/*
 * Program:	Winsock TCP/IP routines
 *
 * Author:	Mark Crispin from Mike Seibel's Winsock code
 *		Networks and Distributed Computing
 *		Computing & Communications
 *		University of Washington
 *		Administration Building, AG-44
 *		Seattle, WA  98195
 *		Internet: MRC@CAC.Washington.EDU
 *
 * Date:	11 April 1989
 * Last Edited:	3 September 2004
 * 
 * The IMAP toolkit provided in this Distribution is
 * Copyright 2004 University of Washington.
 * The full text of our legal notices is contained in the file called
 * CPYRIGHT, included with this Distribution.
 */


#define TCPMAXSEND 32768

/* Private functions */

int tcp_socket_open (struct sockaddr_in *sin,char *tmp,char *hst,
		     unsigned long port);
long tcp_abort (SOCKET *sock);
char *tcp_name (struct sockaddr_in *sin,long flag);
char *tcp_name_valid (char *s);


/* Private data */

int wsa_initted = 0;		/* init ? */
static int wsa_sock_open = 0;	/* keep track of open sockets */
static tcptimeout_t tmoh = NIL;	/* TCP timeout handler routine */
static long ttmo_read = 0;	/* TCP timeouts, in seconds */
static long ttmo_write = 0;
static long allowreversedns = T;/* allow reverse DNS lookup */
static long tcpdebug = NIL;	/* extra TCP debugging telemetry */

/* 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_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;
  }
  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 i;
  SOCKET sock = INVALID_SOCKET;
  int silent = (port & NET_SILENT) ? T : NIL;
  char *s;
  struct sockaddr_in sin;
  struct hostent *he;
  char hostname[MAILTMPLEN];
  char tmp[MAILTMPLEN];
  struct servent *sv = NIL;
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  if (!wsa_initted++) {		/* init Windows Sockets */
    WSADATA wsock;
    if (i = (int) WSAStartup (WSA_VERSION,&wsock)) {
      wsa_initted = 0;		/* in case we try again */
      sprintf (tmp,"Unable to start Windows Sockets (%d)",i);
      mm_log (tmp,ERROR);
      return NIL;
    }
  }
  port &= 0xffff;		/* erase flags */
				/* lookup service */
  if (service && (sv = getservbyname (service,"tcp")))
    port = ntohs (sin.sin_port = sv->s_port);
 				/* copy port number in network format */
  else sin.sin_port = htons ((u_short) port);
  /* The domain literal form is used (rather than simply the dotted decimal
     as with other Windows programs) because it has to be a valid "host name"
     in mailsystem terminology. */
  sin.sin_family = AF_INET;	/* family is always Internet */
				/* 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 ((sin.sin_addr.s_addr = inet_addr (tmp)) == INADDR_NONE) {
      sprintf (tmp,"Bad format domain-literal: %.80s",host);
      mm_log (tmp,ERROR);
      return NIL;
    }
    else {
      sin.sin_family = AF_INET;	/* family is always Internet */
      strcpy (hostname,host);
      (*bn) (BLOCK_TCPOPEN,NIL);
      sock = tcp_socket_open (&sin,tmp,hostname,port);
      (*bn) (BLOCK_NONE,NIL);
    }
  }

