Messages in this thread | | | Date | Thu, 28 Dec 2006 19:15:10 +0100 | From | Pablo Neira Ayuso <> | Subject | Re: skb->h not initialized |
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Jan Engelhardt wrote: > while writing a netfilter match module I found that, when run, > skb->h.th is not set to the TCP header (it is assured that the packet > _is_ TCP), as this printk shows me: > > skb: h.th=cb5bc4dc nh.iph=cb5bc4dc mac.raw=cb5bc4ce head=cb5bc400 > data=cb5bc4dc tail=cb5bc510 end=cb5bc580 > > Is it intended that skb->h.th is not set to skb->data + length of ip > header (skb->data+protoff as far as netfilter matches are concerned)?
The netfilter hooks are placed in the network layer, therefore skb->h.th is not set in the input path since the packet did not reach the transport layer yet (prerouting/input), but it is set in the output path because it already passed by the transport layer (output/postrouting).
BTW, I'm unsure that this can be of interest in the linux-kernel list, please there's no need to cc everyone. Use netfilter or linux-net instead next time.
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