netdev - [PATCH AUTOSEL 5.4 075/130] net/lapb: fix t1 timer handling for LAPB_STATE

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Message-Id: <20201223021813.2791612-75-sashal@kernel.org>
Date:   Tue, 22 Dec 2020 21:17:18 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Martin Schiller <ms@....tdt.de>, Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-x25@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 075/130] net/lapb: fix t1 timer handling for LAPB_STATE_0

From: Martin Schiller <ms@....tdt.de>

[ Upstream commit 62480b992ba3fb1d7260b11293aed9d6557831c7 ]

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.

Signed-off-by: Martin Schiller <ms@....tdt.de>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 8f5b17001a076..baa247fe4ed05 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;
 
 		/*
-- 
2.27.0