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Add options ClientAliveInterval and ClientAliveCountMax to sshd.
This gives the ability to do a "keepalive" via the encrypted channel
which can't be spoofed (unlike TCP keepalives). Useful for when you want
to use ssh connections to authenticate people for something, and know
relatively quickly when they are no longer authenticated. Disabled
by default (of course). ok markus@

/*
 * 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) 2000 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.
 */
/* RCSID("$OpenBSD: channels.h,v 1.31 2001/04/13 22:46:53 beck Exp $"); */

#ifndef CHANNELS_H
#define CHANNELS_H

#include "buffer.h"

/* Definitions for channel types. */
#define SSH_CHANNEL_FREE		0	/* This channel is free (unused). */
#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_MAX_TYPE		14

/*
 * Data structure for channel data.  This is iniailized in channel_allocate
 * and cleared in channel_free.
 */
struct Channel;
typedef struct Channel Channel;

typedef void channel_callback_fn(int id, void *arg);
typedef int channel_filter_fn(struct Channel *c, char *buf, int len);

struct Channel {
	int     type;		/* channel type/state */
	int     self;		/* my own channel identifier */
	int     remote_id;	/* channel identifier for remote peer */
	/* peer can be reached over encrypted connection, via packet-sent */
	int     istate;		/* input from channel (state of receive half) */
	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     isatty;		/* rfd is a tty */
	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[200];	/* path for unix domain sockets, or host name
				 * for forwards */
	int     listening_port;	/* port being listened for forwards */
	int     host_port;	/* remote port to connect for forwards */
	char   *remote_name;	/* remote hostname */

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

	char   *ctype;		/* type */

	/* callback */
	channel_callback_fn	*cb_fn;
	void	*cb_arg;
	int	cb_event;
	channel_callback_fn	*dettach_user;

	/* filter */
	channel_filter_fn	*input_filter;
};

#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_WINDOW_DEFAULT	(32*1024)
#define CHAN_SES_PACKET_DEFAULT	(CHAN_SES_WINDOW_DEFAULT/2)
#define CHAN_TCP_WINDOW_DEFAULT	(32*1024)
#define CHAN_TCP_PACKET_DEFAULT	(CHAN_TCP_WINDOW_DEFAULT/2)
#define CHAN_X11_WINDOW_DEFAULT	(4*1024)
#define CHAN_X11_PACKET_DEFAULT	(CHAN_X11_WINDOW_DEFAULT/2)


void	channel_open(int id);
void	channel_request(int id, char *service, int wantconfirm);
void	channel_request_start(int id, char *service, int wantconfirm);
void	channel_register_callback(int id, int mtype, channel_callback_fn *fn, void *arg);
void	channel_register_cleanup(int id, channel_callback_fn *fn);
void	channel_register_filter(int id, channel_filter_fn *fn);
void	channel_cancel_cleanup(int id);
Channel	*channel_lookup(int id);

int
channel_new(char *ctype, int type, int rfd, int wfd, int efd,
    int window, int maxpack, int extended_usage, char *remote_name,
    int nonblock);
void
channel_set_fds(int id, int rfd, int wfd, int efd,
    int extusage, int nonblock);

void	deny_input_open(int type, int plen, void *ctxt);

void	channel_input_channel_request(int type, int plen, void *ctxt);
void	channel_input_close(int type, int plen, void *ctxt);
void	channel_input_close_confirmation(int type, int plen, void *ctxt);
void	channel_input_data(int type, int plen, void *ctxt);
void	channel_input_extended_data(int type, int plen, void *ctxt);
void	channel_input_ieof(int type, int plen, void *ctxt);
void	channel_input_oclose(int type, int plen, void *ctxt);
void	channel_input_open_confirmation(int type, int plen, void *ctxt);
void	channel_input_open_failure(int type, int plen, void *ctxt);
void	channel_input_port_open(int type, int plen, void *ctxt);
void	channel_input_window_adjust(int type, int plen, void *ctxt);

/* Sets specific protocol options. */
void    channel_set_options(int hostname_in_open);

/*
 * Allocate a new channel object and set its type and socket.  Remote_name
 * must have been allocated with xmalloc; this will free it when the channel
 * is freed.
 */
int     channel_allocate(int type, int sock, char *remote_name);

