Hi list,
I am using kernel 2.6.18.6. I have written a module,which will
register a function at local_in hook, i have found a strange behavior
with the packets getting in my callback function i.e
MTU=1500 varified with ifconfig.
[let say i am sending 1500 bytes to this machine from the network]
ping -s 1500 <ip>
1>in case of fragmention i am getting only one packet at the
hook,While analyzing the ip header it says this is the assembled
packet.
VER:4 hlen:5 tos:0
total-len:1528 id:40330 frag-offt:0
ttl:125 proto:1 cksum:64065
src=10.77.139.252 dst:10.77.152.6
skb->len:1528 tail-data len:1500
{This is where my doubt is,how these two lengths are varying, With 2.4
i got both same. Is it a bug with kernel 2.6 or its a design change.}
While dumping the data(for 0 to 1528 print skb->data[i]) it shows that
only 1472 bytes are valid data and rest 28 bytes are something
garbage.
I verified this with ethereal.
Also i have verified that the skb i got containes the 1472 bytes of
valid dat and rest 28 bytes are contained in
skb_shinfo(skb)->frag_list.
So i am doing the assemble in my hook like this....
if(skb->len > skb->tail-skb->data){
temp=skb_shinfo(skb)->frag_list;
while(skb->len > skb->tail-skb->data){
if(temp==NULL)
printk("Fragmented Data is NULL\n");
else if((skb->end-skb->tail)>temp->len){
strncpy(skb->tail,temp->data,temp->len);
skb->tail+=temp->len;
}
if(temp->next != NULL) temp=temp->next;
else{ printk("Fragmentation finished\n"); break ;}
}
Doing this i am able to get the complete packet, Is it the right way ?
or
Is there any other way to get the complete packet in local in hook ?
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