channels.h - security/openssh-library - Rivoreo Source Code Repositories

 /* $OpenBSD: channels.h,v 1.118 2015/07/01 02:26:31 djm Exp $ */

 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
  *
  * As far as I am concerned, the code I have written for this software
  * can be used freely for any purpose.  Any derived versions of this
  * software must be clearly marked as such, and if the derived work is
  * incompatible with the protocol description in the RFC file, it must be
  * called by a name other than "ssh" or "Secure Shell".
  */
 /*
  * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #ifndef CHANNEL_H
 #define CHANNEL_H

 /* Definitions for channel types. */
 #define SSH_CHANNEL_X11_LISTENER	1	/* Listening for inet X11 conn. */
 #define SSH_CHANNEL_PORT_LISTENER	2	/* Listening on a port. */
 #define SSH_CHANNEL_OPENING		3	/* waiting for confirmation */
 #define SSH_CHANNEL_OPEN		4	/* normal open two-way channel */
 #define SSH_CHANNEL_CLOSED		5	/* waiting for close confirmation */
 #define SSH_CHANNEL_AUTH_SOCKET		6	/* authentication socket */
 #define SSH_CHANNEL_X11_OPEN		7	/* reading first X11 packet */
 #define SSH_CHANNEL_INPUT_DRAINING	8	/* sending remaining data to conn */
 #define SSH_CHANNEL_OUTPUT_DRAINING	9	/* sending remaining data to app */
 #define SSH_CHANNEL_LARVAL		10	/* larval session */
 #define SSH_CHANNEL_RPORT_LISTENER	11	/* Listening to a R-style port  */
 #define SSH_CHANNEL_CONNECTING		12
 #define SSH_CHANNEL_DYNAMIC		13
 #define SSH_CHANNEL_ZOMBIE		14	/* Almost dead. */
 #define SSH_CHANNEL_MUX_LISTENER	15	/* Listener for mux conn. */
 #define SSH_CHANNEL_MUX_CLIENT		16	/* Conn. to mux slave */
 #define SSH_CHANNEL_ABANDONED		17	/* Abandoned session, eg mux */
 #define SSH_CHANNEL_UNIX_LISTENER	18	/* Listening on a domain socket. */
 #define SSH_CHANNEL_RUNIX_LISTENER	19	/* Listening to a R-style domain socket. */
 #define SSH_CHANNEL_MAX_TYPE		20

 #define CHANNEL_CANCEL_PORT_STATIC	-1

 struct Channel;
 typedef struct Channel Channel;

 typedef void channel_open_fn(int, int, void *);
 typedef void channel_callback_fn(int, void *);
 typedef int channel_infilter_fn(struct Channel *, char *, int);
 typedef void channel_filter_cleanup_fn(int, void *);
 typedef u_char *channel_outfilter_fn(struct Channel *, u_char **, u_int *);

 /* Channel success/failure callbacks */
 typedef void channel_confirm_cb(int, struct Channel *, void *);
 typedef void channel_confirm_abandon_cb(struct Channel *, void *);
 struct channel_confirm {
 	TAILQ_ENTRY(channel_confirm) entry;
 	channel_confirm_cb *cb;
 	channel_confirm_abandon_cb *abandon_cb;
 	void *ctx;
 };
 TAILQ_HEAD(channel_confirms, channel_confirm);

 /* Context for non-blocking connects */
 struct channel_connect {
 	char *host;
 	int port;
 	struct addrinfo *ai, *aitop;
 };

 /* Callbacks for mux channels back into client-specific code */
 typedef int mux_callback_fn(struct Channel *);

