// SPDX-License-Identifier: GPL-2.0-only #include <linux/module.h> #include <linux/kernel.h> #include <linux/netdevice.h> #include <linux/netlink.h> #include <net/net_namespace.h> #include <linux/if_arp.h> #include <net/rtnetlink.h> static netdev_tx_t nlmon_xmit(struct sk_buff *skb, struct net_device *dev) { dev_lstats_add(dev, skb->len); dev_kfree_skb(skb); return NETDEV_TX_OK; } static int nlmon_dev_init(struct net_device *dev) { dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats); return dev->lstats == NULL ? -ENOMEM : 0; } static void nlmon_dev_uninit(struct net_device *dev) { free_percpu(dev->lstats); } struct nlmon { struct netlink_tap nt; }; static int nlmon_open(struct net_device *dev) { struct nlmon *nlmon = netdev_priv(dev); nlmon->nt.dev = dev; nlmon->nt.module = THIS_MODULE; return netlink_add_tap(&nlmon->nt); } static int nlmon_close(struct net_device *dev) { struct nlmon *nlmon = netdev_priv(dev); return netlink_remove_tap(&nlmon->nt); } static void nlmon_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats) { u64 packets, bytes; dev_lstats_read(dev, &packets, &bytes); stats->rx_packets = packets; stats->tx_packets = 0; stats->rx_bytes = bytes; stats->tx_bytes = 0; } static u32 always_on(struct net_device *dev) { return 1; } static const struct ethtool_ops nlmon_ethtool_ops = { .get_link = always_on, }; static const struct net_device_ops nlmon_ops = { .ndo_init = nlmon_dev_init, .ndo_uninit = nlmon_dev_uninit, .ndo_open = nlmon_open, .ndo_stop = nlmon_close, .ndo_start_xmit = nlmon_xmit, .ndo_get_stats64 = nlmon_get_stats64, }; static void nlmon_setup(struct net_device *dev) { dev->type = ARPHRD_NETLINK; dev->priv_flags |= IFF_NO_QUEUE; dev->netdev_ops = &nlmon_ops; dev->ethtool_ops = &nlmon_ethtool_ops; dev->needs_free_netdev = true; dev->features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA | NETIF_F_LLTX; dev->flags = IFF_NOARP; /* That's rather a softlimit here, which, of course, * can be altered. Not a real MTU, but what is to be * expected in most cases. */ dev->mtu = NLMSG_GOODSIZE; dev->min_mtu = sizeof(struct nlmsghdr); } static int nlmon_validate(struct nlattr *tb[], struct nlattr *data[], struct netlink_ext_ack *extack) { if (tb[IFLA_ADDRESS]) return -EINVAL; return 0; } static struct rtnl_link_ops nlmon_link_ops __read_mostly = { .kind = "nlmon", .priv_size = sizeof(struct nlmon), .setup = nlmon_setup, .validate = nlmon_validate, }; static __init int nlmon_register(void) { return rtnl_link_register(&nlmon_link_ops); } static __exit void nlmon_unregister(void) { rtnl_link_unregister(&nlmon_link_ops); } module_init(nlmon_register); module_exit(nlmon_unregister); MODULE_LICENSE("GPL v2"); MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>"); MODULE_AUTHOR("Mathieu Geli <geli@enseirb.fr>"); MODULE_DESCRIPTION("Netlink monitoring device"); MODULE_ALIAS_RTNL_LINK("nlmon");