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net: centralize net_device min/max MTU checking

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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>
This commit is contained in:
Jarod Wilson 2016-10-07 22:04:33 -04:00 committed by David S. Miller
parent 1b830996c1
commit 61e84623ac
2 changed files with 15 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
include/linux/netdevice.h
View file

@ -1506,6 +1506,8 @@ enum netdev_priv_flags {
* @if_port: Selectable AUI, TP, ... * @if_port: Selectable AUI, TP, ...
* @dma: DMA channel * @dma: DMA channel
* @mtu: Interface MTU value * @mtu: Interface MTU value
* @min_mtu: Interface Minimum MTU value
* @max_mtu: Interface Maximum MTU value
* @type: Interface hardware type * @type: Interface hardware type
* @hard_header_len: Maximum hardware header length. * @hard_header_len: Maximum hardware header length.
* *
@ -1726,6 +1728,8 @@ struct net_device {
unsigned char dma; unsigned char dma;
unsigned int mtu; unsigned int mtu;
unsigned int min_mtu;
unsigned int max_mtu;
unsigned short type; unsigned short type;
unsigned short hard_header_len; unsigned short hard_header_len;

13
net/core/dev.c
View file

@ -6499,9 +6499,18 @@ int dev_set_mtu(struct net_device *dev, int new_mtu)
if (new_mtu == dev->mtu) if (new_mtu == dev->mtu)
return 0; return 0;
/* MTU must be positive. */ /* MTU must be positive, and in range */
if (new_mtu < 0) 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; 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)) if (!netif_device_present(dev))
return -ENODEV; return -ENODEV;