/* Copyright status: this file is in the public domain. */

/*
 * <termios.h>, the documented include file for termios stuff, defines
 *  struct termios and many associated manifest constants.  Including
 *  it does not, however, define TIOCSCTTY - even though tty_ioctl(4)
 *  describes TIOCSCTTY and says <termios.h> is the correct file to
 *  include for it.
 *
 * TIOCSCTTY is actually defined in exactly one place:
 *  /usr/include/asm-generic/ioctls.h.  (All further relative paths in
 *  this paragraph are relative to /usr/include.)  asm-generic/ioctls.h
 *  is included from exactly one place, x86_64-linux-gnu/asm/ioctls.h.
 *  asm/ioctls.h is included from a handful of places.  The correct one
 *  for us to get it from is bits/ioctls.h, via sys/ioctl.h, but it
 *  also included from asm-generic/termios.h, which is included from
 *  x86_64-linux-gnu/asm/termios.h, which is included from
 *  linux/termios.h.  But if we include <linux/termios.h>, we get a
 *  struct termios that is substantially smaller than the real thing,
 *  leading tcgetattr to scribble on the stack frame!  (The proper
 *  struct termios has 32 c_cc entries and c_[io]speed members.  If we
 *  include <linux/termios.h>, we get asm-generic/termbits.h, by way of
 *  various other files, and that version has only 19 entries in c_cc
 *  and no c_[io]speed.)
 *
 * So, <termios.h> is not enough without <sys/ioctl.h>, contrary to the
 *  documentation, and there are severely broken variants of things
 *  lurking in the include files to surprise the unwary.
 */

#define _XOPEN_SOURCE /* necessary to get ptsname() declared (!) */
#define _XOPEN_SOURCE_EXTENDED /* necessary to get strdup() declared (!!) */
#define _BSD_SOURCE /* necessary to get ECHOKE and ECHOCTL (!!!) */
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <termios.h>
#include <strings.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/ttydefaults.h>

extern const char *__progname;

#include "ptyimpl.h"

static int ptypair(int *mfdp, int *sfdp, char **spathp)
{
 int i;
 int mfd;
 int sfd;
 int tfd;
 char *p;
 struct termios tio;
 struct termios tty_tio;

 tfd = open("/dev/tty",O_RDONLY,0);
 if (tfd >= 0)
  { if (tcgetattr(tfd,&tty_tio) == 0)
     { close(tfd);
       tfd = 1;
     }
    else
     { close(tfd);
       tfd = 0;
     }
  }
 else
  { tfd = 0;
  }
 mfd = posix_openpt(O_RDWR|O_NOCTTY);
 if (mfd < 0) return(-1);
 if (grantpt(mfd) < 0) return(-1);
 if (unlockpt(mfd) < 0) return(-1);
 p = ptsname(mfd);
 if (! p) return(-1);
 sfd = open(p,O_RDWR,0);
 if (sfd < 0) return(-1);
 if (tcgetattr(sfd,&tio) == 0)
  { tio.c_iflag = ICRNL | IXON | IXANY | IMAXBEL;
    tio.c_oflag = OPOST | ONLCR;
    tio.c_cflag = (tio.c_cflag & (CSIZE|CSTOPB|PARENB|PARODD)) | CREAD | HUPCL;
    tio.c_lflag = ICANON | ISIG | IEXTEN | ECHO | ECHOE | ECHOKE | ECHOCTL;
    tio.c_cc[VEOF] = CEOF;
    tio.c_cc[VEOL] = CEOL;
    tio.c_cc[VERASE] = CERASE;
    tio.c_cc[VINTR] = CINTR;
    tio.c_cc[VKILL] = CKILL;
    tio.c_cc[VQUIT] = CQUIT;
    tio.c_cc[VSUSP] = CSUSP;
    tio.c_cc[VSTART] = CSTART;
    tio.c_cc[VSTOP] = CSTOP;
    tio.c_cc[VLNEXT] = CLNEXT;
    tio.c_cc[VDISCARD] = CDISCARD;
    tio.c_cc[VWERASE] = CWERASE;
    tio.c_cc[VREPRINT] = CREPRINT;
    if (tfd)
     { for (i=(sizeof(tio.c_cc)/sizeof(tio.c_cc[0]))-1;i>=0;i--) tio.c_cc[i] = tty_tio.c_cc[i];
     }
    tio.c_cc[VMIN] = CMIN;
    tio.c_cc[VTIME] = CTIME;
    tcsetattr(sfd,TCSANOW,&tio);
  }
 *mfdp = mfd;
 *sfdp = sfd;
 *spathp = strdup(p);
 return(0);
}

