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/*
* Generic netlink sample -- kernel module
* Use `make` to compile and `insmod` to load the module
*
* Sergiy Lozovsky <sergiy.lozovsky@gmail.com>
* Peter V. Saveliev <peter@svinota.eu>
*
* Requires kernel 4.10+
*/
#include <linux/module.h> /* Needed by all modules */
#include <linux/kernel.h> /* Needed for KERN_INFO */
#include <linux/init.h> /* Needed for the macros */
#include <net/genetlink.h>
/* attributes (variables): the index in this enum is used as a reference for the type,
* userspace application has to indicate the corresponding type
* the policy is used for security considerations
*/
enum {
EXMPL_NLA_UNSPEC,
EXMPL_NLA_DATA,
EXMPL_NLA_LEN,
__EXMPL_NLA_MAX,
};
/* ... and the same for commands
*/
enum {
EXMPL_CMD_UNSPEC,
EXMPL_CMD_MSG,
};
/* attribute policy: defines which attribute has which type (e.g int, char * etc)
* possible values defined in net/netlink.h
*/
static struct nla_policy exmpl_genl_policy[__EXMPL_NLA_MAX] = {
[EXMPL_NLA_DATA] = { .type = NLA_NUL_STRING },
[EXMPL_NLA_LEN] = { .type = NLA_U32 },
};
#define VERSION_NR 1
static struct genl_family exmpl_gnl_family;
static int get_length(struct sk_buff *request, struct genl_info *info)
{
struct sk_buff *reply;
char *buffer;
void *msg_head;
if (info == NULL)
return -EINVAL;
if (!info->attrs[EXMPL_NLA_DATA])
return -EINVAL;
/* get the data */
buffer = nla_data(info->attrs[EXMPL_NLA_DATA]);
/* send a message back*/
/* allocate some memory, since the size is not yet known use NLMSG_GOODSIZE*/
reply = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
if (reply == NULL)
return -ENOMEM;
/* start the message */
msg_head = genlmsg_put_reply(reply, info, &exmpl_gnl_family, 0, info->genlhdr->cmd);
if (msg_head == NULL) {
return -ENOMEM;
}
/* add a EXMPL_LEN attribute -- report the data length */
if (0 != nla_put_u32(reply, EXMPL_NLA_LEN, strlen(buffer)))
return -EINVAL;
/* finalize the message */
genlmsg_end(reply, msg_head);
/* send the message back */
if (0 != genlmsg_reply(reply, info))
return -EINVAL;
return 0;
}
/* commands: mapping between commands and actual functions*/
static const struct genl_ops exmpl_gnl_ops_echo[] = {
{
.cmd = EXMPL_CMD_MSG,
.policy = exmpl_genl_policy,
.doit = get_length,
},
};
/* family definition */
static struct genl_family exmpl_gnl_family __ro_after_init = {
.name = "EXMPL_GENL", //the name of this family, used by userspace application
.version = VERSION_NR, //version number
.maxattr = __EXMPL_NLA_MAX - 1,
.module = THIS_MODULE,
.ops = exmpl_gnl_ops_echo,
.n_ops = ARRAY_SIZE(exmpl_gnl_ops_echo),
};
static int __init exmpl_gnl_init(void)
{
int rc;
rc = genl_register_family(&exmpl_gnl_family);
if (rc != 0) {
printk(KERN_INFO "rkmod: genl_register_family failed %d\n", rc);
return 1;
}
printk(KERN_INFO "Generic netlink example loaded, protocol version %d\n", VERSION_NR);
return 0;
}
static void __exit exmpl_gnl_exit(void)
{
int ret;
/*unregister the family*/
ret = genl_unregister_family(&exmpl_gnl_family);
if(ret !=0){
printk("unregister family %i\n",ret);
}
}
module_init(exmpl_gnl_init);
module_exit(exmpl_gnl_exit);
MODULE_LICENSE("GPL");
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