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
nlmon_xmit(struct sk_buff * skb,struct net_device * dev)10 static netdev_tx_t nlmon_xmit(struct sk_buff *skb, struct net_device *dev)
11 {
12 int len = skb->len;
13 struct pcpu_lstats *stats = this_cpu_ptr(dev->lstats);
14
15 u64_stats_update_begin(&stats->syncp);
16 stats->bytes += len;
17 stats->packets++;
18 u64_stats_update_end(&stats->syncp);
19
20 dev_kfree_skb(skb);
21
22 return NETDEV_TX_OK;
23 }
24
nlmon_dev_init(struct net_device * dev)25 static int nlmon_dev_init(struct net_device *dev)
26 {
27 dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
28 return dev->lstats == NULL ? -ENOMEM : 0;
29 }
30
nlmon_dev_uninit(struct net_device * dev)31 static void nlmon_dev_uninit(struct net_device *dev)
32 {
33 free_percpu(dev->lstats);
34 }
35
36 struct nlmon {
37 struct netlink_tap nt;
38 };
39
nlmon_open(struct net_device * dev)40 static int nlmon_open(struct net_device *dev)
41 {
42 struct nlmon *nlmon = netdev_priv(dev);
43
44 nlmon->nt.dev = dev;
45 nlmon->nt.module = THIS_MODULE;
46 return netlink_add_tap(&nlmon->nt);
47 }
48
nlmon_close(struct net_device * dev)49 static int nlmon_close(struct net_device *dev)
50 {
51 struct nlmon *nlmon = netdev_priv(dev);
52
53 return netlink_remove_tap(&nlmon->nt);
54 }
55
56 static void
nlmon_get_stats64(struct net_device * dev,struct rtnl_link_stats64 * stats)57 nlmon_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
58 {
59 int i;
60 u64 bytes = 0, packets = 0;
61
62 for_each_possible_cpu(i) {
63 const struct pcpu_lstats *nl_stats;
64 u64 tbytes, tpackets;
65 unsigned int start;
66
67 nl_stats = per_cpu_ptr(dev->lstats, i);
68
69 do {
70 start = u64_stats_fetch_begin_irq(&nl_stats->syncp);
71 tbytes = nl_stats->bytes;
72 tpackets = nl_stats->packets;
73 } while (u64_stats_fetch_retry_irq(&nl_stats->syncp, start));
74
75 packets += tpackets;
76 bytes += tbytes;
77 }
78
79 stats->rx_packets = packets;
80 stats->tx_packets = 0;
81
82 stats->rx_bytes = bytes;
83 stats->tx_bytes = 0;
84 }
85
always_on(struct net_device * dev)86 static u32 always_on(struct net_device *dev)
87 {
88 return 1;
89 }
90
91 static const struct ethtool_ops nlmon_ethtool_ops = {
92 .get_link = always_on,
93 };
94
95 static const struct net_device_ops nlmon_ops = {
96 .ndo_init = nlmon_dev_init,
97 .ndo_uninit = nlmon_dev_uninit,
98 .ndo_open = nlmon_open,
99 .ndo_stop = nlmon_close,
100 .ndo_start_xmit = nlmon_xmit,
101 .ndo_get_stats64 = nlmon_get_stats64,
102 };
103
nlmon_setup(struct net_device * dev)104 static void nlmon_setup(struct net_device *dev)
105 {
106 dev->type = ARPHRD_NETLINK;
107 dev->priv_flags |= IFF_NO_QUEUE;
108
109 dev->netdev_ops = &nlmon_ops;
110 dev->ethtool_ops = &nlmon_ethtool_ops;
111 dev->needs_free_netdev = true;
112
113 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST |
114 NETIF_F_HIGHDMA | NETIF_F_LLTX;
115 dev->flags = IFF_NOARP;
116
117 /* That's rather a softlimit here, which, of course,
118 * can be altered. Not a real MTU, but what is to be
119 * expected in most cases.
120 */
121 dev->mtu = NLMSG_GOODSIZE;
122 dev->min_mtu = sizeof(struct nlmsghdr);
123 }
124
nlmon_validate(struct nlattr * tb[],struct nlattr * data[],struct netlink_ext_ack * extack)125 static int nlmon_validate(struct nlattr *tb[], struct nlattr *data[],
126 struct netlink_ext_ack *extack)
127 {
128 if (tb[IFLA_ADDRESS])
129 return -EINVAL;
130 return 0;
131 }
132
133 static struct rtnl_link_ops nlmon_link_ops __read_mostly = {
134 .kind = "nlmon",
135 .priv_size = sizeof(struct nlmon),
136 .setup = nlmon_setup,
137 .validate = nlmon_validate,
138 };
139
nlmon_register(void)140 static __init int nlmon_register(void)
141 {
142 return rtnl_link_register(&nlmon_link_ops);
143 }
144
nlmon_unregister(void)145 static __exit void nlmon_unregister(void)
146 {
147 rtnl_link_unregister(&nlmon_link_ops);
148 }
149
150 module_init(nlmon_register);
151 module_exit(nlmon_unregister);
152
153 MODULE_LICENSE("GPL v2");
154 MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
155 MODULE_AUTHOR("Mathieu Geli <geli@enseirb.fr>");
156 MODULE_DESCRIPTION("Netlink monitoring device");
157 MODULE_ALIAS_RTNL_LINK("nlmon");
158