ppp question

ppp question

[Davy Leon]

Hi folks

I have a question. Every time I dialup to the internet pppd executes an 
script called ip-up. My question is, everytime someone dials in it's 
executed too? If the answer is yes, how can I handle the script to execute 
one part when dianing out and another part when dialing in. I meant 
something like

if dialing in then

...
...

if dialing out then

...
....



Thanks in advance

David 

Re: ppp question

[Bill Unruh]

On Mon, 5 Oct 2009, Davy Leon wrote:

> Hi folks
>
> I have a question. Every time I dialup to the internet pppd executes an 
> script called ip-up. My question is, everytime someone dials in it's executed 
> too? If the answer is yes, how can I handle the script to execute one part 
> when dianing out and another part when dialing in. I meant something like

One of the arguments given to ip-up is the IP addresses assigned to the remote
and local systems. Since when someone calls in the IP address is assigned by
you and is almost certainly different from the IP address assigned to you when
you dial out. You can base the response on the IP address range

man pppd

>
> if dialing in then
>
> ...
> ...
>
> if dialing out then
>
> ...
> ....
>
>
>
> Thanks in advance
>
> David 
> --

Re: ppp question

[James Carlson]

Davy Leon wrote:
> I have a question. Every time I dialup to the internet pppd executes an
> script called ip-up. My question is, everytime someone dials in it's
> executed too?

Yes.  It's executed every time an IP interface is brought up by PPP.

Note that PPP itself knows nothing about dialing in or out; those are
attributes of the lower layer -- the chat script and modems or other
communications gear involved.  PPP is symmetric and peer-to-peer.
There's no "client" or "server."

> If the answer is yes, how can I handle the script to
> execute one part when dianing out and another part when dialing in. I
> meant something like

The man page has a number of environment variables documented that you
could use for this task.  $PEERNAME is fairly useful -- it will be set
only if you have an authenticated peer name.

If you have different devices for dialing in and out (it's often a good
idea to do this, but not always done), then $DEVICE might tell you what
you want to know.

If you want to get fancier, you can use $LINKNAME with the "linkname"
option.

The simple answer would be:

	if [[ -n ${PEERNAME:+I_am_server} ]]; then
		# the peer probably called me
	else
		# I'm probably dialing out
	fi

But note that this is making a big assumption about authentication
configuration: that you always authenticate people calling you, and you
never authenticate people you call.  That's how PPP is commonly used,
but there's nothing in the standards that _requires_ it to be used that way.

-- 
James Carlson         42.703N 71.076W         <carlsonj@workingcode.com>