c# - how to sniff packets in an app without relyin

Question

BACKGROUND: I now understand how to write a C# application that can monitor packets going in/out of the network card on the PC the application is running on. The approach I know relies on http://www.winpcap.org/ being already installed on the PC however, and then I use a C# wrapper such as http://pcapdotnet.codeplex.com/ or http://sourceforge.net/projects/sharppcap/ .

QUESTION: My question however, what would I need to do to be able to have a C# application that can sniff packets that does NOT require a 3rd party application/drivers to be pre-installed?

CLARIFICATION: That is I really want the application I currently have but without any requirement for me to tell the user to have to go and download/install XYZ prior to being able to use the application. For the purpose of the question assume that automating the download and install of a 3rd party application/drivers is not allowed either. (with WinPCap I'm not sure if you can bundle it, however I believe you're not supposed to in any case unfortunately)

thanks

Answer 1

Personally I would stick to WinPCap. But since you asked, it is possible to sniff packets from the network using for the following code to enable raw sockets.

Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP);
s.Bind(new IPEndPoint(IPAddress.Parse("<IP Address Here of NIC to sniff>"), 0));
s.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.HeaderIncluded, 1);
byte[] inBytes = new byte[] { 1, 0, 0, 0 };
byte[] outBytes = new byte[] { 0, 0, 0, 0 };
s.IOControl(IOControlCode.ReceiveAll, inBytes, outBytes);

Once this is done, you can use Socket.Receive or Socket.BeginReceive to read the raw IP packets.

Answer 2

There is a way to capture incoming/outgoing packets on .NET using just the standard winsocks implementation. I've seen a blog with example of how but I don't have the link anymore.

Long story short, it's an extreme edge case because that's not what winsocks (the standard windows networking driver) was intended for.

The reason Pcap is usually necessary to capture packets is, it uses its own NDIS networking driver that unlocks the full capabilities of your NIC. On top of that, it also provides an easy way to set filters to limit the amount of packets being captured on the specified interface.

IE, the driver will ignore packets of a specific type at the kernel level instead of the usermode level. Therefore, you'll be able to filter packets much more efficiently and capture under larger loads on the network.

In .NET, to filter packets, you'd need to provide your own application layer packet filtering scheme that would be much less efficient.

Windows blocks access to non-standard protocols for 'security reasons' so they don't really support the use of RAW packets for networking (even though code may exist to make it possible). RAW packets were always intended for researching the design of new protocols, not general use.

For all of those reasons it is usually a good idea to pick up Winpcap and a wrapper for your specific language to implement any type of capturing application.

Note: I personally prefer SharpPcap, but I'm also biased as I do development on the project. Pcap.net is very similar in its implementation when it comes to capturing, it mainly diverges when it comes to how packets are parsed.