Hi I have a kernel module that has hook call back functions for both POST_ROUTING and LOCAL_OUT. If I insert a new raw packet into the kernel with the dest ip address == ip address of this machine(the same machine on which hooks functions lie) then the packets are caught by POST_ROUTING and NOT by IP_LOCAL_OUT and if i insert a packet with ip address==some other ip(other than this machine's ip address), they are first caught by the LOCAL_OUT hooks function. Can someone explain this . This effectively means that only those packets hit IP_LOCAL_OUT hook fn that come from applications on this machine and are destined to go out. (addressed to same machine do not hit this hook). And all packets originating from this machine hit POST_ROUTING hook. irrespective of whether the dest ip address is of this machine or someother machine.(offcourse IP_POST_ROUTING is also hit in another scenarios but here I am concentrating on packets originating from the host machine itself). Even rustys unreliable guide says "The NF_IP_LOCAL_OUT [5] hook is called for packets that are created locally. Here you can see that routing occurs after this hook is called: in fact, the routing code is called first (to figure out the source IP address and some IP options): if you want to alter the routing, you must alter the `skb->dst' field yourself, as is done in the NAT code.". But this is incomplete, NF_IP_LOCAL_OUT is hit for those local packets that have foriegn destinations. And also in the hook traversal diagram we should probably have a different arrow showing packets that hit IP_POST_ROUTING but do not hit IP_LOCAL_OUT (locally generated packets with local destination ip address, i.e ip address of the host machine ). regards Amit "DISCLAIMER: This message is proprietary to Hughes Software Systems Limited (HSS) and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error, please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. HSS accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus."
