drivers/net/nlmon.c

   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
  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
  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
  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
  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
  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
  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
  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
  99 static __init int nlmon_register(void)
 100 {
 101         return rtnl_link_register(&nlmon_link_ops);
 102 }
 103
 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");