Why is my program soooo slow in Windows

CodeBlox

I wrote a simple port scanner and under linux it's lightning fast while on windows (After small modifications to port over) it's dog slow:

Usage is: portscan.exe [ip address]

#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <stdlib.h>


#define PORT_MIN 0x0000
#define PORT_MAX 0xFFFF


void test_port(SOCKET, struct sockaddr_in *, unsigned short, char *);

int main(int argc, char ** argv){


    SOCKET client_socket;
    WSADATA wsaData;
    struct sockaddr_in target;
    unsigned short port = PORT_MIN;


    WSAStartup(MAKEWORD(2, 2), &wsaData);


    memset(&target, sizeof(target), 0);


    if((target.sin_addr.s_addr = inet_addr(argv[1])) != INADDR_NONE)
        while(port++ < PORT_MAX)
            test_port(client_socket, &target, port, "tcp");


    return 0;
}


void test_port(SOCKET client_socket, struct sockaddr_in * target, unsigned short port, char * svc_proto){


    struct servent * service;


    printf("Testing %s port %u\r", svc_proto, port);


    target->sin_family = AF_INET;
    target->sin_port = htons(port);


    if((client_socket = socket(AF_INET, SOCK_STREAM, 0)) != INVALID_SOCKET)
        if(connect(client_socket, (struct sockaddr *)target, sizeof(*target)) != SOCKET_ERROR){
            closesocket(client_socket);
            if(service = getservbyport(port, svc_proto))
                printf("Discovered open port %u (%s)/%s\n", port, service->s_name, svc_proto);
            else
                printf("Discovered open port %u/%s\n", port, svc_proto);
        }


}

What could cause it to be significantly slower?

paul78

It because you are using a blocking connect(). Not sure if Windows supports using setsockopt() timeout options on connect() but that's one thing you can try.

I vaguely recall (its been a while) that in Windows to do what you want efficiently, you would use an async/nonblocking connect() and write your own handler with select().

Good luck - sounds like a fun project.

newt.chapman

(Anthony) wrote:

most likely due to the connection recycling wait and tcp connection limit in windows.

Quoted from a programming friendly board that I took the liberty of posting this problem on.

paul78

newt.chapman wrote: »

connection recycling wait

That's the cause of a blocking connect(). That's why it's normally done with an async connect() and then you can poll with select().

CodeBlox

Sooo, I revised the program to scan a whole subnet and it seems to work, only now under even Linux, it starts going at a snails pace after the second IP... Any thoughts?

usage: ./portscan [subnet] [mask]

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>


#define NET_MASK 0XFFFFFFFF
#define PORT_LIMIT 65535
#define BASE_PORT 0


void get_addr_space(unsigned long int *, unsigned long int *, struct in_addr, struct in_addr);
void scan_addr(unsigned long int, struct sockaddr_in *, unsigned short);
int test_port(int, unsigned short, struct sockaddr_in *, char *);
void port_info(unsigned short, char *);




int main(int argc, char ** argv){


  unsigned short port = BASE_PORT;
  unsigned long int curr_addr = 0, max_addr = 0;
  struct sockaddr_in target;
  struct in_addr mask;
  
  inet_pton(AF_INET, argv[1], &target.sin_addr);
  inet_pton(AF_INET, argv[2], &mask);
  
  get_addr_space(&curr_addr, &max_addr, target.sin_addr, mask);
  
  target.sin_family = AF_INET;
  
  curr_addr = ntohl(curr_addr);
  max_addr = ntohl(max_addr);
  
  while(curr_addr < max_addr - 1)
    scan_addr(curr_addr++, &target, port);
  
  return 0;
}


void get_addr_space(unsigned long int * min, unsigned long int * max, struct in_addr subnet, struct in_addr mask){
  
  unsigned long int subnet_bits = subnet.s_addr & mask.s_addr;
  
  *min = subnet_bits;
  *max = subnet_bits;
  
  //*max = ((~*max + subnet_bits) & ~mask.s_addr) + *max;
  *max = NET_MASK & ~mask.s_addr + *max;
}


void scan_addr(unsigned long int dec_addr, struct sockaddr_in * target, unsigned short port){
  
  int client_socket = 0;
  char ipv4[INET_ADDRSTRLEN];
  
  target->sin_addr.s_addr = htonl(dec_addr);
  target->sin_port = port;
  printf("\nTrying IP %s\n", inet_ntop(AF_INET, &target->sin_addr, ipv4, INET_ADDRSTRLEN)); 
  
  while(port < PORT_LIMIT)
    if(!test_port(client_socket, port++, target, "tcp"))
      port_info(port - 1, "tcp");
  
}


int test_port(int client_socket, unsigned short port, struct sockaddr_in * target, char * svc_proto){
  
  printf("\t - Trying %s port %u\r", svc_proto, port); 
  
  target->sin_family = AF_INET;
  target->sin_port = htons(port);
  
  if((client_socket = socket(AF_INET, (svc_proto == "tcp" ? SOCK_STREAM : SOCK_DGRAM), 0)) > 0){
    if(connect(client_socket, (struct sockaddr *)target, sizeof(*target))){
      close();
      return 1;
    }
    else
      return 0;
  }else
    perror("");
  
}


void port_info(unsigned short port, char * svc_proto){
  
  struct servent * service;
  
  if((service = getservbyport(htons(port), svc_proto)))
    printf("\t - %s port %u (%s) is open\n", svc_proto, port, service->s_name);
  else
    printf("\t - %s port %u is open\n", svc_proto, port);
  
  
}

paul78

I just tried it on Linux - it seems to work pretty quick for me. About 1000 tcp ports per second. Are you expecting something else?

