/***********************************************
 2020 Hacker Factor. Public domain, use at your own risk.
 Neal's quick and easy "let's test everything" test
 to see how many sockets are available.

 To compile: gcc -o sockettest sockettest.c
 To run: ./sockettest
 ***********************************************/

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <ulimit.h>
#include <poll.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/socket.h>

void	main	()
{
  struct rlimit rlim;
  struct pollfd *fds;
  int s;
  int RealMax,Count,SocketCount;

  // Check the default limits
  printf("Initial limits\n");
  getrlimit(RLIMIT_NOFILE, &rlim);
  printf("  getrlimit(RLIMIT_NOFILE): soft=%d hard=%d\n",
	(int)rlim.rlim_cur, (int)rlim.rlim_max);

  RealMax = sysconf(_SC_OPEN_MAX);
  printf("  sysconf(_SC_OPEN_MAX): %d\n",RealMax);
  printf("  sysconf(_SC_STREAM_MAX): %ld\n",(long)sysconf(_SC_STREAM_MAX));
  printf("  ulimit(4): %d\n",(int)ulimit(4,0)); // use getrlimit

  // How many sockets are currently in use?
  fds = (struct pollfd*)calloc(sizeof(struct pollfd),RealMax);
  for(s=0; s < RealMax; s++) { fds[s].fd=s; }
  poll(fds,RealMax,0);
  Count=0;
  for(s=0; s < RealMax; s++)
    {
    if (!(fds[s].revents&POLLNVAL)) { Count++; }
    }
  free(fds);
  printf("Sockets in use: %d\n",Count);

  // Now let's actually see how many we can do!
  SocketCount=0;
  while(1)
    {
    s=socket(AF_INET,SOCK_STREAM,0);
    if (s >= 0) { SocketCount++; }
    else { break; } // s==-1
    }
  printf("Managed to create %d sockets before failing.\n",SocketCount);

  /*****
   In Tor's ./src/lib/process/restrict.c, they set the soft limit to
   be the hard limit.  Let's try that!
   *****/
  printf("Resetting limits so soft=max\n");
  rlim.rlim_cur = rlim.rlim_max;
  setrlimit(RLIMIT_NOFILE, &rlim);

  // Now check the limits after the reset...
  getrlimit(RLIMIT_NOFILE, &rlim);
  printf("  getrlimit(RLIMIT_NOFILE): soft=%d hard=%d\n",
	(int)rlim.rlim_cur, (int)rlim.rlim_max);

  RealMax = sysconf(_SC_OPEN_MAX);
  printf("  sysconf(_SC_OPEN_MAX): %d\n",RealMax);
  printf("  sysconf(_SC_STREAM_MAX): %ld\n",(long)sysconf(_SC_STREAM_MAX));
  printf("  ulimit(4): %d\n",(int)ulimit(4,0)); // use getrlimit

  // How many sockets are currently in use?
  fds = (struct pollfd*)calloc(sizeof(struct pollfd),RealMax);
  for(s=0; s < RealMax; s++) { fds[s].fd=s; }
  poll(fds,RealMax,0);
  Count=0;
  for(s=0; s < RealMax; s++)
    {
    if (!(fds[s].revents&POLLNVAL)) { Count++; }
    }
  free(fds);
  printf("Sockets in use: %d (including the previous %d test)\n",Count,SocketCount);
  printf("  There should be %d more sockets available.\n",RealMax-Count);

  // Now let's actually see how many more we can allocate!
  while(1)
    {
    s=socket(AF_INET,SOCK_STREAM,0);
    if (s >= 0) { SocketCount++; }
    else { break; } // s==-1
    }
  printf("Managed to create %d sockets before failing.\n",SocketCount);
}