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"); 158