 struct Channel {
 	int     type;		/* channel type/state */
 	int     self;		/* my own channel identifier */
 	int     remote_id;	/* channel identifier for remote peer */
 	u_int   istate;		/* input from channel (state of receive half) */
 	u_int   ostate;		/* output to channel  (state of transmit half) */
 	int     flags;		/* close sent/rcvd */
 	int     rfd;		/* read fd */
 	int     wfd;		/* write fd */
 	int     efd;		/* extended fd */
 	int     sock;		/* sock fd */
 	int     ctl_chan;	/* control channel (multiplexed connections) */
 	int     isatty;		/* rfd is a tty */
 #ifdef _AIX
 	int     wfd_isatty;	/* wfd is a tty */
 #endif
 	int	client_tty;	/* (client) TTY has been requested */
 	int     force_drain;	/* force close on iEOF */
 	time_t	notbefore;	/* Pause IO until deadline (time_t) */
 	int     delayed;	/* post-select handlers for newly created
 				 * channels are delayed until the first call
 				 * to a matching pre-select handler.
 				 * this way post-select handlers are not
 				 * accidentally called if a FD gets reused */
 	Buffer  input;		/* data read from socket, to be sent over
 				 * encrypted connection */
 	Buffer  output;		/* data received over encrypted connection for
 				 * send on socket */
 	Buffer  extended;
 	char    *path;
 		/* path for unix domain sockets, or host name for forwards */
 	int     listening_port;	/* port being listened for forwards */
 	char   *listening_addr;	/* addr being listened for forwards */
 	int     host_port;	/* remote port to connect for forwards */
 	char   *remote_name;	/* remote hostname */

 	u_int	remote_window;
 	u_int	remote_maxpacket;
 	u_int	local_window;
 	u_int	local_window_max;
 	u_int	local_consumed;
 	u_int	local_maxpacket;
 	int     extended_usage;
 	int	single_connection;

 	char   *ctype;		/* type */

 	/* callback */
 	channel_open_fn		*open_confirm;
 	void			*open_confirm_ctx;
 	channel_callback_fn	*detach_user;
 	int			detach_close;
 	struct channel_confirms	status_confirms;

 	/* filter */
 	channel_infilter_fn	*input_filter;
 	channel_outfilter_fn	*output_filter;
 	void			*filter_ctx;
 	channel_filter_cleanup_fn *filter_cleanup;

 	/* keep boundaries */
 	int     		datagram;

 	/* non-blocking connect */
 	struct channel_connect	connect_ctx;

 	/* multiplexing protocol hook, called for each packet received */
 	mux_callback_fn		*mux_rcb;
 	void			*mux_ctx;
 	int			mux_pause;
 };

 #define CHAN_EXTENDED_IGNORE		0
 #define CHAN_EXTENDED_READ		1
 #define CHAN_EXTENDED_WRITE		2

 /* 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_open_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 */

 struct ssh;
 int	 channel_input_close(struct ssh *, int, uint32_t, void *);
 int	 channel_input_close_confirmation(struct ssh *, int, uint32_t, void *);
 int	 channel_input_data(struct ssh *, int, uint32_t, void *);
 int	 channel_input_extended_data(struct ssh *, int, uint32_t, void *);
 int	 channel_input_ieof(struct ssh *, int, uint32_t, void *);
 int	 channel_input_oclose(struct ssh *, int, uint32_t, void *);
 int	 channel_input_open_confirmation(struct ssh *, int, uint32_t, void *);
 int	 channel_input_open_failure(struct ssh *, int, uint32_t, void *);
 int	 channel_input_port_open(struct ssh *, int, uint32_t, void *);
 int	 channel_input_window_adjust(struct ssh *, int, uint32_t, void *);
 int	 channel_input_status_confirm(struct ssh *, int, uint32_t, void *);

 /* file descriptor handling (read/write) */

 void	 channel_prepare_select(fd_set **, fd_set **, int *, u_int*,
 	     time_t*, 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 */
 struct Forward;
 struct ForwardOptions;
 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_disable_adm_local_opens(void);
 void	 channel_update_permitted_opens(int, 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, struct ForwardOptions *);
 Channel	*channel_connect_to_port(const char *, u_short, char *, char *);
 Channel *channel_connect_to_path(const char *, char *, char *);
 Channel	*channel_connect_stdio_fwd(const char*, u_short, int, int);
 Channel	*channel_connect_by_listen_address(const char *, u_short,
 	     char *, char *);
 Channel	*channel_connect_by_listen_path(const char *, char *, char *);
 int	 channel_request_remote_forwarding(struct Forward *);
 int	 channel_setup_local_fwd_listener(struct Forward *, struct ForwardOptions *);
 int	 channel_request_rforward_cancel(struct Forward *);
 int	 channel_setup_remote_fwd_listener(struct Forward *, int *, struct ForwardOptions *);
 int	 channel_cancel_rport_listener(struct Forward *);
 int	 channel_cancel_lport_listener(struct Forward *, int, struct ForwardOptions *);
 int	 permitopen_port(const char *);