CodeBlox

Well, it works fine for the first IP, really fast but when it gets to 192.168.0.2 it goes at a snails pace... Come to think of it... I think I know why that is. There is no host at that address! :P

paul78

Opps - I was reading your note incorrectly - yes - in that situation - connect() will block while it waits for the SYN packet response.

[edit] - Actually - I'm not sure that my theory makes sense. The connect() will block even if there is a host at that address but the target host doesn't respond to the SYN.

CodeBlox

What I could do is assume some threshold of ports that I fail to connect on and test errno for ETIMEDOUT... Maybe this is a valid way of checking for now until I buckle down on raw sockets. As far as I know though, connect won't block forever, it'll eventuall return something and if failed set errno.

paul78

Yeah - that could work. I looked a bit closer and it looks like my hosts are returning RST so getting ECPNNREFUSED - so that explains why I was seeing the faster connect() fails. It's the ETIMEDOUT that's the issue.

Sounds like you understand that the right way is to use SOCK_RAW. Big fun!

CodeBlox

Got it working as desired for now (continues past "offline" host) by checking if errno == EHOSTUNREACH. See below:

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>


#define NET_MASK 0XFFFFFFFF
#define PORT_LIMIT 0XFFFF
#define BASE_PORT 0X0000


void get_addr_space(unsigned long int *, unsigned long int *, struct in_addr, struct in_addr);
void scan_addr(unsigned long int, struct sockaddr_in *, unsigned short);
int test_port(int, unsigned short, struct sockaddr_in *, char *);
void port_info(unsigned short, char *);




int main(int argc, char ** argv){
  
  unsigned short port = BASE_PORT;
  unsigned long int curr_addr = 0, max_addr = 0;
  struct sockaddr_in target;
  struct in_addr mask;
  
  inet_pton(AF_INET, argv[1], &target.sin_addr);
  inet_pton(AF_INET, argv[2], &mask);
  
  get_addr_space(&curr_addr, &max_addr, target.sin_addr, mask);
  
  target.sin_family = AF_INET;
  
  curr_addr = ntohl(curr_addr);
  max_addr = ntohl(max_addr);
  
  //printf("Min: %u, Max: %u\n", curr_addr, max_addr + 1);
  
  
  while(curr_addr < max_addr - 1)
    scan_addr(++curr_addr, &target, port);
  
  return 0;
}


void get_addr_space(unsigned long int * min, unsigned long int * max, struct in_addr subnet, struct in_addr mask){
  
  unsigned long int subnet_bits = subnet.s_addr & mask.s_addr;
  
  *min = subnet_bits;
  *max = subnet_bits;
  
  //*max = ((~*max + subnet_bits) & ~mask.s_addr) + *max;
  *max = NET_MASK & ~mask.s_addr + *max;
}


void scan_addr(unsigned long int dec_addr, struct sockaddr_in * target, unsigned short port){
  
  int client_socket = 0;
  char ipv4[INET_ADDRSTRLEN];
  
  target->sin_addr.s_addr = htonl(dec_addr);
  
  target->sin_port = htons(port);
  
  printf("Trying IP %s\n\n", inet_ntop(AF_INET, &target->sin_addr, ipv4, INET_ADDRSTRLEN)); 
  
  
  while(port < PORT_LIMIT){
    if(test_port(client_socket, port++, target, "tcp"))
      port_info(port - 1, "tcp");
    
    else if(errno == EHOSTUNREACH)
      break;
    else
      continue;
  }
  
}


int test_port(int client_socket, unsigned short port, struct sockaddr_in * target, char * svc_proto){
  
  printf("Trying %s port %u\r", svc_proto, port); 
  
  target->sin_family = AF_INET;
  target->sin_port = htons(port);
  
  if((client_socket = socket(AF_INET, (svc_proto == "tcp" ? SOCK_STREAM : SOCK_DGRAM), 0)) > 0){
    if(!connect(client_socket, (struct sockaddr *)target, sizeof(*target))){
      close(client_socket);
      return 1;
    }
    else
      close(client_socket);
    return 0;
  }else
    perror("");
  
}


void port_info(unsigned short port, char * svc_proto){
  
  struct servent * service;
  
  if((service = getservbyport(htons(port), svc_proto)))
    printf("%s port %u (%s) is open\n", svc_proto, port, service->s_name);
  else
    printf("%s port %u is open\n", svc_proto, port);
  
  
}

paul78

Nice work CodeBlox!!! Now if you thread it, you can even make it more efficient What you can do is to create a separate threads as well - perhaps one thread per IP.