Use SipHash-2-4 for address relay selection

Author: sipa

src/main.cpp

@@ -4698,25 +4698,23 @@ 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 addrKnowns of the chosen nodes prevent repeats
-                    static uint256 hashSalt;
-                    if (hashSalt.IsNull())
-                        hashSalt = GetRandHash();
+                    static uint64_t salt0 = 0, salt1 = 0;
+                    while (salt0 == 0 && salt1 == 0) {
+                        GetRandBytes((unsigned char*)&salt0, sizeof(salt0));
+                        GetRandBytes((unsigned char*)&salt1, sizeof(salt1));
+                    }
                     uint64_t hashAddr = addr.GetHash();
-                    uint256 hashRand = ArithToUint256(UintToArith256(hashSalt) ^ (hashAddr<<32) ^ ((GetTime()+hashAddr)/(24*60*60)));
-                    hashRand = Hash(BEGIN(hashRand), END(hashRand));
-                    multimap<uint256, CNode*> mapMix;
+                    multimap<uint64_t, CNode*> mapMix;
+                    const CSipHasher hasher = CSipHasher(salt0, salt1).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24*60*60));
                     BOOST_FOREACH(CNode* pnode, vNodes)
                     {
                         if (pnode->nVersion < CADDR_TIME_VERSION)
                             continue;
-                        unsigned int nPointer;
-                        memcpy(&nPointer, &pnode, sizeof(nPointer));
-                        uint256 hashKey = ArithToUint256(UintToArith256(hashRand) ^ nPointer);
-                        hashKey = Hash(BEGIN(hashKey), END(hashKey));
+                        uint64_t hashKey = CSipHasher(hasher).Write(pnode->id).Finalize();
                         mapMix.insert(make_pair(hashKey, pnode));
                     }
                     int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
-                    for (multimap<uint256, CNode*>::iterator mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
+                    for (multimap<uint64_t, CNode*>::iterator mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
                         ((*mi).second)->PushAddress(addr);
                 }
             }