 /* x11 forwarding */

 void	 channel_set_x11_refuse_time(u_int);
 int	 x11_connect_display(void);
 int	 x11_create_display_inet(int, int, int, u_int *, int **);
 int      x11_input_open(struct ssh *, int, uint32_t, void *);
 void	 x11_request_forwarding_with_spoofing(int, const char *, const char *,
 	     const char *, int);
 int	 deny_input_open(struct ssh *, int, uint32_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 *);

 #endif
	/* $OpenBSD: channels.h,v 1.118 2015/07/01 02:26:31 djm Exp $ */

	/*
	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	* All rights reserved
	*
	* As far as I am concerned, the code I have written for this software
	* can be used freely for any purpose. Any derived versions of this
	* software must be clearly marked as such, and if the derived work is
	* incompatible with the protocol description in the RFC file, it must be
	* called by a name other than "ssh" or "Secure Shell".
	*/
	/*
	* Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#ifndef CHANNEL_H
	#define CHANNEL_H

	/* Definitions for channel types. */
	#define SSH_CHANNEL_X11_LISTENER 1 /* Listening for inet X11 conn. */
	#define SSH_CHANNEL_PORT_LISTENER 2 /* Listening on a port. */
	#define SSH_CHANNEL_OPENING 3 /* waiting for confirmation */
	#define SSH_CHANNEL_OPEN 4 /* normal open two-way channel */
	#define SSH_CHANNEL_CLOSED 5 /* waiting for close confirmation */
	#define SSH_CHANNEL_AUTH_SOCKET 6 /* authentication socket */
	#define SSH_CHANNEL_X11_OPEN 7 /* reading first X11 packet */
	#define SSH_CHANNEL_INPUT_DRAINING 8 /* sending remaining data to conn */
	#define SSH_CHANNEL_OUTPUT_DRAINING 9 /* sending remaining data to app */
	#define SSH_CHANNEL_LARVAL 10 /* larval session */
	#define SSH_CHANNEL_RPORT_LISTENER 11 /* Listening to a R-style port */
	#define SSH_CHANNEL_CONNECTING 12
	#define SSH_CHANNEL_DYNAMIC 13
	#define SSH_CHANNEL_ZOMBIE 14 /* Almost dead. */
	#define SSH_CHANNEL_MUX_LISTENER 15 /* Listener for mux conn. */
	#define SSH_CHANNEL_MUX_CLIENT 16 /* Conn. to mux slave */
	#define SSH_CHANNEL_ABANDONED 17 /* Abandoned session, eg mux */
	#define SSH_CHANNEL_UNIX_LISTENER 18 /* Listening on a domain socket. */
	#define SSH_CHANNEL_RUNIX_LISTENER 19 /* Listening to a R-style domain socket. */
	#define SSH_CHANNEL_MAX_TYPE 20

	#define CHANNEL_CANCEL_PORT_STATIC -1

	struct Channel;
	typedef struct Channel Channel;

	typedef void channel_open_fn(int, int, void *);
	typedef void channel_callback_fn(int, void *);
	typedef int channel_infilter_fn(struct Channel , char , int);
	typedef void channel_filter_cleanup_fn(int, void *);
	typedef u_char channel_outfilter_fn(struct Channel , u_char *, u_int );

	/* Channel success/failure callbacks */
	typedef void channel_confirm_cb(int, struct Channel , void );
	typedef void channel_confirm_abandon_cb(struct Channel , void );
	struct channel_confirm {
	TAILQ_ENTRY(channel_confirm) entry;
	channel_confirm_cb *cb;
	channel_confirm_abandon_cb *abandon_cb;
	void *ctx;
	};
	TAILQ_HEAD(channel_confirms, channel_confirm);

	/* Context for non-blocking connects */
	struct channel_connect {
	char *host;
	int port;
	struct addrinfo ai, aitop;
	};

