Init with small code example

kernel/Makefile

@@ -0,0 +1,8 @@
+
+obj-m += netlink-test.o
+
+all:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
+
+clean:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

kernel/netlink-test.c

@@ -0,0 +1,81 @@
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <net/sock.h>
+#include <net/netlink.h>
+
+#define NETLINK_TESTPROTO (30)
+
+static struct sock *my_nl_sock;
+
+
+static void nl_test_recv(struct sk_buff *skb)
+{
+	
+struct nlmsghdr *nlh;
+int pid;
+struct sk_buff *skb_out;
+int msg_size;
+char *msg="Hello from kernel";
+int res;
+
+printk(KERN_INFO "Entering: %s\n", __FUNCTION__);
+
+msg_size=strlen(msg);
+
+nlh=(struct nlmsghdr*)skb->data;
+printk(KERN_INFO "Netlink received msg payload:%s\n",(char*)nlmsg_data(nlh));
+pid = nlh->nlmsg_pid; /*pid of sending process */
+
+skb_out = nlmsg_new(msg_size,0);
+
+if(!skb_out)
+{
+
+    printk(KERN_ERR "Failed to allocate new skb\n");
+    return;
+
+} 
+nlh=nlmsg_put(skb_out,0,0,NLMSG_DONE,msg_size,0);  
+NETLINK_CB(skb_out).dst_group = 0; /* not in mcast group */
+strncpy(nlmsg_data(nlh),msg,msg_size);
+
+res=nlmsg_unicast(my_nl_sock,skb_out,pid);
+
+if(res<0)
+    printk(KERN_INFO "Error while sending bak to user\n");
+
+}
+
+static struct netlink_kernel_cfg nl_cfg = {
+	.groups = 0,
+	.input = nl_test_recv,
+};
+
+static int nl_test_init(void)
+{	
+
+	my_nl_sock = netlink_kernel_create(&init_net, NETLINK_TESTPROTO, &nl_cfg);
+	
+	if (!my_nl_sock) {
+        	printk(KERN_ERR "%s: receive handler registration failed\n", __func__);
+        	return -ENOMEM;
+	}
+
+	printk(KERN_INFO "Hello :)\n");
+	return 0;
+}
+
+static void nl_test_exit(void)
+{
+	if (my_nl_sock)
+		netlink_kernel_release(my_nl_sock);
+
+	printk(KERN_INFO "Goodbye :(\n");
+}
+
+module_init(nl_test_init);
+module_exit(nl_test_exit);
+
+MODULE_AUTHOR("Mario Huettel <mario.huettel@gmx.net>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Netlink communication test");