1 files changed, 136 insertions, 0 deletions
diff --git a/drivers/net/nlmon.c b/drivers/net/nlmon.c
new file mode 100644
index 000000000..5e19a6839
--- /dev/null
+++ b/drivers/net/nlmon.c
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/ethtool.h>
+#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");