netdev - [PATCH 1/1] net: usb: qmi_wwan: restore mtu min/max values after raw

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Message-Id: <20200221131705.26053-1-dnlplm@gmail.com>
Date:   Fri, 21 Feb 2020 14:17:05 +0100
From:   Daniele Palmas <dnlplm@...il.com>
To:     Bjørn Mork <bjorn@...k.no>
Cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Daniele Palmas <dnlplm@...il.com>
Subject: [PATCH 1/1] net: usb: qmi_wwan: restore mtu min/max values after raw_ip switch

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@...il.com>
---
 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 3b7a3b8a5e06..5754bb6ca0ee 100644
--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -337,6 +337,9 @@ 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");
 	}
-- 
2.17.1