void
read_incoming_tun (struct context *c)
{
  /*
   * Setup for read() call on TUN/TAP device.
   */
  /*ASSERT (!c->c2.to_link.len);*/

  perf_push (PERF_READ_IN_TUN);

  c->c2.buf = c->c2.buffers->read_tun_buf;
#ifdef TUN_PASS_BUFFER
  read_tun_buffered (c->c1.tuntap, &c->c2.buf, MAX_RW_SIZE_TUN (&c->c2.frame));
#else
  ASSERT (buf_init (&c->c2.buf, FRAME_HEADROOM (&c->c2.frame)));
  ASSERT (buf_safe (&c->c2.buf, MAX_RW_SIZE_TUN (&c->c2.frame)));
  c->c2.buf.len = read_tun (c->c1.tuntap, BPTR (&c->c2.buf), MAX_RW_SIZE_TUN (&c->c2.frame));
#endif

#ifdef PACKET_TRUNCATION_CHECK
  ipv4_packet_size_verify (BPTR (&c->c2.buf),
			   BLEN (&c->c2.buf),
			   TUNNEL_TYPE (c->c1.tuntap),
			   "READ_TUN",
			   &c->c2.n_trunc_tun_read);
#endif

  /* Was TUN/TAP interface stopped? */
  if (tuntap_stop (c->c2.buf.len))
    {
      register_signal (c, SIGTERM, "tun-stop");
      msg (M_INFO, "TUN/TAP interface has been stopped, exiting");
      perf_pop ();
      return;		  
    }

  /* Was TUN/TAP I/O operation aborted? */
  if (tuntap_abort(c->c2.buf.len))
  {
     register_signal(c, SIGHUP, "tun-abort");
     c->persist.restart_sleep_seconds = 10;
     msg(M_INFO, "TUN/TAP I/O operation aborted, restarting");
     perf_pop();
     return;
  }

  /* Check the status return from read() */
  check_status (c->c2.buf.len, "read from TUN/TAP", NULL, c->c1.tuntap);

  perf_pop ();
}

/**
 * Main event loop for OpenVPN in client mode, where only one VPN tunnel
 * is active.
 * @ingroup eventloop
 *
 * @param c - The context structure of the single active VPN tunnel.
 */
static void
tunnel_point_to_point(struct context *c)
{
    context_clear_2(c);

    /* set point-to-point mode */
    c->mode = CM_P2P;

    /* initialize tunnel instance */
    init_instance_handle_signals(c, c->es, CC_HARD_USR1_TO_HUP);
    if (IS_SIG(c))
    {
        return;
    }

    /* main event loop */
    while (true)
    {
        perf_push(PERF_EVENT_LOOP);

        /* process timers, TLS, etc. */
        pre_select(c);
        P2P_CHECK_SIG();

        /* set up and do the I/O wait */
        io_wait(c, p2p_iow_flags(c));
        P2P_CHECK_SIG();

        /* timeout? */
        if (c->c2.event_set_status == ES_TIMEOUT)
        {
            perf_pop();
            continue;
        }

        /* process the I/O which triggered select */
        process_io(c);
        P2P_CHECK_SIG();

        perf_pop();
    }

    uninit_management_callback();

    /* tear down tunnel instance (unless --persist-tun) */
    close_instance(c);
}

int
key_state_write_plaintext_const (struct key_state_ssl *ks_ssl, const uint8_t *data, int len)
{
  int ret = 0;
  perf_push (PERF_BIO_WRITE_PLAINTEXT);

  ASSERT (NULL != ks_ssl);

  ret = bio_write (ks_ssl->ssl_bio, data, len, "tls_write_plaintext_const");

  perf_pop ();
  return ret;
}

void
process_incoming_link (struct context *c)
{
  perf_push (PERF_PROC_IN_LINK);

  struct link_socket_info *lsi = get_link_socket_info (c);
  const uint8_t *orig_buf = c->c2.buf.data;

  process_incoming_link_part1(c, lsi, false);
  process_incoming_link_part2(c, lsi, orig_buf);

  perf_pop ();
}

int
key_state_read_plaintext (struct key_state_ssl *ks_ssl, struct buffer *buf,
    int maxlen)
{
  int ret = 0;
  perf_push (PERF_BIO_READ_PLAINTEXT);

