.Net UDP 数据包丢失，尽管所有数据包都到达(Wireshark) - ReceiveBuffer 不是问题

Question

这与 C# UDP packetloss though all packets arrive (WireShark) 相同的问题，但我确实设置了 ReceiverBuffer到 10MB，我还监控 Socket.Available这表明缓冲区甚至没有达到 200k 的利用率。

在一个简单的测试案例中，使用 tcpreplay 以 40Mbps 的速率发送相同的小(多播)UDP 数据包(净数据大小:137)25,000 次，通常不是所有数据包都到达我的程序，尽管所有数据包都到达了 Wireshark，我在那个盒子上同时运行。有时只丢失一个数据包，有时大约十几个，有时更多。

代码

static void Main()
{
    int udpPacketsReceived = 0;
    var bindAddress = IPAddress.Parse("192.168.20.54");
    var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
    socket.ReceiveBufferSize = 10485760; // 10M

    socket.Bind(new IPEndPoint(bindAddress, 51001));
    socket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.AddMembership, new MulticastOption(IPAddress.Parse("239.193.1.1")));
    Console.WriteLine("Effective ReceiveBuffer size: " + socket.GetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveBuffer));

    var t = new Thread(ipAndClient =>
    {
        var buffer = new byte[2000];
        int maxAvail = 0;
        while (true)
        {
            socket.Receive(buffer);
            Interlocked.Increment(ref udpPacketsReceived);
            var available = socket.Available;
            if (available > maxAvail)
            {
                Console.WriteLine("available new max: " + available);
                maxAvail = available;
            }
        }
    });
    t.Start();
    int lastValue = -1;
    while (true)
    {
        var newValue = Thread.VolatileRead(ref udpPacketsReceived);
        if (newValue != lastValue)
        {
            Console.WriteLine("Total UDP packets received: {0}", newValue);
            lastValue = newValue;
        }
        Thread.Sleep(1000);
    }
}

示例输出

Effective ReceiveBuffer size: 10485760
Total UDP packets received: 0
available new max: 685
available new max: 3288
available new max: 3836
available new max: 6165
available new max: 8220
available new max: 10960
Total UDP packets received: 14307
available new max: 18632
available new max: 140425
available new max: 141521
available new max: 143439
Total UDP packets received: 24996

怎么了？

重要补充 (事后证明这一点至关重要，请参阅 my own answer ):我正在 VirtualBox 主机中的 Windows 客户机上运行，​​使用 “桥接”虚拟网卡 .

Answer 1

Wireshark 在数据包被传递到协议(protocol)栈之前获取数据包，而接收缓冲区位于内核协议(protocol)栈的末尾。有很多内存分配和其他处理正在进行，在高负载时，它可能会在一些数据包到达接收缓冲区之前简单地丢弃它们。

这是MS support had to say :

Winsock layer sits on top of the transport layer. Datagrams may be dropped at various layers within the networking stack.