why memory is wasted in skbuff for received packet skb_alloc?

[linux lover <linux_lover2004@xxxxxxxxx>]

hello,
          In kernel 2.4.30 i observe that when my
ethernet card received packet and uses alloc_skb its
not placing all pointers skb->data,skb->head,skb->tail
to same starting location instead i found it places
skb->data and skb->tail have 10 locations more than
skb->head.
          For what purpose this 10 bytes are reserved
in skbuff also i am not able to see that skb_reserve
as theres no call to skb_reserve and i am printing
skbuff pointer values just after it gets allocated by
alloc_skb.

Thanks in advance,
linux_lover

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