/* ========================================================================
 * Copyright 1988-2008 University of Washington
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * 
 * ========================================================================
 */

/*
 * Program:	UNIX TCP/IP routines
 *
 * Author:	Mark Crispin
 *		Networks and Distributed Computing
 *		Computing & Communications
 *		University of Washington
 *		Administration Building, AG-44
 *		Seattle, WA  98195
 *		Internet: MRC@CAC.Washington.EDU
 *
 * Date:	1 August 1988
 * Last Edited:	13 January 2008
 */

#include "ip_unix.c"

#undef write			/* don't use redefined write() */
 
static tcptimeout_t tmoh = NIL;	/* TCP timeout handler routine */
static long ttmo_open = 0;	/* TCP timeouts, in seconds */
static long ttmo_read = 0;
static long ttmo_write = 0;
static long rshtimeout = 15;	/* rsh timeout */
static char *rshcommand = NIL;	/* rsh command */
static char *rshpath = NIL;	/* rsh path */
static long sshtimeout = 15;	/* ssh timeout */
static char *sshcommand = NIL;	/* ssh command */
static char *sshpath = NIL;	/* ssh path */
static long allowreversedns = T;/* allow reverse DNS lookup */
static long tcpdebug = NIL;	/* extra TCP debugging telemetry */
static char *myClientAddr = NIL;/* client IP address */
static char *myClientHost = NIL;/* client DNS name */
static long myClientPort = -1;	/* client port number */
static char *myServerAddr = NIL;/* server IP address */
static char *myServerHost = NIL;/* server DNS name */
static long myServerPort = -1;	/* server port number */

extern long maxposint;		/* get this from write.c */

/* Local function prototypes */

int tcp_socket_open (int family,void *adr,size_t adrlen,unsigned short port,
		     char *tmp,int *ctr,char *hst);
static char *tcp_getline_work (TCPSTREAM *stream,unsigned long *size,
			       long *contd);
long tcp_abort (TCPSTREAM *stream);
char *tcp_name (struct sockaddr *sadr,long flag);
char *tcp_name_valid (char *s);

/* TCP/IP manipulate parameters
 * Accepts: function code
 *	    function-dependent value
 * Returns: function-dependent return value
 */

void *tcp_parameters (long function,void *value)
{
  void *ret = NIL;
  switch ((int) function) {
  case SET_TIMEOUT:
    tmoh = (tcptimeout_t) value;
  case GET_TIMEOUT:
    ret = (void *) tmoh;
    break;
  case SET_OPENTIMEOUT:
    ttmo_open = (long) value;
  case GET_OPENTIMEOUT:
    ret = (void *) ttmo_open;
    break;
  case SET_READTIMEOUT:
    ttmo_read = (long) value;
  case GET_READTIMEOUT:
    ret = (void *) ttmo_read;
    break;
  case SET_WRITETIMEOUT:
    ttmo_write = (long) value;
  case GET_WRITETIMEOUT:
    ret = (void *) ttmo_write;
    break;
  case SET_ALLOWREVERSEDNS:
    allowreversedns = (long) value;
  case GET_ALLOWREVERSEDNS:
    ret = (void *) allowreversedns;
    break;
  case SET_TCPDEBUG:
    tcpdebug = (long) value;
  case GET_TCPDEBUG:
    ret = (void *) tcpdebug;
    break;

  case SET_RSHTIMEOUT:
    rshtimeout = (long) value;
  case GET_RSHTIMEOUT:
    ret = (void *) rshtimeout;
    break;
  case SET_RSHCOMMAND:
    if (rshcommand) fs_give ((void **) &rshcommand);
    rshcommand = cpystr ((char *) value);
  case GET_RSHCOMMAND:
    ret = (void *) rshcommand;
    break;
  case SET_RSHPATH:
    if (rshpath) fs_give ((void **) &rshpath);
    rshpath = cpystr ((char *) value);
  case GET_RSHPATH:
    ret = (void *) rshpath;
    break;
  case SET_SSHTIMEOUT:
    sshtimeout = (long) value;
  case GET_SSHTIMEOUT:
    ret = (void *) sshtimeout;
    break;
  case SET_SSHCOMMAND:
    if (sshcommand) fs_give ((void **) &sshcommand);
    sshcommand = cpystr ((char *) value);
  case GET_SSHCOMMAND:
    ret = (void *) sshcommand;
    break;
  case SET_SSHPATH:
    if (sshpath) fs_give ((void **) &sshpath);
    sshpath = cpystr ((char *) value);
  case GET_SSHPATH:
    ret = (void *) sshpath;
    break;
  }
  return ret;
}

/* TCP/IP open
 * Accepts: host name
 *	    contact service name
 *	    contact port number and optional silent flag
 * Returns: TCP/IP stream if success else NIL
 */