  else {			/* lookup host name */
    if (tcpdebug) {
      sprintf (tmp,"DNS resolution %.80s",host);
      mm_log (tmp,TCPDEBUG);
    }
    (*bn) (BLOCK_DNSLOOKUP,NIL);/* look up name */
    if (!(he = gethostbyname (lcase (strcpy (tmp,host)))))
      sprintf (tmp,"Host not found (#%d): %s",WSAGetLastError(),host);
    (*bn) (BLOCK_NONE,NIL);
    if (he) {			/* DNS resolution won? */
      if (tcpdebug) mm_log ("DNS resolution done",TCPDEBUG);
				/* copy address type */
      sin.sin_family = he->h_addrtype;
				/* copy host name */
      strcpy (hostname,he->h_name);
      wsa_sock_open++;		/* prevent tcp_abort() from freeing in loop */
      for (i = 0; (sock == INVALID_SOCKET) && (s = he->h_addr_list[i]); i++) {
	if (i && !silent) mm_log (tmp,WARN);
	memcpy (&sin.sin_addr,s,he->h_length);
	(*bn) (BLOCK_TCPOPEN,NIL);
	sock = tcp_socket_open (&sin,tmp,hostname,port);
	(*bn) (BLOCK_NONE,NIL);
      }
      wsa_sock_open--;		/* undo protection */
    }
  }
  if (sock == INVALID_SOCKET) {	/* error? */
    if (!silent) mm_log (tmp,ERROR);
    tcp_abort (&sock);		/* do possible cleanup action */
  }
  else {			/* got a socket, create TCP/IP stream */
    stream = (TCPSTREAM *) memset (fs_get (sizeof (TCPSTREAM)),0,
				   sizeof (TCPSTREAM));
    stream->port = port;	/* port number */
				/* init socket */
    stream->tcpsi = stream->tcpso = sock;
    stream->ictr = 0;		/* init input counter */
				/* copy official host name */
    stream->host = cpystr (hostname);
    if (tcpdebug) mm_log ("Stream open and ready for read",TCPDEBUG);
  }
  return stream;		/* return success */
}

/* Open a TCP socket
 * Accepts: Internet socket address block
 *	    scratch buffer
 *	    host name for error message
 *	    port number for error message
 * Returns: socket if success, else -1 with error string in scratch buffer
 */

int tcp_socket_open (struct sockaddr_in *sin,char *tmp,char *hst,
		     unsigned long port)
{
  int sock;
  char *s;
  sprintf (tmp,"Trying IP address [%s]",inet_ntoa (sin->sin_addr));
  mm_log (tmp,NIL);
				/* get a TCP stream */
  if ((sock = socket (sin->sin_family,SOCK_STREAM,0)) == INVALID_SOCKET) {
    sprintf (tmp,"Unable to create TCP socket (%d)",WSAGetLastError());
    return -1;
  }
  wsa_sock_open++;		/* count this socket as open */
				/* open connection */
  if (connect (sock,(struct sockaddr *) sin,sizeof (struct sockaddr_in)) ==
      SOCKET_ERROR) {
    switch (WSAGetLastError ()){/* analyze error */
    case WSAECONNREFUSED:
      s = "Refused";
      break;
    case WSAENOBUFS:
      s = "Insufficient system resources";
      break;
    case WSAETIMEDOUT:
      s = "Timed out";
      break;
    case WSAEHOSTUNREACH:
      s = "Host unreachable";
      break;
    default:
      s = "Unknown error";
      break;
    }
    sprintf (tmp,"Can't connect to %.80s,%ld: %s (%d)",hst,port,s,
	     WSAGetLastError ());
    tcp_abort (&sock);		/* flush socket */
    sock = INVALID_SOCKET;
  }
  return sock;			/* return the socket */
}
  
/* TCP/IP authenticated open
 * Accepts: NETMBX specifier
 *	    service name
 *	    returned user name buffer
 * Returns: TCP/IP stream if success else NIL
 */

TCPSTREAM *tcp_aopen (NETMBX *mb,char *service,char *usrbuf)
{
  return NIL;			/* always NIL on Windows */
}

/* TCP/IP receive line
 * Accepts: TCP/IP stream
 * Returns: text line string or NIL if failure
 */

