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xen-netfront: reduce gso_max_size to account for max TCP header

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The maximum packet including header that can be handled by netfront / netback
wire format is 65535. Reduce gso_max_size accordingly.

Drop skb and print warning when skb->len > 65535. This can 1) save the effort
to send malformed packet to netback, 2) help spotting misconfiguration of
netfront in the future.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Liu 2013-04-22 02:20:41 +00:00 committed by David S. Miller
parent 697089dc13
commit 9ecd1a75d9
2 changed files with 16 additions and 2 deletions
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17
drivers/net/xen-netfront.c
View File

@ -36,7 +36,7 @@
#include <linux/skbuff.h>
#include <linux/ethtool.h>
#include <linux/if_ether.h>
#include <linux/tcp.h>
#include <net/tcp.h>
#include <linux/udp.h>
#include <linux/moduleparam.h>
#include <linux/mm.h>
@ -547,6 +547,16 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
unsigned int len = skb_headlen(skb);
unsigned long flags;
/* If skb->len is too big for wire format, drop skb and alert
* user about misconfiguration.
*/
if (unlikely(skb->len > XEN_NETIF_MAX_TX_SIZE)) {
net_alert_ratelimited(
"xennet: skb->len = %u, too big for wire format\n",
skb->len);
goto drop;
}
slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +
xennet_count_skb_frag_slots(skb);
if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
@ -1058,7 +1068,8 @@ err:
static int xennet_change_mtu(struct net_device *dev, int mtu)
{
int max = xennet_can_sg(dev) ? 65535 - ETH_HLEN : ETH_DATA_LEN;
int max = xennet_can_sg(dev) ?
XEN_NETIF_MAX_TX_SIZE - MAX_TCP_HEADER : ETH_DATA_LEN;
if (mtu > max)
return -EINVAL;
@ -1362,6 +1373,8 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
SET_ETHTOOL_OPS(netdev, &xennet_ethtool_ops);
SET_NETDEV_DEV(netdev, &dev->dev);
netif_set_gso_max_size(netdev, XEN_NETIF_MAX_TX_SIZE - MAX_TCP_HEADER);
np->netdev = netdev;
netif_carrier_off(netdev);

1
include/xen/interface/io/netif.h
View File

@ -47,6 +47,7 @@
#define _XEN_NETTXF_extra_info (3)
#define XEN_NETTXF_extra_info (1U<<_XEN_NETTXF_extra_info)
#define XEN_NETIF_MAX_TX_SIZE 0xFFFF
struct xen_netif_tx_request {
grant_ref_t gref; /* Reference to buffer page */
uint16_t offset; /* Offset within buffer page */