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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Daniele Palmas <dnlplm@gmail.com>,
        =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn@mork.no>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.14 88/99] net: usb: qmi_wwan: restore mtu min/max values after raw_ip switch
Date:   Thu, 19 Mar 2020 14:04:06 +0100
Message-Id: <20200319124006.527255358@linuxfoundation.org>
In-Reply-To: <20200319123941.630731708@linuxfoundation.org>
References: <20200319123941.630731708@linuxfoundation.org>
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From: Daniele Palmas <dnlplm@gmail.com>

[ Upstream commit eae7172f8141eb98e64e6e81acc9e9d5b2add127 ]

usbnet creates network interfaces with min_mtu = 0 and
max_mtu = ETH_MAX_MTU.

These values are not modified by qmi_wwan when the network interface
is created initially, allowing, for example, to set mtu greater than 1500.

When a raw_ip switch is done (raw_ip set to 'Y', then set to 'N') the mtu
values for the network interface are set through ether_setup, with
min_mtu = ETH_MIN_MTU and max_mtu = ETH_DATA_LEN, not allowing anymore to
set mtu greater than 1500 (error: mtu greater than device maximum).

The patch restores the original min/max mtu values set by usbnet after a
raw_ip switch.

Signed-off-by: Daniele Palmas <dnlplm@gmail.com>
Acked-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/usb/qmi_wwan.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
index 189715438328f..a8d5561afc7d4 100644
--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -274,6 +274,9 @@ static void qmi_wwan_netdev_setup(struct net_device *net)
 		netdev_dbg(net, "mode: raw IP\n");
 	} else if (!net->header_ops) { /* don't bother if already set */
 		ether_setup(net);
+		/* Restoring min/max mtu values set originally by usbnet */
+		net->min_mtu = 0;
+		net->max_mtu = ETH_MAX_MTU;
 		clear_bit(EVENT_NO_IP_ALIGN, &dev->flags);
 		netdev_dbg(net, "mode: Ethernet\n");
 	}
-- 
2.20.1