From mboxrd@z Thu Jan  1 00:00:00 1970
From: "David S. Miller" <davem@redhat.com>
Subject: Re: [PATCH] Handle shared SKBs in VLAN receive code
Date: Sat, 11 Oct 2003 12:54:26 -0700
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To: Ben Greear <greearb@candelatech.com>
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On Sat, 11 Oct 2003 12:55:23 -0700
Ben Greear <greearb@candelatech.com> wrote:

> I have read the sk_buf.h file repeatedly trying to get this all straight
> in my head, and I think I'm still missing things.  Is there any other
> documentation around that describes in detail exactly the things you must
> do to handle shared skbs in all contexts?

No there isn't, sorry.

If you just want to read the IP address in a packet, or anything else
in general you have two options:

1) if (pskb_may_pull(skb, len))
	goto drop;

   After this call, it is guarenteed you may look at
   the all bytes up to 'len' from the start of the SKB
   using skb->data et al.

2) Use skb_peek_bits().