	/* Callbacks for mux channels back into client-specific code */
	typedef int mux_callback_fn(struct Channel *);

	struct Channel {
	int type; /* channel type/state */
	int self; /* my own channel identifier */
	int remote_id; /* channel identifier for remote peer */
	u_int istate; /* input from channel (state of receive half) */
	u_int ostate; /* output to channel (state of transmit half) */
	int flags; /* close sent/rcvd */
	int rfd; /* read fd */
	int wfd; /* write fd */
	int efd; /* extended fd */
	int sock; /* sock fd */
	int ctl_chan; /* control channel (multiplexed connections) */
	int isatty; /* rfd is a tty */
	#ifdef _AIX
	int wfd_isatty; /* wfd is a tty */
	#endif
	int client_tty; /* (client) TTY has been requested */
	int force_drain; /* force close on iEOF */
	time_t notbefore; /* Pause IO until deadline (time_t) */
	int delayed; /* post-select handlers for newly created
	* channels are delayed until the first call
	* to a matching pre-select handler.
	* this way post-select handlers are not
	* accidentally called if a FD gets reused */
	Buffer input; /* data read from socket, to be sent over
	* encrypted connection */
	Buffer output; /* data received over encrypted connection for
	* send on socket */
	Buffer extended;
	char *path;
	/* path for unix domain sockets, or host name for forwards */
	int listening_port; /* port being listened for forwards */
	char listening_addr; / addr being listened for forwards */
	int host_port; /* remote port to connect for forwards */
	char remote_name; / remote hostname */

	u_int remote_window;
	u_int remote_maxpacket;
	u_int local_window;
	u_int local_window_max;
	u_int local_consumed;
	u_int local_maxpacket;
	int extended_usage;
	int single_connection;

	char ctype; / type */

	/* callback */
	channel_open_fn *open_confirm;
	void *open_confirm_ctx;
	channel_callback_fn *detach_user;
	int detach_close;
	struct channel_confirms status_confirms;

	/* filter */
	channel_infilter_fn *input_filter;
	channel_outfilter_fn *output_filter;
	void *filter_ctx;
	channel_filter_cleanup_fn *filter_cleanup;

	/* keep boundaries */
	int datagram;

	/* non-blocking connect */
	struct channel_connect connect_ctx;

	/* multiplexing protocol hook, called for each packet received */
	mux_callback_fn *mux_rcb;
	void *mux_ctx;
	int mux_pause;
	};

	#define CHAN_EXTENDED_IGNORE 0
	#define CHAN_EXTENDED_READ 1
	#define CHAN_EXTENDED_WRITE 2

	/* 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_open_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 */

	struct ssh;
	int channel_input_close(struct ssh , int, uint32_t, void );
	int channel_input_close_confirmation(struct ssh , int, uint32_t, void );
	int channel_input_data(struct ssh , int, uint32_t, void );
	int channel_input_extended_data(struct ssh , int, uint32_t, void );
	int channel_input_ieof(struct ssh , int, uint32_t, void );
	int channel_input_oclose(struct ssh , int, uint32_t, void );
	int channel_input_open_confirmation(struct ssh , int, uint32_t, void );
	int channel_input_open_failure(struct ssh , int, uint32_t, void );
	int channel_input_port_open(struct ssh , int, uint32_t, void );
	int channel_input_window_adjust(struct ssh , int, uint32_t, void );
	int channel_input_status_confirm(struct ssh , int, uint32_t, void );

	/* file descriptor handling (read/write) */

	void channel_prepare_select(fd_set , fd_set , int , u_int,
	time_t*, 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 */
	struct Forward;
	struct ForwardOptions;
	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_disable_adm_local_opens(void);
	void channel_update_permitted_opens(int, 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, struct ForwardOptions *);
	Channel channel_connect_to_port(const char , u_short, char , char );
	Channel channel_connect_to_path(const char , char , char );
	Channel channel_connect_stdio_fwd(const char, u_short, int, int);
	Channel channel_connect_by_listen_address(const char , u_short,
	char , char );
	Channel channel_connect_by_listen_path(const char , char , char );
	int channel_request_remote_forwarding(struct Forward *);
	int channel_setup_local_fwd_listener(struct Forward , struct ForwardOptions );
	int channel_request_rforward_cancel(struct Forward *);
	int channel_setup_remote_fwd_listener(struct Forward , int , struct ForwardOptions *);
	int channel_cancel_rport_listener(struct Forward *);
	int channel_cancel_lport_listener(struct Forward , int, struct ForwardOptions );
	int permitopen_port(const char *);

	/* x11 forwarding */

	void channel_set_x11_refuse_time(u_int);
	int x11_connect_display(void);
	int x11_create_display_inet(int, int, int, u_int , int *);
	int x11_input_open(struct ssh , int, uint32_t, void );
	void x11_request_forwarding_with_spoofing(int, const char , const char ,
	const char *, int);
	int deny_input_open(struct ssh , int, uint32_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 *);

	#endif