Add some notes/comments about DHT message handling

llarp/dht/context.cpp

@@ -499,6 +499,10 @@ namespace llarp
       router->PersistSessionUntil(peer, now + 1min);
     }
 
+    // this function handles incoming DHT messages sent down a path by a client
+    // note that IMessage here is different than that found in the routing
+    // namespace. by the time this is called, we are inside
+    // llarp::routing::DHTMessage::HandleMessage()
     bool
     Context::RelayRequestForPath(const llarp::PathID_t& id, const IMessage& msg)
     {

llarp/path/path.cpp

@@ -710,6 +710,8 @@ namespace llarp
       return false;
     }
 
+    /// this is the Client's side of handling a DHT message. it's handled
+    /// in-place.
     bool
     Path::HandleDHTMessage(const dht::IMessage& msg, AbstractRouter* r)
     {

llarp/path/transit_hop.cpp

@@ -262,6 +262,8 @@ namespace llarp
       m_DownstreamQueue = nullptr;
     }
 
+    /// this is where a DHT message is handled at the end of a path, that is,
+    /// where a SNode receives a DHT message from a client along a path.
     bool
     TransitHop::HandleDHTMessage(const llarp::dht::IMessage& msg,
                                  AbstractRouter* r)

llarp/routing/dht_message.cpp

@@ -45,6 +45,11 @@ namespace llarp
       return bencode_end(buf);
     }
 
+    /// 'h' here is either TransitHop or Path.
+    /// TransitHop chains to dht::Context::RelayRequestForPath and is where the
+    /// end of a path handles a client's DHT message Path handles the message
+    /// (e.g. dht::IMessage::HandleMessage()) in-place and is the case where a
+    /// client receives a DHT message
     bool
     DHTMessage::HandleMessage(IMessageHandler* h, AbstractRouter* r) const
     {