On Wednesday 02 March 2016 08:17:12 Andreas Pape wrote:
Hello Sven,
Sven Eckelmann sven@narfation.org schrieb am 01.03.2016 17:02:57:
You definitely have to check the size for the IP header. The vlan
ethernet
header check is a different playground and mostly unrelated to your
problem.
If I understood you correctly I am supposed to implement something like this:
switch (ntohs(ethhdr->h_proto)) { case ETH_P_IP: if (unlikely(!pskb_may_pull(skb, sizeof(struct iphdr)))) goto dropped; iphdr = (struct iphdr *)(skb->data + ETH_HLEN); /* snoop incoming traffic for dat update using the sourcemac * and source ip to speed up dat. */ batadv_dat_entry_check(bat_priv, iphdr->saddr, ethhdr->h_source, vid);
I doubt that you should drop the data. You new feature is just a nice enhancement but should not decide whether packet is valid or not. This is why I told you about skb_header_pointer. Maybe it would also be better to move your stuff in an extra function and avoid to add extra stuff in the softif loop check. Maybe I will even move the softif loop check in an extra function which would be named in a way that doesn't sound like you should add your stuff there :)
break; case ETH_P_8021Q: if (unlikely(!pskb_may_pull(skb, sizeof(structvlan_ethhdr)))) goto dropped; vhdr = (struct vlan_ethhdr *)(skb->data + ETH_HLEN);
if (vhdr->h_vlan_encapsulated_proto != ethertype) { /* snoop incoming traffic for dat update also forvlan * tagged frames. */ if (ntohs(vhdr->h_vlan_encapsulated_proto) == ETH_P_IP) { iphdr = (struct iphdr *)(vhdr + 1); batadv_dat_entry_check(bat_priv, iphdr->saddr, vhdr->h_source, vid);
Dont forget to check the size here too.
} break; }Correctly understood?
Looking through the code of this function batadv_interface_rx leads me to another question: Am I right that skb->data is pointing to the beginning of the mac layer 2 header of the packet at that point in time as it isn't advanced to the beginning of the layer 3 header by calling eth_type_trans yet(which is called a few lines later)?
I think this should be correct.
Kind regards, Sven