void ptypair_setup(int *mfdp, int *sfdp, char **spathp, char **errp)
{
 char *spath;

 if (ptypair(mfdp,sfdp,&spath) < 0)
  { *errp = strdup("no pty pairs available");
    return;
  }
 if (spathp) *spathp = spath; else free(spath);
 *errp = 0;
}

void conspty_setup(int *mfdp, int *sfdp, const char **spathp, char **errp)
{
 char *spath;

 if (ptypair(mfdp,sfdp,&spath) < 0)
  { asprintf(errp,"no pty pairs available: %s",strerror(errno));
    return;
  }
 if (spathp) *spathp = spath; else free(spath);
 *errp = 0;
}

void ptyexport_setup(const char *prog, int *ptymp, int *ptysp, char **errp)
{
 int mfd;
 int sfd;
 char *spath;
 pid_t kid;
 int xp[2];
 int e;
 int r;
 pid_t wk;
 int ws;

 if (ptypair(&mfd,&sfd,&spath) < 0)
  { asprintf(errp,"no pty pairs available: %s",strerror(errno));
    return;
  }
 do
  { if (socketpair(AF_LOCAL,SOCK_STREAM,0,&xp[0]) < 0)
     { asprintf(errp,"socketpair: %s",strerror(errno));
       break;
     }
    do <"err">
     { fflush(0);
       kid = fork();
       if (kid < 0)
	{ asprintf(errp,"fork: %s",strerror(errno));
	  break;
	}
       if (kid == 0)
	{ close(xp[0]);
	  fcntl(xp[1],F_SETFD,1);
	  execlp(prog,prog,"up",spath,(char *)0);
	  e = errno;
	  send(xp[1],&e,sizeof(int),0);
	  _exit(0);
	}
       close(xp[1]);
       xp[1] = -1;
       r = recv(xp[0],&e,sizeof(int),MSG_WAITALL);
       if (r < 0)
	{ asprintf(errp,"exec pipe recv: %s",strerror(errno));
	  break;
	}
       if (r == sizeof(int))
	{ asprintf(errp,"exec: %s",strerror(e));
	  break;
	}
       if (r != 0)
	{ asprintf(errp,"exec protocol error (wanted %d, got %d)",(int)sizeof(int),r);
	  break;
	}
       close(xp[0]);
       while (1)
	{ wk = waitpid(kid,&ws,0);
	  if (wk < 0)
	   { asprintf(errp,"exec protocol wait: %s",strerror(errno));
	     break <"err">;
	   }
	  if (wk == 0)
	   { *errp = strdup("exec protocol lost child");
	     break <"err">;
	   }
	  if (wk == kid) break;
	}
       if (WIFEXITED(ws))
	{ if (WEXITSTATUS(ws) == 0)
	   { *ptymp = mfd;
	     *ptysp = sfd;
	     *errp = 0;
	     return;
	   }
	  asprintf(errp,"%s: exit %d",prog,WEXITSTATUS(ws));
	}
       else if (WIFSIGNALED(ws))
	{ asprintf(errp,"%s: signal %d",prog,WTERMSIG(ws));
	}
       else if (WIFSTOPPED(ws))
	{ asprintf(errp,"%s: stopped on signal %d",prog,WSTOPSIG(ws));
	}
       else
	{ asprintf(errp,"%s: mystery exit status %#x",prog,ws);
	}
     } while (0);
    if (xp[0] >= 0) close(xp[0]);
    if (xp[1] >= 0) close(xp[1]);
  } while (0);
 close(mfd);
 close(sfd);
}

void pty_ctty(int sfd)
{
 int arg;

 setsid();
 arg = 0;
 ioctl(sfd,TIOCSCTTY,&arg);
}