Hi, I am having problems computing the IP checksum with the th ip_fast_csum. I would REALLY appreciate if any of you can help me. This is the function I am using to compute the IP checksum. void computeIPChecksum(struct iphdr* ip) { printk("*** IP checksum (before) : %d\n", ip->check); ip->check = 0; /* it must be pre-zero'd */ ip->check = ip_fast_csum((unsigned char *)ip, ip->ihl); printk("*** IP checksum (after) : %d\n", ip->check); } Please notice that because I am not modifying the packet at all yet, I should get the same result. Well, I don't. I have no clue why. Any thoughts? Please, reply directly to norka@ecs.syr.edu. Thank you so much, in advance, Norka -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/