I'm trying to write a tcp syn port scanner with golang, I found a solution in C version here: http://www.binarytides.com/tcp-syn-portscan-in-c-with-linux-sockets/
I'd like to implement it in go, how can I send a tcp header like this in golang:
//TCP Header
tcph->source = htons ( source_port );
tcph->dest = htons (80);
tcph->seq = htonl(1105024978);
tcph->ack_seq = 0;
tcph->doff = sizeof(struct tcphdr) / 4; //Size of tcp header
tcph->fin=0;
tcph->syn=1;
tcph->rst=0;
tcph->psh=0;
tcph->ack=0;
tcph->urg=0;
tcph->window = htons ( 14600 ); // maximum allowed window size
tcph->check = 0; //if you set a checksum to zero, your kernel's IP stack should fill in the correct checksum during transmission
tcph->urg_ptr = 0;
Do I have to use syscall or cgo? I'm really appreciated if someone could help me out.
You're going to want to use syscall. However the syscall package is not necessarily portable across different Operating Systems so if that matters to you then you'll have to write per os versions and use the file_os.go naming scheme to hold the os specific code.
Related
I am trying to design a load balancer using ebpf. I want to transmit the incoming packet to different destinations (devices connected in the same network). Although I have used the clone_bpf_redirect() helper function to redirect the packet to real/ virtual interfaces and it's working fine, now I want to broadcast/unicast the packet to other devices connected in the same network.
XDP does not support it, as far as I know. Therefore, using tc bpf hook. Is there any helper function or which action should I use? Can anyone please guide me on how can I do this?
**eBpf load divider**: 192.168.98.178 (load divider)
**Receiver 1**: 192.168.98.131
**Receiver 2**: 192.168.98.138
iph->daddr = htonl(3232260739); //Dest: 192.168.98.131
iph->check = 0;
iph->check = checksum((unsigned short *)iph, sizeof(struct iphdr));
// Update upd packet checksum of
sum = old_daddr + (~ntohs(*(unsigned short *)&iph->daddr) & 0xffff);
sum += ntohs(udp->check);
sum = (sum & 0xffff) + (sum>>16);
udp->check = htons(sum + (sum>>16) - 1);
// clone the packet and redirect to infdex
bpf_clone_redirect(skb, skb->ifindex, 0);
//clone the packet and redirect to infdex (virtual interface 2)
bpf_clone_redirect(skb, skb->ifindex + 2, 0);
//clone the packet and redirect to infdex (virtual interface 4)
bpf_clone_redirect(skb, skb->ifindex + 4, 0);
return TC_ACT_OK;
// Or
// return TC_ACT_REDIRECT;
sudo tc filter add dev ens33 ingress bpf da obj bpf_loadbalancer.o sec ingress
after this, I am getting the 1 packet to 3 different ifindex but I want to get the same packet to other devices connected into the network. How can I redirect the packet out of the device, not the interfaces?
I want to simulate a server that receives packets from multiple clients and process the data of these packets simultaneously together in NS-3. I have simulated one single server and client in NS-3 by modifying udp-echo-server and udp-echo-client applications in NS-3. Now, for implementing multiple clients, I modified the end lines of StartApplication function in udp-echo-server application as follows:
if((childpid=fork())==0)
{
m_socket->SetRecvCallback (MakeCallback(&UdpEchoServer::HandleRead, this));
m_socket6->SetRecvCallback (MakeCallback(&UdpEchoServer::HandleRead, this));
}
But it does not work. Actually, by connecting two clients, it just reads the first client and ignores the second client. It just runs StartApplication function once. Can anyone help me with this?
