Solve the ``first connection'' problem that occurs on

demand-dial links with dynamic IP numbers where the program
that causes the dial bind()s to an interface address that is
subsequently changed after ppp negotiation.

The problem is defeated by adding negotiated addresses to the
tun interface as additional alias addresses and providing a set
of ``iface'' commands for managing the interface.  Libalias is
also required (and what a name clash!) - it happily IP-aliases
the address so that the source is that of the primary (negotiated)
interface and un-IP-aliases it on the way back.

An ``enable iface-alias'' is done implicitly by the -alias command
line switch.  If -alias isn't given, iface-aliasing is disabled by
default and can't be enabled 'till an ``alias enable yes'' is done.
``alias enable no'' silently disables iface-alias.

So, for dynamic-IP-type-connections, running ``ppp -alias -auto blah''
will work for the first connection, although existing bindings will
not survive a disconnect/connect as the TCP peer will be trying to
send to the old IP address - the packets won't route.

It's now a lot easier to add IPXCP to ppp with minor updates to
the new iface.[ch] (if anyone ever gets 'round to it).

It's also now possible to manually add interface aliases with
something like ``iface add 1.2.3.4/24 5.6.7.8''.  This allows
multi-homed ppp links :-)

1 files changed, 96 insertions, 31 deletions

diff --git a/usr.sbin/ppp/ppp.8 b/usr.sbin/ppp/ppp.8
index 4ed85be..de37467 100644
--- a/usr.sbin/ppp/ppp.8
+++ b/usr.sbin/ppp/ppp.8
@@ -1,4 +1,4 @@
-.\" $Id: ppp.8,v 1.125 1998/09/17 00:45:12 brian Exp $
+.\" $Id: ppp.8,v 1.126 1998/09/18 23:28:10 brian Exp $
 .Dd 20 September 1995
 .Os FreeBSD
 .Dt PPP 8
@@ -408,13 +408,10 @@ PPP ON awfulhak> add default HISADDR
 .Pp
 The string
 .Sq HISADDR
-represents the IP address of the connected peer.  It is possible to
-use the keyword
-.Sq INTERFACE
-in place of
-.Sq HISADDR .
-This will create a direct route on the tun interface.
-If it fails due to an existing route, you can overwrite the existing
+represents the IP address of the connected peer.
+If the
+.Dq add
+command fails due to an existing route, you can overwrite the existing
 route using
 .Bd -literal -offset indent
 PPP ON awfulhak> add! default HISADDR
@@ -514,18 +511,15 @@ connection is established.  See the provided
 .Dq pmdemand
 example in
 .Pa /etc/ppp/ppp.conf.sample
-which runs a script in the background after the connection is established.
-The literal strings
-.Dv HISADDR ,
-.Dv MYADDR
+which runs a script in the background after the connection is established
+(refer to the
+.Dq shell
 and
-.Dv INTERFACE
-may be used, and will be replaced with the relevant IP addresses and interface
-name.  Similarly, when a connection is closed, the
-contents of the
+.Dq bg
+commands below for a description of possible substition strings).  Similarly,
+when a connection is closed, the contents of the
 .Pa /etc/ppp/ppp.linkdown
-file are executed.
-Both of these files have the same format as
+file are executed.  Both of these files have the same format as
 .Pa /etc/ppp/ppp.conf .
 .Pp
 In previous versions of
@@ -2134,6 +2128,28 @@ this option will tell
 .Nm
 not to make any utmp or wtmp entries.  This is usually only necessary if
 you require the user to both login and authenticate themselves.
+.It iface-alias
+Default: Enabled if
+.Fl alias
+is specified.  This option simply tells
+.Nm
+to add new interface addresses to the interface rather than replacing them.
+The option can only be enabled if IP aliasing is enabled
+.Pq Dq alias enable yes .
+.Pp
+With this option enabled,
+.Nm
+will pass traffic for old interface addresses through the IP alias engine
+.Pq see Xr libalias 5 ,
