Sample Netgraph code that unhooks and rehooks without losing connection

[Julian Elischer]

your mail was ZVERY hard to read becosue you mixed you comments in with my mail 
without distinguishing them in any way.. I missed two of them on first reading.


Martha Pasikatan wrote:
> Julian Elischer <julian at elischer.org> wrote: Alexander Motin wrote:
>> Martha Pasikatan wrote:
>>> I would like to be able to unhook a pppoe node hooked to link0 and 
>>> rehook it to a tee node.  Can anyone give me a sample on how to do this?  
>> That's impossible. As soon as pppoe node hook is disconnected all 
>> related info will be destroyed and session will be terminated. You 
>> should put there some other node like ng_tee to prevent session 
>> termination.
>>

> That means I need to create another hook through make peer, right? 
> Is that at the same path as link0? or inside link0?  

I believe he means you need to add the tee at creation time. "just in case".


> Are some programs dependent on this behavior, because that might cause 
> side-effects on them.  Is netgraph already widely-used by the way? 

yes. it is used by a lot of people for all kinds of strange things.

> 
> Would connecting it to a tee node allow me to forward the packets to 
> another node, without disconnecting the session and at the same time, 
> not have the session processed anymore by the previous node?  Is there already 
> a functionality in netgraph that does this?  I might just not know about it 
> but it already exist.   I could really use something like a divert function 
> not just a copy.

probably another kind of node would be better for that.

maybe you could use a bpf node, or possibly one of the one2many  
modes may be good for you.

Possibly you could write a new note type. "switchpoint" which can be 
switched from one connection to another using a command message.

New netgraph types are very easy to write. The ng_sample.c file 
is a good starting point. take some of the logic from tee
and some of the message handling from one2many (mode setting messages)
and grapfdt them together into a node that does what you want exactly.



(but first look at all the nodes that already exist to see if one 
doesn't already do what you want).