Appendix E. Example for a Network-Layer Protocol

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 /********************************************************** * Example for a network-layer protocol * Compile: * gcc -I/lib/modules/'uname -r'/build/include -c file.c **********************************************************/ #ifndef _KERNEL_ #define _KERNEL_ #endif #ifndef MODULE #define MODULE #endif #include <linux/module.h> #include <linux/version.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/skbuff.h> #include <linux/in.h> #include <linux/netdevice.h> MODULE_AUTHOR("Test Author ([e-mail])"); MODULE_DESCRIPTION("Module with a layer-3 test protocol"); #define TEST_PROTO_ID 0x1234 int test_pack_rcv(struct sk_buff *skb, struct net_device *dev, struct   packet_type *pt); static struct packet_type test_protocol = {        _constant_htons(TEST_PROTO_ID),        NULL,        test_pack_rcv,       (void *) 1,       NULL }; int test_pack_rcv(struct sk_buff *skb, struct net_device *dev, struct   packet_type *pt) {        printk(KERN_DEBUG "Test protocol: Packet Received with length: %u\n",               skb->len);        return skb->len; } int init_module(void) {        dev_add_pack(&test_protocol);        return 0; } void cleanup_module(void) {        dev_remove_pack(&test_protocol); }

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