  ASSERT (NULL != ks_ssl);

  ret = bio_read (ks_ssl->ssl_bio, buf, maxlen, "tls_read_plaintext");

  perf_pop ();
  return ret;
}

int
key_state_write_ciphertext (struct key_state_ssl *ks_ssl, struct buffer *buf)
{
  int ret = 0;
  perf_push (PERF_BIO_WRITE_CIPHERTEXT);

  ASSERT (NULL != ks_ssl);

  ret = bio_write (ks_ssl->ct_in, BPTR(buf), BLEN(buf), "tls_write_ciphertext");
  bio_write_post (ret, buf);

  perf_pop ();
  return ret;
}

int
key_state_read_ciphertext (struct key_state_ssl *ks_ssl, struct buffer *buf,
    int maxlen)
{
  int ret = 0;
  perf_push (PERF_BIO_READ_CIPHERTEXT);

  ASSERT (NULL != ks_ssl);

  ret = bio_read (ks_ssl->ct_out, buf, maxlen, "tls_read_ciphertext");

  perf_pop ();
  return ret;
}

int
key_state_write_plaintext (struct key_state_ssl *ks_ssl, struct buffer *buf)
{
  int ret = 0;
  perf_push (PERF_BIO_WRITE_PLAINTEXT);

#ifdef ENABLE_CRYPTO_OPENSSL
  ASSERT (NULL != ks_ssl);

  ret = bio_write (ks_ssl->ssl_bio, BPTR(buf), BLEN(buf),
      "tls_write_plaintext");
  bio_write_post (ret, buf);
#endif /* ENABLE_CRYPTO_OPENSSL */

  perf_pop ();
  return ret;
}

void
process_incoming_tun (struct context *c)
{
  struct gc_arena gc = gc_new ();

  perf_push (PERF_PROC_IN_TUN);

  if (c->c2.buf.len > 0)
    c->c2.tun_read_bytes += c->c2.buf.len;

#ifdef LOG_RW
  if (c->c2.log_rw && c->c2.buf.len > 0)
    fprintf (stderr, "r");
#endif

  /* Show packet content */
  dmsg (D_TUN_RW, "TUN READ [%d]", BLEN (&c->c2.buf));

  if (c->c2.buf.len > 0)
    {
      if ((c->options.mode == MODE_POINT_TO_POINT) && (!c->options.allow_recursive_routing))
	drop_if_recursive_routing (c, &c->c2.buf);
      /*
       * The --passtos and --mssfix options require
       * us to examine the IP header (IPv4 or IPv6).
       */
      process_ip_header (c, PIPV4_PASSTOS|PIP_MSSFIX|PIPV4_CLIENT_NAT, &c->c2.buf);

#ifdef PACKET_TRUNCATION_CHECK
      /* if (c->c2.buf.len > 1) --c->c2.buf.len; */
      ipv4_packet_size_verify (BPTR (&c->c2.buf),
			       BLEN (&c->c2.buf),
			       TUNNEL_TYPE (c->c1.tuntap),
			       "PRE_ENCRYPT",
			       &c->c2.n_trunc_pre_encrypt);
#endif

      encrypt_sign (c, true);
    }
  else
    {
      buf_reset (&c->c2.to_link);
    }
  perf_pop ();
  gc_free (&gc);
}

/**
 * Main event loop for OpenVPN in UDP server mode.
 * @ingroup eventloop
 *
 * This function implements OpenVPN's main event loop for UDP server mode.
 *  At this time, OpenVPN does not yet support multithreading.  This
 * function's name is therefore slightly misleading.
 *
 * @param top - Top-level context structure.
 */
static void
tunnel_server_udp_single_threaded (struct context *top)
{
  struct multi_context multi;

  top->mode = CM_TOP;
  context_clear_2 (top);

  /* initialize top-tunnel instance */
  init_instance_handle_signals (top, top->es, CC_HARD_USR1_TO_HUP);
  if (IS_SIG (top))
    return;
  
  /* initialize global multi_context object */
  multi_init (&multi, top, false, MC_SINGLE_THREADED);

  /* initialize our cloned top object */
  multi_top_init (&multi, top, true);

  /* initialize management interface */
  init_management_callback_multi (&multi);

  /* finished with initialization */
  initialization_sequence_completed (top, ISC_SERVER); /* --mode server --proto udp */

  /* per-packet event loop */
  while (true)
    {
      perf_push (PERF_EVENT_LOOP);

      /* set up and do the io_wait() */
      multi_get_timeout (&multi, &multi.top.c2.timeval);
      io_wait (&multi.top, p2mp_iow_flags (&multi));
      MULTI_CHECK_SIG (&multi);

