Where is filled udph->check field?
I am writing a Kernel Module (will become GPL when ended) to backup VANETS using Cellular Data Network (UMTS)
I'm using Netfilter hooks: The idea seems simple you put an OUTPUT hook and if the dest address is in a list of adrresses to be backuped, you change the dest address
Of course you have to recalculate
IP checksum: ip_send_ceck()
TCP/UDP checksums these are build using a fake header with ip addresses and ports. After changing an address you haye to call
The problem is when my hook is called UDP checksum isnīt in place yet, I donīt know where it is calculated (I know that because I always get the same check value but my datagrams have an increasing order field)
Could any one help me