linux/drivers/net/nlmon.c
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   1#include <linux/module.h>
   2#include <linux/kernel.h>
   3#include <linux/netdevice.h>
   4#include <linux/netlink.h>
   5#include <net/net_namespace.h>
   6#include <linux/if_arp.h>
   7#include <net/rtnetlink.h>
   8
   9struct pcpu_lstats {
  10        u64 packets;
  11        u64 bytes;
  12        struct u64_stats_sync syncp;
  13};
  14
  15static netdev_tx_t nlmon_xmit(struct sk_buff *skb, struct net_device *dev)
  16{
  17        int len = skb->len;
  18        struct pcpu_lstats *stats = this_cpu_ptr(dev->lstats);
  19
  20        u64_stats_update_begin(&stats->syncp);
  21        stats->bytes += len;
  22        stats->packets++;
  23        u64_stats_update_end(&stats->syncp);
  24
  25        dev_kfree_skb(skb);
  26
  27        return NETDEV_TX_OK;
  28}
  29
  30static int nlmon_is_valid_mtu(int new_mtu)
  31{
  32        /* Note that in netlink we do not really have an upper limit. On
  33         * default, we use NLMSG_GOODSIZE. Here at least we should make
  34         * sure that it's at least the header size.
  35         */
  36        return new_mtu >= (int) sizeof(struct nlmsghdr);
  37}
  38
  39static int nlmon_change_mtu(struct net_device *dev, int new_mtu)
  40{
  41        if (!nlmon_is_valid_mtu(new_mtu))
  42                return -EINVAL;
  43
  44        dev->mtu = new_mtu;
  45        return 0;
  46}
  47
  48static int nlmon_dev_init(struct net_device *dev)
  49{
  50        dev->lstats = alloc_percpu(struct pcpu_lstats);
  51
  52        return dev->lstats == NULL ? -ENOMEM : 0;
  53}
  54
  55static void nlmon_dev_uninit(struct net_device *dev)
  56{
  57        free_percpu(dev->lstats);
  58}
  59
  60struct nlmon {
  61        struct netlink_tap nt;
  62};
  63
  64static int nlmon_open(struct net_device *dev)
  65{
  66        struct nlmon *nlmon = netdev_priv(dev);
  67
  68        nlmon->nt.dev = dev;
  69        nlmon->nt.module = THIS_MODULE;
  70        return netlink_add_tap(&nlmon->nt);
  71}
  72
  73static int nlmon_close(struct net_device *dev)
  74{
  75        struct nlmon *nlmon = netdev_priv(dev);
  76
  77        return netlink_remove_tap(&nlmon->nt);
  78}
  79
  80static struct rtnl_link_stats64 *
  81nlmon_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
  82{
  83        int i;
  84        u64 bytes = 0, packets = 0;
  85
  86        for_each_possible_cpu(i) {
  87                const struct pcpu_lstats *nl_stats;
  88                u64 tbytes, tpackets;
  89                unsigned int start;
  90
  91                nl_stats = per_cpu_ptr(dev->lstats, i);
  92
  93                do {
  94                        start = u64_stats_fetch_begin_bh(&nl_stats->syncp);
  95                        tbytes = nl_stats->bytes;
  96                        tpackets = nl_stats->packets;
  97                } while (u64_stats_fetch_retry_bh(&nl_stats->syncp, start));
  98
  99                packets += tpackets;
 100                bytes += tbytes;
 101        }
 102
 103        stats->rx_packets = packets;
 104        stats->tx_packets = 0;
 105
 106        stats->rx_bytes = bytes;
 107        stats->tx_bytes = 0;
 108
 109        return stats;
 110}
 111
 112static u32 always_on(struct net_device *dev)
 113{
 114        return 1;
 115}
 116
 117static const struct ethtool_ops nlmon_ethtool_ops = {
 118        .get_link = always_on,
 119};
 120
 121static const struct net_device_ops nlmon_ops = {
 122        .ndo_init = nlmon_dev_init,
 123        .ndo_uninit = nlmon_dev_uninit,
 124        .ndo_open = nlmon_open,
 125        .ndo_stop = nlmon_close,
 126        .ndo_start_xmit = nlmon_xmit,
 127        .ndo_get_stats64 = nlmon_get_stats64,
 128        .ndo_change_mtu = nlmon_change_mtu,
 129};
 130
 131static void nlmon_setup(struct net_device *dev)
 132{
 133        dev->type = ARPHRD_NETLINK;
 134        dev->tx_queue_len = 0;
 135
 136        dev->netdev_ops = &nlmon_ops;
 137        dev->ethtool_ops = &nlmon_ethtool_ops;
 138        dev->destructor = free_netdev;
 139
 140        dev->features = NETIF_F_FRAGLIST | NETIF_F_HIGHDMA;
 141        dev->flags = IFF_NOARP;
 142
 143        /* That's rather a softlimit here, which, of course,
 144         * can be altered. Not a real MTU, but what is to be
 145         * expected in most cases.
 146         */
 147        dev->mtu = NLMSG_GOODSIZE;
 148}
 149
 150static int nlmon_validate(struct nlattr *tb[], struct nlattr *data[])
 151{
 152        if (tb[IFLA_ADDRESS])
 153                return -EINVAL;
 154        return 0;
 155}
 156
 157static struct rtnl_link_ops nlmon_link_ops __read_mostly = {
 158        .kind                   = "nlmon",
 159        .priv_size              = sizeof(struct nlmon),
 160        .setup                  = nlmon_setup,
 161        .validate               = nlmon_validate,
 162};
 163
 164static __init int nlmon_register(void)
 165{
 166        return rtnl_link_register(&nlmon_link_ops);
 167}
 168
 169static __exit void nlmon_unregister(void)
 170{
 171        rtnl_link_unregister(&nlmon_link_ops);
 172}
 173
 174module_init(nlmon_register);
 175module_exit(nlmon_unregister);
 176
 177MODULE_LICENSE("GPL v2");
 178MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
 179MODULE_AUTHOR("Mathieu Geli <geli@enseirb.fr>");
 180MODULE_DESCRIPTION("Netlink monitoring device");
 181MODULE_ALIAS_RTNL_LINK("nlmon");
 182
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