Kernel packet trace

Path of UDP packet in linux kernel
http://stackoverflow.com/questions/14407452/path-of-udp-packet-in-linux-kernel

PATH OF A PACKET IN THE LINUX KERNEL STACK
http://www.hsnlab.hu/twiki/pub/Targyak/Mar11Cikkek/Network_stack.pdf

Inside the Linux Packet Filter
http://www.linuxjournal.com/article/4852

kernel_flow
http://www.linuxfoundation.org/collaborate/workgroups/networking/kernel_flow

Networking in the Linux Kernel
http://wiki.openwrt.org/doc/networking/praxis