On Wednesday, July 22, 2009 08:15:12 Michael Blizek wrote: > Hi! > > On 18:28 Tue 21 Jul , Loránd Jakab wrote: > > Hello, > > > > I am working on implementing an experimental network protocol. I > > have netfilter hook which changes the payload after the IP header > > and the destination IP in packets with a certain protocol id. This > > part works. > > > > For some packets, I need to generate an extra packet. To do this, I > > copy the sk_buff, modify stuff on the copy and try sending it with > > dev_queue_xmit(), then modify the original and return NF_ACCEPT. > > The result is: the original get through (the one with NF_ACCEPT) > > but the copy doesn't. > > > > Here's the code for copying and sending the copy: > > > > static void send_payload(struct sk_buff *skb, struct in_addr rloc) > > Where do you call this function? Immediately before the ip stack > calls dev_queue_xmit? If not, the ip stack might not have finished > building the packet. > > -Michi Hi, This function is called from an ipfilter hook, which is registered at IP_PRE_ROUTING. I replace some data, but I don't do the routing so the correct MAC header is not created. After discovering this, I tried three approaches: * Calling ip_route_input and then dev_queue_xmit() - same as before, I get the IP header in place of the MAC header * Calling ip_queue_xmit() - which does routing as well, I checked the implementation - I get a kernel panic * Futile, but just in case, ip_route_input() and ip_queue_xmit() - kernel panic It seems that ip_queue_xmit should be what I need, I don't know why it crashes... Thanks and regards, Lori -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
