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// 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;
}
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)
{
dev_lstats_read(dev, &stats->rx_packets, &stats->rx_bytes);
}
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_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;
dev->pcpu_stat_type = NETDEV_PCPU_STAT_LSTATS;
/* 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");
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