNode::CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn, bool fInboundIn) : ssSend(SER_NETWORK, INIT_PROTO_VERSION), addrKnown(5000, 0.001, insecure_rand())
 {
     nServices = 0;
     hSocket = hSocketIn;

src/net.h

@@ -300,7 +300,7 @@ public:
 
     // flood relay
     std::vector<CAddress> vAddrToSend;
-    mruset<CAddress> setAddrKnown;
+    CRollingBloomFilter addrKnown;
     bool fGetAddr;
     std::set<uint256> setKnown;
 
@@ -380,7 +380,7 @@ public:
 
     void AddAddressKnown(const CAddress& addr)
     {
-        setAddrKnown.insert(addr);
+        addrKnown.insert(addr.GetKey());
     }
 
     void PushAddress(const CAddress& addr)
@@ -388,7 +388,7 @@ public:
         // Known checking here is only to save space from duplicates.
         // SendMessages will filter it again for knowns that were added
         // after addresses were pushed.
-        if (addr.IsValid() && !setAddrKnown.count(addr)) {
+        if (addr.IsValid() && !addrKnown.contains(addr.GetKey())) {
             if (vAddrToSend.size() >= MAX_ADDR_TO_SEND) {
                 vAddrToSend[insecure_rand() % vAddrToSend.size()] = addr;
             } else {