From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C42111C03 for ; Mon, 20 Mar 2023 15:16:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44D7DC433EF; Mon, 20 Mar 2023 15:16:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1679325380; bh=XNO6FNRo6VpeSNRFLv1P8DqjJQ6kZcfjL15csuKJjwI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ui/mcQjF5gQpIh8h69oGkvcRbxl1E5EUzg/K8kakntxZPFrOGp6dKYjS+la4dAKrv yymnaVFBnyzbpLQ0r3cOhzv4X/jznCnDpUfuICQUpMzLo+uMgRSl4KHRymgnqj8NDN dNCtCWlgT8hy+Soy9ZCRj6PQdXviUI4hhwErXxO0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vladimir Oltean , Simon Horman , Florian Fainelli , "David S. Miller" , Sasha Levin Subject: [PATCH 6.1 078/198] net: dsa: dont error out when drivers return ETH_DATA_LEN in .port_max_mtu() Date: Mon, 20 Mar 2023 15:53:36 +0100 Message-Id: <20230320145510.800895802@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230320145507.420176832@linuxfoundation.org> References: <20230320145507.420176832@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Vladimir Oltean [ Upstream commit 636e8adf7878eab3614250234341bde45537f47a ] Currently, when dsa_slave_change_mtu() is called on a user port where dev->max_mtu is 1500 (as returned by ds->ops->port_max_mtu()), the code will stumble upon this check: if (new_master_mtu > mtu_limit) return -ERANGE; because new_master_mtu is adjusted for the tagger overhead but mtu_limit is not. But it would be good if the logic went through, for example if the DSA master really depends on an MTU adjustment to accept DSA-tagged frames. To make the code pass through the check, we need to adjust mtu_limit for the overhead as well, if the minimum restriction was caused by the DSA user port's MTU (dev->max_mtu). A DSA user port MTU and a DSA master MTU are always offset by the protocol overhead. Currently no drivers return 1500 .port_max_mtu(), but this is only temporary and a bug in itself - mv88e6xxx should have done that, but since commit b9c587fed61c ("dsa: mv88e6xxx: Include tagger overhead when setting MTU for DSA and CPU ports") it no longer does. This is a preparation for fixing that. Fixes: bfcb813203e6 ("net: dsa: configure the MTU for switch ports") Signed-off-by: Vladimir Oltean Reviewed-by: Simon Horman Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/dsa/slave.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/net/dsa/slave.c b/net/dsa/slave.c index a9fde48cffd43..5fe075bf479ec 100644 --- a/net/dsa/slave.c +++ b/net/dsa/slave.c @@ -1852,6 +1852,7 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu) int new_master_mtu; int old_master_mtu; int mtu_limit; + int overhead; int cpu_mtu; int err; @@ -1880,9 +1881,10 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu) largest_mtu = slave_mtu; } - mtu_limit = min_t(int, master->max_mtu, dev->max_mtu); + overhead = dsa_tag_protocol_overhead(cpu_dp->tag_ops); + mtu_limit = min_t(int, master->max_mtu, dev->max_mtu + overhead); old_master_mtu = master->mtu; - new_master_mtu = largest_mtu + dsa_tag_protocol_overhead(cpu_dp->tag_ops); + new_master_mtu = largest_mtu + overhead; if (new_master_mtu > mtu_limit) return -ERANGE; @@ -1917,8 +1919,7 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu) out_port_failed: if (new_master_mtu != old_master_mtu) - dsa_port_mtu_change(cpu_dp, old_master_mtu - - dsa_tag_protocol_overhead(cpu_dp->tag_ops)); + dsa_port_mtu_change(cpu_dp, old_master_mtu - overhead); out_cpu_failed: if (new_master_mtu != old_master_mtu) dev_set_mtu(master, old_master_mtu); -- 2.39.2