Prevent Timer's lock with wrong dns

src/neo/Network/P2P/LocalNode.cs

@@ -10,17 +10,24 @@
 using System.Net.Sockets;
 using System.Reflection;
 using System.Threading;
+using System.Threading.Tasks;
 
 namespace Neo.Network.P2P
 {
     public class LocalNode : Peer
     {
+        public class Seed
+        {
+            public string HostAndPort;
+            public IPEndPoint EndPoint;
+        }
         public class Relay { public IInventory Inventory; }
         internal class RelayDirectly { public IInventory Inventory; }
         internal class SendDirectly { public IInventory Inventory; }
 
         public const uint ProtocolVersion = 0;
         private const int MaxCountFromSeedList = 5;
+        private readonly Seed[] SeedList;
 
         private static readonly object lockObj = new object();
         private readonly NeoSystem system;
@@ -56,6 +63,17 @@ public LocalNode(NeoSystem system)
                     throw new InvalidOperationException();
                 this.system = system;
                 singleton = this;
+
+                SeedList = ProtocolSettings.Default.SeedList
+                    .Select(u => new Seed() { HostAndPort = u })
+                    .ToArray();
+
+                // Start dns resolution in parallel
+
+                foreach (var seed in SeedList)
+                {
+                    Task.Run(() => seed).PipeTo(Self, Sender);
+                }
             }
         }
 
@@ -97,33 +115,18 @@ private static IPEndPoint GetIPEndpointFromHostPort(string hostNameOrAddress, in
             return new IPEndPoint(ipAddress, port);
         }
 
-        /// <summary>
-        /// Return an amount of random seeds nodes from the default SeedList file defined on <see cref="ProtocolSettings"/>.
-        /// </summary>
-        /// <param name="seedsToTake">Limit of random seed nodes to be obtained, also limited by the available seeds from file.</param>
-        private static IEnumerable<IPEndPoint> GetIPEndPointsFromSeedList(int seedsToTake)
+        internal static IPEndPoint GetIpEndPoint(string hostAndPort)
         {
-            if (seedsToTake > 0)
+            if (string.IsNullOrEmpty(hostAndPort)) return null;
+
+            try
             {
-                Random rand = new Random();
-                foreach (string hostAndPort in ProtocolSettings.Default.SeedList.OrderBy(p => rand.Next()))
-                {
-                    if (seedsToTake == 0) break;
-                    string[] p = hostAndPort.Split(':');
-                    IPEndPoint seed;
-                    try
-                    {
-                        seed = GetIPEndpointFromHostPort(p[0], int.Parse(p[1]));
-                    }
-                    catch (AggregateException)
-                    {
-                        continue;
-                    }
-                    if (seed == null) continue;
-                    seedsToTake--;
-                    yield return seed;
-                }
+                string[] p = hostAndPort.Split(':');
+                return GetIPEndpointFromHostPort(p[0], int.Parse(p[1]));
             }
+            catch { }
+
+            return null;
         }
 
         public IEnumerable<RemoteNode> GetRemoteNodes()
@@ -153,7 +156,9 @@ protected override void NeedMorePeers(int count)
             {
                 // Will call AddPeers with default SeedList set cached on <see cref="ProtocolSettings"/>.
                 // It will try to add those, sequentially, to the list of currently uncconected ones.
-                AddPeers(GetIPEndPointsFromSeedList(count));
+
+                Random rand = new Random();
+                AddPeers(SeedList.Where(u => u.EndPoint != null).OrderBy(p => rand.Next()).Select(u => u.EndPoint).Take(count));
             }
         }
 
@@ -165,6 +170,9 @@ protected override void OnReceive(object message)
                 case Message msg:
                     BroadcastMessage(msg);
                     break;
+                case Seed seed:
+                    if (seed.EndPoint == null) seed.EndPoint = GetIpEndPoint(seed.HostAndPort);
+                    break;
                 case Relay relay:
                     OnRelay(relay.Inventory);
                     break;