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 B7C3D4E77FE; Thu, 17 Sep 2026 17:55:48 +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=1789667749; cv=none; b=OiOsOaeTjtZSRPDkxK84dRSchXqXJXNQBLbciMvGFG2PpDXBr8zIdiMaO7a1ALx0Q6p5sd0zA/oguoxj0fR9pDZEgy9mi6ECe+E91J509abZg5+MBhfwk97A3l8//xaSci4+HVXegLSAXpDvuqBmhgL3L6GPN//+JCHCwy3dYvU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789667749; c=relaxed/simple; bh=AEMRvhDkszrGcnFxSR76bsPAjxuXZo82m6Em1Q/X2hA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VHUHfhE0hioPQUMQDX7T2EjzPzJ4jOZOLdDlUIUNQpuf/Eq4umPP5cGiOLZaI/vwnOUlLIyEC9h8u2zcu++fzjbUoK0Qe5bm2Tj6vM5p4l99KFhsWWA1nZxpZjfd6uIfmJEVrTb1ZClvFHctbfruE9f7TTZGg+C5orNVaEqN7hw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zbJI/3Nv; 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="zbJI/3Nv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B77351F000FF; Thu, 17 Sep 2026 17:55:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789667748; bh=4nhoObzJTJbiNUvFt1goiBfudtpMb3Dxj4fIAn1dwKo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zbJI/3NvtHBfbY1017ZHGSiCVdWfiNohuwV990Y+VNVwio+x3BYUdPgEAq6KLdwAc 7bgRL5FAw7Dp+I8oJWgw59H1mIR2vzEum0QrcbithVT5tUbrudS647zfTo/TdxxVMf K5f8cdQGM1CSSXBzbTu76ZAG59+Q9gD9IHw3w6Qc= 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 6.12 0196/1102] net: ibm: emac: Reserve VLAN header in MJS limit Date: Thu, 17 Sep 2026 16:02:19 +0100 Message-ID: <20260917151544.490719120@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151539.408551884@linuxfoundation.org> References: <20260917151539.408551884@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 6.12-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 0db3f558c95bb..a7aef2fb668d2 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 @@ -457,7 +458,7 @@ 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