Add local ipv4 and ipv6 multicast peer discovery for DHT.

Update tests for same.

closes #15

WORKSPACE

@@ -68,7 +68,8 @@ pinned_maven_install()
 git_repository(
   name = "snowblossom",
   remote = "https://github.com/snowblossomcoin/snowblossom",
-	commit = "b35a663e16735068a60f625a9baaf8d669c4cf30", 
+	commit = "dbefa041f19a2e3aed2108da9131c2e519ec7fa5", 
+  shallow_since = "1578077101 -0800"
 )
 
 git_repository(

protolib/channels.proto

@@ -127,6 +127,7 @@ message SignedMessagePayload {
     ChannelBlockHeader channel_block_header = 20;
     ContentInfo content_info = 21;
     ChannelSettings channel_settings = 22;
+    LocalPeerDisco local_peer_disco = 23;
   }
   TxOutPoint fbo_utxo = 50;
 }
@@ -137,9 +138,21 @@ message ChannelPeerInfo {
   bytes address_spec_hash = 3; //Also the node ID
 }
 
+// This message being signed indicates that the peer is in fact using
+// multicast announcement to find local network peers
+// and a node should try to connect to this node via whatever address this multicast appears
+// to come from.
+// Note: this does open up a MITM attack/DOS attack if an attacker for connections from node A to node B
+// if the attack is both on local network B (to get this signed LocalPeerDisco ) and network A (to 
+// multicast that signed message).  In this case, the TLS will still protect the connection.
+message LocalPeerDisco {
+  repeated string ip_addresses = 1;
+  int32 port = 2;
+  SignedMessage signed_peer_info = 3;
+}
+
 // The local information we store about a peer
 message LocalPeerInfo {
-
   ChannelPeerInfo info = 1;
   SignedMessage signed_peer_info = 2;
   int64 last_connected = 3;

src/ChannelGateway.java

@@ -29,3 +29,4 @@ public ChannelInterface getChannelInterface(ChannelID cid)
 
 
 }
+

src/ChannelGlobals.java

@@ -1,8 +1,9 @@
 package snowblossom.channels;
 
+
 public class ChannelGlobals
 {
-  public static final String VERSION = "dev.2019.12.20.0";
+  public static final String VERSION = "dev.2020.01.03.00";
 
   public static final String NODE_ADDRESS_STRING="node";
   public static final String CHANNEL_ADDRESS_STRING="chan";
@@ -11,6 +12,11 @@ public class ChannelGlobals
 
   public static final int NETWORK_PORT=4862;
 
+  public static final String MULTICAST_IPV4_ADDRESS="224.48.62.1";
+
+  // Subject to change after I understand WTF https://tools.ietf.org/html/rfc7371 is on about
+  public static final String MULTICAST_IPV6_ADDRESS="FFFF::e030:3e01";
+
   public static final long ALLOWED_CLOCK_SKEW=45000; //ms
 
   public static final String NODE_TAG = "node";
@@ -35,6 +41,10 @@ public class ChannelGlobals
   public static final long PEER_LINK_TIMEOUT=60000L;
   public static final long CHANNEL_LINK_TIMEOUT=60000L;
 
+  public static final long MULTICAST_BROADCAST_PERIOD=60000L;
+  public static final long MULTICAST_CACHE_EXPIRE=MULTICAST_BROADCAST_PERIOD*2L;
+
+
   // 2500 channels, 100 elements each
   public static final int DHT_CACHE_ELEMENTS = 2500 * 100;
   public static final long DHT_CACHE_EXPIRE = 120000L;
@@ -68,3 +78,4 @@ public class ChannelGlobals
 
 
 
+

src/ChannelNode.java

@@ -47,6 +47,7 @@ public class ChannelNode
   private ChannelTipSender channel_tip_sender;
   private ChannelChunkGetter channel_chunk_getter;
   private ChannelOutsiderSender channel_outsider_sender;
+  private LocalPeerFinder local_peer_finder;
 
   private HashMap<ChannelID, SingleChannelDB> db_map;
   private boolean autojoin = false;
@@ -133,6 +134,7 @@ else if (db_type.equals("lobstack"))
     channel_tip_sender = new ChannelTipSender(this);
     channel_chunk_getter = new ChannelChunkGetter(this);
     channel_outsider_sender = new ChannelOutsiderSender(this);
+    local_peer_finder = new LocalPeerFinder(this);
 
     startServer();
 
@@ -143,8 +145,8 @@ else if (db_type.equals("lobstack"))
     channel_chunk_getter.start();
     channel_outsider_sender.start();
 
-    channel_subscriber.loadFromDB();    
-
+    channel_subscriber.loadFromDB();
+    local_peer_finder.start();
 
     if (config.isSet("web_port"))
     {
@@ -221,6 +223,7 @@ private void startServer()
   public Config getConfig(){ return config;}
   public WalletDatabase getWalletDB() {return wallet_db; }
   public StubHolder getStubHolder() {return stub_holder; }
+  public LocalPeerFinder getLocalPeerFinder() {return local_peer_finder;}
   public boolean getAutoJoin(){ return autojoin;}
 
   public AddressSpecHash getNodeID()

src/ChannelSigUtil.java

@@ -5,6 +5,8 @@
 import snowblossom.channels.proto.*;
 import snowblossom.lib.ChainHash;
 import snowblossom.lib.DigestUtil;
+import snowblossom.lib.AddressSpecHash;
+import snowblossom.lib.AddressUtil;
 import snowblossom.lib.SignatureUtil;
 import snowblossom.lib.ValidationException;
 import snowblossom.proto.AddressSpec;
@@ -131,5 +133,23 @@ public static ChannelID getChannelId(ChainHash message_id)
     return new ChannelID( md.digest(message_id.toByteArray() ));
   }
 
