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authorDavid S. Miller <davem@davemloft.net>2009-02-08 19:24:13 -0800
committerDavid S. Miller <davem@davemloft.net>2009-02-08 19:24:13 -0800
commitd6301d3dd1c287b32132dda15272a50c11e92a14 (patch)
treed4e329fc83fd47331be454b916e4bf770c5371c4
parent409f0a9014fe24d906ba21aaccff80eb7f7304da (diff)
net: Increase default NET_SKB_PAD to 32.
Several devices need to insert some "pre headers" in front of the main packet data when they transmit a packet. Currently we allocate only 16 bytes of pad room and this ends up not being enough for some types of hardware (NIU, usb-net, s390 qeth, etc.) So increase this to 32. Note that drivers still need to check in their transmit routine whether enough headroom exists, and if not use skb_realloc_headroom(). Tunneling, IPSEC, and other encapsulation methods can cause the padding area to be used up. Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/skbuff.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 08670d01747..5eba4007e07 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1287,7 +1287,7 @@ static inline int skb_network_offset(const struct sk_buff *skb)
* The networking layer reserves some headroom in skb data (via
* dev_alloc_skb). This is used to avoid having to reallocate skb data when
* the header has to grow. In the default case, if the header has to grow
- * 16 bytes or less we avoid the reallocation.
+ * 32 bytes or less we avoid the reallocation.
*
* Unfortunately this headroom changes the DMA alignment of the resulting
* network packet. As for NET_IP_ALIGN, this unaligned DMA is expensive
@@ -1295,11 +1295,11 @@ static inline int skb_network_offset(const struct sk_buff *skb)
* perhaps setting it to a cacheline in size (since that will maintain
* cacheline alignment of the DMA). It must be a power of 2.
*
- * Various parts of the networking layer expect at least 16 bytes of
+ * Various parts of the networking layer expect at least 32 bytes of
* headroom, you should not reduce this.
*/
#ifndef NET_SKB_PAD
-#define NET_SKB_PAD 16
+#define NET_SKB_PAD 32
#endif
extern int ___pskb_trim(struct sk_buff *skb, unsigned int len);