char *tcp_getline (TCPSTREAM *stream)
{
  int n,m;
  char *st,*ret,*stp;
  char c = '\0';
  char d;
				/* make sure have data */
  if (!tcp_getdata (stream)) return NIL;
  st = stream->iptr;		/* save start of string */
  n = 0;			/* init string count */
  while (stream->ictr--) {	/* look for end of line */
    d = *stream->iptr++;	/* slurp another character */
    if ((c == '\015') && (d == '\012')) {
      ret = (char *) fs_get (n--);
      memcpy (ret,st,n);	/* copy into a free storage string */
      ret[n] = '\0';		/* tie off string with null */
      return ret;
    }
    n++;			/* count another character searched */
    c = d;			/* remember previous character */
  }
				/* copy partial string from buffer */
  memcpy ((ret = stp = (char *) fs_get (n)),st,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[n - 1] = '\0';		/* tie off string with null */
  }
				/* else recurse to get remainder */
  else if (st = tcp_getline (stream)) {
    ret = (char *) fs_get (n + 1 + (m = strlen (st)));
    memcpy (ret,stp,n);		/* copy first part */
    memcpy (ret + n,st,m);	/* and second part */
    fs_give ((void **) &stp);	/* flush first part */
    fs_give ((void **) &st);	/* flush second part */
    ret[n + m] = '\0';		/* tie off string with null */
  }
  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 == INVALID_SOCKET) 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;
    struct timeval tmo;
    time_t tc,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);
      if (tcpdebug) mm_log ("Reading TCP buffer",TCPDEBUG);
      FD_ZERO (&fds);		/* initialize selection vector */
      FD_SET (stream->tcpsi,&fds);/* set bit in selection vector */
      tmo.tv_sec = ttmo_read;
      tmo.tv_usec = 0;
				/* block and read */
      switch ((stream->tcpsi == stream->tcpso) ?
	      select (stream->tcpsi+1,&fds,0,0,
		      ttmo_read ? &tmo : (struct timeval *) 0) : 1) {
      case SOCKET_ERROR:		/* error */
	if (WSAGetLastError () != WSAEINTR) return tcp_abort (&stream->tcpsi);
	break;
      case 0:			/* timeout */
	tc = time (0);
	if (tmoh && ((*tmoh) (tc - t,tc - tl))) break;
	return tcp_abort (&stream->tcpsi);
      default:
	if (stream->tcpsi == stream->tcpso)
	  while (((i = recv (stream->tcpsi,s,(int) min (maxposint,size),0)) ==
		  SOCKET_ERROR) && (WSAGetLastError () == WSAEINTR));
	else while (((i = read (stream->tcpsi,s,(int) min (maxposint,size))) <
		     0) && (errno == EINTR));
	switch (i) {
	case SOCKET_ERROR:	/* error */
	case 0:			/* no data read */
	  return tcp_abort (&stream->tcpsi);
	default:
	  s += i;		/* point at new place to write */
	  size -= i;		/* reduce byte count */
	  if (tcpdebug) mm_log ("Successfully read TCP buffer",TCPDEBUG);
	}
      }
    }
    (*bn) (BLOCK_NONE,NIL);
  }
  *s = '\0';			/* tie off string */
  return T;
}

/* TCP/IP receive data
 * Accepts: TCP/IP stream
 * Returns: T if success, NIL otherwise
 */

