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Thu, 09 Jul 2026 03:52:47 -0700 (PDT) Received: from ala-exchng01.corp.ad.wrs.com (10.11.224.121) by ALA-EXCHNG02.corp.ad.wrs.com (10.11.224.122) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.61; Thu, 9 Jul 2026 03:52:46 -0700 Received: from pek-yzhou-d3.wrs.com (10.11.232.110) by ala-exchng01.corp.ad.wrs.com (10.11.224.121) with Microsoft SMTP Server id 15.1.2507.61 via Frontend Transport; Thu, 9 Jul 2026 03:52:44 -0700 From: Yun Zhou To: , , , , , , CC: , , Subject: [PATCH] net: gre: fix lltx regression for GRE tunnels with SEQ/CSUM Date: Thu, 9 Jul 2026 18:52:43 +0800 Message-ID: <20260709105243.864835-1-yun.zhou@windriver.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Proofpoint-ORIG-GUID: orP29TGAcc_p0bFjhlYFd1CxclJbsE4s X-Proofpoint-Spam-Info: AW1haW4tMjYwNzA5MDEwNSBTYWx0ZWRfXxV04wVr/eQMK sirk8NohBtKzCzstQ18GF+K6glUBWTQTY8J8Ptsdms+rrOZOg4ivXV83BdGLEGiAc480+hkWTtV 4t8brFvxnZT0Iquf13VmIHV/mJRPfgTTTpXG8uHWLhpfFqLVfYmW X-Proofpoint-GUID: orP29TGAcc_p0bFjhlYFd1CxclJbsE4s X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzA5MDEwNSBTYWx0ZWRfX/gidtCm3i2Z4 ZwICXEQILUcD6BCB8B0PhfyJ0RE02yI6xmTR/wt3BA1ZXVe1oYdT4wNSFSKXjg08Dhb5xeZA5EP 5tZTpIP+nTN4XaSl2OMG94ZENHbcSt3NtE5UmPT0VZ55ISK6qh8VinXJIgO0WCf/UePmdmVLbGl bPHia8ataoDmb4OvOCAoGrZC4AE9EFT8eNY/6JghA+iHvxAy/66a5hLJmV0wPISb3XhwieBEYR+ BxmdsJcncT5+ejndP6/4/+g6wAmo/U7aGunn96X2QAuJmpH4+MsituydLCW/MKPoPlTX9SPCj/Y ucRxuA0861f6Nkm7j5Tomcgy6ikPVicwOHlfyAvxUthmKonqwxLQKTnBzaq1tzOmHE5/Kq4UL74 PpuM1WbPpFmM+rlGsrVH9e7ffZJ1QnUaRpTYR2wDjUC6lW8WyEMx96d6l/a/lLD2wtZE7Ia1jXT WcsHSEJeOOB8Sf5/Xgw== X-Authority-Analysis: v=2.4 cv=P7IKQCAu c=1 sm=1 tr=0 ts=6a4f7d7f cx=c_pps a=Lg6ja3A245NiLSnFpY5YKQ==:117 a=Lg6ja3A245NiLSnFpY5YKQ==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=bi6dqmuHe4P4UrxVR6um:22 a=iKiJcTA2PjBS6x5JeXcw:22 a=t7CeM3EgAAAA:8 a=493gFeiaP1eb9wWiEwEA:9 a=FdTzh2GWekK77mhwV6Dw:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-09_02,2026-07-08_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 priorityscore=1501 adultscore=0 clxscore=1015 malwarescore=0 phishscore=0 suspectscore=0 impostorscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607090105 Before commit 00d066a4d4ed ("netdev_features: convert NETIF_F_LLTX to dev->lltx"), NETIF_F_LLTX was set unconditionally in __gre_tunnel_init() alongside GRE_FEATURES: dev->features |= GRE_FEATURES | NETIF_F_LLTX; When that commit converted NETIF_F_LLTX to the dev->lltx flag, it placed 'dev->lltx = true' after the SEQ/CSUM early returns instead of before them. This causes GRE/GRETAP tunnels with SEQ or CSUM+encap to lose lockless TX, reintroducing _xmit_lock acquisition around their ndo_start_xmit. Since GRE xmit re-enters the stack via ip_tunnel_xmit(), holding _xmit_lock risks ABBA deadlock with the underlay device. CPU0 CPU1 ---- ---- lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); lock(&qdisc_xmit_lock_key#6); lock(&qdisc_xmit_lock_key#3); Fix by moving dev->lltx = true before the early returns, restoring the original unconditional behavior. Fixes: 00d066a4d4ed ("netdev_features: convert NETIF_F_LLTX to dev->lltx") Signed-off-by: Yun Zhou --- net/ipv4/ip_gre.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 9fbff16cda1d..8c5ad8ec8d09 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -1018,6 +1018,8 @@ static void __gre_tunnel_init(struct net_device *dev) dev->features |= GRE_FEATURES; dev->hw_features |= GRE_FEATURES; + dev->lltx = true; + /* TCP offload with GRE SEQ is not supported, nor can we support 2 * levels of outer headers requiring an update. */ @@ -1029,8 +1031,6 @@ static void __gre_tunnel_init(struct net_device *dev) dev->features |= NETIF_F_GSO_SOFTWARE; dev->hw_features |= NETIF_F_GSO_SOFTWARE; - - dev->lltx = true; } static int ipgre_tunnel_init(struct net_device *dev) -- 2.43.0