Re: ip_nat_mangle_udp_packet problems

[Patrick McHardy <kaber@trash.net>]

Christian Hentschel wrote:
> What i see in enlarge_skb() is that if packet is larger than 65536 it
> does as u said a copy.

No, it drops it if it gets this large. skb_copy_expand(), as it name
implies, copies the packet to a new one with more room.

> I see that enlarge_skb() does the "reload" of the pointer to pskb,
> pointing it to the enlarged skbuff. This is what u meant?
> 
>         kfree_skb(*pskb);
>         *pskb = nskb;
>         return 1;

Not really. What I meant is that if you have something like this before
the call to ip_nat_mangle_udp_packet():

struct udphdr *uh = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4;

then you need to reload the pointer after the call like this:

uh = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4;

otherwise it might point to the old and already freed skb.

> what is happening is really obscure for me.

Just post your code if this doesn't help.

Regards
Patrick