net: cdc_ncm: update datagram size after changing mtu

Current implementation updates the mtu size and notify cdc_ncm
device using USB_CDC_SET_MAX_DATAGRAM_SIZE request about datagram
size change instead of changing rx_urb_size.

Whenever mtu is being changed, datagram size should also be
updated. Also updating maxmtu formula so it takes max_datagram_size with
use of cdc_ncm_max_dgram_size() and not ctx.

Signed-off-by: Robert Dobrowolski <robert.dobrowolski@linux.intel.com>
Signed-off-by: Rafal Redzimski <rafal.f.redzimski@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 2fb31edab125..53759c315b97 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -740,12 +740,14 @@ static void cdc_ncm_free(struct cdc_ncm_ctx *ctx)
 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);
+        int maxmtu = cdc_ncm_max_dgram_size(dev) - cdc_ncm_eth_hlen(dev);
 
         if (new_mtu <= 0 || new_mtu > maxmtu)
                 return -EINVAL;
+
         net->mtu = new_mtu;
+        cdc_ncm_set_dgram_size(dev, new_mtu + cdc_ncm_eth_hlen(dev));
+
         return 0;
 }
 EXPORT_SYMBOL_GPL(cdc_ncm_change_mtu);