/* gcc -Wall -O2 -g vsyssh.c -o vsyssh */
#define _XOPEN_SOURCE
#define _XOPEN_SOURCE_EXTENDED
#define _SVID_SOURCE
#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/select.h>
#include <sys/resource.h>
#include <sys/mount.h>
#include <sys/vfs.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <sched.h>
#include <stdarg.h>
#include <dirent.h>

void pipe_handler (int sig) {
  printf("SIGPIPE");
}

#define FILELEN 256

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

  if ( (argc<2) || (strcmp(argv[1],"--help")==0) ) {
    printf("Usage: vsyssh <vsys entry> [cmd]\n");
    exit(1);
  }

  {
    uid_t uid=getuid();
    if (uid!=0) {
      printf ("%s requires root privileges, please run under sudo\n",argv[0]);
      exit(1);
    }
  }

  {
    int vfd0,vfd1;
    char inf[FILELEN], outf[FILELEN];
    int fatal=0;

    signal(SIGPIPE,pipe_handler);
    
    sprintf(inf,"/vsys/%s.in",argv[1]);
    sprintf(outf,"/vsys/%s.out",argv[1]);
    vfd0 = open(outf,O_RDONLY|O_NONBLOCK);
    if (vfd0<0) {
      printf("Error opening vsys channel %s (%m)\n",outf);
      fatal=1;
    }
    vfd1 = open(inf,O_WRONLY);
    if (vfd1<0) {
      printf("Error opening vsys channel %s (%m)\n",inf);
      fatal=1;
    }

    if (fcntl(vfd0, F_SETFL, O_RDONLY) == -1) {
      printf("Error making pipe blocking: %m\n");
      fatal=1;
    }

    if (fatal) { exit(1);}

    if (argc<3) {
      /* interactive mode */
      fd_set set;
      char do_input = 1, do_output = 1;

      while (1) {
	  int ret;
	  printf("vsys>");fflush(stdout);
	  FD_ZERO(&set);
	  if (do_input)
	    FD_SET(0, &set);
	  if (do_output)
	    FD_SET(vfd0, &set);
	  ret = select(vfd0+1, &set, NULL, NULL, NULL);
	  if (FD_ISSET(0,&set)) {
	    char lineread[2048];
	    int ret;
	    ret=read(0,lineread,2048);
	    /*printf ("read=%d\n",ret);*/
	    if (ret == 0)
	      do_input = 0;
	    lineread[ret]='\0';
	    printf ("writing %s\n",lineread);
	    write(vfd1,lineread,ret);
	  }
	  if (FD_ISSET(vfd0,&set)) {
	    char lineread[2048];
	    int ret;
	    ret = read(vfd0,lineread,2048);
	    if (ret == 0)
	      break;
	    write(1,lineread,ret);
	  }
	}

    } else {
      /* line mode */
      close(0);
      close(1);

      dup2(vfd0,0);
      dup2(vfd1,1);
      execve(argv[2],argv+2,envp);
    }
  }

  return -1;

}