TCPSTREAM *tcp_open (char *host,char *service,unsigned long port)
{
  TCPSTREAM *stream = NIL;
  int family;
  int sock = -1;
  int ctr = 0;
  int silent = (port & NET_SILENT) ? T : NIL;
  int *ctrp = (port & NET_NOOPENTIMEOUT) ? NIL : &ctr;
  char *s,*hostname,tmp[MAILTMPLEN];
  void *adr;
  size_t adrlen;
  struct servent *sv = NIL;
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  void *data,*next;
  port &= 0xffff;		/* erase flags */
				/* lookup service */
  if (service && (sv = getservbyname (service,"tcp")))
    port = ntohs (sv->s_port);
  /* The domain literal form is used (rather than simply the dotted decimal
     as with other Unix programs) because it has to be a valid "host name"
     in mailsystem terminology. */
				/* look like domain literal? */
  if (host[0] == '[' && host[(strlen (host))-1] == ']') {
    strcpy (tmp,host+1);	/* yes, copy number part */
    tmp[(strlen (tmp))-1] = '\0';
    if (adr = ip_stringtoaddr (tmp,&adrlen,&family)) {
      (*bn) (BLOCK_TCPOPEN,NIL);
				/* get an open socket for this system */
      sock = tcp_socket_open (family,adr,adrlen,port,tmp,ctrp,hostname = host);
      (*bn) (BLOCK_NONE,NIL);
      fs_give ((void **) &adr);
    }
    else sprintf (tmp,"Bad format domain-literal: %.80s",host);
  }

  else {			/* lookup host name */
    if (tcpdebug) {
      sprintf (tmp,"DNS resolution %.80s",host);
      mm_log (tmp,TCPDEBUG);
    }
    (*bn) (BLOCK_DNSLOOKUP,NIL);/* quell alarms */
    data = (*bn) (BLOCK_SENSITIVE,NIL);
    if (!(s = ip_nametoaddr (host,&adrlen,&family,&hostname,&next)))
      sprintf (tmp,"No such host as %.80s",host);
    (*bn) (BLOCK_NONSENSITIVE,data);
    (*bn) (BLOCK_NONE,NIL);
    if (s) {			/* DNS resolution won? */
      if (tcpdebug) mm_log ("DNS resolution done",TCPDEBUG);
      do {
	(*bn) (BLOCK_TCPOPEN,NIL);
	if (((sock = tcp_socket_open (family,s,adrlen,port,tmp,ctrp,
				      hostname)) < 0) &&
	    (s = ip_nametoaddr (NIL,&adrlen,&family,&hostname,&next)) &&
	    !silent) mm_log (tmp,WARN);
	(*bn) (BLOCK_NONE,NIL);
      } while ((sock < 0) && s);/* repeat until success or no more addreses */
    }
  }
  if (sock >= 0)  {		/* won */
    stream = (TCPSTREAM *) memset (fs_get (sizeof (TCPSTREAM)),0,
				   sizeof (TCPSTREAM));
    stream->port = port;	/* port number */
				/* init sockets */
    stream->tcpsi = stream->tcpso = sock;
				/* stash in the snuck-in byte */
    if (stream->ictr = ctr) *(stream->iptr = stream->ibuf) = tmp[0];
				/* copy official host name */
    stream->host = cpystr (hostname);
    if (tcpdebug) mm_log ("Stream open and ready for read",TCPDEBUG);
  }
  else if (!silent) mm_log (tmp,ERROR);
  return stream;		/* return success */
}

/* Open a TCP socket
 * Accepts: protocol family
 *	    address to connect to
 *	    address length
 *	    port
 *	    scratch buffer
 *	    pointer to "first byte read in" storage or NIL
 *	    host name for error message
 * Returns: socket if success, else -1 with error string in scratch buffer
 */

int tcp_socket_open (int family,void *adr,size_t adrlen,unsigned short port,
		     char *tmp,int *ctr,char *hst)
{
  int i,ti,sock,flgs;
  size_t len;
  time_t now;
  struct protoent *pt = getprotobyname ("tcp");
  fd_set fds,efds;
  struct timeval tmo;
  struct sockaddr *sadr = ip_sockaddr (family,adr,adrlen,port,&len);
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
				/* fetid Solaris */
  void *data = (*bn) (BLOCK_SENSITIVE,NIL);
  sprintf (tmp,"Trying IP address [%s]",ip_sockaddrtostring (sadr));
  mm_log (tmp,NIL);
				/* make a socket */
  if ((sock = socket (sadr->sa_family,SOCK_STREAM,pt ? pt->p_proto : 0)) < 0) {
    sprintf (tmp,"Unable to create TCP socket: %s",strerror (errno));
    (*bn) (BLOCK_NONSENSITIVE,data);
  }
  else if (sock >= FD_SETSIZE) {/* unselectable sockets are useless */
    sprintf (tmp,"Unable to create selectable TCP socket (%d >= %d)",
	     sock,FD_SETSIZE);
    (*bn) (BLOCK_NONSENSITIVE,data);
    close (sock);
    sock = -1;
    errno = EMFILE;
  }

