/*************************************************
*         Write bytes down TLS channel           *
*************************************************/

/*
Arguments:
  ct_ctx    client context pointer, or NULL for the one global server context
  buff      buffer of data
  len       number of bytes
  more	    further data expected soon

Returns:    the number of bytes after a successful write,
            -1 after a failed write

Used by both server-side and client-side TLS.
*/

int
tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more)
{
size_t olen = len;
int outbytes, error;
SSL * ssl = ct_ctx
  ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl;
static gstring * server_corked = NULL;
gstring ** corkedp = ct_ctx
  ? &((exim_openssl_client_tls_ctx *)ct_ctx)->corked : &server_corked;
gstring * corked = *corkedp;

DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__,
  buff, (unsigned long)len, more ? ", more" : "");

/* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when
"more" is notified.  This hack is only ok if small amounts are involved AND only
one stream does it, in one context (i.e. no store reset).  Currently it is used
for the responses to the received SMTP MAIL , RCPT, DATA sequence, only.
We support callouts done by the server process by using a separate client
context for the stashed information. */
/* + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's
a store reset there, so use POOL_PERM. */
/* + if CHUNKING, cmds EHLO,MAIL,RCPT(s),BDAT */

if ((more || corked))
  {
#ifdef SUPPORT_PIPE_CONNECT
  int save_pool = store_pool;
  store_pool = POOL_PERM;
#endif

  corked = string_catn(corked, buff, len);

#ifdef SUPPORT_PIPE_CONNECT
  store_pool = save_pool;
#endif

  if (more)
    {
    *corkedp = corked;
    return len;
    }
  buff = CUS corked->s;
  len = corked->ptr;
  *corkedp = NULL;
  }

for (int left = len; left > 0;)
  {
  DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left);
  outbytes = SSL_write(ssl, CS buff, left);
  error = SSL_get_error(ssl, outbytes);
  DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error);
  switch (error)
    {
    case SSL_ERROR_SSL:
      ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring));
      log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring);
      return -1;

    case SSL_ERROR_NONE:
      left -= outbytes;
      buff += outbytes;
      break;

    case SSL_ERROR_ZERO_RETURN:
      log_write(0, LOG_MAIN, "SSL channel closed on write");
      return -1;

    case SSL_ERROR_SYSCALL:
      log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s",
	sender_fullhost ? sender_fullhost : US"<unknown>",
	strerror(errno));
      return -1;

    default:
      log_write(0, LOG_MAIN, "SSL_write error %d", error);
      return -1;
    }
  }
return olen;
}

 /* Growable-string */
typedef struct gstring {
  int	size;		/* Current capacity of string memory */
  int	ptr;		/* Offset at which to append further chars */
  uschar * s;		/* The string memory */
} gstring;

corked = string_catn(corked, buff, len);