v4.19.13 snapshot.
diff --git a/drivers/net/nlmon.c b/drivers/net/nlmon.c
new file mode 100644
index 0000000..4b22955
--- /dev/null
+++ b/drivers/net/nlmon.c
@@ -0,0 +1,162 @@
+#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>
+
+struct pcpu_lstats {
+ u64 packets;
+ u64 bytes;
+ struct u64_stats_sync syncp;
+};
+
+static netdev_tx_t nlmon_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+ int len = skb->len;
+ struct pcpu_lstats *stats = this_cpu_ptr(dev->lstats);
+
+ u64_stats_update_begin(&stats->syncp);
+ stats->bytes += len;
+ stats->packets++;
+ u64_stats_update_end(&stats->syncp);
+
+ 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)
+{
+ int i;
+ u64 bytes = 0, packets = 0;
+
+ for_each_possible_cpu(i) {
+ const struct pcpu_lstats *nl_stats;
+ u64 tbytes, tpackets;
+ unsigned int start;
+
+ nl_stats = per_cpu_ptr(dev->lstats, i);
+
+ do {
+ start = u64_stats_fetch_begin_irq(&nl_stats->syncp);
+ tbytes = nl_stats->bytes;
+ tpackets = nl_stats->packets;
+ } while (u64_stats_fetch_retry_irq(&nl_stats->syncp, start));
+
+ packets += tpackets;
+ bytes += tbytes;
+ }
+
+ 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");