Subject: Re: Fwd: Question on SCTP ABORT chunk is generated when the association_max_retrans is reached

From: Daniel Borkmann <[email-masked]>
Date: Fri, 23 Jan 2015 12:50:25 +0100

Hi,

On 01/23/2015 11:25 AM, Sun Paul wrote:
...
> I would like to check the behave in LKSCTP.
>
> we are running DIAMETER message over SCTP, and we have set the
> parameter "net.sctp.association_max_retrans = 4" in the LinuxOS.
>
> We noticed that when remote peer have retry to send the same request
> for 4 times, the LKSCTP will initiate an ABORT chunk with reason
> "association exceeded its max_retrans count".
>
> We would like to know whether this is the correct behavior? is there
> any other option that we can alter in order to avoid the ABORT chunk
> being sent?

I don't recall the RFC saying to send an ABORT, but let me double
check in the mean time.

Hmm, untested, but could you try something like that?

diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index fef2acd..5ce198d 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -584,7 +584,8 @@ static void sctp_cmd_assoc_failed(sctp_cmd_seq_t *commands,
  		sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP,
  				SCTP_ULPEVENT(event));

-	if (asoc->overall_error_count >= asoc->max_retrans) {
+	if (asoc->overall_error_count >= asoc->max_retrans &&
+	    error != SCTP_ERROR_NO_ERROR) {
  		abort = sctp_make_violation_max_retrans(asoc, chunk);
  		if (abort)
  			sctp_add_cmd_sf(commands, SCTP_CMD_REPLY,