  else {			/* get current socket flags */
    flgs = fcntl (sock,F_GETFL,0);
				/* set non-blocking if want open timeout */
    if (ctr) fcntl (sock,F_SETFL,flgs | FNDELAY);
				/* open connection */
    while ((i = connect (sock,sadr,len)) < 0 && (errno == EINTR));
    (*bn) (BLOCK_NONSENSITIVE,data);
    if (i < 0) switch (errno) {	/* failed? */
    case EAGAIN:		/* DG brain damage */
    case EINPROGRESS:		/* what we expect to happen */
    case EALREADY:		/* or another form of it */
    case EISCONN:		/* restart after interrupt? */
    case EADDRINUSE:		/* restart after interrupt? */
      break;			/* well, not really, it was interrupted */
    default:
      sprintf (tmp,"Can't connect to %.80s,%u: %s",hst,(unsigned int) port,
	       strerror (errno));
      close (sock);		/* flush socket */
      sock = -1;
    }
    if ((sock >= 0) && ctr) {	/* want open timeout? */
      now = time (0);		/* open timeout */
      ti = ttmo_open ? now + ttmo_open : 0;
      tmo.tv_usec = 0;
      FD_ZERO (&fds);		/* initialize selection vector */
      FD_ZERO (&efds);		/* handle errors too */
      FD_SET (sock,&fds);	/* block for error or readable */
      FD_SET (sock,&efds);
      do {			/* block under timeout */
	tmo.tv_sec = ti ? ti - now : 0;
	i = select (sock+1,&fds,NIL,&efds,ti ? &tmo : NIL);
	now = time (0);		/* fake timeout if interrupt & time expired */
	if ((i < 0) && (errno == EINTR) && ti && (ti <= now)) i = 0;
      } while ((i < 0) && (errno == EINTR));
      if (i > 0) {		/* success, make sure really connected */
				/* restore blocking status */
	fcntl (sock,F_SETFL,flgs);
	/* This used to be a zero-byte read(), but that crashes Solaris */
				/* get socket status */
	while (((i = *ctr = read (sock,tmp,1)) < 0) && (errno == EINTR));
      }	
      if (i <= 0) {		/* timeout or error? */
	i = i ? errno : ETIMEDOUT;/* determine error code */
	close (sock);		/* flush socket */
	sock = -1;
	errno = i;		/* return error code */
	sprintf (tmp,"Connection failed to %.80s,%lu: %s",hst,
		 (unsigned long) port,strerror (errno));
      }
    }
  }
  fs_give ((void **) &sadr);
  return sock;			/* return the socket */
}
  
/* TCP/IP authenticated open
 * Accepts: host name
 *	    service name
 *	    returned user name buffer
 * Returns: TCP/IP stream if success else NIL
 */

#define MAXARGV 20

TCPSTREAM *tcp_aopen (NETMBX *mb,char *service,char *usrbuf)
{
  TCPSTREAM *stream = NIL;
  void *adr;
  char host[MAILTMPLEN],tmp[MAILTMPLEN],*path,*argv[MAXARGV+1],*r;
  int i,ti,pipei[2],pipeo[2];
  size_t len;
  time_t now;
  struct timeval tmo;
  fd_set fds,efds;
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
#ifdef SSHPATH			/* ssh path defined yet? */
  if (!sshpath) sshpath = cpystr (SSHPATH);
#endif
#ifdef RSHPATH			/* rsh path defined yet? */
  if (!rshpath) rshpath = cpystr (RSHPATH);
#endif
  if (*service == '*') {	/* want ssh? */
				/* return immediately if ssh disabled */
    if (!(sshpath && (ti = sshtimeout))) return NIL;
				/* ssh command prototype defined yet? */
    if (!sshcommand) sshcommand = cpystr ("%s %s -l %s exec /etc/r%sd");
  }
				/* want rsh? */
  else if (rshpath && (ti = rshtimeout)) {
				/* rsh command prototype defined yet? */
    if (!rshcommand) rshcommand = cpystr ("%s %s -l %s exec /etc/r%sd");
  }
  else return NIL;		/* rsh disabled */
				/* look like domain literal? */
  if (mb->host[0] == '[' && mb->host[i = (strlen (mb->host))-1] == ']') {
    strcpy (host,mb->host+1);	/* yes, copy without brackets */
    host[i-1] = '\0';
				/* validate domain literal */
    if (adr = ip_stringtoaddr (host,&len,&i)) fs_give ((void **) &adr);
    else {
      sprintf (tmp,"Bad format domain-literal: %.80s",host);
      mm_log (tmp,ERROR);
      return NIL;
    }
  }
  else strcpy (host,tcp_canonical (mb->host));

