From: "David S. Miller" <davem@redhat.com>
To: rahul b jain cs student <rbj2@oak.njit.edu>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Question about ip_rcv() function
Date: Wed, 23 Jun 2004 11:50:27 -0700 [thread overview]
Message-ID: <20040623115027.11ef0902.davem@redhat.com> (raw)
In-Reply-To: <Pine.GSO.4.58.0406231441500.7099@chrome.njit.edu>
On Wed, 23 Jun 2004 14:45:47 -0400 (EDT)
rahul b jain cs student <rbj2@oak.njit.edu> wrote:
> can anyone explain what is the difference between the following two pieces
> of code.
>
> 1. if (!pskb_may_pull(skb, sizeof(struct iphdr)))
> goto inhdr_error;
>
> iph = skb->nh.iph;
>
> 2. if (!pskb_may_pull(skb, iph->ihl*4))
> goto inhdr_error;
>
> iph = skb->nh.iph;
We can't dereference any of the iphdr fields (such as iph->ihl) until
we know that at least "sizeof(struct iphdr)" bytes are there first.
next prev parent reply other threads:[~2004-06-23 18:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-22 20:48 sk_buff structure rahul b jain cs student
2004-06-22 21:24 ` Jonathan Corbet
2004-06-22 23:03 ` rahul b jain cs student
2004-06-23 18:45 ` Question about ip_rcv() function rahul b jain cs student
2004-06-23 18:50 ` David S. Miller [this message]
2004-06-23 20:22 ` rahul b jain cs student
2004-06-23 20:32 ` David S. Miller
2004-06-23 20:43 ` rahul b jain cs student
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