From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC9862F8BEE; Wed, 30 Sep 2026 18:53:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790794400; cv=none; b=rzopV6aBioEdKLF9UGuQPKk5+f21RjxX6CEYqrFegfnyzCsONbEZP3CaFAKVVduMirs6ogS2YuEJCHthNwJzIIjts+seW53YcG23iXZINq6WKQ+GCCYxYKUZOIqI7owiy2q8oRpFZAJRIEWwXH+hbpkNp1oLJU3vWgcNUm7mqUE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790794400; c=relaxed/simple; bh=iaN+Hy9mxlTL19JBBo/yEOVOUXEtpzp19pB+rDullI0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=N4XhKD/jcTg0XmJzk0As2wcGCs0VI226LGOnL9cRdzSswPP+37rMrwe4nbzFGA5kI0CkCP6cC8Y4Gz/P71q7t+28ErngNyy/bnMd+kpHihyMqm8+lTm7ZnsHfVbxCrfaFmx3rTFOWCxUm8gcqPSv57mJ6AzJ2KIs/yIIJsElAuc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BmeI8iLX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BmeI8iLX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53EA11F000FF; Wed, 30 Sep 2026 18:53:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790794398; bh=RN7GG/77dtnAhhbNwEyWm/SMeA9lRA1VkSRZ9EKTXRs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BmeI8iLX399dU4RMQ2ajz+37R4t4wZ9KBYqRkbNECj1R8OPkK1gNARHf/R5c1sgYF 7eWbgHGcWUL9XbHDhbJq2wYgOOFzooC3P71Y3tQeIi0GGOc5GP7egvQtYMv5Y9ydhd ZX777PQzhtz0Ao8Lw+31wP7u4kFwpE1CoLyjk4r0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Rosen Penev , Paolo Abeni , Sasha Levin Subject: [PATCH 6.6 0149/1193] net: ibm: emac: Reserve VLAN header in MJS limit Date: Wed, 30 Sep 2026 17:13:53 +0200 Message-ID: <20260930152437.519611294@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Rosen Penev [ Upstream commit 0906c117f81c2ae6e6dbfa82719f79c75e1c9325 ] The IBM EMAC programs its Maximum Jumbo Size (MJS) drop threshold from ndev->mtu directly. The hardware sizes the threshold against the L2 frame minus the ethernet header, but does not discount the 802.1Q tag, so a frame carrying a VLAN tag and a full 1500-byte payload exceeds MJS by exactly 4 bytes and is dropped. This is normally hidden because JPSM (and therefore the MJS check) only engages when the MTU is raised above ETH_DATA_LEN. With the qca8k DSA tagger the conduit MTU is bumped by QCA_HDR_LEN to 1502 during dsa_conduit_setup(), which is enough to enable JPSM and expose the off-by-VLAN-tag in the limit. Pad MJS by VLAN_HLEN so a VLAN-tagged full-MTU frame passes. Reported on Meraki MX60 (qca8k switch): tagged VLAN traffic drops at 1500-byte payload, while 1496 bytes works and untagged 1500 bytes works. Assisted-by: Claude:Opus-4.7 Signed-off-by: Rosen Penev Link: https://patch.msgid.link/20260526202247.13823-1-rosenp@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- drivers/net/ethernet/ibm/emac/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c index 0c314bf974808..5a602697c5748 100644 --- a/drivers/net/ethernet/ibm/emac/core.c +++ b/drivers/net/ethernet/ibm/emac/core.c @@ -30,6 +30,7 @@ #include #include #include +#include #include #include #include @@ -466,7 +467,7 @@ static inline u32 emac_iff2rmr(struct net_device *ndev) if (emac_has_feature(dev, EMAC_APM821XX_REQ_JUMBO_FRAME_SIZE)) { r &= ~EMAC4_RMR_MJS_MASK; - r |= EMAC4_RMR_MJS(ndev->mtu); + r |= EMAC4_RMR_MJS(ndev->mtu + VLAN_HLEN); } return r; -- 2.53.0