  if (*service == '*')		/* build ssh command */
    sprintf (tmp,sshcommand,sshpath,host,
	     mb->user[0] ? mb->user : myusername (),service + 1);
  else sprintf (tmp,rshcommand,rshpath,host,
		mb->user[0] ? mb->user : myusername (),service);
  if (tcpdebug) {
    char msg[MAILTMPLEN];
    sprintf (msg,"Trying %.100s",tmp);
    mm_log (msg,TCPDEBUG);
  }
				/* parse command into argv */
  for (i = 1,path = argv[0] = strtok_r (tmp," ",&r);
       (i < MAXARGV) && (argv[i] = strtok_r (NIL," ",&r)); i++);
  argv[i] = NIL;		/* make sure argv tied off */
				/* make command pipes */
  if (pipe (pipei) < 0) return NIL;
  if ((pipei[0] >= FD_SETSIZE) || (pipei[1] >= FD_SETSIZE) ||
      (pipe (pipeo) < 0)) {
    close (pipei[0]); close (pipei[1]);
    return NIL;
  }
  (*bn) (BLOCK_TCPOPEN,NIL);	/* quell alarm up here for NeXT */
  if ((pipeo[0] >= FD_SETSIZE) || (pipeo[1] >= FD_SETSIZE) ||
      ((i = fork ()) < 0)) {	/* make inferior process */
    close (pipei[0]); close (pipei[1]);
    close (pipeo[0]); close (pipeo[1]);
    (*bn) (BLOCK_NONE,NIL);
    return NIL;
  }
  if (!i) {			/* if child */
    alarm (0);			/* never have alarms in children */
    if (!fork ()) {		/* make grandchild so it's inherited by init */
      int cf;			/* don't alter parent vars in case vfork() */
      int maxfd = max (20,max (max(pipei[0],pipei[1]),max(pipeo[0],pipeo[1])));
      dup2 (pipei[1],1);	/* parent's input is my output */
      dup2 (pipei[1],2);	/* parent's input is my error output too */
      dup2 (pipeo[0],0);	/* parent's output is my input */
				/* close all unnecessary descriptors */
      for (cf = 3; cf <= maxfd; cf++) close (cf);
      setpgrp (0,getpid ());	/* be our own process group */
      _exit (execv (path,argv));/* now run it */
    }
    _exit (1);			/* child is done */
  }
  grim_pid_reap (i,NIL);	/* reap child; grandchild now owned by init */
  close (pipei[1]);		/* close child's side of the pipes */
  close (pipeo[0]);

				/* create TCP/IP stream */
  stream = (TCPSTREAM *) memset (fs_get (sizeof (TCPSTREAM)),0,
				 sizeof (TCPSTREAM));
				/* copy remote host name from argument */
  stream->remotehost = cpystr (stream->host = cpystr (host));
  stream->tcpsi = pipei[0];	/* init sockets */
  stream->tcpso = pipeo[1];
  stream->ictr = 0;		/* init input counter */
  stream->port = 0xffffffff;	/* no port number */
  ti += now = time (0);		/* open timeout */
  tmo.tv_usec = 0;		/* initialize usec timeout */
  FD_ZERO (&fds);		/* initialize selection vector */
  FD_ZERO (&efds);		/* handle errors too */
  FD_SET (stream->tcpsi,&fds);	/* set bit in selection vector */
  FD_SET (stream->tcpsi,&efds);	/* set bit in error selection vector */
  FD_SET (stream->tcpso,&efds);	/* set bit in error selection vector */
  do {				/* block under timeout */
    tmo.tv_sec = ti - now;
    i = select (max (stream->tcpsi,stream->tcpso)+1,&fds,NIL,&efds,&tmo);
    now = time (0);		/* fake timeout if interrupt & time expired */
    if ((i < 0) && (errno == EINTR) && ti && (ti <= now)) i = 0;
  } while ((i < 0) && (errno == EINTR));
  if (i <= 0) {			/* timeout or error? */
    sprintf (tmp,i ? "error in %s to IMAP server" :
	     "%s to IMAP server timed out",(*service == '*') ? "ssh" : "rsh");
    mm_log (tmp,WARN);
    tcp_close (stream);		/* punt stream */
    stream = NIL;
  }
  (*bn) (BLOCK_NONE,NIL);
				/* return user name */
  strcpy (usrbuf,mb->user[0] ? mb->user : myusername ());
  return stream;		/* return success */
}

/* TCP receive line
 * Accepts: TCP stream
 * Returns: text line string or NIL if failure
 */

char *tcp_getline (TCPSTREAM *stream)
{
  unsigned long n,contd;
  char *ret = tcp_getline_work (stream,&n,&contd);
  if (ret && contd) {		/* got a line needing continuation? */
    STRINGLIST *stl = mail_newstringlist ();
    STRINGLIST *stc = stl;
    do {			/* collect additional lines */
      stc->text.data = (unsigned char *) ret;
      stc->text.size = n;
      stc = stc->next = mail_newstringlist ();
      ret = tcp_getline_work (stream,&n,&contd);
    } while (ret && contd);
    if (ret) {			/* stash final part of line on list */
      stc->text.data = (unsigned char *) ret;
      stc->text.size = n;
				/* determine how large a buffer we need */
      for (n = 0, stc = stl; stc; stc = stc->next) n += stc->text.size;
      ret = fs_get (n + 1);	/* copy parts into buffer */
      for (n = 0, stc = stl; stc; n += stc->text.size, stc = stc->next)
	memcpy (ret + n,stc->text.data,stc->text.size);
      ret[n] = '\0';
    }
    mail_free_stringlist (&stl);/* either way, done with list */
  }
  return ret;
}