+  public static ChannelPeerInfo validatePeerInfo(SignedMessage peer_signed_message)
+    throws ValidationException
+  {
+		SignedMessagePayload payload = validateSignedMessage(peer_signed_message);
+
+		if (!payload.hasPeerInfo()) throw new ValidationException("Signed peer info has no peer info");
 
+		ChannelPeerInfo peer_info = payload.getPeerInfo();
+
+		AddressSpecHash signed_address = AddressUtil.getHashForSpec(payload.getClaim());
+		AddressSpecHash node_id = new AddressSpecHash(peer_info.getAddressSpecHash());
+		if (!signed_address.equals(node_id))
+		{ 
+			throw new ValidationException("Signed address does not match node id");
+		}
+
+		return peer_info;
+
+  }
 }

src/ChannelSubscriber.java

@@ -1,20 +1,19 @@
 package snowblossom.channels;
 
 
+import com.google.common.collect.ImmutableList;
 import com.google.protobuf.ByteString;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.Set;
 import java.util.LinkedList;
-import snowblossom.channels.proto.*;
-
+import java.util.List;
+import java.util.Set;
 import java.util.concurrent.Executor;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
+import snowblossom.channels.proto.*;
 import snowblossom.lib.DaemonThreadFactory;
-import com.google.common.collect.ImmutableList;
-import java.util.List;
 
 /** 
  * Manage channels we are tracking 

src/ChannelWatcherInterface.java

@@ -2,7 +2,6 @@
 
 import snowblossom.channels.proto.*;
 
-
 public interface ChannelWatcherInterface
 {
 

src/DHTMaintainer.java

@@ -33,6 +33,11 @@ public class DHTMaintainer extends PeriodicThread
   private HashMap<AddressSpecHash, Long> connection_attempt_times = new HashMap<>(16,0.5f);
   private ImmutableSet<AddressSpecHash> current_links;
 
+  // TODO - select older nodes if we get don't have any links
+  // Something like max_age = 1h.
+  // If not enough links, max_age = Math.max(max_age * 2, 1 year)
+  // else max_age = 1h (to reset to one hour once we have some reasonable number)
+  // https://github.com/snowblossomcoin/channels/issues/21
   public DHTMaintainer(ChannelNode node)
   {
     super(5000L);
@@ -88,12 +93,19 @@ public void runPass() throws Exception
     if (connected_peers.size() + connect_map.size() < ChannelGlobals.NEAR_POINTS)
     {
       // Add Seeds
-      for(ChannelPeerInfo info : getSeeds())
+      if (node.getConfig().getBoolean("testing_skip_seeds"))
       {
-        AddressSpecHash id = new AddressSpecHash(info.getAddressSpecHash());
-        if (!connected_peers.contains(id))
+        logger.warning("Not using seeds - config option 'testing_skip_seeds'");
+      }
+      else
+      {
+        for(ChannelPeerInfo info : getSeeds())
         {
-          connect_map.put(id, info);
+          AddressSpecHash id = new AddressSpecHash(info.getAddressSpecHash());
+          if (!connected_peers.contains(id))
+          {
+            connect_map.put(id, info);
+          }
         }
       }
     }
@@ -297,7 +309,6 @@ public static List<ChannelPeerInfo> getSeeds()
         .build())
       .build());
 
-
     return seed_list;
 
   }

src/DHTServer.java

@@ -63,18 +63,10 @@ public void importPeer(SignedMessage peer_signed_message)
   {
     try
     {
-      SignedMessagePayload payload = ChannelSigUtil.validateSignedMessage(peer_signed_message);
+      ChannelPeerInfo peer_info = ChannelSigUtil.validatePeerInfo(peer_signed_message);
 
-      if (payload.getPeerInfo() == null) throw new ValidationException("Signed peer info has no peer info");
-
-      ChannelPeerInfo peer_info = payload.getPeerInfo();
-
-      AddressSpecHash signed_address = AddressUtil.getHashForSpec(payload.getClaim());
       AddressSpecHash node_id = new AddressSpecHash(peer_info.getAddressSpecHash());
-      if (!signed_address.equals(node_id))
-      {
-        throw new ValidationException("Signed address does not match node id");
-      }
+      SignedMessagePayload payload = ChannelSigUtil.quickPayload(peer_signed_message);
 
       LocalPeerInfo.Builder new_local_info = LocalPeerInfo.newBuilder();
 
@@ -105,8 +97,8 @@ public SignedMessage getSignedPeerInfoSelf()
   {
     SignedMessagePayload.Builder p = SignedMessagePayload.newBuilder();
     p.setPeerInfo( node.getNetworkExaminer().createPeerInfo() );
-
-    return node.signMessage(p.build());
+    SignedMessage spi = node.signMessage(p.build());
+    return spi;
   }
 
   @Override