Hi; This may require some hacking but in order to isolate which layer is causing the error; you can use the *_INC_STATS hook. basically these are macros that are called when an error occurs in the transmit/receive path(I guess to inform via SNMP). The inputpath uses the INC_STATS_BH hook; so tcp uses the TCP_INC_STATS_BH and IP uses the IP_INC_STATS_BH hook. So put a printk in this macro whenever this gets called; you will know whether the packets is getrting dropped at the IP or the TCP layer. Then using the __FUNCTION__, __LINE__ and __FILE__; you can get the exact place in the code that is dropping the packet. Let me know if this works... regards Ed --- aksingh@hss.hns.com wrote: > > > > > Hi, > > I am trying to spoof a packet, I have written a > kernel module, once it > gets a modified TCP packet(source and dest > interchanged, ack seq > interchanged) it calls netif_rx (skb) to inject this > into the routing path. > but I am unable to make this packet reach the > correct socket. Any clues on > this, can I check some kernel stats to know where > and why the packet is > being dropped. > The various reasons cld be : > > 1. incorrect tcp or ip check sums, i calculate both > myself > 2. in the skb->dev field i set the value to the > value of skb->dev field of > any incoming valid packet : > when i get the first packet on netfilter pre > routing hook -- i do a > memcpy(&my_net_dev, skb->dev, sizeof(struct > net_device)); > then for the modified TCP packet i set > skb->dev=&my_net_dev. So maybe it > gets dropped cos of some problem here(or is there > any obvious problem here > ?) > > so how do i isolate the problem ? any clues ?? > > thanks > 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." > > > -- > Kernelnewbies: Help each other learn about the Linux > kernel. > Archive: > http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
