From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756457AbbAWTHq (ORCPT ); Fri, 23 Jan 2015 14:07:46 -0500 Received: from mail-n.franken.de ([193.175.24.27]:35984 "EHLO mail-n.franken.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752237AbbAWTHl convert rfc822-to-8bit (ORCPT ); Fri, 23 Jan 2015 14:07:41 -0500 X-Greylist: delayed 1830 seconds by postgrey-1.27 at vger.kernel.org; Fri, 23 Jan 2015 14:07:40 EST Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 8.1 \(1993\)) Subject: Re: Question on SCTP ABORT chunk is generated when the association_max_retrans is reached From: Michael Tuexen In-Reply-To: <54C2935F.2000105@gmail.com> Date: Fri, 23 Jan 2015 19:36:38 +0100 Cc: Daniel Borkmann , Sun Paul , linux-sctp@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8BIT Message-Id: <628C9A19-FFC7-4D98-9FBB-D59F45BF6915@fh-muenster.de> References: <54C23581.9060809@redhat.com> <54C27137.5010405@gmail.com> <54C2807E.8080607@redhat.com> <54C2935F.2000105@gmail.com> To: Vlad Yasevich X-Mailer: Apple Mail (2.1993) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On 23 Jan 2015, at 19:30, Vlad Yasevich wrote: > > On 01/23/2015 12:10 PM, Daniel Borkmann wrote: >> On 01/23/2015 05:05 PM, Vlad Yasevich wrote: >>> On 01/23/2015 06:50 AM, Daniel Borkmann wrote: >>>> 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. >>> >>> The RFC is silent on the matter. The abort got added in 3.8 so >>> it's been there for a while. >> >> I see, commit de4594a51c90 ("sctp: send abort chunk when max_retrans >> exceeded") added the behaviour. >> >>>> 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, >>> >>> This would pretty much stop all ABORTs due to excessive rtx. Might >>> as well take the code out :). >>> >>> I was a bit concerned about this ABORT when it went in. >> >> So effectively, if I understand the argument from the commit, the >> assumption is that the ABORT would never reach the peer anyway, but >> is a way for tcpdump users to see on the wire that rtx limit has >> been exceeded and since there's not mentioned anything in the RFC >> about this, it doesn't break it. Hm. >> > > Additionally I seem to recall BSD sending this type of ABORT for pretty > much the same reason. Yepp. Best regards Michael > > -vlad > >> Sun Paul, what exactly broke in your scenario? Can you be more explicit? >> >> Thanks, >> Daniel > >