      /* check on status of coarse timers */
      multi_process_per_second_timers (&multi);

      /* timeout? */
      if (multi.top.c2.event_set_status == ES_TIMEOUT)
	{
	  multi_process_timeout (&multi, MPP_PRE_SELECT|MPP_CLOSE_ON_SIGNAL);
	}
      else
	{
	  /* process I/O */
	  multi_process_io_udp (&multi);
	  MULTI_CHECK_SIG (&multi);
	}
      
      perf_pop ();
    }

  /* shut down management interface */
  uninit_management_callback_multi (&multi);

  /* save ifconfig-pool */
  multi_ifconfig_pool_persist (&multi, true);

  /* tear down tunnel instance (unless --persist-tun) */
  multi_uninit (&multi);
  multi_top_free (&multi);
  close_instance (top);
}

//.........这里部分代码省略.........
	      interval_action (&c->c2.tmp_int);

	      /* reset packet received timer if TLS packet */
	      if (c->options.ping_rec_timeout)
		event_timeout_reset (&c->c2.ping_rec_interval);
	    }
	}
#if P2MP_SERVER
      /*
       * Drop non-TLS packet if client-connect script/plugin has not
       * yet succeeded.
       */
      if (c->c2.context_auth != CAS_SUCCEEDED)
	c->c2.buf.len = 0;
#endif
#endif /* ENABLE_SSL */

      /* authenticate and decrypt the incoming packet */
      decrypt_status = openvpn_decrypt (&c->c2.buf, c->c2.buffers->decrypt_buf, &c->c2.crypto_options, &c->c2.frame);

      if (!decrypt_status && link_socket_connection_oriented (c->c2.link_socket))
	{
	  /* decryption errors are fatal in TCP mode */
	  register_signal (c, SIGUSR1, "decryption-error"); /* SOFT-SIGUSR1 -- decryption error in TCP mode */
	  msg (D_STREAM_ERRORS, "Fatal decryption error (process_incoming_link), restarting");
	  goto done;
	}

#endif /* ENABLE_CRYPTO */

#ifdef ENABLE_FRAGMENT
      if (c->c2.fragment)
	fragment_incoming (c->c2.fragment, &c->c2.buf, &c->c2.frame_fragment);
#endif

#ifdef ENABLE_LZO
      /* decompress the incoming packet */
      if (lzo_defined (&c->c2.lzo_compwork))
	lzo_decompress (&c->c2.buf, c->c2.buffers->lzo_decompress_buf, &c->c2.lzo_compwork, &c->c2.frame);
#endif

#ifdef PACKET_TRUNCATION_CHECK
      /* if (c->c2.buf.len > 1) --c->c2.buf.len; */
      ipv4_packet_size_verify (BPTR (&c->c2.buf),
			       BLEN (&c->c2.buf),
			       TUNNEL_TYPE (c->c1.tuntap),
			       "POST_DECRYPT",
			       &c->c2.n_trunc_post_decrypt);
#endif

      /*
       * Set our "official" outgoing address, since
       * if buf.len is non-zero, we know the packet
       * authenticated.  In TLS mode we do nothing
       * because TLS mode takes care of source address
       * authentication.
       *
       * Also, update the persisted version of our packet-id.
       */
      if (!TLS_MODE (c))
	link_socket_set_outgoing_addr (&c->c2.buf, lsi, &c->c2.from, NULL, c->c2.es);

      /* reset packet received timer */
      if (c->options.ping_rec_timeout && c->c2.buf.len > 0)
	event_timeout_reset (&c->c2.ping_rec_interval);

      /* increment authenticated receive byte count */
      if (c->c2.buf.len > 0)
	{
	  c->c2.link_read_bytes_auth += c->c2.buf.len;
	  c->c2.max_recv_size_local = max_int (c->c2.original_recv_size, c->c2.max_recv_size_local);
	}

      /* Did we just receive an openvpn ping packet? */
      if (is_ping_msg (&c->c2.buf))
	{
	  dmsg (D_PING, "RECEIVED PING PACKET");
	  c->c2.buf.len = 0; /* drop packet */
	}

#ifdef ENABLE_OCC
      /* Did we just receive an OCC packet? */
      if (is_occ_msg (&c->c2.buf))
	process_received_occ_msg (c);
#endif

      buffer_turnover (orig_buf, &c->c2.to_tun, &c->c2.buf, &c->c2.buffers->read_link_buf);

