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fix mdns crash on scoped IPv6 link-local #4

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fix mdns crash on scoped IPv6 link-local #4

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13 changes: 12 additions & 1 deletion TinyDNS/MDNS.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
// along with this program. If not, see <http://www.gnu.org/licenses/>.

using System.Buffers;
using System.Collections.Concurrent;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;
Expand All @@ -32,6 +33,7 @@ public class MDNS : IDisposable
private Socket? listenerV4;
private Socket? listenerV6;
private readonly List<Socket> senders = [];
private readonly ConcurrentDictionary<long, IPAddress> multicastAddressV6Scoped = [];

public delegate Task MessageEventHandler(DNSMessageEvent e);
public event MessageEventHandler? AnswerReceived;
Expand Down Expand Up @@ -441,7 +443,7 @@ private async Task SendMessage(Message msg)
if (sender.AddressFamily == AddressFamily.InterNetwork)
await sender.SendToAsync(buffer.Slice(0, len), SocketFlags.None, new IPEndPoint(MulticastAddress, PORT), stop.Token);
else
await sender.SendToAsync(buffer.Slice(0, len), SocketFlags.None, new IPEndPoint(MulticastAddressV6, PORT), stop.Token);
await sender.SendToAsync(buffer.Slice(0, len), SocketFlags.None, new IPEndPoint(GetMulticastAddressV6(sender.LocalEndPoint), PORT), stop.Token);
await Task.Delay(5);
}
}finally
Expand All @@ -450,6 +452,15 @@ private async Task SendMessage(Message msg)
}
}

private IPAddress GetMulticastAddressV6(EndPoint? endPoint)
{
if (endPoint is not IPEndPoint { Address.IsIPv6LinkLocal: true } ip)
return MulticastAddressV6;

Func<long, IPAddress> factory = scope => new IPAddress(new byte[] { 0xFF, 0x02, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xFB }, scope);
return multicastAddressV6Scoped.GetOrAdd(ip.Address.ScopeId, factory);
}

public void Stop()
{
stop.Cancel();
Expand Down