hack to support bootstraping with non standard ports using dns seeder

src/net.cpp

@@ -1219,6 +1219,29 @@ void _ThreadDNSAddressSeed(const char *strDNS)
                     vAdd.push_back(addr);
                     found++;
                 }
+                
+                // non std ports hack: see twister-seeder
+                string nonStdHost = "nonstd." + seed.host;
+                if (LookupHost(nonStdHost.c_str(), vIPs))
+                {
+                    BOOST_FOREACH(CNetAddr& ip, vIPs)
+                    {
+                        unsigned short crcAddr = ip.crc16();
+                        
+                        BOOST_FOREACH(CNetAddr& ipPort, vIPs)
+                        {
+                            if( ipPort.GetByte(3) == (crcAddr >> 8) &&
+                                ipPort.GetByte(2) == (crcAddr & 0xff) ) {
+                                int port = (ipPort.GetByte(1) << 8) + ipPort.GetByte(0);
+                                int nOneDay = 24*3600;
+                                CAddress addr = CAddress(CService(ip, port));
+                                addr.nTime = GetTime() - 3*nOneDay - GetRand(4*nOneDay); // use a random age between 3 and 7 days old
+                                vAdd.push_back(addr);
+                                found++;
+                            }
+                        }
+                    }
+                }
             }
             addrman.Add(vAdd, CNetAddr(seed.name, true));
         }

src/netbase.cpp

@@ -894,6 +894,21 @@ uint64 CNetAddr::GetHash() const
     return nRet;
 }
 
+unsigned short CNetAddr::crc16() const
+{
+    unsigned char x;
+    unsigned short crc = 0xFFFF;
+    const unsigned char* data_p = IsIPv4() ? &ip[12] : &ip[0];
+    unsigned char length = IsIPv4() ? 4 : 16;
+
+    while (length--){
+        x = crc >> 8 ^ *data_p++;
+        x ^= x>>4;
+        crc = (crc << 8) ^ ((unsigned short)(x << 12)) ^ ((unsigned short)(x <<5)) ^ ((unsigned short)x);
+    }
+    return crc;
+}
+
 void CNetAddr::print() const
 {
     printf("CNetAddr(%s)\n", ToString().c_str());

src/netbase.h

@@ -66,6 +66,7 @@ class CNetAddr
         std::string ToStringIP() const;
         unsigned int GetByte(int n) const;
         uint64 GetHash() const;
+        unsigned short crc16() const;
         bool GetInAddr(struct in_addr* pipv4Addr) const;
         std::vector<unsigned char> GetGroup() const;
         int GetReachabilityFrom(const CNetAddr *paddrPartner = NULL) const;