@@ -100,7 +100,7 @@ static const struct net_device_ops cdc_mbim_netdev_ops = {
.ndo_stop = usbnet_stop,
.ndo_start_xmit = usbnet_start_xmit,
.ndo_tx_timeout = usbnet_tx_timeout,
- .ndo_change_mtu = usbnet_change_mtu,
+ .ndo_change_mtu = cdc_ncm_change_mtu,
.ndo_set_mac_address = eth_mac_addr,
.ndo_validate_addr = eth_validate_addr,
.ndo_vlan_rx_add_vid = cdc_mbim_rx_add_vid,
@@ -41,6 +41,7 @@
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/ctype.h>
+#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/workqueue.h>
#include <linux/mii.h>
@@ -732,6 +733,33 @@ static void cdc_ncm_free(struct cdc_ncm_ctx *ctx)
kfree(ctx);
}
+/* we need to override the usbnet change_mtu ndo for two reasons:
+ * - respect the negotiated maximum datagram size
+ * - avoid unwanted changes to rx and tx buffers
+ */
+int cdc_ncm_change_mtu(struct net_device *net, int new_mtu)
+{
+ struct usbnet *dev = netdev_priv(net);
+ struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
+ int maxmtu = ctx->max_datagram_size - cdc_ncm_eth_hlen(dev);
+
+ if (new_mtu <= 0 || new_mtu > maxmtu)
+ return -EINVAL;
+ net->mtu = new_mtu;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(cdc_ncm_change_mtu);
+
+static const struct net_device_ops cdc_ncm_netdev_ops = {
+ .ndo_open = usbnet_open,
+ .ndo_stop = usbnet_stop,
+ .ndo_start_xmit = usbnet_start_xmit,
+ .ndo_tx_timeout = usbnet_tx_timeout,
+ .ndo_change_mtu = cdc_ncm_change_mtu,
+ .ndo_set_mac_address = eth_mac_addr,
+ .ndo_validate_addr = eth_validate_addr,
+};
+
int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting, int drvflags)
{
struct cdc_ncm_ctx *ctx;
@@ -866,6 +894,9 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
/* add our sysfs attrs */
dev->net->sysfs_groups[0] = &cdc_ncm_sysfs_attr_group;
+ /* must handle MTU changes */
+ dev->net->netdev_ops = &cdc_ncm_netdev_ops;
+
return 0;
error2:
@@ -138,6 +138,7 @@ struct cdc_ncm_ctx {
};
u8 cdc_ncm_select_altsetting(struct usb_interface *intf);
+int cdc_ncm_change_mtu(struct net_device *net, int new_mtu);
int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting, int drvflags);
void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf);
struct sk_buff *cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign);
NCM buffer sizes are negotiated with the device independently of the network device MTU. The RX buffers are allocated by the usbnet framework based on the rx_urb_size value set by cdc_ncm. A single RX buffer can hold a number of MTU sized packets. The default usbnet change_mtu ndo only modifies rx_urb_size if it is equal to hard_mtu. And the cdc_ncm driver will set rx_urb_size and hard_mtu independently of each other, based on dwNtbInMaxSize and dwNtbOutMaxSize respectively. It was therefore assumed that usbnet_change_mtu() would never touch rx_urb_size. This failed to consider the case where dwNtbInMaxSize and dwNtbOutMaxSize happens to be equal. Fix by implementing an NCM specific change_mtu ndo, modifying the netdev MTU without touching the buffer size settings. Signed-off-by: Bjørn Mork <bjorn@mork.no> --- drivers/net/usb/cdc_mbim.c | 2 +- drivers/net/usb/cdc_ncm.c | 31 +++++++++++++++++++++++++++++++ include/linux/usb/cdc_ncm.h | 1 + 3 files changed, 33 insertions(+), 1 deletion(-)