long tcp_getdata (TCPSTREAM *stream)
{
  struct timeval tmo;
  int i;
  fd_set fds;
  time_t tc,t = time (0);
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  FD_ZERO (&fds);		/* initialize selection vector */
  if (stream->tcpsi == INVALID_SOCKET) return NIL;
  (*bn) (BLOCK_TCPREAD,NIL);
  tmo.tv_sec = ttmo_read;
  tmo.tv_usec = 0;
  while (stream->ictr < 1) {	/* if nothing in the buffer */
    time_t tl = time (0);
    if (tcpdebug) mm_log ("Reading TCP data",TCPDEBUG);
    FD_SET (stream->tcpsi,&fds);/* set bit in selection vector */
				/* block and read */
    switch ((stream->tcpsi == stream->tcpso) ?
	    select (stream->tcpsi+1,&fds,0,0,
		    ttmo_read ? &tmo : (struct timeval *) 0) : 1) {
    case SOCKET_ERROR:		/* error */
      if (WSAGetLastError () != WSAEINTR) return tcp_abort (&stream->tcpsi);
      break;
    case 0:			/* timeout */
      tc = time (0);
      if (tmoh && ((*tmoh) (tc - t,tc - tl))) break;
      return tcp_abort (&stream->tcpsi);
    default:
      if (stream->tcpsi == stream->tcpso)
	while (((i = recv (stream->tcpsi,stream->ibuf,BUFLEN,0)) ==
		SOCKET_ERROR) && (WSAGetLastError () == WSAEINTR));
      else while (((i = read (stream->tcpsi,stream->ibuf,BUFLEN)) < 0) &&
		  (errno == EINTR));
      switch (i) {
      case SOCKET_ERROR:	/* error */
      case 0:			/* no data read */
	return tcp_abort (&stream->tcpsi);
      default:
	stream->ictr = i;	/* set new byte count */
				/* point at TCP buffer */
	stream->iptr = stream->ibuf;
	if (tcpdebug) mm_log ("Successfully read TCP data",TCPDEBUG);
      }
    }
  }
  (*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;
  struct timeval tmo;
  fd_set fds;
  time_t tc,t = time (0);
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  tmo.tv_sec = ttmo_write;
  tmo.tv_usec = 0;
  FD_ZERO (&fds);		/* initialize selection vector */
  if (stream->tcpso == INVALID_SOCKET) return NIL;
  (*bn) (BLOCK_TCPWRITE,NIL);
  while (size > 0) {		/* until request satisfied */
    time_t tl = time (0);
    if (tcpdebug) mm_log ("Writing to TCP",TCPDEBUG);
    FD_SET (stream->tcpso,&fds);/* set bit in selection vector */
				/* block and write */
    switch ((stream->tcpsi == stream->tcpso) ?
	    select (stream->tcpso+1,NULL,&fds,NULL,
		    tmo.tv_sec ? &tmo : (struct timeval *) 0) : 1) {
    case SOCKET_ERROR:		/* error */
      if (WSAGetLastError () != WSAEINTR) return tcp_abort (&stream->tcpsi);
      break;
    case 0:			/* timeout */
      tc = time (0);
      if (tmoh && ((*tmoh) (tc - t,tc - tl))) break;
      return tcp_abort (&stream->tcpsi);
    default:
      if (stream->tcpsi == stream->tcpso)
	while (((i = send (stream->tcpso,string,
			   (int) min (size,TCPMAXSEND),0)) == SOCKET_ERROR) &&
	       (WSAGetLastError () == WSAEINTR));
      else while (((i = write (stream->tcpso,string,
			       min (size,TCPMAXSEND))) < 0) &&
		  (errno == EINTR));
      if (i == SOCKET_ERROR) return tcp_abort (&stream->tcpsi);
      size -= i;		/* count this size */
      if (tcpdebug) mm_log ("successfully wrote to TCP",TCPDEBUG);
      string += i;
    }
  }
  (*bn) (BLOCK_NONE,NIL);
  return T;			/* all done */
}


/* TCP/IP close
 * Accepts: TCP/IP stream
 */

void tcp_close (TCPSTREAM *stream)
{
  tcp_abort (&stream->tcpsi);	/* nuke the socket */
				/* 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: WinSock socket
 * Returns: NIL, always
 */

long tcp_abort (SOCKET *sock)
{
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
				/* something to close? */
  if (sock && (*sock != INVALID_SOCKET)) {
    (*bn) (BLOCK_TCPCLOSE,NIL);
    closesocket (*sock);	/* WinSock socket close */
    *sock = INVALID_SOCKET;
    (*bn) (BLOCK_NONE,NIL);
    wsa_sock_open--;		/* drop this socket */
  }
				/* no more open streams? */
  if (wsa_initted && !wsa_sock_open) {
    mm_log ("Winsock cleanup",NIL);
    wsa_initted = 0;		/* no more sockets, so... */
    WSACleanup ();		/* free up resources until needed */
  }
  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) {
    struct sockaddr_in sin;
    int sinlen = sizeof (struct sockaddr_in);
    stream->remotehost =	/* get socket's peer name */
      ((getpeername (stream->tcpsi,(struct sockaddr *) &sin,&sinlen) ==
	SOCKET_ERROR) || (sinlen <= 0)) ?
	  cpystr (stream->host) : tcp_name (&sin,NIL);
  }
  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) {
    struct sockaddr_in sin;
    int sinlen = sizeof (struct sockaddr_in);
    stream->localhost =		/* get socket's name */
      ((stream->port & 0xffff000) ||
       ((getsockname (stream->tcpsi,(struct sockaddr *) &sin,&sinlen) ==
	 SOCKET_ERROR) || (sinlen <= 0))) ?
	   cpystr (mylocalhost ()) : tcp_name (&sin,NIL);
  }
  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) {
    struct sockaddr_in sin;
    int sinlen = sizeof (struct sockaddr_in);
    myClientAddr =		/* get stdin's peer name */
      ((getpeername (0,(struct sockaddr *) &sin,&sinlen) == SOCKET_ERROR) ||
       (sinlen <= 0)) ? cpystr ("UNKNOWN") : cpystr (inet_ntoa (sin.sin_addr));
  }
  return myClientAddr;
}