      /* to_tun defined + unopened tuntap can cause deadlock */
      if (!tuntap_defined (c->c1.tuntap))
	c->c2.to_tun.len = 0;
    }
  else
    {
      buf_reset (&c->c2.to_tun);
    }
 done:
  perf_pop ();
  gc_free (&gc);
}

void
read_incoming_link (struct context *c)
{
  /*
   * Set up for recvfrom call to read datagram
   * sent to our TCP/UDP port.
   */
  int status;

  /*ASSERT (!c->c2.to_tun.len);*/

  perf_push (PERF_READ_IN_LINK);

  c->c2.buf = c->c2.buffers->read_link_buf;
  ASSERT (buf_init (&c->c2.buf, FRAME_HEADROOM_ADJ (&c->c2.frame, FRAME_HEADROOM_MARKER_READ_LINK)));

  status = link_socket_read (c->c2.link_socket,
			     &c->c2.buf,
			     MAX_RW_SIZE_LINK (&c->c2.frame),
			     &c->c2.from);

  if (socket_connection_reset (c->c2.link_socket, status))
    {
#if PORT_SHARE
      if (port_share && socket_foreign_protocol_detected (c->c2.link_socket))
	{
	  const struct buffer *fbuf = socket_foreign_protocol_head (c->c2.link_socket);
	  const int sd = socket_foreign_protocol_sd (c->c2.link_socket);
	  port_share_redirect (port_share, fbuf, sd);
	  register_signal (c, SIGTERM, "port-share-redirect");
	}
      else
#endif
      {
	/* received a disconnect from a connection-oriented protocol */
	if (c->options.inetd)
	  {
	    register_signal (c, SIGTERM, "connection-reset-inetd");
	    msg (D_STREAM_ERRORS, "Connection reset, inetd/xinetd exit [%d]", status);
	  }
	else
	  {
#ifdef ENABLE_OCC
	    if (event_timeout_defined(&c->c2.explicit_exit_notification_interval))
	      {
		msg (D_STREAM_ERRORS, "Connection reset during exit notification period, ignoring [%d]", status);
		openvpn_sleep(1);
	      }
	    else
#endif
	      {
		register_signal (c, SIGUSR1, "connection-reset"); /* SOFT-SIGUSR1 -- TCP connection reset */
		msg (D_STREAM_ERRORS, "Connection reset, restarting [%d]", status);
	      }
	  }
      }
      perf_pop ();
      return;
    }

  /* check recvfrom status */
  check_status (status, "read", c->c2.link_socket, NULL);

#ifdef ENABLE_SOCKS
  /* Remove socks header if applicable */
  socks_postprocess_incoming_link (c);
#endif

  perf_pop ();
}

void
process_outgoing_tun (struct context *c)
{
  struct gc_arena gc = gc_new ();

  /*
   * Set up for write() call to TUN/TAP
   * device.
   */
  if (c->c2.to_tun.len <= 0)
    return;

  perf_push (PERF_PROC_OUT_TUN);

  /*
   * The --mssfix option requires
   * us to examine the IPv4 header.
   */
  process_ipv4_header (c, PIPV4_MSSFIX|PIPV4_EXTRACT_DHCP_ROUTER|PIPV4_CLIENT_NAT|PIPV4_OUTGOING, &c->c2.to_tun);

  if (c->c2.to_tun.len <= MAX_RW_SIZE_TUN (&c->c2.frame))
    {
      /*
       * Write to TUN/TAP device.
       */
      int size;

#ifdef LOG_RW
      if (c->c2.log_rw)
	fprintf (stderr, "w");
#endif
      dmsg (D_TUN_RW, "TUN WRITE [%d]", BLEN (&c->c2.to_tun));

#ifdef PACKET_TRUNCATION_CHECK
      ipv4_packet_size_verify (BPTR (&c->c2.to_tun),
			       BLEN (&c->c2.to_tun),
			       TUNNEL_TYPE (c->c1.tuntap),
			       "WRITE_TUN",
			       &c->c2.n_trunc_tun_write);
#endif

#ifdef TUN_PASS_BUFFER
      size = write_tun_buffered (c->c1.tuntap, &c->c2.to_tun);
#else
      size = write_tun (c->c1.tuntap, BPTR (&c->c2.to_tun), BLEN (&c->c2.to_tun));
#endif

      if (size > 0)
	c->c2.tun_write_bytes += size;
      check_status (size, "write to TUN/TAP", NULL, c->c1.tuntap);

