To implement network port access in ns3, we need to follow several steps. For controlling access to specific ports, we have to configure the network nodes. This is typically used for simulating firewall rules, network address translation (NAT), or other access control mechanisms. Here the steps given below will guide on how to implement basic port access control in ns3.
Step-by-step guide to implement Network Port Access:
- Set Up ns-3 Environment
Make sure ns3 is installed on the system.
- Create a New Simulation Script
Create a new C++ script for simulation. For this example, we’ll use C++.
- Include Necessary Headers
Include the necessary ns3 headers in the script.
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/internet-module.h”
#include “ns3/point-to-point-module.h”
#include “ns3/applications-module.h”
#include “ns3/mobility-module.h”
#include “ns3/ipv4-static-routing-helper.h”
4. Define the Network Topology
Set up the basic network topology, including nodes, devices, and links. For this example, we’ll set up a simple network with three nodes: a client, a server, and a router that will act as a firewall
using namespace ns3;
NS_LOG_COMPONENT_DEFINE (“PortAccessExample”);
int main (int argc, char *argv[]) {
CommandLine cmd;
cmd.Parse (argc, argv);
// Create nodes
NodeContainer nodes;
nodes.Create (3); // Create 3 nodes: client, server, and router
// Set up point-to-point links
PointToPointHelper p2p;
p2p.SetDeviceAttribute (“DataRate”, StringValue (“5Mbps”));
p2p.SetChannelAttribute (“Delay”, StringValue (“2ms”));
NetDeviceContainer devices;
devices.Add (p2p.Install (nodes.Get (0), nodes.Get (2))); // Client to Router
devices.Add (p2p.Install (nodes.Get (2), nodes.Get (1))); // Router to Server
// Install the internet stack
InternetStackHelper stack;
stack.Install (nodes);
Ipv4AddressHelper address;
address.SetBase (“10.1.1.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces = address.Assign (devices.Get (0));
address.SetBase (“10.1.2.0”, “255.255.255.0”);
interfaces.Add (address.Assign (devices.Get (1)));
// Set up routing
Ipv4StaticRoutingHelper ipv4RoutingHelper;
Ptr<Ipv4StaticRouting> clientStaticRouting = ipv4RoutingHelper.GetStaticRouting (nodes.Get (0)->GetObject<Ipv4> ());
clientStaticRouting->AddNetworkRouteTo (Ipv4Address (“10.1.2.0”), Ipv4Mask (“255.255.255.0”), Ipv4Address (“10.1.1.2”), 1);
Ptr<Ipv4StaticRouting> serverStaticRouting = ipv4RoutingHelper.GetStaticRouting (nodes.Get (1)->GetObject<Ipv4> ());
serverStaticRouting->AddNetworkRouteTo (Ipv4Address (“10.1.1.0”), Ipv4Mask (“255.255.255.0”), Ipv4Address (“10.1.2.2”), 1);
// Implement port access control
// Define allowed port
uint16_t allowedPort = 8080;
// Define a custom packet filter function
bool PacketFilter(Ptr<const Packet> packet, const Address &from, const Address &to) {
PppHeader pppHeader;
Ipv4Header ipv4Header;
UdpHeader udpHeader;
TcpHeader tcpHeader;
packet->PeekHeader(pppHeader);
packet->PeekHeader(ipv4Header);
if (ipv4Header.GetProtocol() == UdpL4Protocol::PROT_NUMBER) {
packet->PeekHeader(udpHeader);
if (udpHeader.GetDestinationPort() == allowedPort) {
return true;
}
} else if (ipv4Header.GetProtocol() == TcpL4Protocol::PROT_NUMBER) {
packet->PeekHeader(tcpHeader);
if (tcpHeader.GetDestinationPort() == allowedPort) {
return true;
}
}
return false;
}
// Install a packet filter on the router
Ptr<Node> routerNode = nodes.Get(2);
Ptr<NetDevice> routerDevice1 = routerNode->GetDevice(0);
Ptr<NetDevice> routerDevice2 = routerNode->GetDevice(1);
routerDevice1->SetReceiveCallback(MakeCallback(PacketFilter));
routerDevice2->SetReceiveCallback(MakeCallback(PacketFilter));
// Set up mobility (optional)
MobilityHelper mobility;
mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);
mobility.Install (nodes);
// Install applications
// Client: Send a UDP packet to the server on the allowed port and on a blocked port
UdpEchoClientHelper echoClient (interfaces.GetAddress (1), allowedPort);
