net: centralize net_device min/max MTU checking

While looking into an MTU issue with sfc, I started noticing that almost
every NIC driver with an ndo_change_mtu function implemented almost
exactly the same range checks, and in many cases, that was the only
practical thing their ndo_change_mtu function was doing. Quite a few
drivers have either 68, 64, 60 or 46 as their minimum MTU value checked,
and then various sizes from 1500 to 65535 for their maximum MTU value. We
can remove a whole lot of redundant code here if we simple store min_mtu
and max_mtu in net_device, and check against those in net/core/dev.c's
dev_set_mtu().

In theory, there should be zero functional change with this patch, it just
puts the infrastructure in place. Subsequent patches will attempt to start
using said infrastructure, with theoretically zero change in
functionality.

CC: netdev@vger.kernel.org
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 136ae6bbe81e12f769b38776ccbceac9f151360e..fbdf923af4d38d691e0069311395a7475689f69b 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1506,6 +1506,8 @@ enum netdev_priv_flags {
  *     @if_port:       Selectable AUI, TP, ...
  *     @dma:           DMA channel
  *     @mtu:           Interface MTU value
+ *     @min_mtu:       Interface Minimum MTU value
+ *     @max_mtu:       Interface Maximum MTU value
  *     @type:          Interface hardware type
  *     @hard_header_len: Maximum hardware header length.
  *
@@ -1726,6 +1728,8 @@ struct net_device {
        unsigned char           dma;
 
        unsigned int            mtu;
+       unsigned int            min_mtu;
+       unsigned int            max_mtu;
        unsigned short          type;
        unsigned short          hard_header_len;
 

diff --git a/net/core/dev.c b/net/core/dev.c
index f1fe26f6645883a54126300adc030f1c3a04652d..f376639e8774efb61bf9546ef9cdfd6eca054644 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6499,9 +6499,18 @@ int dev_set_mtu(struct net_device *dev, int new_mtu)
        if (new_mtu == dev->mtu)
                return 0;
 
-       /*      MTU must be positive.    */
-       if (new_mtu < 0)
+       /* MTU must be positive, and in range */
+       if (new_mtu < 0 || new_mtu < dev->min_mtu) {
+               net_err_ratelimited("%s: Invalid MTU %d requested, hw min %d\n",
+                                   dev->name, new_mtu, dev->min_mtu);
                return -EINVAL;
+       }
+
+       if (dev->max_mtu > 0 && new_mtu > dev->max_mtu) {
+               net_err_ratelimited("%s: Invalid MTU %d requested, hw max %d\n",
+                                   dev->name, new_mtu, dev->min_mtu);
+               return -EINVAL;
+       }
 
        if (!netif_device_present(dev))
                return -ENODEV;