Hi,
I'm pretty new to kernel development and I'm currently attempting to modify
a loadable kernel module. This module intercepts some of the networking
calls (connect, accept, sendmsg, recvmsg, etc), presents them to a security
engine and either completes or denies the calls based on the engine's
decision. This is done on RH3, kernel 2.4.21-4.
My trouble stems from determining the destination IP addr in an incoming UDP
packet. I understand the information should be available in the msghdr
struct that is returned from the 5 parameter version of sock->ops->recvmsg()
function (as used in net/socket.c but defined God knows where).
I further gather that I must provide some space/memory in msghdr when
calling recvmsg() to receive the ancillary data (IP_PKTINFO) that will
eventually contain the ipi_spec_dst local IP address I'm looking for.
Finally, I think I need to call the equivalent to the userspace setsockopt()
to tell the socket I want this ancillary data. But, I don't think I can use
that system call in kernel space, right? Is sys_setsockopt() the way to go?
Whatever I try, I keep getting error -14 (EFAULT?) which seems to be a show
stopper.
Could someone tell me whether I'm in the right direction or how to piece
this all together?
Many thanks,
JP
--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/
