.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
-.\" $OpenBSD: ssh_config.5,v 1.50 2005/04/21 06:17:50 djm Exp $
+.\" $OpenBSD: ssh_config.5,v 1.64 2005/10/30 08:43:47 jmc Exp $
.Dd September 25, 1999
.Dt SSH_CONFIG 5
.Os
The default is
.Dq no .
.It Cm BindAddress
-Specify the interface to transmit from on machines with multiple
-interfaces or aliased addresses.
+Use the specified address on the local machine as the source address of
+the connection.
+Only useful on systems with more than one address.
Note that this option does not work if
.Cm UsePrivilegedPort
is set to
.Dq aes128-ctr ,
.Dq aes192-ctr ,
.Dq aes256-ctr ,
+.Dq arcfour128 ,
+.Dq arcfour256 ,
.Dq arcfour ,
.Dq blowfish-cbc ,
and
.Dq cast128-cbc .
The default is
.Bd -literal
- ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
- aes192-cbc,aes256-cbc''
+ ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
+ arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
+ aes192-ctr,aes256-ctr''
.Ed
.It Cm ClearAllForwardings
Specifies that all local, remote and dynamic port forwardings
set to
.Dq no
(the default).
-These sessions will reuse the master instance's network connection rather
-than initiating new ones.
+These sessions will try to reuse the master instance's network connection
+rather than initiating new ones, but will fall back to connecting normally
+if the control socket does not exist, or is not listening.
+.Pp
Setting this to
.Dq ask
will cause
program before they are accepted (see
.Xr ssh-add 1
for details).
+If the
+.Cm ControlPath
+can not be opened,
+.Nm ssh
+will continue without connecting to a master instance.
+.Pp
+X11 and
+.Xr ssh-agent 1
+forwarding is supported over these multiplexed connections, however the
+display and agent fowarded will be the one belonging to the master
+connection i.e. it is not possible to forward multiple displays or agents.
+.Pp
+Two additional options allow for opportunistic multiplexing: try to use a
+master connection but fall back to creating a new one if one does not already
+exist.
+These options are:
+.Dq auto
+and
+.Dq autoask .
+The latter requires confirmation like the
+.Dq ask
+option.
.It Cm ControlPath
-Specify the path to the control socket used for connection sharing.
-See
+Specify the path to the control socket used for connection sharing as described
+in the
.Cm ControlMaster
-above.
+section above or the string
+.Dq none
+to disable connection sharing.
+In the path,
+.Ql %h
+will be substituted by the target host name,
+.Ql %p
+the port and
+.Ql %r
+by the remote login username.
+It is recommended that any
+.Cm ControlPath
+used for opportunistic connection sharing include
+all three of these escape sequences.
+This ensures that shared connections are uniquely identified.
.It Cm DynamicForward
Specifies that a TCP/IP port on the local machine be forwarded
over the secure channel, and the application
protocol is then used to determine where to connect to from the
remote machine.
-The argument must be a port number.
+.Pp
+The argument must be
+.Sm off
+.Oo Ar bind_address : Oc Ar port .
+.Sm on
+IPv6 addresses can be specified by enclosing addresses in square brackets or
+by using an alternative syntax:
+.Oo Ar bind_address Ns / Oc Ns Ar port .
+By default, the local port is bound in accordance with the
+.Cm GatewayPorts
+setting.
+However, an explicit
+.Ar bind_address
+may be used to bind the connection to a specific address.
+The
+.Ar bind_address
+of
+.Dq localhost
+indicates that the listening port be bound for local use only, while an
+empty address or
+.Sq *
+indicates that the port should be available from all interfaces.
+.Pp
Currently the SOCKS4 and SOCKS5 protocols are supported, and
.Nm ssh
will act as a SOCKS server.
.Cm CheckHostIP
is not available for connects with a proxy command.
.Pp
+This directive is useful in conjunction with
+.Xr nc 1
+and its proxy support.
+For example, the following directive would connect via an HTTP proxy at
+192.0.2.0:
+.Bd -literal -offset 3n
+ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
+.Ed
.It Cm PubkeyAuthentication
Specifies whether to try public key authentication.
The argument to this keyword must be