// SPDX-License-Identifier: GPL-2.0-only#include <linux/ethtool.h>#include <linux/module.h>#include <linux/kernel.h>#include <linux/netdevice.h>#include <linux/netlink.h>#include <net/net_namespace.h>#include <linux/if_arp.h>#include <net/rtnetlink.h> static netdev_tx_t nlmon_xmit(struct sk_buff *skb, struct net_device *dev){	dev_lstats_add(dev, skb->len); 	dev_kfree_skb(skb); 	return NETDEV_TX_OK;} struct nlmon {	struct netlink_tap nt;}; static int nlmon_open(struct net_device *dev){	struct nlmon *nlmon = netdev_priv(dev); 	nlmon->nt.dev = dev;	nlmon->nt.module = THIS_MODULE;	return netlink_add_tap(&nlmon->nt);} static int nlmon_close(struct net_device *dev){	struct nlmon *nlmon = netdev_priv(dev); 	return netlink_remove_tap(&nlmon->nt);} static voidnlmon_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats){	dev_lstats_read(dev, &stats->rx_packets, &stats->rx_bytes);} static u32 always_on(struct net_device *dev){	return 1;} static const struct ethtool_ops nlmon_ethtool_ops = {	.get_link = always_on,}; static const struct net_device_ops nlmon_ops = {	.ndo_open = nlmon_open,	.ndo_stop = nlmon_close,	.ndo_start_xmit = nlmon_xmit,	.ndo_get_stats64 = nlmon_get_stats64,}; static void nlmon_setup(struct net_device *dev){	dev->type = ARPHRD_NETLINK;	dev->priv_flags |= IFF_NO_QUEUE;	dev->lltx = true; 	dev->netdev_ops	= &nlmon_ops;	dev->ethtool_ops = &nlmon_ethtool_ops;	dev->needs_free_netdev = true; 	dev->features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA;	dev->flags = IFF_NOARP;	dev->pcpu_stat_type = NETDEV_PCPU_STAT_LSTATS; 	/* That's rather a softlimit here, which, of course,	 * can be altered. Not a real MTU, but what is to be	 * expected in most cases.	 */	dev->mtu = NLMSG_GOODSIZE;	dev->min_mtu = sizeof(struct nlmsghdr);} static int nlmon_validate(struct nlattr *tb[], struct nlattr *data[],			  struct netlink_ext_ack *extack){	if (tb[IFLA_ADDRESS])		return -EINVAL;	return 0;} static struct rtnl_link_ops nlmon_link_ops __read_mostly = {	.kind			= "nlmon",	.priv_size		= sizeof(struct nlmon),	.setup			= nlmon_setup,	.validate		= nlmon_validate,}; static __init int nlmon_register(void){	return rtnl_link_register(&nlmon_link_ops);} static __exit void nlmon_unregister(void){	rtnl_link_unregister(&nlmon_link_ops);} module_init(nlmon_register);module_exit(nlmon_unregister); MODULE_LICENSE("GPL v2");MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");MODULE_AUTHOR("Mathieu Geli <geli@enseirb.fr>");MODULE_DESCRIPTION("Netlink monitoring device");MODULE_ALIAS_RTNL_LINK("nlmon");