      /* check written packet size */
      if (size > 0)
	{
	  /* Did we write a different size packet than we intended? */
	  if (size != BLEN (&c->c2.to_tun))
	    msg (D_LINK_ERRORS,
		 "TUN/TAP packet was destructively fragmented on write to %s (tried=%d,actual=%d)",
		 c->c1.tuntap->actual_name,
		 BLEN (&c->c2.to_tun),
		 size);

	  /* indicate activity regarding --inactive parameter */
	  register_activity (c, size);
	}
    }
  else
    {
      /*
       * This should never happen, probably indicates some kind
       * of MTU mismatch.
       */
      msg (D_LINK_ERRORS, "tun packet too large on write (tried=%d,max=%d)",
	   c->c2.to_tun.len,
	   MAX_RW_SIZE_TUN (&c->c2.frame));
    }

  buf_reset (&c->c2.to_tun);

  perf_pop ();
  gc_free (&gc);
}

//.........这里部分代码省略.........
	    shaper_wrote_bytes (&c->c2.shaper, BLEN (&c->c2.to_link)
				+ datagram_overhead (c->options.ce.proto));
#endif
	  /*
	   * Let the pinger know that we sent a packet.
	   */
	  if (c->options.ping_send_timeout)
	    event_timeout_reset (&c->c2.ping_send_interval);

#if PASSTOS_CAPABILITY
	  /* Set TOS */
	  link_socket_set_tos (c->c2.link_socket);
#endif

	  /* Log packet send */
#ifdef LOG_RW
	  if (c->c2.log_rw)
	    fprintf (stderr, "W");
#endif
	  msg (D_LINK_RW, "%s WRITE [%d] to %s: %s",
	       proto2ascii (c->c2.link_socket->info.proto, true),
	       BLEN (&c->c2.to_link),
	       print_link_socket_actual (c->c2.to_link_addr, &gc),
	       PROTO_DUMP (&c->c2.to_link, &gc));

	  /* Packet send complexified by possible Socks5 usage */
	  {
	    struct link_socket_actual *to_addr = c->c2.to_link_addr;
#ifdef ENABLE_SOCKS
	    int size_delta = 0;
#endif

#ifdef ENABLE_SOCKS
	    /* If Socks5 over UDP, prepend header */
	    socks_preprocess_outgoing_link (c, &to_addr, &size_delta);
#endif
	    /* Send packet */
	    size = link_socket_write (c->c2.link_socket,
				      &c->c2.to_link,
				      to_addr);

#ifdef ENABLE_SOCKS
	    /* Undo effect of prepend */
	    link_socket_write_post_size_adjust (&size, size_delta, &c->c2.to_link);
#endif
	  }

	  if (size > 0)
	    {
	      c->c2.max_send_size_local = max_int (size, c->c2.max_send_size_local);
	      c->c2.link_write_bytes += size;
	      link_write_bytes_global += size;
#ifdef ENABLE_MEMSTATS
	      if (mmap_stats)
		mmap_stats->link_write_bytes = link_write_bytes_global;
#endif
#ifdef ENABLE_MANAGEMENT
	      if (management)
		{
		  management_bytes_out (management, size);
#ifdef MANAGEMENT_DEF_AUTH
		  management_bytes_server (management, &c->c2.link_read_bytes, &c->c2.link_write_bytes, &c->c2.mda_context);
#endif
		}
#endif
	    }
	}

      /* Check return status */
      check_status (size, "write", c->c2.link_socket, NULL);

      if (size > 0)
	{
	  /* Did we write a different size packet than we intended? */
	  if (size != BLEN (&c->c2.to_link))
	    msg (D_LINK_ERRORS,
		 "TCP/UDP packet was truncated/expanded on write to %s (tried=%d,actual=%d)",
		 print_link_socket_actual (c->c2.to_link_addr, &gc),
		 BLEN (&c->c2.to_link),
		 size);
	}

      /* if not a ping/control message, indicate activity regarding --inactive parameter */
      if (c->c2.buf.len > 0 )
        register_activity (c, size);
    }
  else
    {
      if (c->c2.to_link.len > 0)
	msg (D_LINK_ERRORS, "TCP/UDP packet too large on write to %s (tried=%d,max=%d)",
	     print_link_socket_actual (c->c2.to_link_addr, &gc),
	     c->c2.to_link.len,
	     EXPANDED_SIZE (&c->c2.frame));
    }

  buf_reset (&c->c2.to_link);

  perf_pop ();
  gc_free (&gc);
}

/*
 * Top level event loop for single-threaded operation.
 * TCP mode.
 */
void
tunnel_server_tcp(struct context *top)
{
    struct multi_context multi;
    int status;

    top->mode = CM_TOP;
    context_clear_2(top);

