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 584463AF66E; Wed, 30 Sep 2026 17:54:21 +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=1790790862; cv=none; b=lNo0BFmf5n6zZDSmlEO1jmOkMFYFcOT3VqeuhdZdJcQoK9LEiZIjPvJR1X8co5/ri8yBJASSKeOv6Rd002NTyJEor9WyNqK0iR5oO3Tcn3ADQ+UmuR43hb8KjzvrqiLQvdC23zT3EDCagBWuuFjUgcGw3PfKJPsFUBFlSRtc8ic= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790790862; c=relaxed/simple; bh=RA3yUKdaoyAKEACq0EiX9S+tHieELIQPMwXL3Wn1KBE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=k1Gq7wXLBGKEEFesedWBafRY+Q07UjHH8EFIu9NrUQfwVJRA2iqrle8DCnx20yjvoTj5NH/b7aICFRNI/6YsrL/wyUmRmbFgnBMjCJV4zkYV7eqA+96465XAsDaKfOEG5BN6dOTQ1v0jRZVBTmY71Q2LN5MgjCL3HCyCGe3zdo8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dWSaoBw2; 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="dWSaoBw2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB0151F000FF; Wed, 30 Sep 2026 17:54:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790790861; bh=Sd08zk+RzL9rmMektSGGmnvV4h+oY7hiaBfhdHfJYcM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dWSaoBw2CASN2dKZxOJk5k4wHqoeIIKYFZkgSUwSbnpm/KVoJxnaIgZPZC/ck+gVG lngAB40TkoqfGLYoXX8KXdaYgleP0XTgKTTERp23R3ZW52Nn3PXp3G0xgfRoe1eK92 +HTTakEiKwgoDDCPRAvr4oPTYJIVpFPfP5t+0w3c= 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 5.15 100/752] net: ibm: emac: Reserve VLAN header in MJS limit Date: Wed, 30 Sep 2026 17:19:30 +0200 Message-ID: <20260930152400.330395032@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152358.131179731@linuxfoundation.org> References: <20260930152358.131179731@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 5.15-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 664a91af662df..018fd19d1ce74 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 @@ -465,7 +466,7 @@ 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