/* TCP receive line or partial line
 * Accepts: TCP stream
 *	    pointer to return size
 *	    pointer to return continuation flag
 * Returns: text line string, size and continuation flag, or NIL if failure
 */

static char *tcp_getline_work (TCPSTREAM *stream,unsigned long *size,
			       long *contd)
{
  unsigned long n;
  char *s,*ret,c,d;
  *contd = NIL;			/* assume no continuation */
				/* make sure have data */
  if (!tcp_getdata (stream)) return NIL;
  for (s = stream->iptr, n = 0, c = '\0'; stream->ictr--; n++, c = d) {
    d = *stream->iptr++;	/* slurp another character */
    if ((c == '\015') && (d == '\012')) {
      ret = (char *) fs_get (n--);
      memcpy (ret,s,*size = n);	/* copy into a free storage string */
      ret[n] = '\0';		/* tie off string with null */
      return ret;
    }
  }
				/* copy partial string from buffer */
  memcpy ((ret = (char *) fs_get (n)),s,*size = n);
				/* get more data from the net */
  if (!tcp_getdata (stream)) fs_give ((void **) &ret);
				/* special case of newline broken by buffer */
  else if ((c == '\015') && (*stream->iptr == '\012')) {
    stream->iptr++;		/* eat the line feed */
    stream->ictr--;
    ret[*size = --n] = '\0';	/* tie off string with null */
  }
  else *contd = LONGT;		/* continuation needed */
  return ret;
}

/* TCP/IP receive buffer
 * Accepts: TCP/IP stream
 *	    size in bytes
 *	    buffer to read into
 * Returns: T if success, NIL otherwise
 */

long tcp_getbuffer (TCPSTREAM *stream,unsigned long size,char *s)
{
  unsigned long n;
				/* make sure socket still alive */
  if (stream->tcpsi < 0) return NIL;
				/* can transfer bytes from buffer? */
  if (n = min (size,stream->ictr)) {
    memcpy (s,stream->iptr,n);	/* yes, slurp as much as we can from it */
    s += n;			/* update pointer */
    stream->iptr +=n;
    size -= n;			/* update # of bytes to do */
    stream->ictr -=n;
  }
  if (size) {
    int i;
    fd_set fds,efds;
    struct timeval tmo;
    time_t t = time (0);
    blocknotify_t bn=(blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
    (*bn) (BLOCK_TCPREAD,NIL);
    while (size > 0) {		/* until request satisfied */
      time_t tl = time (0);
      time_t now = tl;
      time_t ti = ttmo_read ? now + ttmo_read : 0;
      if (tcpdebug) mm_log ("Reading TCP buffer",TCPDEBUG);
      tmo.tv_usec = 0;
      FD_ZERO (&fds);		/* initialize selection vector */
      FD_ZERO (&efds);		/* handle errors too */
				/* set bit in selection vectors */
      FD_SET (stream->tcpsi,&fds);
      FD_SET (stream->tcpsi,&efds);
      errno = NIL;		/* initially no error */
      do {			/* block under timeout */
	tmo.tv_sec = ti ? ti - now : 0;
	i = select (stream->tcpsi+1,&fds,NIL,&efds,ti ? &tmo : NIL);
	now = time (0);		/* fake timeout if interrupt & time expired */
	if ((i < 0) && (errno == EINTR) && ti && (ti <= now)) i = 0;
      } while ((i < 0) && (errno == EINTR));
      if (i) {			/* non-timeout result from select? */
	if (i > 0)		/* read what we can */
	  while (((i = read (stream->tcpsi,s,(int) min (maxposint,size))) < 0)
		 && (errno == EINTR));
	if (i <= 0) {		/* error seen? */
	  if (tcpdebug) {
	    char tmp[MAILTMPLEN];
	    if (i) sprintf (s = tmp,"TCP buffer read I/O error %d",errno);
	    else s = "TCP buffer read end of file";
	    mm_log (s,TCPDEBUG);
	  }
	  return tcp_abort (stream);
	}
	s += i;			/* success, point at new place to write */
	size -= i;		/* reduce byte count */
	if (tcpdebug) mm_log ("Successfully read TCP buffer",TCPDEBUG);
      }
				/* timeout, punt unless told not to */
      else if (!tmoh || !(*tmoh) (now - t,now - tl)) {
	if (tcpdebug) mm_log ("TCP buffer read timeout",TCPDEBUG);
	return tcp_abort (stream);
      }
    }
    (*bn) (BLOCK_NONE,NIL);
  }
  *s = '\0';			/* tie off string */
  return LONGT;
}

