fix ping with SendIpHeader on FreeBSD (#63531)

* fix ping with SendIpHeader on FreeBSD

* update to fix command line and DF

* add comment

src/libraries/Common/src/System/Net/NetworkInformation/UnixCommandLinePing.cs

@@ -90,7 +90,8 @@ public static string ConstructCommandLine(int packetSize, int timeout, string ad
             // OSX: ping requires -W flag which accepts timeout in MILLISECONDS; ping6 doesn't support timeout
             if (OperatingSystem.IsFreeBSD())
             {
-                if (ipv4)
+                // Syntax changed in FreeBSD 13.0 and options are not common for both address families
+                if (ipv4 || Environment.OSVersion.Version.Major > 12)
                 {
                     sb.Append(" -W ");
                 }
@@ -135,7 +136,8 @@ public static string ConstructCommandLine(int packetSize, int timeout, string ad
                 if (OperatingSystem.IsFreeBSD() || OperatingSystem.IsMacOS())
                 {
                     // OSX and FreeBSD use -h to set hop limit for IPv6 and -m ttl for IPv4
-                    if (ipv4)
+                    // Syntax changed in FreeBSD 13.0 and options are not common for both address families
+                    if (ipv4 || (OperatingSystem.IsFreeBSD() && Environment.OSVersion.Version.Major > 12))
                     {
                         sb.Append(" -m ");
                     }

src/libraries/System.Net.Ping/src/System/Net/NetworkInformation/Ping.RawSocket.cs

@@ -19,6 +19,7 @@ public partial class Ping
         private const int MinIpHeaderLengthInBytes = 20;
         private const int MaxIpHeaderLengthInBytes = 60;
         private const int IpV6HeaderLengthInBytes = 40;
+        private static ushort DontFragment = OperatingSystem.IsFreeBSD() ? (ushort)IPAddress.HostToNetworkOrder((short)0x4000) : (ushort)0x4000;
 
         private unsafe SocketConfig GetSocketConfig(IPAddress address, byte[] buffer, int timeout, PingOptions? options)
         {
@@ -29,15 +30,17 @@ private unsafe SocketConfig GetSocketConfig(IPAddress address, byte[] buffer, in
 
             bool ipv4 = address.AddressFamily == AddressFamily.InterNetwork;
             bool sendIpHeader = ipv4 && options != null && SendIpHeader;
+            int totalLength = 0;
 
              if (sendIpHeader)
              {
                 iph.VersionAndLength = 0x45;
+                totalLength = sizeof(IpHeader) + checked(sizeof(IcmpHeader) +  buffer.Length);
                 // On OSX this strangely must be host byte order.
-                iph.TotalLength = (ushort)(sizeof(IpHeader) + checked(sizeof(IcmpHeader) +  buffer.Length));
+                iph.TotalLength = OperatingSystem.IsFreeBSD() ? (ushort)IPAddress.HostToNetworkOrder((short)totalLength) : (ushort)totalLength;
                 iph.Protocol = 1; // ICMP
                 iph.Ttl = (byte)options!.Ttl;
-                iph.Flags = (ushort)(options.DontFragment ? 0x4000 : 0);
+                iph.Flags = (ushort)(options.DontFragment ? DontFragment : 0);
 #pragma warning disable 618
                 iph.DestinationAddress = (uint)address.Address;
 #pragma warning restore 618
@@ -52,7 +55,7 @@ private unsafe SocketConfig GetSocketConfig(IPAddress address, byte[] buffer, in
                 {
                     Type = ipv4 ? (byte)IcmpV4MessageType.EchoRequest : (byte)IcmpV6MessageType.EchoRequest,
                     Identifier = id,
-                }, buffer));
+                }, buffer, totalLength));
         }
 
         private Socket GetRawSocket(SocketConfig socketConfig)
@@ -405,14 +408,14 @@ public SocketConfig(EndPoint endPoint, int timeout, PingOptions? options, bool i
             public readonly byte[] SendBuffer;
         }
 
-        private static unsafe byte[] CreateSendMessageBuffer(IpHeader ipHeader, IcmpHeader icmpHeader, byte[] payload)
+        private static unsafe byte[] CreateSendMessageBuffer(IpHeader ipHeader, IcmpHeader icmpHeader, byte[] payload, int totalLength = 0)
         {
             int icmpHeaderSize = sizeof(IcmpHeader);
             int offset = 0;
-            int packetSize = ipHeader.TotalLength != 0 ? ipHeader.TotalLength : checked(icmpHeaderSize + payload.Length);
+            int packetSize = totalLength != 0 ? totalLength : checked(icmpHeaderSize + payload.Length);
             byte[] result = new byte[packetSize];
 
-            if (ipHeader.TotalLength != 0)
+            if (totalLength != 0)
             {
                 int ipHeaderSize = sizeof(IpHeader);
                 new Span<byte>(&ipHeader, sizeof(IpHeader)).CopyTo(result);

src/libraries/System.Net.Ping/src/System/Net/NetworkInformation/Ping.Unix.cs

@@ -15,7 +15,7 @@ namespace System.Net.NetworkInformation
 {
     public partial class Ping
     {
-        private static bool SendIpHeader => false;
+        private static bool SendIpHeader => OperatingSystem.IsFreeBSD();
         private static bool NeedsConnect => OperatingSystem.IsLinux();
         private static bool SupportsDualMode => true;
 

src/libraries/System.Net.Ping/tests/FunctionalTests/TestSettings.cs

@@ -14,7 +14,9 @@ internal static class TestSettings
         public const int PingTimeout = 10 * 1000;
 
         public const string PayloadAsString = "'Post hoc ergo propter hoc'. 'After it, therefore because of it'. It means one thing follows the other, therefore it was caused by the other. But it's not always true. In fact it's hardly ever true.";
-        public static readonly byte[] PayloadAsBytes = Encoding.UTF8.GetBytes(TestSettings.PayloadAsString);
+
+        // By default, FreeBSD supports buffer only up to 56 bytes
+        public static readonly byte[] PayloadAsBytes = Encoding.UTF8.GetBytes(OperatingSystem.IsFreeBSD() ? TestSettings.PayloadAsString.Substring(0, 55) : TestSettings.PayloadAsString);
 
         public static readonly byte[] PayloadAsBytesShort = Encoding.UTF8.GetBytes("ABCDEF0123456789");