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Re: [SCTP-Discussion] Ip forwarding; ASCONF SUCCEEDED ; home address;


Chronological Thread 
  • From: Andreas Jungmaier <ajung AT exp-math.uni-essen.de>
  • To: "Gurpreet Virdi" <gurpreetvirdi AT hotmail.com>, <discussion AT sctp.de>
  • Subject: Re: [SCTP-Discussion] Ip forwarding; ASCONF SUCCEEDED ; home address;
  • Date: Mon Jun 28 11:32:02 2004
  • List-id: SCTP Discussions <discussion.sctp.de>
  • Organization: University Duisburg-Essen
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Am Samstag, 26. Juni 2004 20:48 schrieben Sie:
> Hi,
>
> I was wondering if there is any way to tell SCTP client servers to only
> form associations between IP's of the same network/subnet if IP forwarding
> is enabled. I mean I could deactivate IP forwarding in the kernel, but if i
> didn't want to then is there still a way to tell SCTP to form paths only
> between same subnets/networks.

This is generally done by the routing layer in IP configuration.
Not by SCTP.

Don't know what you mean by IP forwarding.

> Also when a new IP is added, lets say on the client side, the network
> status change functions enters the mode of "ASCONF SUCCEEDED". I was
> wondering if there is any way to find out if this ASCONF SUCCEEDED was for
> a path that was added or deleted. I mean on the seerver side you know the
> path is added or deleted, but how do you find out on the client side if
> ASCONF SUCCEEDED was a path added or deleted.

The side that is receiving a valid ASCONF will notify its
application with a NETWORK STATUS CHANGE notification, and send
along either of the constants SCTP_PATH_ADDED or SCTP_PATH_REMOVED,
together with the path id (that is what you call server).

Right now, the other side is notified only of the fact that an ASCONF
it sent has been successfully acknowledged.

I agree that this is not very well thought out.

*Right now*, the only way to go is use the status functions to find out
what has actually happenend (e.g. compare the numbers local addresses
before and after the notification).

How would you suggest we change the API ?

Any other comments from people on this list ?

> Lastly, for any association , by using pathStatus.destinationAddress, you
> can find out the destination address; how can you find out your own home
> address for that path. Is there any API or function or call.

No. The outgoing address is selected by the operating system, and the routing,
as it is configured. I have seen a program use UDP sockets, and a
"pseudo"-send call, to find out what would have been the address that the
underlying OS had selected, but we have not implemented something like that.

If you need this functionality, try to create a patch against the latest
release of sctplib (i.e. sctplib-1.1.6) and post it either to me or to the
sctp discussion list. We will then consider adding this functionality.

Best regards,
Andreas

- --
Dipl.-Ing. Andreas Jungmaier
Computer Networking Technology Group
University of Duisburg-Essen
http://www.exp-math.uni-essen.de/~ajung
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