Wei Liu
2013-Apr-15 17:06 UTC
[PATCH V5 5/7] xen-netfront: reduce gso_max_size to account for max TCP header
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>
---
drivers/net/xen-netfront.c | 16 ++++++++++++++--
include/xen/interface/io/netif.h | 1 +
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 1bb2e20..7c53d0c 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -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 +1068,7 @@ 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) ? 65535 - MAX_TCP_HEADER : ETH_DATA_LEN;
if (mtu > max)
return -EINVAL;
@@ -1362,6 +1372,8 @@ 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, 65535 - MAX_TCP_HEADER);
+
np->netdev = netdev;
netif_carrier_off(netdev);
diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h
index 9dfc120..58fadca 100644
--- a/include/xen/interface/io/netif.h
+++ b/include/xen/interface/io/netif.h
@@ -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 */
--
1.7.10.4
Ian Campbell
2013-Apr-17 13:51 UTC
Re: [PATCH V5 5/7] xen-netfront: reduce gso_max_size to account for max TCP header
On Mon, 2013-04-15 at 18:06 +0100, Wei Liu wrote:> 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> (one commentlet is that you''ve used 65535 a few times (or left existing uses) but you''ve also just defined XEN_NETIF_MAX_TX_SIZE which would be a better thing to use)> --- > drivers/net/xen-netfront.c | 16 ++++++++++++++-- > include/xen/interface/io/netif.h | 1 + > 2 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c > index 1bb2e20..7c53d0c 100644 > --- a/drivers/net/xen-netfront.c > +++ b/drivers/net/xen-netfront.c > @@ -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 +1068,7 @@ 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) ? 65535 - MAX_TCP_HEADER : ETH_DATA_LEN; > > if (mtu > max) > return -EINVAL; > @@ -1362,6 +1372,8 @@ 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, 65535 - MAX_TCP_HEADER); > + > np->netdev = netdev; > > netif_carrier_off(netdev); > diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h > index 9dfc120..58fadca 100644 > --- a/include/xen/interface/io/netif.h > +++ b/include/xen/interface/io/netif.h > @@ -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 */