From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932086AbbAWSbA (ORCPT ); Fri, 23 Jan 2015 13:31:00 -0500 Received: from mail-qc0-f177.google.com ([209.85.216.177]:55239 "EHLO mail-qc0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752780AbbAWSa6 (ORCPT ); Fri, 23 Jan 2015 13:30:58 -0500 Message-ID: <54C2935F.2000105@gmail.com> Date: Fri, 23 Jan 2015 13:30:55 -0500 From: Vlad Yasevich User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Daniel Borkmann CC: Sun Paul , linux-sctp@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, tuexen@fh-muenster.de Subject: Re: Fwd: Question on SCTP ABORT chunk is generated when the association_max_retrans is reached References: <54C23581.9060809@redhat.com> <54C27137.5010405@gmail.com> <54C2807E.8080607@redhat.com> In-Reply-To: <54C2807E.8080607@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -vlad > Sun Paul, what exactly broke in your scenario? Can you be more explicit? > > Thanks, > Daniel