From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Schiller Subject: Re: [PATCH net-next v5 3/5] net/lapb: fix t1 timer handling for LAPB_STATE_0 Date: Tue, 24 Nov 2020 13:29:05 +0100 Message-ID: <3d3f3733c08168bc8417021206cd93b9@dev.tdt.de> References: <20201124093538.21177-1-ms@dev.tdt.de> <20201124093538.21177-4-ms@dev.tdt.de> <2d40b42aee314611b9ba1627e5eab30b@AcuMS.aculab.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <2d40b42aee314611b9ba1627e5eab30b@AcuMS.aculab.com> List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" 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 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)