fix: support rootless ICMP and verify SELinux deployment [CI]

backend/shared/MoShiro.Measurement/Blocks/Session.cs

@@ -1,6 +1,7 @@
 using System.Net.NetworkInformation;
 using System.Net.Sockets;
 using System.Security.Authentication;
+using Fleet.Core;
 using MoShiro.Protocol;
 
 namespace MoShiro.Measurement;
@@ -306,7 +307,8 @@ public sealed class IcmpEchoSolo : BlockBase
         TimeSpan interval = TimeSpan.FromSeconds(1.0 / Spec.Int("rate_hz"));
         int size = (int)Spec.Int("size");
         byte[] payload = new byte[Math.Max(0, size - 28)];
-        using var ping = new Ping();
+        using LinuxIcmpEcho? linuxPing = OperatingSystem.IsLinux() ? LinuxIcmpEcho.TryCreate(Env.PeerAddress!, payload.Length) : null;
+        using Ping? ping = linuxPing is null ? new Ping() : null;
         try
         {
             while (!ct.IsCancellationRequested)
@@ -315,8 +317,10 @@ public sealed class IcmpEchoSolo : BlockBase
                 long? t4 = null;
                 try
                 {
-                    PingReply reply = await ping.SendPingAsync(Env.PeerAddress!, TimeSpan.FromSeconds(2), payload, null, ct);
-                    if (reply.Status == IPStatus.Success)
+                    bool receivedReply = linuxPing is not null
+                        ? await linuxPing.SendAsync(TimeSpan.FromSeconds(2), ct)
+                        : (await ping!.SendPingAsync(Env.PeerAddress!, TimeSpan.FromSeconds(2), payload, null, ct)).Status == IPStatus.Success;
+                    if (receivedReply)
                     {
                         t4 = Env.Clock.NowUs();
                     }
@@ -325,6 +329,11 @@ public sealed class IcmpEchoSolo : BlockBase
                 {
                     // 发送失败（例如本机没有路由）：记为丢失
                 }
+                catch (PlatformNotSupportedException) when (OperatingSystem.IsLinux())
+                {
+                    Env.Log.Warn("ICMP permission unavailable", ("hint", "allow the mapped process GID in net.ipv4.ping_group_range, or grant effective NET_RAW"));
+                    throw;
+                }
 
                 long key = _log.Store.Append();
                 _log.Store.Set(key, _seq, key);

backend/shared/MoShiro.Measurement/Net/LinuxIcmpEcho.cs

@@ -0,0 +1,84 @@
+using System.Buffers.Binary;
+using System.Net;
+using System.Net.Sockets;
+
+namespace MoShiro.Measurement;
+
+/// <summary>Linux ping sockets permit ICMP echo without CAP_NET_RAW when ping_group_range allows the process group.</summary>
+internal sealed class LinuxIcmpEcho : IDisposable
+{
+    private readonly Socket _socket;
+    private readonly byte[] _request;
+    private readonly byte[] _response;
+    private readonly byte _replyType;
+    private ushort _sequence;
+
+    private LinuxIcmpEcho(IPAddress address, int payloadSize)
+    {
+        bool ipv6 = address.AddressFamily == AddressFamily.InterNetworkV6;
+        _socket = new Socket(address.AddressFamily, SocketType.Dgram, ipv6 ? ProtocolType.IcmpV6 : ProtocolType.Icmp);
+        try
+        {
+            _socket.Connect(new IPEndPoint(address, 0));
+        }
+        catch
+        {
+            _socket.Dispose();
+            throw;
+        }
+
+        _request = new byte[8 + payloadSize];
+        _request[0] = ipv6 ? (byte)128 : (byte)8;
+        _replyType = ipv6 ? (byte)129 : (byte)0;
+        _response = new byte[_request.Length + 64];
+        // The Linux ping socket supplies the identifier and checksum.
+        Random.Shared.NextBytes(_request.AsSpan(8));
+    }
+
+    public static LinuxIcmpEcho? TryCreate(IPAddress address, int payloadSize)
+    {
+        try
+        {
+            return new LinuxIcmpEcho(address, payloadSize);
+        }
+        catch (SocketException)
+        {
+            // Preserve System.Net.Ping's raw-socket path for hosts that allow NET_RAW instead.
+            return null;
+        }
+    }
+
+    public async ValueTask<bool> SendAsync(TimeSpan timeout, CancellationToken ct)
+    {
+        ushort sequence = unchecked(++_sequence);
+        BinaryPrimitives.WriteUInt16BigEndian(_request.AsSpan(6), sequence);
+        using var deadline = CancellationTokenSource.CreateLinkedTokenSource(ct);
+        deadline.CancelAfter(timeout);
+        try
+        {
+            await _socket.SendAsync(_request, SocketFlags.None, deadline.Token);
+            while (true)
+            {
+                int count = await _socket.ReceiveAsync(_response, SocketFlags.None, deadline.Token);
+                if (IsReply(_response.AsSpan(0, count), _request, _replyType, sequence))
+                {
+                    return true;
+                }
+            }
+        }
+        catch (OperationCanceledException) when (!ct.IsCancellationRequested)
+        {
+            return false;
+        }
+        catch (SocketException)
+        {
+            return false;
+        }
+    }
+
+    internal static bool IsReply(ReadOnlySpan<byte> reply, ReadOnlySpan<byte> request, byte replyType, ushort sequence) =>
+        reply.Length == request.Length && reply.Length >= 8 && reply[0] == replyType && reply[1] == 0 &&
+        BinaryPrimitives.ReadUInt16BigEndian(reply[6..]) == sequence && reply[8..].SequenceEqual(request[8..]);
+
+    public void Dispose() => _socket.Dispose();
+}