/* TCP/IP receive data
 * Accepts: TCP/IP stream
 * Returns: T if success, NIL otherwise
 */

long tcp_getdata (TCPSTREAM *stream)
{
  int i;
  fd_set fds,efds;
  struct timeval tmo;
  time_t t = time (0);
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  if (stream->tcpsi < 0) return NIL;
  (*bn) (BLOCK_TCPREAD,NIL);
  while (stream->ictr < 1) {	/* if nothing in the buffer */
    time_t tl = time (0);	/* start of request */
    time_t now = tl;
    time_t ti = ttmo_read ? now + ttmo_read : 0;
    if (tcpdebug) mm_log ("Reading TCP data",TCPDEBUG);
    tmo.tv_usec = 0;
    FD_ZERO (&fds);		/* initialize selection vector */
    FD_ZERO (&efds);		/* handle errors too */
    FD_SET (stream->tcpsi,&fds);/* set bit in selection vectors */
    FD_SET (stream->tcpsi,&efds);
    errno = NIL;		/* initially no error */
    do {			/* block under timeout */
      tmo.tv_sec = ti ? ti - now : 0;
      i = select (stream->tcpsi+1,&fds,NIL,&efds,ti ? &tmo : NIL);
      now = time (0);		/* fake timeout if interrupt & time expired */
      if ((i < 0) && (errno == EINTR) && ti && (ti <= now)) i = 0;
    } while ((i < 0) && (errno == EINTR));
    if (i) {			/* non-timeout result from select? */
				/* read what we can */
      if (i > 0) while (((i = read (stream->tcpsi,stream->ibuf,BUFLEN)) < 0) &&
			(errno == EINTR));
      if (i <= 0) {		/* error seen? */
	if (tcpdebug) {
	  char *s,tmp[MAILTMPLEN];
	  if (i) sprintf (s = tmp,"TCP data read I/O error %d",errno);
	  else s = "TCP data read end of file";
	  mm_log (s,TCPDEBUG);
	}
	return tcp_abort (stream);
      }
      stream->ictr = i;		/* success, set new count and pointer */
      stream->iptr = stream->ibuf;
      if (tcpdebug) mm_log ("Successfully read TCP data",TCPDEBUG);
    }
				/* timeout, punt unless told not to */
    else if (!tmoh || !(*tmoh) (now - t,now - tl)) {
      if (tcpdebug) mm_log ("TCP data read timeout",TCPDEBUG);
      return tcp_abort (stream);/* error or timeout no-continue */
    }
  }
  (*bn) (BLOCK_NONE,NIL);
  return T;
}

/* TCP/IP send string as record
 * Accepts: TCP/IP stream
 *	    string pointer
 * Returns: T if success else NIL
 */

long tcp_soutr (TCPSTREAM *stream,char *string)
{
  return tcp_sout (stream,string,(unsigned long) strlen (string));
}


/* TCP/IP send string
 * Accepts: TCP/IP stream
 *	    string pointer
 *	    byte count
 * Returns: T if success else NIL
 */

long tcp_sout (TCPSTREAM *stream,char *string,unsigned long size)
{
  int i;
  fd_set fds,efds;
  struct timeval tmo;
  time_t t = time (0);
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  if (stream->tcpso < 0) return NIL;
  (*bn) (BLOCK_TCPWRITE,NIL);
  while (size > 0) {		/* until request satisfied */
    time_t tl = time (0);	/* start of request */
    time_t now = tl;
    time_t ti = ttmo_write ? now + ttmo_write : 0;
    if (tcpdebug) mm_log ("Writing to TCP",TCPDEBUG);
    tmo.tv_usec = 0;
    FD_ZERO (&fds);		/* initialize selection vector */
    FD_ZERO (&efds);		/* handle errors too */
    FD_SET (stream->tcpso,&fds);/* set bit in selection vector */
    FD_SET(stream->tcpso,&efds);/* set bit in error selection vector */
    errno = NIL;		/* block and write */
    do {			/* block under timeout */
      tmo.tv_sec = ti ? ti - now : 0;
      i = select (stream->tcpso+1,NIL,&fds,&efds,ti ? &tmo : NIL);
      now = time (0);		/* fake timeout if interrupt & time expired */
      if ((i < 0) && (errno == EINTR) && ti && (ti <= now)) i = 0;
    } while ((i < 0) && (errno == EINTR));
    if (i) {			/* non-timeout result from select? */
				/* write what we can */
      if (i > 0) while (((i = write (stream->tcpso,string,size)) < 0) &&
			(errno == EINTR));
      if (i <= 0) {		/* error seen? */
	if (tcpdebug) {
	  char tmp[MAILTMPLEN];
	  sprintf (tmp,"TCP write I/O error %d",errno);
	  mm_log (tmp,TCPDEBUG);
	}
	return tcp_abort (stream);
      }
      string += i;		/* how much we sent */
      size -= i;		/* count this size */
      if (tcpdebug) mm_log ("successfully wrote to TCP",TCPDEBUG);
    }
				/* timeout, punt unless told not to */
    else if (!tmoh || !(*tmoh) (now - t,now - tl)) {
      if (tcpdebug) mm_log ("TCP write timeout",TCPDEBUG);
      return tcp_abort (stream);
    }
  }
  (*bn) (BLOCK_NONE,NIL);
  return T;			/* all done */
}

/* TCP/IP close
 * Accepts: TCP/IP stream
 */

void tcp_close (TCPSTREAM *stream)
{
  tcp_abort (stream);		/* nuke the stream */
				/* flush host names */
  if (stream->host) fs_give ((void **) &stream->host);
  if (stream->remotehost) fs_give ((void **) &stream->remotehost);
  if (stream->localhost) fs_give ((void **) &stream->localhost);
  fs_give ((void **) &stream);	/* flush the stream */
}


