Prevent Timer's lock with wrong dns

src/neo/Network/P2P/LocalNode.cs

@@ -7,7 +7,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
-using System.Net.Sockets;
 using System.Reflection;
 using System.Threading;
 
@@ -79,53 +78,6 @@ private void BroadcastMessage(Message message)
             Connections.Tell(message);
         }
 
-        private static IPEndPoint GetIPEndpointFromHostPort(string hostNameOrAddress, int port)
-        {
-            if (IPAddress.TryParse(hostNameOrAddress, out IPAddress ipAddress))
-                return new IPEndPoint(ipAddress, port);
-            IPHostEntry entry;
-            try
-            {
-                entry = Dns.GetHostEntry(hostNameOrAddress);
-            }
-            catch (SocketException)
-            {
-                return null;
-            }
-            ipAddress = entry.AddressList.FirstOrDefault(p => p.AddressFamily == AddressFamily.InterNetwork || p.IsIPv6Teredo);
-            if (ipAddress == null) return null;
-            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)
-        {
-            if (seedsToTake > 0)
-            {
-                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;
-                }
-            }
-        }
-
         public IEnumerable<RemoteNode> GetRemoteNodes()
         {
             return RemoteNodes.Values;
@@ -153,7 +105,9 @@ 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(ProtocolSettings.Default.SeedList.OrderBy(p => rand.Next()).Take(count));
             }
         }
 

src/neo/ProtocolSettings.cs

@@ -1,6 +1,8 @@
 using Microsoft.Extensions.Configuration;
 using System;
 using System.Linq;
+using System.Net;
+using System.Net.Sockets;
 using System.Threading;
 
 namespace Neo
@@ -10,7 +12,7 @@ public class ProtocolSettings
         public uint Magic { get; }
         public byte AddressVersion { get; }
         public string[] StandbyValidators { get; }
-        public string[] SeedList { get; }
+        public IPEndPoint[] SeedList { get; }
         public uint MillisecondsPerBlock { get; }
         public int MemoryPoolMaxTransactions { get; }
 
@@ -61,18 +63,54 @@ private ProtocolSettings(IConfigurationSection section)
                 };
             IConfigurationSection section_sl = section.GetSection("SeedList");
             if (section_sl.Exists())
-                this.SeedList = section_sl.GetChildren().Select(p => p.Get<string>()).ToArray();
+                this.SeedList = section_sl.GetChildren()
+                    .AsParallel()
+                    .Select(p => GetIpEndPoint(p.Get<string>()))
+                    .Where(u => u != null)
+                    .ToArray();
             else
                 this.SeedList = new[]
                 {
-                    "seed1.neo.org:10333",
-                    "seed2.neo.org:10333",
-                    "seed3.neo.org:10333",
-                    "seed4.neo.org:10333",
-                    "seed5.neo.org:10333"
+                    GetIpEndPoint("seed1.neo.org:10333"),
+                    GetIpEndPoint("seed2.neo.org:10333"),
+                    GetIpEndPoint("seed3.neo.org:10333"),
+                    GetIpEndPoint("seed4.neo.org:10333"),
+                    GetIpEndPoint("seed5.neo.org:10333")
                 };
             this.MillisecondsPerBlock = section.GetValue("MillisecondsPerBlock", 15000u);
             this.MemoryPoolMaxTransactions = Math.Max(1, section.GetValue("MemoryPoolMaxTransactions", 50_000));
         }
+
+        private static IPEndPoint GetIPEndpointFromHostPort(string hostNameOrAddress, int port)
+        {
+            if (IPAddress.TryParse(hostNameOrAddress, out IPAddress ipAddress))
+                return new IPEndPoint(ipAddress, port);
+            IPHostEntry entry;
+            try
+            {
+                entry = Dns.GetHostEntry(hostNameOrAddress);
+            }
+            catch (SocketException)
+            {
+                return null;
+            }
+            ipAddress = entry.AddressList.FirstOrDefault(p => p.AddressFamily == AddressFamily.InterNetwork || p.IsIPv6Teredo);
+            if (ipAddress == null) return null;
+            return new IPEndPoint(ipAddress, port);
+        }
+
+        internal static IPEndPoint GetIpEndPoint(string hostAndPort)
+        {
+            if (string.IsNullOrEmpty(hostAndPort)) return null;
+
+            try
+            {
+                string[] p = hostAndPort.Split(':');
+                return GetIPEndpointFromHostPort(p[0], int.Parse(p[1]));
+            }
+            catch { }
+
+            return null;
+        }
     }
 }

tests/neo.UnitTests/UT_ProtocolSettings.cs

@@ -116,7 +116,15 @@ public void TestGetMillisecondsPerBlock()
         [TestMethod]
         public void TestGetSeedList()
         {
-            ProtocolSettings.Default.SeedList.Should().BeEquivalentTo(new string[] { "seed1.neo.org:10333", "seed2.neo.org:10333", "seed3.neo.org:10333", "seed4.neo.org:10333", "seed5.neo.org:10333", });
+            ProtocolSettings.Default.SeedList.Should().BeEquivalentTo(
+                new IPEndPoint[]
+                {
+                    ProtocolSettings.GetIpEndPoint("seed1.neo.org:10333"),
+                    ProtocolSettings.GetIpEndPoint("seed2.neo.org:10333"),
+                    ProtocolSettings.GetIpEndPoint("seed3.neo.org:10333"),
+                    ProtocolSettings.GetIpEndPoint("seed4.neo.org:10333"),
+                    ProtocolSettings.GetIpEndPoint("seed5.neo.org:10333"),
+                });
         }
     }
 }