This is a note to let you know that I've just added the patch titled
net: cdc_ncm: avoid changing RX/TX buffers on MTU changes
to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-cdc_ncm-avoid-changing-rx-tx-buffers-on-mtu-changes.patch
and it can be found in the queue-4.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Jan 26 21:35:03 PST 2016
From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn@xxxxxxx>
Date: Wed, 23 Dec 2015 13:42:43 +0100
Subject: net: cdc_ncm: avoid changing RX/TX buffers on MTU changes
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From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn@xxxxxxx>
[ Upstream commit 1dfddff5fcd869fcab0c52fafae099dfa435a935 ]
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@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(-)
--- 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_m
.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,
--- 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_
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)
{
const struct usb_cdc_union_desc *union_desc = NULL;
@@ -874,6 +902,9 @@ advance:
/* 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:
--- 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);
Patches currently in stable-queue which might be from bjorn@xxxxxxx are
queue-4.3/net-cdc_ncm-avoid-changing-rx-tx-buffers-on-mtu-changes.patch
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