target/linux/generic-2.4/patches/230-tun_get_user_backport.patch

   1 Index: linux-2.4.35.4/include/linux/skbuff.h
   2 ===================================================================
   3 --- linux-2.4.35.4.orig/include/linux/skbuff.h  2007-12-15 05:19:38.654623841 +0100
   4 +++ linux-2.4.35.4/include/linux/skbuff.h       2007-12-15 05:20:05.060128604 +0100
   5 @@ -912,6 +912,49 @@
   6         skb->tail+=len;
   7  }
   8
   9 +/*
  10 + * CPUs often take a performance hit when accessing unaligned memory
  11 + * locations. The actual performance hit varies, it can be small if the
  12 + * hardware handles it or large if we have to take an exception and fix it
  13 + * in software.
  14 + *
  15 + * Since an ethernet header is 14 bytes network drivers often end up with
  16 + * the IP header at an unaligned offset. The IP header can be aligned by
  17 + * shifting the start of the packet by 2 bytes. Drivers should do this
  18 + * with:
  19 + *
  20 + * skb_reserve(NET_IP_ALIGN);
  21 + *
  22 + * The downside to this alignment of the IP header is that the DMA is now
  23 + * unaligned. On some architectures the cost of an unaligned DMA is high
  24 + * and this cost outweighs the gains made by aligning the IP header.
  25 + *
  26 + * Since this trade off varies between architectures, we allow NET_IP_ALIGN
  27 + * to be overridden.
  28 + */
  29 +#ifndef NET_IP_ALIGN
  30 +#define NET_IP_ALIGN    2
  31 +#endif
  32 +
  33 +/*
  34 + * The networking layer reserves some headroom in skb data (via
  35 + * dev_alloc_skb). This is used to avoid having to reallocate skb data when
  36 + * the header has to grow. In the default case, if the header has to grow
  37 + * 16 bytes or less we avoid the reallocation.
  38 + *
  39 + * Unfortunately this headroom changes the DMA alignment of the resulting
  40 + * network packet. As for NET_IP_ALIGN, this unaligned DMA is expensive
  41 + * on some architectures. An architecture can override this value,
  42 + * perhaps setting it to a cacheline in size (since that will maintain
  43 + * cacheline alignment of the DMA). It must be a power of 2.
  44 + *
  45 + * Various parts of the networking layer expect at least 16 bytes of
  46 + * headroom, you should not reduce this.
  47 + */
  48 +#ifndef NET_SKB_PAD
  49 +#define NET_SKB_PAD     16
  50 +#endif
  51 +
  52  extern int ___pskb_trim(struct sk_buff *skb, unsigned int len, int realloc);
  53
  54  static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
  55 Index: linux-2.4.35.4/drivers/net/tun.c
  56 ===================================================================
  57 --- linux-2.4.35.4.orig/drivers/net/tun.c       2007-12-15 05:19:38.642623156 +0100
  58 +++ linux-2.4.35.4/drivers/net/tun.c    2007-12-15 05:20:05.056128377 +0100
  59 @@ -185,22 +185,31 @@
  60  {
  61         struct tun_pi pi = { 0, __constant_htons(ETH_P_IP) };
  62         struct sk_buff *skb;
  63 -       size_t len = count;
  64 +       size_t len = count, align = 0;
  65
  66         if (!(tun->flags & TUN_NO_PI)) {
  67                 if ((len -= sizeof(pi)) > count)
  68                         return -EINVAL;
  69
  70 -               memcpy_fromiovec((void *)&pi, iv, sizeof(pi));
  71 +               if(memcpy_fromiovec((void *)&pi, iv, sizeof(pi)))
  72 +                       return -EFAULT;
  73         }
  74 -
  75 -       if (!(skb = alloc_skb(len + 2, GFP_KERNEL))) {
  76 +
  77 +       if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV)
  78 +               align = NET_IP_ALIGN;
  79 +
  80 +       if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
  81                 tun->stats.rx_dropped++;
  82                 return -ENOMEM;
  83         }
  84
  85 -       skb_reserve(skb, 2);
  86 -       memcpy_fromiovec(skb_put(skb, len), iv, len);
  87 +       if (align)
  88 +               skb_reserve(skb, align);
  89 +       if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
  90 +               tun->stats.rx_dropped++;
  91 +               kfree_skb(skb);
  92 +               return -EFAULT;
  93 +       }
  94
  95         skb->dev = &tun->dev;
  96         switch (tun->flags & TUN_TYPE_MASK) {
  97 @@ -271,7 +280,8 @@
  98                         pi.flags |= TUN_PKT_STRIP;
  99                 }
 100
 101 -               memcpy_toiovec(iv, (void *) &pi, sizeof(pi));
 102 +               if(memcpy_toiovec(iv, (void *) &pi, sizeof(pi)))
 103 +                       return -EFAULT;
 104                 total += sizeof(pi);
 105         }
 106