Thanks
The fundamental problem with what you're trying to do is that ns-3 is a single threaded simulator. You should not use fork to simulate forking. If you want multiple clients, you have to explicitly create them. I have quickly whipped up a simple example:
/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
// simple udp multi-client, single-server simulation to answer
// https://stackoverflow.com/q/59632211/13040392
#include "ns3/core-module.h"
#include "ns3/internet-module.h"
#include "ns3/point-to-point-module.h"
#include "ns3/ipv4-global-routing-helper.h"
#include "ns3/applications-module.h"
#include "ns3/point-to-point-grid.h"
#include "ns3/flow-monitor-module.h"
using namespace ns3;
NS_LOG_COMPONENT_DEFINE("UdpMultiClient");
int
main(int argc, char *argv[]) {
// create grid structure of network
// not necessary. Could just create topology manually
PointToPointHelper p2pLink;
PointToPointGridHelper grid (2, 2, p2pLink);
InternetStackHelper stack;
grid.InstallStack(stack);
// assign IP addresses to NetDevices
grid.AssignIpv4Addresses (Ipv4AddressHelper ("10.1.1.0", "255.255.255.0"),
Ipv4AddressHelper ("10.2.1.0", "255.255.255.0"));
Ipv4GlobalRoutingHelper::PopulateRoutingTables();
// configure and install server app
int serverPort = 8080;
UdpEchoServerHelper serverApp (serverPort);
serverApp.Install(grid.GetNode(0,0));
Address serverAddress = InetSocketAddress(grid.GetIpv4Address(0,0), serverPort);
// configure and install client apps
UdpEchoClientHelper clientApp (serverAddress);
clientApp.Install(grid.GetNode(0,1));
clientApp.Install(grid.GetNode(1,0));
clientApp.Install(grid.GetNode(1,1));
// install FlowMonitor to collect simulation statistics
FlowMonitorHelper flowHelper;
Ptr<FlowMonitor> flowMonitor = flowHelper.InstallAll();
// configure and run simulation
Simulator::Stop(Seconds(10));
NS_LOG_UNCOND("Starting simulation.");
Simulator::Run();
Simulator::Destroy();
NS_LOG_UNCOND("Simulation completed.");
// simulation complete
// get statistics of simlation from FlowMonitor
flowMonitor->CheckForLostPackets();
std::map<FlowId, FlowMonitor::FlowStats> stats = flowMonitor->GetFlowStats();
uint64_t txPacketsum = 0;
uint64_t rxPacketsum = 0;
uint64_t DropPacketsum = 0;
uint64_t LostPacketsum = 0;
double Delaysum = 0;
for (std::map<FlowId, FlowMonitor::FlowStats>::const_iterator i = stats.begin(); i != stats.end(); ++i) {
txPacketsum += i->second.txPackets;
rxPacketsum += i->second.rxPackets;
LostPacketsum += i->second.lostPackets;
DropPacketsum += i->second.packetsDropped.size();
Delaysum += i->second.delaySum.GetSeconds();
}
NS_LOG_UNCOND(std::endl << " SIMULATION STATISTICS");
NS_LOG_UNCOND(" All Tx Packets: " << txPacketsum);
NS_LOG_UNCOND(" All Rx Packets: " << rxPacketsum);
NS_LOG_UNCOND(" All Delay: " << Delaysum / txPacketsum);
NS_LOG_UNCOND(" All Lost Packets: " << LostPacketsum);
NS_LOG_UNCOND(" All Drop Packets: " << DropPacketsum);
NS_LOG_UNCOND(" Packets Delivery Ratio: " << ((rxPacketsum * 100) / txPacketsum) << "%");
NS_LOG_UNCOND(" Packets Lost Ratio: " << ((LostPacketsum * 100) / txPacketsum) << "%");
// flowMonitor->SerializeToXmlFile("test.xml", true, true);
return 0;
}
As a quick note, in
UdpEchoClientHelper clientApp (serverAddress);
clientApp.Install(grid.GetNode(0,1));
clientApp.Install(grid.GetNode(1,0));
clientApp.Install(grid.GetNode(1,1));
we installed the UdpEchoClient on three Nodes. According to the documentation for this Application, UdpEchoClient sends a packet every 1000000000 ns = 1 s by default. Since we set the length of the simulation to 10 seconds using Simulator::Stop(Seconds(10));, we expect that each client will send 10 packets to the server. So, a total of 30 packets should be sent by clients. Also, since we are using UdpEchoServerHelper on the server, each packet will be echoed back by the server. Therefore, a total of 30 x 2 = 60 packets should be transmitted on the network.
The output of the script is
Starting simulation.
Simulation completed.
SIMULATION STATISTICS
All Tx Packets: 60
All Rx Packets: 60
All Delay: 0.0423177
All Lost Packets: 0
All Drop Packets: 0
Packets Delivery Ratio: 100%
Packets Lost Ratio: 0%
This answer actually demonstrates several features of ns-3, so feel free to ask any followup questions. I highly encourage you to check out the ns-3 documentation for classes you haven't encountered yet.
I have been injecting packets on the network and watching the effects via wireshark. I am able to correctly set and change tcp ports and set the source and destination. However, I am now having an issue. One of the things I need to do is to set a source port from port 66,000. Every time I try it just puts the number to 1163 in wireshark which is because it is supposed to be a short integer. Does anyone know how to make it accept the big number. I know the big endian and htonl should work so I tried that as well but that didn't solve the issue.
Here is the code I am using
void extract(u_char *user, struct pcap_pkthdr *h, u_char *pack ) {
struct eth_hdr *ethhdr;
struct ip_hdr *iphdr;
struct tcp_hdr *tcphdr;
ethhdr = (struct eth_hdr *)pack;
iphdr = (struct ip_hdr *)(pack + ETH_HDR_LEN);
tcphdr = (struct tcp_hdr *) (pack + ETH_HDR_LEN + (4*iphdr->ip_hl));
//Set the ports
tcphdr->th_sport = htons(66666);
tcphdr->th_dport = htons(atoi(destString));
The port number is 16 bit. With 16 bit you can get only up to 65535. No way around it. See also the TCP header at http://en.wikipedia.org/wiki/Transmission_Control_Protocol#TCP_segment_structure.
