From mboxrd@z Thu Jan  1 00:00:00 1970
From: "David S. Miller" <davem@redhat.com>
Subject: Re: [Bridge] RE: [VLAN] Re: [PATCH/RFC] Let {ip, arp}tables "see"
 bridged VLAN tagged{I,AR}P packets
Date: Wed, 8 Oct 2003 09:33:54 -0700
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To: Ben Greear <greearb@candelatech.com>
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On Wed, 08 Oct 2003 09:34:20 -0700
Ben Greear <greearb@candelatech.com> wrote:

> So, what good is skb_share_check then?
> Maybe we should have a skb_share_or_cloned_check() ?

What input handlers are supposed to do is first:

	skb = skb_share_check(...);


then look at packet contents etc., then if they need to write
to the header do something like skb_cow().

The best example, as usual, is ipv4 input.  Look at how ip_rcv()
makes sure it can safely get at the packet header parts it needs
to parse, then look at ip_forward and how it cows the IPV4 header
so it can modify the TTL field.