net: cdc_ncm: avoid changing RX/TX buffers on MTU changes

[md.git] / drivers / net / usb / cdc_ncm.c

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 3694052714371e65d63e8ae8437d1d7d6d44a463..e8a1144c5a8bfa28c1ddca137c56c888b176ab32 100644 (file)
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -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>
@@ -689,6 +690,33 @@ 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;
@@ -823,6 +851,9 @@ 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: