net: take the first 4 random bits from CJDNS addresses in GetGroup()

CJDNS addresses start with constant 8 bits, so in order to account for
the first 4 random ones, we must take the first 12. Otherwise the entire
CJDNS network will belong to one group.

Author: vasild

src/netaddress.cpp

@@ -794,8 +794,14 @@ std::vector<unsigned char> CNetAddr::GetGroup(const std::vector<bool> &asmap) co
         vchRet.push_back((ipv4 >> 24) & 0xFF);
         vchRet.push_back((ipv4 >> 16) & 0xFF);
         return vchRet;
-    } else if (IsTor() || IsI2P() || IsCJDNS()) {
+    } else if (IsTor() || IsI2P()) {
         nBits = 4;
+    } else if (IsCJDNS()) {
+        // Treat in the same way as Tor and I2P because the address in all of
+        // them is "random" bytes (derived from a public key). However in CJDNS
+        // the first byte is a constant 0xfc, so the random bytes come after it.
+        // Thus skip the constant 8 bits at the start.
+        nBits = 12;
     } else if (IsHeNet()) {
         // for he.net, use /36 groups
         nBits = 36;