+resulting in the ability (in
+.Fl auto
+mode) to properly connect the process that caused the PPP link to
+come up in the first place.
+.Pp
+Disabling IP aliasing with
+.Dq alias enable off
+will also disable
+.Sq iface-alias .
 .El
 .Pp
 .It add[!] Ar dest[/nn] [mask] gateway
@@ -2162,24 +2178,14 @@ It is possible to use the symbolic names
 .Sq MYADDR
 or
 .Sq HISADDR
-as the destination, and either
+as the destination, and
 .Sq HISADDR
-or
-.Sq INTERFACE
 as the
 .Ar gateway .
 .Sq MYADDR
-is replaced with the interface address,
+is replaced with the interface address and
 .Sq HISADDR
-is replaced with the interface destination address and
-.Sq INTERFACE
-is replaced with the current interface name.  If the interfaces destination
-address has not yet been assigned
-.Pq via Dq set ifaddr ,
-the current
-.Sq INTERFACE
-is used instead of
-.Sq HISADDR .
+is replaced with the interface destination (peer) address.
 .Pp
 If the
 .Ar add!
@@ -2476,6 +2482,52 @@ is specified, only the relevant compression layer(s) are terminated.
 Show a list of available commands.  If
 .Ar command
 is specified, show the usage string for that command.
+.It iface Ar command Op args
+This command is used to control the interface used by
+.Nm ppp .
+.Ar Command
+may be one of the following:
+.Bl -tag -width XX
+.It iface add[!] Ar addr[/bits| mask] peer
+Add the given
+.Ar addr mask peer
+combination to the interface.  Instead of specifying
+.Ar mask ,
+.Ar /bits
+can be used
+.Pq with no space between \&it and Ar addr .
+If the given address already exists, the command fails unless the
+.Dq \&!
+is used - in which case the previous interface address entry is overwritten
+with the new one, allowing a change of netmask or peer address.
+.It iface clear
+If this command is used while
+.Nm
+is in the OPENED state, all addresses except for the IPCP negotiated
+address are deleted from the interface.  If
+.Nm
+is not in the OPENED state, all interface addresses are deleted.
+.Pp
+.It iface delete[!]|rm[!] Ar addr
+This command deletes the given
+.Ar addr
+from the interface.  If the
+.Dq \&!
+is used, no error is given if the address isn't currently assigned to
+the interface (and no deletion takes place).
+.It iface show
+Shows the current state and current addresses for the interface.  It is
+much the same as running
+.Dq ifconfig INTERFACE .
+.It iface help Op Ar sub-command
+This command, when invoked without
+.Ar sub-command ,
+will show a list of possbile
+.Dq iface
+sub-commands and a brief synopsis for each.  When invoked with
+.Ar sub-command ,
+only the synopsis for the given sub-command is shown.
+.El
 .It [data]link Ar name[,name...] command Op Ar args
 This command may prefix any other command if the user wishes to
 specify which link the command should affect.  This is only
@@ -3160,6 +3212,16 @@ It is not possible to change a link that is
 .Sq direct
 or
 .Sq dedicated .
+.Pp
+Note: If you issue the command
+.Dq set mode auto ,
+and have IP aliasing enabled, it may be useful to
+.Dq enable iface-alias
+afterwards.  This will allow
+.Nm
+to do the necessary address translations to enable the process that
+triggers the connection to connect once the link is up despite the
+peer assigning us a new (dynamic) IP address.
 .It set mrru Op Ar value
 Setting this option enables Multi-link PPP negotiations, also known as
 Multi-link Protocol or MP.  There is no default MRRU (Maximum
@@ -3409,6 +3471,9 @@ is not specified, all filters are shown.
 Show the current HDLC statistics.
 .It show help|?
 Give a summary of available show commands.
+.It show iface
+Show the current interface information
+.Pq the same \&as Dq iface show .
 .It show ipcp
 Show the current IPCP statistics.
 .It show lcp