Looking for a way to read ARP table on iOS device using C# and Xamarin

Question

Any help, code examples will be greatly appreciated.

Thank you

Answer 1

Let me answer my own question.

Based on the following SO question Getting ARP table on iPhone/iPad and Apple source here is C#/mono version of it

    [DllImport (MonoTouch.Constants.SystemLibrary)]
    static internal extern int sysctl ([MarshalAs (UnmanagedType.LPArray)] int[] mib, int mibsize, IntPtr output, IntPtr oldLen, IntPtr newp, uint newlen);

    public static Dictionary<String,String> AllMac = null;
    public static String GetMACAddressByIp(String ip)
    {
        return GetMACAddressByIp (ip, false);
    }
    public static String GetMACAddressByIp (String ip, bool reset)
    {
        try 
        {
            if (AllMac == null || reset) 
            {
                AllMac=new Dictionary<string, string>();
                int CTL_NET = 4;
                int PF_ROUTE = 17;
                int AF_INET = 2;
                int NET_RT_FLAGS = 2;
                int RTF_LLINFO = 0x400;
                int[] mib = { CTL_NET, PF_ROUTE, 0, AF_INET, NET_RT_FLAGS, RTF_LLINFO };
                var pLen = Marshal.AllocHGlobal (sizeof(int));
                sysctl (mib, 6, IntPtr.Zero, pLen, IntPtr.Zero, 0);
                var length = Marshal.ReadInt32 (pLen);
                if (length == 0) {
                    Marshal.FreeHGlobal (pLen);
                    return string.Empty;
                }
                var pBuf = Marshal.AllocHGlobal (length);
                sysctl (mib, 6, pBuf, pLen, IntPtr.Zero, 0);
                int off = 0;
                while (true) {
                    short len = Marshal.ReadInt16 (pBuf + off);
                    IntPtr paddr = pBuf + off + 36 + 56;
                    byte sinlen = Marshal.ReadByte (paddr);  
                    uint addr = (uint)Marshal.ReadInt32 (paddr + 4);
                    string ipAddress = new IPAddress (BitConverter.GetBytes (addr)).ToString ();
                    paddr += sinlen; 
                    StringBuilder sb = new StringBuilder ();
                    bool allZero = true;
                    for (int m = 0; m < 6; m++) {
                        byte b = Marshal.ReadByte (paddr + 8 + m);
                        if (b != 0) {
                            allZero = false;
                        }
                        if (sb.Length > 0) {
                            sb.Append (":");
                        }
                        sb.Append (b.ToString ("X2"));
                    }

                    String mac = sb.ToString ();
                    if (!allZero) {
                        AllMac[ipAddress]=mac;
                    }
                    off += len;
                    if (length <= off) {
                        break;
                    }
                }
                Marshal.FreeHGlobal (pLen);
                Marshal.FreeHGlobal (pBuf);
            }
            if (AllMac.ContainsKey (ip)) {
                return AllMac [ip];
            }
        } catch (Exception ex) {
            Console.WriteLine ("Exception in GetMACAddressByIp:" + ex.ToString ());
        }
        return "";
    }