/* Free the channel and close its socket. */
void    channel_free(int channel);

/*
 * Allocate/update select bitmasks and add any bits relevant to channels in
 * select bitmasks.
 */
void
channel_prepare_select(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
    int rekeying);

/*
 * After select, perform any appropriate operations for channels which have
 * events pending.
 */
void    channel_after_select(fd_set * readset, fd_set * writeset);

/* If there is data to send to the connection, send some of it now. */
void    channel_output_poll(void);

/* Returns true if no channel has too much buffered data. */
int     channel_not_very_much_buffered_data(void);

/* This closes any sockets that are listening for connections; this removes
   any unix domain sockets. */
void    channel_stop_listening(void);

/*
 * Closes the sockets of all channels.  This is used to close extra file
 * descriptors after a fork.
 */
void    channel_close_all(void);

/* Returns true if there is still an open channel over the connection. */
int     channel_still_open(void);

/*
 * Returns a string containing a list of all open channels.  The list is
 * suitable for displaying to the user.  It uses crlf instead of newlines.
 * The caller should free the string with xfree.
 */
char   *channel_open_message(void);

/*
 * Initiate forwarding of connections to local port "port" through the secure
 * channel to host:port from remote side.
 */
int
channel_request_local_forwarding(u_short listen_port,
    const char *host_to_connect, u_short port_to_connect, int gateway_ports);
int
channel_request_forwarding(const char *listen_address, u_short listen_port,
    const char *host_to_connect, u_short port_to_connect, int gateway_ports,
    int remote_fwd);

/*
 * Initiate forwarding of connections to port "port" on remote host through
 * the secure channel to host:port from local side.  This never returns if
 * there was an error.  This registers that open requests for that port are
 * permitted.
 */
void
channel_request_remote_forwarding(u_short port, const char *host,
    u_short remote_port);

/*
 * Permits opening to any host/port if permitted_opens[] is empty.  This is
 * usually called by the server, because the user could connect to any port
 * anyway, and the server has no way to know but to trust the client anyway.
 */
void    channel_permit_all_opens(void);

/* Add host/port to list of allowed targets for port forwarding */
void	channel_add_permitted_opens(char *host, int port);

/* Flush list */
void	channel_clear_permitted_opens(void);

/*
 * This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
 * listening for the port, and sends back a success reply (or disconnect
 * message if there was an error).  This never returns if there was an error.
 */
void    channel_input_port_forward_request(int is_root, int gateway_ports);

/*
 * Creates a port for X11 connections, and starts listening for it. Returns
 * the display name, or NULL if an error was encountered.
 */
char   *x11_create_display(int screen);

/*
 * Creates an internet domain socket for listening for X11 connections.
 * Returns a suitable value for the DISPLAY variable, or NULL if an error
 * occurs.
 */
char   *x11_create_display_inet(int screen, int x11_display_offset);

/*
 * This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
 * the remote channel number.  We should do whatever we want, and respond
 * with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
 */
void    x11_input_open(int type, int plen, void *ctxt);

/*
 * Requests forwarding of X11 connections.  This should be called on the
 * client only.
 */
void    x11_request_forwarding(void);

/*
 * Requests forwarding for X11 connections, with authentication spoofing.
 * This should be called in the client only.
 */
void
x11_request_forwarding_with_spoofing(int client_session_id,
    const char *proto, const char *data);

/* Sends a message to the server to request authentication fd forwarding. */
void    auth_request_forwarding(void);

/*
 * Returns the name of the forwarded authentication socket.  Returns NULL if
 * there is no forwarded authentication socket.  The returned value points to
 * a static buffer.
 */
char   *auth_get_socket_name(void);

/*
 * This is called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
 * This starts forwarding authentication requests.
 */
int     auth_input_request_forwarding(struct passwd * pw);

/* This is called to process an SSH_SMSG_AGENT_OPEN message. */
void    auth_input_open_request(int type, int plen, void *ctxt);

/* XXX */
int	channel_connect_to(const char *host, u_short host_port);
int	channel_connect_by_listen_adress(u_short listen_port);
int	x11_connect_display(void);

int	channel_find_open(void);

#endif