/* TCP/IP abort stream
 * Accepts: TCP/IP stream
 * Returns: NIL always
 */

long tcp_abort (TCPSTREAM *stream)
{
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  if (stream->tcpsi >= 0) {	/* no-op if no socket */
    (*bn) (BLOCK_TCPCLOSE,NIL);
    close (stream->tcpsi);	/* nuke the socket */
    if (stream->tcpsi != stream->tcpso) close (stream->tcpso);
    stream->tcpsi = stream->tcpso = -1;
  }
  (*bn) (BLOCK_NONE,NIL);
  return NIL;
}

/* TCP/IP get host name
 * Accepts: TCP/IP stream
 * Returns: host name for this stream
 */

char *tcp_host (TCPSTREAM *stream)
{
  return stream->host;		/* use tcp_remotehost() if want guarantees */
}


/* TCP/IP get remote host name
 * Accepts: TCP/IP stream
 * Returns: host name for this stream
 */

char *tcp_remotehost (TCPSTREAM *stream)
{
  if (!stream->remotehost) {
    size_t sadrlen;
    struct sockaddr *sadr = ip_newsockaddr (&sadrlen);
    stream->remotehost =	/* get socket's peer name */
      getpeername (stream->tcpsi,sadr,(void *) &sadrlen) ?
        cpystr (stream->host) : tcp_name (sadr,NIL);
    fs_give ((void **) &sadr);
  }
  return stream->remotehost;
}


/* TCP/IP return port for this stream
 * Accepts: TCP/IP stream
 * Returns: port number for this stream
 */

unsigned long tcp_port (TCPSTREAM *stream)
{
  return stream->port;		/* return port number */
}


/* TCP/IP get local host name
 * Accepts: TCP/IP stream
 * Returns: local host name
 */

char *tcp_localhost (TCPSTREAM *stream)
{
  if (!stream->localhost) {
    size_t sadrlen;
    struct sockaddr *sadr = ip_newsockaddr (&sadrlen);
    stream->localhost =		/* get socket's name */
      ((stream->port & 0xffff000) ||
       getsockname (stream->tcpsi,sadr,(void *) &sadrlen)) ?
      cpystr (mylocalhost ()) : tcp_name (sadr,NIL);
    fs_give ((void **) &sadr);
  }
  return stream->localhost;	/* return local host name */
}

/* TCP/IP get client host address (server calls only)
 * Returns: client host address
 */

char *tcp_clientaddr ()
{
  if (!myClientAddr) {
    size_t sadrlen;
    struct sockaddr *sadr = ip_newsockaddr (&sadrlen);
    if (getpeername (0,sadr,(void *) &sadrlen))
      myClientAddr = cpystr ("UNKNOWN");
    else {			/* get stdin's peer name */
      myClientAddr = cpystr (ip_sockaddrtostring (sadr));
      if (myClientPort < 0) myClientPort = ip_sockaddrtoport (sadr);
    }
    fs_give ((void **) &sadr);
  }
  return myClientAddr;
}


/* TCP/IP get client host name (server calls only)
 * Returns: client host name
 */

char *tcp_clienthost ()
{
  if (!myClientHost) {
    size_t sadrlen;
    struct sockaddr *sadr = ip_newsockaddr (&sadrlen);
    if (getpeername (0,sadr,(void *) &sadrlen)) {
      char *s,*t,*v,tmp[MAILTMPLEN];
      if ((s = getenv (t = "SSH_CLIENT")) ||
	  (s = getenv (t = "KRB5REMOTEADDR")) ||
	  (s = getenv (t = "SSH2_CLIENT"))) {
	if (v = strchr (s,' ')) *v = '\0';
	sprintf (v = tmp,"%.80s=%.80s",t,s);
      }
      else v = "UNKNOWN";
      myClientHost = cpystr (v);
    }
    else {			/* get stdin's peer name */
      myClientHost = tcp_name (sadr,T);
      if (!myClientAddr) myClientAddr = cpystr (ip_sockaddrtostring (sadr));
      if (myClientPort < 0) myClientPort = ip_sockaddrtoport (sadr);
    }
    fs_give ((void **) &sadr);
  }
  return myClientHost;
}


/* TCP/IP get client port number (server calls only)
 * Returns: client port number
 */

long tcp_clientport ()
{
  if (!myClientHost && !myClientAddr) tcp_clientaddr ();
  return myClientPort;
}

/* TCP/IP get server host address (server calls only)
 * Returns: server host address
 */

char *tcp_serveraddr ()
{
  if (!myServerAddr) {
    size_t sadrlen;
    struct sockaddr *sadr = ip_newsockaddr (&sadrlen);
    if (getsockname (0,sadr,(void *) &sadrlen))
      myServerAddr = cpystr ("UNKNOWN");
    else {			/* get stdin's name */
      myServerAddr = cpystr (ip_sockaddrtostring (sadr));
      if (myServerPort < 0) myServerPort = ip_sockaddrtoport (sadr);
    }
    fs_give ((void **) &sadr);
  }
  return myServerAddr;
}


