From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2EE5C63798 for ; Tue, 24 Nov 2020 12:29:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E904208DB for ; Tue, 24 Nov 2020 12:29:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387579AbgKXM3O (ORCPT ); Tue, 24 Nov 2020 07:29:14 -0500 Received: from mxout70.expurgate.net ([91.198.224.70]:26591 "EHLO mxout70.expurgate.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729172AbgKXM3O (ORCPT ); Tue, 24 Nov 2020 07:29:14 -0500 Received: from [127.0.0.1] (helo=localhost) by relay.expurgate.net with smtp (Exim 4.92) (envelope-from ) id 1khXRU-000H9v-8h; Tue, 24 Nov 2020 13:29:08 +0100 Received: from [195.243.126.94] (helo=securemail.tdt.de) by relay.expurgate.net with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1khXRT-000H8C-5G; Tue, 24 Nov 2020 13:29:07 +0100 Received: from securemail.tdt.de (localhost [127.0.0.1]) by securemail.tdt.de (Postfix) with ESMTP id 9D702240041; Tue, 24 Nov 2020 13:29:06 +0100 (CET) Received: from mail.dev.tdt.de (unknown [10.2.4.42]) by securemail.tdt.de (Postfix) with ESMTP id 10B03240040; Tue, 24 Nov 2020 13:29:06 +0100 (CET) Received: from mail.dev.tdt.de (localhost [IPv6:::1]) by mail.dev.tdt.de (Postfix) with ESMTP id 593DF20049; Tue, 24 Nov 2020 13:29:05 +0100 (CET) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 24 Nov 2020 13:29:05 +0100 From: Martin Schiller To: David Laight Cc: andrew.hendry@gmail.com, davem@davemloft.net, kuba@kernel.org, xie.he.0141@gmail.com, linux-x25@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v5 3/5] net/lapb: fix t1 timer handling for LAPB_STATE_0 Organization: TDT AG In-Reply-To: <2d40b42aee314611b9ba1627e5eab30b@AcuMS.aculab.com> References: <20201124093538.21177-1-ms@dev.tdt.de> <20201124093538.21177-4-ms@dev.tdt.de> <2d40b42aee314611b9ba1627e5eab30b@AcuMS.aculab.com> Message-ID: <3d3f3733c08168bc8417021206cd93b9@dev.tdt.de> X-Sender: ms@dev.tdt.de User-Agent: Roundcube Webmail/1.3.15 X-purgate-type: clean X-purgate: clean X-purgate-ID: 151534::1606220947-00017060-88198D89/0/0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2020-11-24 12:43, David Laight wrote: > From: Martin Schiller >> Sent: 24 November 2020 09:36 >> >> 1. DTE interface changes immediately to LAPB_STATE_1 and start sending >> SABM(E). >> >> 2. DCE interface sends N2-times DM and changes to LAPB_STATE_1 >> afterwards if there is no response in the meantime. > > Seems reasonable. > It is 35 years since I wrote LAPB and I can't exactly remember > what we did. > If I stole a copy of the code it's on a QIC-150 tape cartridge! > > I really don't remember having a DTE/DCE option. > It is likely that LAPB came up sending DM (response without F) > until level3 requested the link come up when it would send > N2 SABM+P hoping to get a UA+F. > It would then send DM-F until a retry request was made. > > We certainly had several different types of crossover connectors > for DTE-DTE working. > > David > The support for DTE/DCE was already in the LAPB code and I made it configurable from userspace (at least for hdlc interfaces) with this commit: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=f362e5fe0f1f For Layer3 (X.25) I will add it with an addional patch (you already commented on that) on a next step. The described behaviour above is my interpretation of point 2.4.4.1 of the "ITU-T Recommendation X.25 (10/96) aka "Blue Book" [1]. [1] https://www.itu.int/rec/T-REC-X.25-199610-I/ >> >> Signed-off-by: Martin Schiller >> --- >> net/lapb/lapb_timer.c | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/net/lapb/lapb_timer.c b/net/lapb/lapb_timer.c >> index 8f5b17001a07..baa247fe4ed0 100644 >> --- a/net/lapb/lapb_timer.c >> +++ b/net/lapb/lapb_timer.c >> @@ -85,11 +85,18 @@ static void lapb_t1timer_expiry(struct timer_list >> *t) >> switch (lapb->state) { >> >> /* >> - * If we are a DCE, keep going DM .. DM .. DM >> + * If we are a DCE, send DM up to N2 times, then switch to >> + * STATE_1 and send SABM(E). >> */ >> case LAPB_STATE_0: >> - if (lapb->mode & LAPB_DCE) >> + if (lapb->mode & LAPB_DCE && >> + lapb->n2count != lapb->n2) { >> + lapb->n2count++; >> lapb_send_control(lapb, LAPB_DM, LAPB_POLLOFF, LAPB_RESPONSE); >> + } else { >> + lapb->state = LAPB_STATE_1; >> + lapb_establish_data_link(lapb); >> + } >> break; >> >> /* >> -- >> 2.20.1 > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, > MK1 1PT, UK > Registration No: 1397386 (Wales)