Receiving Data on an ICMP socket

icmp

When receiving on an ICMP socket, (SOCK_RAW with IPPROTO_ICMP), since
there is no concept of "port" in the ICMP protocol, how can an
application determine that a received packet is not part of some other
TCP/UDP/whatever socket transmission that is also happening at the
same time?

For example, suppose you have an application with 2 threads. Thread 1
sets up a TCP server socket, and continuously receives data from a
connected client. Thread 2 continuously sends echo request packets
(ping) to the same client using an ICMP socket, and then receives echo
replys. What is to prevent Thread 2 from receiving one of the TCP
packets instead?

Best Answer

ICMP is a different protocol from TCP and UDP, as determined by the protocol field in the IP header. When you open a socket with IPPROTO_ICMP, you're telling the socket to transmit and receive only packets with IP headers whose protocol field is set to ICMP.

Similarly, sockets opened with IPPROTO_TCP or IPPROTO_UDP respond only to packets whose IP headers contain a protocol field that is set to TCP or UDP, respectively.

Related Solutions

C# – Listen for ICMP packets in C#

Nearly 3 years later and I stumbled across http://www.codeproject.com/Articles/17031/A-Network-Sniffer-in-C which gave me enough of a hint to help me find a solution to receiving ICMP packets on Windows 7 (don't know about Vista, which the original question was about but I suspect this solution would work).

The two key points are that the socket has to be bound to a single specific IP address rather than IPAddress.Any and the IOControl call which sets the SIO_RCVALL flag.

Socket icmpListener = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);
icmpListener.Bind(new IPEndPoint(IPAddress.Parse("10.1.1.2"), 0));
icmpListener.IOControl(IOControlCode.ReceiveAll, new byte[] { 1, 0, 0, 0 }, new byte[] { 1, 0, 0, 0 });

byte[] buffer = new byte[4096];
EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
int bytesRead = icmpListener.ReceiveFrom(buffer, ref remoteEndPoint);
Console.WriteLine("ICMPListener received " + bytesRead + " from " + remoteEndPoint);
Console.ReadLine();

I also had to set a firewall rule to allow ICMP Port Unreachable packets to be received.

netsh advfirewall firewall add rule name="All ICMP v4" dir=in action=allow protocol=icmpv4:any,any

Python – How to create an ICMP traceroute in Python

Here is the solution using Scapy - thanks to KillianDS.

Sending the ping

ans,unans=sr(IP(dst="www.google.com",ttl=X)/ICMP())

Accessing the reply

ans.summary(lambda (s,r): r.sprintf("%IP.src%") )

Best Answer

Related Solutions

C# – Listen for ICMP packets in C#

Python – How to create an ICMP traceroute in Python

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