1 files changed, 47 insertions, 0 deletions

diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index 59811cc880e0..8c01fa81a1ae 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -34,6 +34,46 @@ static inline void set_ether_mac(struct net_device *dev, unsigned char *addr)
 static DEFINE_SPINLOCK(opened_lock);
 static LIST_HEAD(opened);
 
+/*
+ * The drop_skb is used when we can't allocate an skb.  The
+ * packet is read into drop_skb in order to get the data off the
+ * connection to the host.
+ * It is reallocated whenever a maximum packet size is seen which is
+ * larger than any seen before.  update_drop_skb is called from
+ * eth_configure when a new interface is added.
+ */
+static DEFINE_SPINLOCK(drop_lock);
+static struct sk_buff *drop_skb;
+static int drop_max;
+
+static int update_drop_skb(int max)
+{
+        struct sk_buff *new;
+        unsigned long flags;
+        int err = 0;
+
+        spin_lock_irqsave(&drop_lock, flags);
+
+        if (max <= drop_max)
+                goto out;
+
+        err = -ENOMEM;
+        new = dev_alloc_skb(max);
+        if (new == NULL)
+                goto out;
+
+        skb_put(new, max);
+
+        kfree_skb(drop_skb);
+        drop_skb = new;
+        drop_max = max;
+        err = 0;
+out:
+        spin_unlock_irqrestore(&drop_lock, flags);
+
+        return err;
+}
+
 static int uml_net_rx(struct net_device *dev)
 {
         struct uml_net_private *lp = dev->priv;
@@ -43,6 +83,9 @@ static int uml_net_rx(struct net_device *dev)
         /* If we can't allocate memory, try again next round. */
         skb = dev_alloc_skb(lp->max_packet);
         if (skb == NULL) {
+                drop_skb->dev = dev;
+                /* Read a packet into drop_skb and don't do anything with it. */
+                (*lp->read)(lp->fd, drop_skb, lp);
                 lp->stats.rx_dropped++;
                 return 0;
         }
@@ -447,6 +490,10 @@ static void eth_configure(int n, void *init, char *mac,
         dev->watchdog_timeo = (HZ >> 1);
         dev->irq = UM_ETH_IRQ;
 
+        err = update_drop_skb(lp->max_packet);
+        if (err)
+                goto out_undo_user_init;
+
         rtnl_lock();
         err = register_netdevice(dev);
         rtnl_unlock();