/* TCP/IP get server host name (server calls only)
 * Returns: server host name
 */

char *tcp_serverhost ()
{
  if (!myServerHost) {		/* once-only */
    size_t sadrlen;
    struct sockaddr *sadr = ip_newsockaddr (&sadrlen);
				/* get stdin's name */
    if (getsockname (0,sadr,(void *) &sadrlen))
      myServerHost = cpystr (mylocalhost ());
    else {			/* get stdin's name */
      myServerHost = tcp_name (sadr,NIL);
      if (!myServerAddr) myServerAddr = cpystr (ip_sockaddrtostring (sadr));
      if (myServerPort < 0) myServerPort = ip_sockaddrtoport (sadr);
    }
    fs_give ((void **) &sadr);
  }
  return myServerHost;
}


/* TCP/IP get server port number (server calls only)
 * Returns: server port number
 */

long tcp_serverport ()
{
  if (!myServerHost && !myServerAddr) tcp_serveraddr ();
  return myServerPort;
}

/* TCP/IP return canonical form of host name
 * Accepts: host name
 * Returns: canonical form of host name
 */

char *tcp_canonical (char *name)
{
  char *ret,host[MAILTMPLEN];
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  void *data;
				/* look like domain literal? */
  if (name[0] == '[' && name[strlen (name) - 1] == ']') return name;
  (*bn) (BLOCK_DNSLOOKUP,NIL);	/* quell alarms */
  data = (*bn) (BLOCK_SENSITIVE,NIL);
  if (tcpdebug) {
    sprintf (host,"DNS canonicalization %.80s",name);
    mm_log (host,TCPDEBUG);
  }
				/* get canonical name */
  if (!ip_nametoaddr (name,NIL,NIL,&ret,NIL)) ret = name;
  (*bn) (BLOCK_NONSENSITIVE,data);
  (*bn) (BLOCK_NONE,NIL);	/* alarms OK now */
  if (tcpdebug) mm_log ("DNS canonicalization done",TCPDEBUG);
  return ret;
}

/* TCP/IP return name from socket
 * Accepts: socket
 *	    verbose flag
 * Returns: cpystr name
 */

char *tcp_name (struct sockaddr *sadr,long flag)
{
  char *ret,*t,adr[MAILTMPLEN],tmp[MAILTMPLEN];
  sprintf (ret = adr,"[%.80s]",ip_sockaddrtostring (sadr));
  if (allowreversedns) {
    blocknotify_t bn = (blocknotify_t)mail_parameters(NIL,GET_BLOCKNOTIFY,NIL);
    void *data;
    if (tcpdebug) {
      sprintf (tmp,"Reverse DNS resolution %s",adr);
      mm_log (tmp,TCPDEBUG);
    }
    (*bn) (BLOCK_DNSLOOKUP,NIL);/* quell alarms */
    data = (*bn) (BLOCK_SENSITIVE,NIL);
				/* translate address to name */
    if (t = tcp_name_valid (ip_sockaddrtoname (sadr))) {
				/* produce verbose form if needed */
      if (flag)	sprintf (ret = tmp,"%s %s",t,adr);
      else ret = t;
    }
    (*bn) (BLOCK_NONSENSITIVE,data);
    (*bn) (BLOCK_NONE,NIL);	/* alarms OK now */
    if (tcpdebug) mm_log ("Reverse DNS resolution done",TCPDEBUG);
  }
  return cpystr (ret);
}


/* TCP/IP validate name
 * Accepts: domain name
 * Returns: name if valid, NIL otherwise
 */

char *tcp_name_valid (char *s)
{
  int c;
  char *ret,*tail;
				/* must be non-empty and not too long */
  if ((ret = (s && *s) ? s : NIL) && (tail = ret + NETMAXHOST)) {
				/* must be alnum, dot, or hyphen */
    while ((c = *s++) && (s <= tail) &&
	   (((c >= 'A') && (c <= 'Z')) || ((c >= 'a') && (c <= 'z')) ||
	    ((c >= '0') && (c <= '9')) || (c == '-') || (c == '.')));
    if (c) ret = NIL;
  }
  return ret;
}

/* TCP/IP check if client is given host name
 * Accepts: candidate host name
 * Returns: T if match, NIL otherwise
 */

long tcp_isclienthost (char *host)
{
  int family;
  size_t adrlen,sadrlen,len;
  void *adr,*next;
  struct sockaddr *sadr;
  long ret = NIL;
				/* make sure that myClientAddr is set */
  if (tcp_clienthost () && myClientAddr)
				/* get sockaddr of client */
    for (adr = ip_nametoaddr (host,&adrlen,&family,NIL,&next); adr && !ret;
	 adr = ip_nametoaddr (NIL,&adrlen,&family,NIL,&next)) {
				/* build sockaddr of given address */
      sadr = ip_sockaddr (family,adr,adrlen,1,&len);
      if (!strcmp (myClientAddr,ip_sockaddrtostring (sadr))) ret = LONGT;
      fs_give ((void **) &sadr);	/* done with client sockaddr */
    }
  return ret;
}

/* Following statement must be at end of this module */

#undef fork			/* undo any use of vfork() */
