1 files changed, 181 insertions, 0 deletions
diff --git a/drivers/net/nlmon.c b/drivers/net/nlmon.c
new file mode 100644
index 0000000..b57ce5f
--- /dev/null
+++ b/drivers/net/nlmon.c
@@ -0,0 +1,181 @@
+#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_is_valid_mtu(int new_mtu)
+{
+	/* Note that in netlink we do not really have an upper limit. On
+	 * default, we use NLMSG_GOODSIZE. Here at least we should make
+	 * sure that it's at least the header size.
+	 */
+	return new_mtu >= (int) sizeof(struct nlmsghdr);
+}
+
+static int nlmon_change_mtu(struct net_device *dev, int new_mtu)
+{
+	if (!nlmon_is_valid_mtu(new_mtu))
+		return -EINVAL;
+
+	dev->mtu = new_mtu;
+	return 0;
+}
+
+static int nlmon_dev_init(struct net_device *dev)
+{
+	dev->lstats = alloc_percpu(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 struct rtnl_link_stats64 *
+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_bh(&nl_stats->syncp);
+			tbytes = nl_stats->bytes;
+			tpackets = nl_stats->packets;
+		} while (u64_stats_fetch_retry_bh(&nl_stats->syncp, start));
+
+		packets += tpackets;
+		bytes += tbytes;
+	}
+
+	stats->rx_packets = packets;
+	stats->tx_packets = 0;
+
+	stats->rx_bytes = bytes;
+	stats->tx_bytes = 0;
+
+	return stats;
+}
+
+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,
+	.ndo_change_mtu = nlmon_change_mtu,
+};
+
+static void nlmon_setup(struct net_device *dev)
+{
+	dev->type = ARPHRD_NETLINK;
+	dev->tx_queue_len = 0;
+
+	dev->netdev_ops	= &nlmon_ops;
+	dev->ethtool_ops = &nlmon_ethtool_ops;
+	dev->destructor	= free_netdev;
+
+	dev->features = NETIF_F_FRAGLIST | NETIF_F_HIGHDMA;
+	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;
+}
+
+static int nlmon_validate(struct nlattr *tb[], struct nlattr *data[])
+{
+	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");