WIP p2p privacy

src/net.cpp

@@ -190,6 +190,16 @@ bool GetLocal(CService& addr, const CNode& peer)
         LOCK(cs_mapLocalHost);
         for (map<CNetAddr, LocalServiceInfo>::iterator it = mapLocalHost.begin(); it != mapLocalHost.end(); it++)
         {
+            // For privacy reasons, don't advertise our privacy-network address
+            // to other networks and don't advertise our other-network address
+            // to privacy networks.
+            const Network our_net{(*it).first.GetNetwork()};
+            const Network peers_net{peer.ConnectedThroughNetwork()};
+            if (our_net != peers_net &&
+                (our_net == NET_ONION || our_net == NET_I2P ||
+                 peers_net == NET_ONION || peers_net == NET_I2P)) {
+                continue;
+            }
             int nScore = (*it).second.nScore;
             int nReachability = (*it).first.GetReachabilityFrom(peer.addr);
             if (nReachability > nBestReachability || (nReachability == nBestReachability && nScore > nBestScore))
@@ -575,6 +585,11 @@ extern int32_t HUSH_NSPV;
 #define HUSH_NSPV_SUPERLITE (HUSH_NSPV > 0)
 #endif // !HUSH_NSPV_SUPERLITE
 
+Network CNode::ConnectedThroughNetwork() const
+{
+    return m_inbound_onion ? NET_ONION : addr.GetNetClass();
+}
+
 void CNode::PushVersion()
 {
     int nBestHeight = g_signals.GetHeight().get_value_or(0);
@@ -1266,6 +1281,7 @@ void CreateNodeFromAcceptedSocket(SOCKET hSocket,
         return;
     }
 
+    // Don't accept connections from banned peers.
     if (CNode::IsBanned(addr) && !allowlisted)
     {
         LogPrintf("connection from %s dropped (banned)\n", addr.ToString());
@@ -1320,6 +1336,8 @@ void CreateNodeFromAcceptedSocket(SOCKET hSocket,
         return;
     }
 
+    const bool inbound_onion = std::find(m_onion_binds.begin(), m_onion_binds.end(), addr_bind) != m_onion_binds.end();
+
     CNode* pnode = new CNode(hSocket, addr, "", true, ssl);
     pnode->AddRef();
     pnode->fAllowlisted = allowlisted;

src/net.h

@@ -403,6 +403,8 @@ public:
     // const CAddress addrBind; // https://github.com/bitcoin/bitcoin/commit/a7e3c2814c8e49197889a4679461be42254e5c51
     std::string addrName;
     CService addrLocal;
+    //! Whether this peer is an inbound onion, i.e. connected via our Tor onion service.
+    const bool m_inbound_onion;
     int nVersion;
     int lasthdrsreq,sendhdrsreq;
     // strSubVer is whatever byte array we read from the wire. However, this field is intended
@@ -418,6 +420,17 @@ public:
     bool fNetworkNode;
     bool fSuccessfullyConnected;
     bool fDisconnect;
+    /**
+     * Get network the peer connected through.
+     *
+     * Returns Network::NET_ONION for *inbound* onion connections,
+     * and CNetAddr::GetNetClass() otherwise. The latter cannot be used directly
+     * because it doesn't detect the former, and it's not the responsibility of
+     * the CNetAddr class to know the actual network a peer is connected through.
+     *
+     * @return network the peer connected through.
+     */
+    Network ConnectedThroughNetwork() const;
     // count blocks seen.
     int8_t nBlocksinARow;
     int8_t nBlocksinARow2;