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 67 dev->netdev_ops = &nlmon_ops; 68 dev->ethtool_ops = &nlmon_ethtool_ops; 69 dev->needs_free_netdev = true; 70 71 dev->features = NETIF_F_SG | NETIF_F_FRAGLIST | 72 NETIF_F_HIGHDMA | NETIF_F_LLTX; 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"); 117