mirror of
git://projects.qi-hardware.com/openwrt-xburst.git
synced 2024-11-24 15:25:20 +02:00
0ec45ff596
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@15860 3c298f89-4303-0410-b956-a3cf2f4a3e73
103 lines
3.2 KiB
Diff
103 lines
3.2 KiB
Diff
--- a/include/linux/skbuff.h
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+++ b/include/linux/skbuff.h
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@@ -912,6 +912,49 @@ static inline void skb_reserve(struct sk
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skb->tail+=len;
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}
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+/*
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+ * CPUs often take a performance hit when accessing unaligned memory
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+ * locations. The actual performance hit varies, it can be small if the
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+ * hardware handles it or large if we have to take an exception and fix it
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+ * in software.
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+ *
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+ * Since an ethernet header is 14 bytes network drivers often end up with
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+ * the IP header at an unaligned offset. The IP header can be aligned by
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+ * shifting the start of the packet by 2 bytes. Drivers should do this
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+ * with:
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+ *
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+ * skb_reserve(NET_IP_ALIGN);
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+ *
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+ * The downside to this alignment of the IP header is that the DMA is now
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+ * unaligned. On some architectures the cost of an unaligned DMA is high
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+ * and this cost outweighs the gains made by aligning the IP header.
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+ *
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+ * Since this trade off varies between architectures, we allow NET_IP_ALIGN
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+ * to be overridden.
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+ */
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+#ifndef NET_IP_ALIGN
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+#define NET_IP_ALIGN 2
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+#endif
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+
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+/*
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+ * The networking layer reserves some headroom in skb data (via
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+ * dev_alloc_skb). This is used to avoid having to reallocate skb data when
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+ * the header has to grow. In the default case, if the header has to grow
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+ * 16 bytes or less we avoid the reallocation.
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+ *
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+ * Unfortunately this headroom changes the DMA alignment of the resulting
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+ * network packet. As for NET_IP_ALIGN, this unaligned DMA is expensive
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+ * on some architectures. An architecture can override this value,
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+ * perhaps setting it to a cacheline in size (since that will maintain
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+ * cacheline alignment of the DMA). It must be a power of 2.
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+ *
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+ * Various parts of the networking layer expect at least 16 bytes of
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+ * headroom, you should not reduce this.
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+ */
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+#ifndef NET_SKB_PAD
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+#define NET_SKB_PAD 16
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+#endif
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+
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extern int ___pskb_trim(struct sk_buff *skb, unsigned int len, int realloc);
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static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
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--- a/drivers/net/tun.c
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+++ b/drivers/net/tun.c
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@@ -185,22 +185,31 @@ static __inline__ ssize_t tun_get_user(s
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{
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struct tun_pi pi = { 0, __constant_htons(ETH_P_IP) };
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struct sk_buff *skb;
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- size_t len = count;
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+ size_t len = count, align = 0;
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if (!(tun->flags & TUN_NO_PI)) {
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if ((len -= sizeof(pi)) > count)
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return -EINVAL;
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- memcpy_fromiovec((void *)&pi, iv, sizeof(pi));
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+ if(memcpy_fromiovec((void *)&pi, iv, sizeof(pi)))
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+ return -EFAULT;
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}
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-
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- if (!(skb = alloc_skb(len + 2, GFP_KERNEL))) {
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+
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+ if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV)
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+ align = NET_IP_ALIGN;
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+
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+ if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
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tun->stats.rx_dropped++;
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return -ENOMEM;
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}
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- skb_reserve(skb, 2);
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- memcpy_fromiovec(skb_put(skb, len), iv, len);
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+ if (align)
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+ skb_reserve(skb, align);
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+ if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
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+ tun->stats.rx_dropped++;
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+ kfree_skb(skb);
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+ return -EFAULT;
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+ }
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skb->dev = &tun->dev;
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switch (tun->flags & TUN_TYPE_MASK) {
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@@ -271,7 +280,8 @@ static __inline__ ssize_t tun_put_user(s
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pi.flags |= TUN_PKT_STRIP;
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}
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- memcpy_toiovec(iv, (void *) &pi, sizeof(pi));
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+ if(memcpy_toiovec(iv, (void *) &pi, sizeof(pi)))
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+ return -EFAULT;
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total += sizeof(pi);
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}
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