The NF_DROP return code means that this packet should be dropped completely and any resources allocated for it should be released. NF_ACCEPT tells Netfilter that so far the packet is still acceptable and that it should move to the next stage of the network stack. NF_STOLEN is an interesting one because it tells Netfilter to forget about the packet.
3/27/2019 · return NF_ACCEPT; The first parameter is the hook number – we can use the same function for more than one hook for example, if we want to log all.
okfn() (okay function): This function is invoked when all filter functions registered with this hook returned NF_ACCEPT, thereby okaying the packet’s transit. Registering and Unregistering Packet-Filter Functions. The packet-filter functions that are actually hooked into the netfilter hooks are so-called hook functions of the type nf_hookfn. The signature of a hook function is defined in as follows:, The function which is called when a packet hits this hook point. Your function must return NF_ACCEPT, NF_DROP or NF_QUEUE. If NF_ACCEPT, the next hook attached to that point will be called. If NF_DROP, the packet is dropped. If NF_QUEUE, it’s queued. You receive a pointer to an skb pointer, so you can entirely replace the skb if you wish. flush, return NF_ACCEPT ; // hook function for filtering outbound packets unsigned int minifw_outbound_filter ( unsigned int hooknum, struct sk_buff *skb, const struct net_device *in,, GitHub Gist: instantly share code, notes, and snippets.
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We are trying to implement a NAT module for linux kernel. The problem being faced is that for the TCP packets at the incoming hook, the pointer that is expected to point to destination port does n…