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

char *tcp_clienthost ()
{
  if (!myClientHost) {
    struct sockaddr_in sin;
    int sinlen = sizeof (struct sockaddr_in);
    myClientHost =		/* get stdin's peer name */
      ((getpeername (0,(struct sockaddr *) &sin,&sinlen) == SOCKET_ERROR) ||
       (sinlen <= 0)) ? cpystr ("UNKNOWN") : tcp_name (&sin,T);
  }
  return myClientHost;
}

/* TCP/IP get server host address (server calls only)
 * Returns: server host address
 */

char *tcp_serveraddr ()
{
  if (!myServerAddr) {
    struct sockaddr_in sin;
    int sinlen = sizeof (struct sockaddr_in);
    myServerAddr =		/* get stdin's peer name */
      ((getsockname (0,(struct sockaddr *) &sin,&sinlen) == SOCKET_ERROR) ||
       (sinlen <= 0)) ? cpystr ("UNKNOWN") : cpystr (inet_ntoa (sin.sin_addr));
  }
  return myServerAddr;
}


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

static long myServerPort = -1;

char *tcp_serverhost ()
{
  if (!myServerHost) {
    struct sockaddr_in sin;
    int sinlen = sizeof (struct sockaddr_in);
    if (!wsa_initted++) {	/* init Windows Sockets */
      WSADATA wsock;
      if (WSAStartup (WSA_VERSION,&wsock)) {
	wsa_initted = 0;
	return "random-pc";	/* try again later? */
      }
    }
				/* get stdin's name */
    if ((getsockname (0,(struct sockaddr *) &sin,&sinlen) == SOCKET_ERROR) ||
	(sinlen <= 0)) myServerHost = cpystr (mylocalhost ());
    else {
      myServerHost = tcp_name (&sin,NIL);
      myServerPort = ntohs (sin.sin_port);
    }
  }
  return myServerHost;
}


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

long tcp_serverport ()
{
  if (!myServerHost) tcp_serverhost ();
  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];
  struct hostent *he;
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
				/* look like domain literal? */
  if (name[0] == '[' && name[strlen (name) - 1] == ']') return name;
  (*bn) (BLOCK_DNSLOOKUP,NIL);
  if (tcpdebug) {
    sprintf (host,"DNS canonicalization %.80s",name);
    mm_log (host,TCPDEBUG);
  }
				/* note that NT requires lowercase! */
  ret = (he = gethostbyname (lcase (strcpy (host,name)))) ? he->h_name : name;
  (*bn) (BLOCK_NONE,NIL);
  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_in *sin,long flag)
{
  char *ret,*t,adr[MAILTMPLEN],tmp[MAILTMPLEN];
  sprintf (ret = adr,"[%.80s]",inet_ntoa (sin->sin_addr));
  if (allowreversedns) {
    struct hostent *he;
    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 ((he = gethostbyaddr ((char *) &sin->sin_addr,
						 sizeof (struct in_addr),
						 sin->sin_family)) ?
			    (char *) he->h_name : NIL)) {
				/* 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);
}

/* Return my local host name
 * Returns: my local host name
 */

char *mylocalhost (void)
{
  if (!myLocalHost) {
    char tmp[MAILTMPLEN];
    if (!wsa_initted++) {	/* init Windows Sockets */
      WSADATA wsock;
      if (WSAStartup (WSA_VERSION,&wsock)) {
	wsa_initted = 0;
	return "random-pc";	/* try again later? */
      }
    }
    myLocalHost = cpystr ((gethostname (tmp,MAILTMPLEN-1) == SOCKET_ERROR) ?
			  "random-pc" : tcp_canonical (tmp));
  }
  return myLocalHost;
}


/* Validate name
 * Accepts: domain name
 * Returns: T 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;
}