xref: /kernel/linux/linux-5.10/drivers/net/nlmon.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/module.h>
3#include <linux/kernel.h>
4#include <linux/netdevice.h>
5#include <linux/netlink.h>
6#include <net/net_namespace.h>
7#include <linux/if_arp.h>
8#include <net/rtnetlink.h>
9
10static netdev_tx_t nlmon_xmit(struct sk_buff *skb, struct net_device *dev)
11{
12	dev_lstats_add(dev, skb->len);
13
14	dev_kfree_skb(skb);
15
16	return NETDEV_TX_OK;
17}
18
19static int nlmon_dev_init(struct net_device *dev)
20{
21	dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
22	return dev->lstats == NULL ? -ENOMEM : 0;
23}
24
25static void nlmon_dev_uninit(struct net_device *dev)
26{
27	free_percpu(dev->lstats);
28}
29
30struct nlmon {
31	struct netlink_tap nt;
32};
33
34static int nlmon_open(struct net_device *dev)
35{
36	struct nlmon *nlmon = netdev_priv(dev);
37
38	nlmon->nt.dev = dev;
39	nlmon->nt.module = THIS_MODULE;
40	return netlink_add_tap(&nlmon->nt);
41}
42
43static int nlmon_close(struct net_device *dev)
44{
45	struct nlmon *nlmon = netdev_priv(dev);
46
47	return netlink_remove_tap(&nlmon->nt);
48}
49
50static void
51nlmon_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
52{
53	u64 packets, bytes;
54
55	dev_lstats_read(dev, &packets, &bytes);
56
57	stats->rx_packets = packets;
58	stats->tx_packets = 0;
59
60	stats->rx_bytes = bytes;
61	stats->tx_bytes = 0;
62}
63
64static u32 always_on(struct net_device *dev)
65{
66	return 1;
67}
68
69static const struct ethtool_ops nlmon_ethtool_ops = {
70	.get_link = always_on,
71};
72
73static const struct net_device_ops nlmon_ops = {
74	.ndo_init = nlmon_dev_init,
75	.ndo_uninit = nlmon_dev_uninit,
76	.ndo_open = nlmon_open,
77	.ndo_stop = nlmon_close,
78	.ndo_start_xmit = nlmon_xmit,
79	.ndo_get_stats64 = nlmon_get_stats64,
80};
81
82static void nlmon_setup(struct net_device *dev)
83{
84	dev->type = ARPHRD_NETLINK;
85	dev->priv_flags |= IFF_NO_QUEUE;
86
87	dev->netdev_ops	= &nlmon_ops;
88	dev->ethtool_ops = &nlmon_ethtool_ops;
89	dev->needs_free_netdev = true;
90
91	dev->features = NETIF_F_SG | NETIF_F_FRAGLIST |
92			NETIF_F_HIGHDMA | NETIF_F_LLTX;
93	dev->flags = IFF_NOARP;
94
95	/* That's rather a softlimit here, which, of course,
96	 * can be altered. Not a real MTU, but what is to be
97	 * expected in most cases.
98	 */
99	dev->mtu = NLMSG_GOODSIZE;
100	dev->min_mtu = sizeof(struct nlmsghdr);
101}
102
103static int nlmon_validate(struct nlattr *tb[], struct nlattr *data[],
104			  struct netlink_ext_ack *extack)
105{
106	if (tb[IFLA_ADDRESS])
107		return -EINVAL;
108	return 0;
109}
110
111static struct rtnl_link_ops nlmon_link_ops __read_mostly = {
112	.kind			= "nlmon",
113	.priv_size		= sizeof(struct nlmon),
114	.setup			= nlmon_setup,
115	.validate		= nlmon_validate,
116};
117
118static __init int nlmon_register(void)
119{
120	return rtnl_link_register(&nlmon_link_ops);
121}
122
123static __exit void nlmon_unregister(void)
124{
125	rtnl_link_unregister(&nlmon_link_ops);
126}
127
128module_init(nlmon_register);
129module_exit(nlmon_unregister);
130
131MODULE_LICENSE("GPL v2");
132MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
133MODULE_AUTHOR("Mathieu Geli <geli@enseirb.fr>");
134MODULE_DESCRIPTION("Netlink monitoring device");
135MODULE_ALIAS_RTNL_LINK("nlmon");
136