C# API to test if a network Adapter is firewalled

Given - .Net 2.0 开发者_运维百科XP machine with SP2 and multiple network adapters

Is there an API that can be used to check if the network adapter is firewalled?

OneGuyInDC

---

Give this c# code below a go. It works for Windows 7 (& Vista) and XP. This will get the status of, and enable/disable the Windows firewall for the current profile, eg: Home/Domain/Public access networks.

Usage:

getFirewallStatus() 
  --> returns true/false for whether the windows firewall is enable/disabled.

setFirewallStatus(newStatus) 
  --> sets the firewall enabled/disabled to the true/false value passed in
      eg, to enable the firewall:
         setFirewallStatus(true)

getCurrPolicy()  
  --> used by the other two methods

isWinXP()
  --> returns whether windows version is WinXP/2000 or newer, ie: Vista/Win7
      used by the other methods to determine which code to use.

Code:

using NetFwTypeLib; 
// (don't forget to add it to your references, its under the COM tab)

public bool isWinXP()
{
   OperatingSystem os = Environment.OSVersion;
   int majorVersion = os.Version.Major;
   // see http://msdn.microsoft.com/en-us/library/ms724832(v=vs.85).aspx
   if (majorVersion < 6) // if O/S is not Vista or Windows7
   {
       return true;
   }
   else
   {
       return false;
   }
}
private static INetFwPolicy2 getCurrPolicy()
{
    INetFwPolicy2 fwPolicy2;
    Type tNetFwPolicy2 = Type.GetTypeFromProgID("HNetCfg.FwPolicy2");
    fwPolicy2 = (INetFwPolicy2)Activator.CreateInstance(tNetFwPolicy2);
    return fwPolicy2;
}
public bool getFirewallStatus()
{
    bool result = false;
    switch (isWinXP())
    {
        case true:
            Type NetFwMgrType = Type.GetTypeFromProgID("HNetCfg.FwMgr", false); 
            INetFwMgr mgr = (INetFwMgr)Activator.CreateInstance(NetFwMgrType);
            result = mgr.LocalPolicy.CurrentProfile.FirewallEnabled;
            break;
        case false:
            INetFwPolicy2 fwPolicy2 = getCurrPolicy();
            NET_FW_PROFILE_TYPE2_ fwCurrentProfileTypes;
            //read Current Profile Types (only to increase Performace)
            //avoids access on CurrentProfileTypes from each Property
            fwCurrentProfileTypes = (NET_FW_PROFILE_TYPE2_)fwPolicy2.CurrentProfileTypes;
            result = (fwPolicy2.get_FirewallEnabled(fwCurrentProfileTypes));
            break;
        default:
            result = false; // assume Win7 by default
            break;
    }
    return result;
}
public void setFirewallStatus(bool newStatus)
{
    switch (isWinXP())
    {
        case true:
            Type NetFwMgrType = Type.GetTypeFromProgID("HNetCfg.FwMgr", false);
            INetFwMgr mgr = (INetFwMgr)Activator.CreateInstance(NetFwMgrType);
            mgr.LocalPolicy.CurrentProfile.FirewallEnabled = newStatus;
            break;
        case false:
            NET_FW_PROFILE_TYPE2_ fwCurrentProfileTypes;
            INetFwPolicy2 currPolicy = getCurrPolicy();
            //read Current Profile Types (only to increase Performace)
            //avoids access on CurrentProfileTypes from each Property
            fwCurrentProfileTypes = (NET_FW_PROFILE_TYPE2_)currPolicy.CurrentProfileTypes;
            currPolicy.set_FirewallEnabled(fwCurrentProfileTypes, newStatus);
            break;
        default:
            NET_FW_PROFILE_TYPE2_ fwCurrentProfileTypes1;
            INetFwPolicy2 currPolicy1 = getCurrPolicy();
            //read Current Profile Types (only to increase Performace)
            //avoids access on CurrentProfileTypes from each Property
            fwCurrentProfileTypes1 = (NET_FW_PROFILE_TYPE2_)currPolicy1.CurrentProfileTypes;
            currPolicy1.set_FirewallEnabled(fwCurrentProfileTypes1, newStatus);
            break;
    }
}

---

It is not possible to know in general (e.g. if there is an external firewall) for the following reasons:

1. If you aren't receiving incoming connections, your external interface may just be down.
2. If you are unable to make outgoing connections, your external interface may just be down.

But there is an API for finding out if the Windows Firewall is enabled on a given network interface. You will need to use COM interop to get the INetFwProfile (for global firewall status) and INetSharingConfiguration (for a specific network interface) interfaces, and check INetFwProfile.FirewallEnabled and INetSharingConfiguration.InternetFirewallEnabled.

See http://msdn.microsoft.com/en-us/library/aa364717%28VS.85%29.aspx for links and for how to use these results to determine the effective firewall status. (It's written in terms of VBScript but should be translatable to C#.)