I am writing an application which is continuously sending and receiving data. My initial send/receive is running successfully but when I am expecting data of size 512 bytes in the recvfrom I get its return value as -1 which is "Resource temporarily unavailable." and errno is set to EAGAIN. If I use a blocking call i.e. without Timeout the application just hangs in recvfrom. Is there any max limit on recvfrom on iPhone? Below is the function which receives data from the server. I am unable to figure out what can be going wrong.
{ struct timeval tv;
tv.tv_sec = 3;
tv.tv_usec = 100000;
setsockopt (mSock, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv, sizeof tv);
NSLog(#"Receiving.. sock:%d",mSock);
recvBuff = (unsigned char *)malloc(1024);
if(recvBuff == NULL)
NSLog(#"Cannot allocate memory to recvBuff");
fromlen = sizeof(struct sockaddr_in);
n = recvfrom(mSock,recvBuff,1024,0,(struct sockaddr *)&from, &fromlen);
if (n == -1) {
[self error:#"Recv From"];
return;
}
else
{
NSLog(#"Recv Addr: %s Recv Port: %d",inet_ntoa(from.sin_addr), ntohs(from.sin_port));
strIPAddr = [[NSString alloc] initWithFormat:#"%s",inet_ntoa(from.sin_addr)];
portNumber = ntohs(from.sin_port);
lIPAddr = [KDefine StrIpToLong:strIPAddr];
write(1,recvBuff,n);
bcopy(recvBuff, data, n);
actualRecvBytes = n;
free(recvBuff);
}
}
Read the manpage:
If no messages are available at the socket, the receive call waits for a message to arrive, unless the socket is nonblocking (see fcntl(2)) in which case the value -1 is returned and the external variable errno set to EAGAIN.
I was writing a UDP application and think I came across a similar issue. Peter Hosey is correct in stating that the given result of recvfrom means that there is no data to be read; but you were wondering, how can there be no data?
If you are sending several UDP datagrams at a time from some host to your iphone, some of those datagrams may be discarded because the receive buffer size (on the iphone) is not large enough to accommodate that much data at once.
The robust way to fix the problem is to implement a feature that allows your application to request a retransmission of missing datagrams. A not as robust solution (that doesn't solve all the issues that the robust solution does) is to simply increase the receive buffer size using setsockopt(2).
The buffer size adjustment can be done as follows:
int rcvbuf_size = 128 * 1024; // That's 128Kb of buffer space.
if (setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF,
&rcvbuf_size, sizeof(rcvbuf_size)) == -1) {
// put your error handling here...
}
You may have to play around with buffer size to find what's optimal for your application.
For me it was a casting issue. Essentially a was assigning the returned value to an int instead of size_t
int rtn = recvfrom(sockfd,... // wrong
instead of:
size_t rtn = recvfrom(sockfd,...// correct
How do you use network sockets in Pascal?
Here's an example taken from http://www.bastisoft.de/programmierung/pascal/pasinet.html
program daytime;
{ Simple client program }
uses
sockets, inetaux, myerror;
const
RemotePort : Word = 13;
var
Sock : LongInt;
sAddr : TInetSockAddr;
sin, sout : Text;
Line : String;
begin
if ParamCount = 0 then GenError('Supply IP address as parameter.');
with sAddr do
begin
Family := af_inet;
Port := htons(RemotePort);
Addr := StrToAddr(ParamStr(1));
if Addr = 0 then GenError('Not a valid IP address.');
end;
Sock := Socket(af_inet, sock_stream, 0);
if Sock = -1 then SockError('Socket: ');
if not Connect(Sock, sAddr, sizeof(sAddr)) then SockError('Connect: ');
Sock2Text(Sock, sin, sout);
Reset(sin);
Rewrite(sout);
while not eof(sin) do
begin
Readln(sin, Line);
Writeln(Line);
end;
Close(sin);
Close(sout);
Shutdown(Sock, 2);
end.
If you're using FPC or Lazarus(which is basically a rad IDE for FPC and a clone of delphi) you could use the Synapse socket library. It's amazing.
If you are using Delphi, I highly recommend Indy sockets, a set of classes for easy manipulation of sockets and many other internet protocols (HTTP, FTP, NTP, POP3 etc.)
You cannot use OpenSSL with Indy version 10.5 that shippes with Delphi 2007. You have to download version 10,6 from http://www.indyproject.org/ and install it into the IDE.
Note that other packages might use Indy, like RemObjects, and therefore they have to be re-compiled too and this can be tricky due to cross-references.