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authorBjørn Mork <bjorn@mork.no>2015-12-23 13:42:43 +0100
committerDavid S. Miller <davem@davemloft.net>2015-12-23 22:52:08 -0500
commit1dfddff5fcd869fcab0c52fafae099dfa435a935 (patch)
treeb0c5d35d7cd42c16f8364f4028a9313cc1eb6666
parent184fc8b5ee601cd83dbbdf3e6cfec5f5b8d3b41a (diff)
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net: cdc_ncm: avoid changing RX/TX buffers on MTU changes
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> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/usb/cdc_mbim.c2
-rw-r--r--drivers/net/usb/cdc_ncm.c31
-rw-r--r--include/linux/usb/cdc_ncm.h1
3 files changed, 33 insertions, 1 deletions
diff --git a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c
index 8973abd..bdd83d9 100644
--- a/drivers/net/usb/cdc_mbim.c
+++ b/drivers/net/usb/cdc_mbim.c
@@ -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,
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 3694052..e8a1144 100644
--- 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:
diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index 1f6526c..3a375d0 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -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);
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