+/* default window/packet sizes for tcp/x11-fwd-channel */
+#define CHAN_SES_PACKET_DEFAULT (32*1024)
+#define CHAN_SES_WINDOW_DEFAULT (64*CHAN_SES_PACKET_DEFAULT)
+#define CHAN_TCP_PACKET_DEFAULT (32*1024)
+#define CHAN_TCP_WINDOW_DEFAULT (64*CHAN_TCP_PACKET_DEFAULT)
+#define CHAN_X11_PACKET_DEFAULT (16*1024)
+#define CHAN_X11_WINDOW_DEFAULT (4*CHAN_X11_PACKET_DEFAULT)
+
+/* possible input states */
+#define CHAN_INPUT_OPEN 0
+#define CHAN_INPUT_WAIT_DRAIN 1
+#define CHAN_INPUT_WAIT_OCLOSE 2
+#define CHAN_INPUT_CLOSED 3
+
+/* possible output states */
+#define CHAN_OUTPUT_OPEN 0
+#define CHAN_OUTPUT_WAIT_DRAIN 1
+#define CHAN_OUTPUT_WAIT_IEOF 2
+#define CHAN_OUTPUT_CLOSED 3
+
+#define CHAN_CLOSE_SENT 0x01
+#define CHAN_CLOSE_RCVD 0x02
+#define CHAN_EOF_SENT 0x04
+#define CHAN_EOF_RCVD 0x08
+#define CHAN_LOCAL 0x10
+
+#define CHAN_RBUF 16*1024
+
+/* check whether 'efd' is still in use */
+#define CHANNEL_EFD_INPUT_ACTIVE(c) \
+ (compat20 && c->extended_usage == CHAN_EXTENDED_READ && \
+ (c->efd != -1 || \
+ buffer_len(&c->extended) > 0))
+#define CHANNEL_EFD_OUTPUT_ACTIVE(c) \
+ (compat20 && c->extended_usage == CHAN_EXTENDED_WRITE && \
+ c->efd != -1 && (!(c->flags & (CHAN_EOF_RCVD|CHAN_CLOSE_RCVD)) || \
+ buffer_len(&c->extended) > 0))
+
+/* channel management */
+
+Channel *channel_by_id(int);
+Channel *channel_lookup(int);
+Channel *channel_new(char *, int, int, int, int, u_int, u_int, int, char *, int);
+void channel_set_fds(int, int, int, int, int, int, int, u_int);
+void channel_free(Channel *);
+void channel_free_all(void);
+void channel_stop_listening(void);
+
+void channel_send_open(int);
+void channel_request_start(int, char *, int);
+void channel_register_cleanup(int, channel_callback_fn *, int);
+void channel_register_open_confirm(int, channel_callback_fn *, void *);
+void channel_register_filter(int, channel_infilter_fn *,
+ channel_outfilter_fn *, channel_filter_cleanup_fn *, void *);
+void channel_register_status_confirm(int, channel_confirm_cb *,
+ channel_confirm_abandon_cb *, void *);
+void channel_cancel_cleanup(int);
+int channel_close_fd(int *);
+void channel_send_window_changes(void);
+
+/* protocol handler */
+
+void channel_input_close(int, u_int32_t, void *);
+void channel_input_close_confirmation(int, u_int32_t, void *);
+void channel_input_data(int, u_int32_t, void *);
+void channel_input_extended_data(int, u_int32_t, void *);
+void channel_input_ieof(int, u_int32_t, void *);
+void channel_input_oclose(int, u_int32_t, void *);
+void channel_input_open_confirmation(int, u_int32_t, void *);
+void channel_input_open_failure(int, u_int32_t, void *);
+void channel_input_port_open(int, u_int32_t, void *);
+void channel_input_window_adjust(int, u_int32_t, void *);
+void channel_input_status_confirm(int, u_int32_t, void *);
+
+/* file descriptor handling (read/write) */
+
+void channel_prepare_select(fd_set **, fd_set **, int *, u_int*, int);
+void channel_after_select(fd_set *, fd_set *);
+void channel_output_poll(void);
+
+int channel_not_very_much_buffered_data(void);
+void channel_close_all(void);
+int channel_still_open(void);
+char *channel_open_message(void);
+int channel_find_open(void);
+
+/* tcp forwarding */
+void channel_set_af(int af);
+void channel_permit_all_opens(void);
+void channel_add_permitted_opens(char *, int);
+int channel_add_adm_permitted_opens(char *, int);
+void channel_clear_permitted_opens(void);
+void channel_clear_adm_permitted_opens(void);
+void channel_print_adm_permitted_opens(void);
+int channel_input_port_forward_request(int, int);
+Channel *channel_connect_to(const char *, u_short, char *, char *);
+Channel *channel_connect_stdio_fwd(const char*, u_short, int, int);
+Channel *channel_connect_by_listen_address(u_short, char *, char *);
+int channel_request_remote_forwarding(const char *, u_short,
+ const char *, u_short);
+int channel_setup_local_fwd_listener(const char *, u_short,
+ const char *, u_short, int);
+void channel_request_rforward_cancel(const char *host, u_short port);
+int channel_setup_remote_fwd_listener(const char *, u_short, int *, int);
+int channel_cancel_rport_listener(const char *, u_short);
+
+/* x11 forwarding */
+
+int x11_connect_display(void);
+int x11_create_display_inet(int, int, int, u_int *, int **);
+void x11_input_open(int, u_int32_t, void *);
+void x11_request_forwarding_with_spoofing(int, const char *, const char *,
+ const char *);
+void deny_input_open(int, u_int32_t, void *);
+
+/* agent forwarding */
+
+void auth_request_forwarding(void);
+
+/* channel close */
+
+int chan_is_dead(Channel *, int);
+void chan_mark_dead(Channel *);
+
+/* channel events */
+
+void chan_rcvd_oclose(Channel *);
+void chan_rcvd_eow(Channel *); /* SSH2-only */
+void chan_read_failed(Channel *);
+void chan_ibuf_empty(Channel *);
+
+void chan_rcvd_ieof(Channel *);
+void chan_write_failed(Channel *);
+void chan_obuf_empty(Channel *);