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