echoClient.SetAttribute (“MaxPackets”, UintegerValue (1));
echoClient.SetAttribute (“Interval”, TimeValue (Seconds (1.0)));
echoClient.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer clientApps = echoClient.Install (nodes.Get (0));
clientApps.Start (Seconds (2.0));
clientApps.Stop (Seconds (10.0));
UdpEchoClientHelper echoClientBlocked (interfaces.GetAddress (1), 9090);
echoClientBlocked.SetAttribute (“MaxPackets”, UintegerValue (1));
echoClientBlocked.SetAttribute (“Interval”, TimeValue (Seconds (1.0)));
echoClientBlocked.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer clientAppsBlocked = echoClientBlocked.Install (nodes.Get (0));
clientAppsBlocked.Start (Seconds (3.0));
clientAppsBlocked.Stop (Seconds (10.0));
// Server: Echo server to receive UDP packets on the allowed port
UdpEchoServerHelper echoServer (allowedPort);
ApplicationContainer serverApps = echoServer.Install (nodes.Get (1));
serverApps.Start (Seconds (1.0));
serverApps.Stop (Seconds (10.0))
// Enable pcap tracing
p2p.EnablePcapAll (“port-access”);
// Run simulation
Simulator::Stop (Seconds (10.0));
Simulator::Run ();
Simulator::Destroy ();
return 0;
}
Explanation
- Network Topology: The script sets up a simple network with three nodes: a client, a router, and a server.
- Point-to-Point Links: The client and server are connected to the router via point-to-point links.
- Internet Stack: The InternetStackHelper is used to install the IP stack on all nodes.
- Routing: To ensure proper packet forwarding between the client and server through the router, static routing is configured.
- Port Access Control: A custom packet filter function is defined to allow packets only on a specific port (8080). This filter is installed on the router’s network devices. The function checks the destination port of incoming packets and allows or blocks them accordingly.
- Applications: To send packets to the server on both allowed and blocked ports, a UDP echo client is installed on the client node. A UDP echo server is installed on the server node to receive packets on the allowed port.
- PCAP Tracing: For analysis, PCAP tracing is enabled to capture packets.
5. Build and Run the Script
Save the script and build it using the ns3 build system (waf).
./waf configure
./waf build
./waf –run port-access
Extending the Example
We can extend this example to include more complex scenarios, such as:
- Dynamic Port Access Control: Implement dynamic port access control rules that change based on network conditions or time.
- Advanced Packet Filtering: Based on various criteria such as source IP, destination IP, protocol type, etc., Use more advanced packet filtering techniques to block or allow packets
- Firewall Rules: Implement firewall rules to block specific types of traffic or enforce security policies.
- Network Address Translation (NAT): To translate private IP addresses to public IP addresses and vice versa implement NAT.
An example of setting up advanced packet filtering based on source IP and protocol type is given below:
bool PacketFilter(Ptr<const Packet> packet, const Address &from, const Address &to) {
PppHeader pppHeader;
Ipv4Header ipv4Header;
UdpHeader udpHeader;
TcpHeader tcpHeader;
packet->PeekHeader(pppHeader);
packet->PeekHeader(ipv4Header);
if (ipv4Header.GetSource() == Ipv4Address(“10.1.1.1”)) { // Check source IP
if (ipv4Header.GetProtocol() == UdpL4Protocol::PROT_NUMBER) {
packet->PeekHeader(udpHeader);
if (udpHeader.GetDestinationPort() == allowedPort) {
return true;
}
} else if (ipv4Header.GetProtocol() == TcpL4Protocol::PROT_NUMBER) {
packet->PeekHeader(tcpHeader);
if (tcpHeader.GetDestinationPort() == allowedPort) {
return true;
}
}
}
return false;
}
From the above given instruction and example, we can completely understand how to implement Network port Access in ns3 and what are the steps involved while extending the basic port access control in ns3.
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