Hi all, I'm working on a test program using libipq and iptables (to route packet to userspace). I have a test program working that does all of the above, now I want to start adding some of my smarts into the program, and one thing I want to do is add some TCP options into certain types of TCP packets. So I believe I understand what I have to do, or at least I'm rather close, but I would just like some confirmation that I'm on the correct path: 1) Create a totally new 'message buffer' of the appropriate size, to house the original packet in it's entirety, plus the extra bytes I need to add for my new TCP option. 2) Copy over all the orignal headers into this new memory space... Then add in my own TCP headers. 3) 'Merge' the tcp data packet itself into the new structure, AFTER my added tcp header. 4) Re-compute all required checksums 5) Reaim - msg->payload to my new structure. 6) ?? Do I need to free the old msg->payload or does the kernel know to do this for me ?? 7) Send back a ipq_set_verdict, with all the params set to show I mangled the packet a bit. I'm concerned about the processing this will take, as it looks like there will need to be 2 different calls to memcopy, totalling the full length of every packet. Can I mangle JUST the header's if I set the mode to IPQ_COPY_META, and would it integrate my header changes in with the packet data automagically? That would save me a lot of the memcopy for large packets. I plan on setting the MTU in accordance with the space needed to add my options, so it shouldn't cause any fragmentation. Thanks, brian
