drivers/net/nlmon.c

   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
  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
  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
  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
  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
  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
  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
  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
 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
 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
 140 static __init int nlmon_register(void)
 141 {
 142         return rtnl_link_register(&nlmon_link_ops);
 143 }
 144
 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");