[Lksctp-developers] SCTP association restart

[Peter H. <pet...@al...>]

Hello,

I'm trying to trigger SCTP ASSOC CHANGE(SCTP_RESTART) notification on my 
server application which is using SCTP socket API. Im trying to do that 
on RHEL 5.1 . The idea is to test the server application whether it 
correctly handles the reboot of the client machine (those reboots 
ussualy create new association instead of triggering restart 
notification thus is not a practical way to test the case).

I'm trying to do that by initiating new SCTP association and capturing 
the INIT and COOKIE_ECHO messages my test client is sending to the 
server application. Then I simply replay those packets again.

So far I've been unable to trigger this restart event notification.


1) identical duplicates:

If I replay INIT and COOKIE_ECHO packet unchanged, server replies with 
INIT_ACK (after INIT) and then COOKIE_ACK (after COOKIE_ECHO) but server 
application does not receive any notification for existing association. 
And no new association is created instead.

I would expect the yes, no new association is created but that my server 
would get "restart" notification from the socket API.


2) modified duplicates:

If I replay modified INIT (different Initiate tag then first INIT), I 
get INIT_ACK from server. Then I replay COOKIE_ACK (using value of 
Initiat tag from INIT_ACK to modify Verification tag in duplicate 
COOKIE_ECHO. But I get no COOKIE_ACK from the server. And server 
application gets no notification nor is there any message from the kernel.

I would expect ... well, do not know. :)


On the other hand, I am able to trigger SCTP ASSOC 
CHANGE(SCTP_COMM_LOST) by sending ABORT.

Additinal information:

# modinfo sctp
filename:       /lib/modules/2.6.18-53.el5/kernel/net/sctp/sctp.ko
license:        GPL
description:    Support for the SCTP protocol (RFC2960)
author:         Linux Kernel SCTP developers 
<lks...@li...>
alias:          net-pf-2-proto-132
srcversion:     EA347AE19CDDAFFDB5A3CA4
depends:        ipv6
vermagic:       2.6.18-53.el5 SMP mod_unload gcc-4.1
module_sig: 
883f35047d39e6836e299a424cb51a112843109e2f64fc6bac16274c9c7feb16ea1f6d43374e6c09f669fbf51166c2dd1e3a393c60983d3444134c0


So the question is: How precisely do I trigger SCTP association restart 
notification in my server application? Or is there some testing tool you 
use for this (and if so, where can I get it and how to use it)?

Btw, I did found this:

http://sourceforge.net/mailarchive/message.php?msg_id=4767E7DB.4090203%40hp.com

"The system reboots yet again and the third INIT is send with the source 
port of 32768. In this case, the ports and addresses are the same, so 
this treated as association restart. In this case, the server will 
re-initialize and re-use the existing association. This is expected 
behavior."

This should be what I simulate with [1] except that my server 
application des not get the restart notification from the socket API.


Thank you in advance for any feedback.

Sincerely

Peter

-- 
Peter Hanecak

MME Developer | MSD | Alcatel-Lucent
Magnetova 11 | Bratislava | Slovak Republic
email: pet...@al...
phone: +421 (0)2 49264 857