    /* initialize top-tunnel instance */
    init_instance_handle_signals(top, top->es, CC_HARD_USR1_TO_HUP);
    if (IS_SIG(top))
    {
        return;
    }

    /* initialize global multi_context object */
    multi_init(&multi, top, true, MC_SINGLE_THREADED);

    /* initialize our cloned top object */
    multi_top_init(&multi, top);

    /* initialize management interface */
    init_management_callback_multi(&multi);

    /* finished with initialization */
    initialization_sequence_completed(top, ISC_SERVER); /* --mode server --proto tcp-server */

#ifdef ENABLE_ASYNC_PUSH
    multi.top.c2.inotify_fd = inotify_init();
    if (multi.top.c2.inotify_fd < 0)
    {
        msg(D_MULTI_ERRORS | M_ERRNO, "MULTI: inotify_init error");
    }
#endif

    /* per-packet event loop */
    while (true)
    {
        perf_push(PERF_EVENT_LOOP);

        /* wait on tun/socket list */
        multi_get_timeout(&multi, &multi.top.c2.timeval);
        status = multi_tcp_wait(&multi.top, multi.mtcp);
        MULTI_CHECK_SIG(&multi);

        /* check on status of coarse timers */
        multi_process_per_second_timers(&multi);

        /* timeout? */
        if (status > 0)
        {
            /* process the I/O which triggered select */
            multi_tcp_process_io(&multi);
            MULTI_CHECK_SIG(&multi);
        }
        else if (status == 0)
        {
            multi_tcp_action(&multi, NULL, TA_TIMEOUT, false);
        }

        perf_pop();
    }

#ifdef ENABLE_ASYNC_PUSH
    close(top->c2.inotify_fd);
#endif

    /* shut down management interface */
    uninit_management_callback_multi(&multi);

    /* save ifconfig-pool */
    multi_ifconfig_pool_persist(&multi, true);

    /* tear down tunnel instance (unless --persist-tun) */
    multi_uninit(&multi);
    multi_top_free(&multi);
    close_instance(top);
}

static int
multi_tcp_wait_lite(struct multi_context *m, struct multi_instance *mi, const int action, bool *tun_input_pending)
{
    struct context *c = multi_tcp_context(m, mi);
    unsigned int looking_for = 0;

    dmsg(D_MULTI_DEBUG, "MULTI TCP: multi_tcp_wait_lite a=%s mi=" ptr_format,
         pract(action),
         (ptr_type)mi);

    tv_clear(&c->c2.timeval); /* ZERO-TIMEOUT */

    switch (action)
    {
        case TA_TUN_READ:
            looking_for = TUN_READ;
            tun_input_pending = NULL;
            io_wait(c, IOW_READ_TUN);
            break;

        case TA_SOCKET_READ:
            looking_for = SOCKET_READ;
            tun_input_pending = NULL;
            io_wait(c, IOW_READ_LINK);
            break;

        case TA_TUN_WRITE:
            looking_for = TUN_WRITE;
            tun_input_pending = NULL;
            c->c2.timeval.tv_sec = 1; /* For some reason, the Linux 2.2 TUN/TAP driver hits this timeout */
            perf_push(PERF_PROC_OUT_TUN_MTCP);
            io_wait(c, IOW_TO_TUN);
            perf_pop();
            break;

        case TA_SOCKET_WRITE:
            looking_for = SOCKET_WRITE;
            io_wait(c, IOW_TO_LINK|IOW_READ_TUN_FORCE);
            break;

        default:
            msg(M_FATAL, "MULTI TCP: multi_tcp_wait_lite, unhandled action=%d", action);
    }

    if (tun_input_pending && (c->c2.event_set_status & TUN_READ))
    {
        *tun_input_pending = true;
    }

    if (c->c2.event_set_status & looking_for)
    {
        return action;
    }
    else
    {
        switch (action)
        {
            /* TCP socket output buffer is full */
            case TA_SOCKET_WRITE:
                return TA_SOCKET_WRITE_DEFERRED;

            /* TUN device timed out on accepting write */
            case TA_TUN_WRITE:
                return TA_TUN_WRITE_TIMEOUT;
        }

        return TA_UNDEF;
    }
}