net/core/drop_monitor.c

   1 /*
   2  * Monitoring code for network dropped packet alerts
   3  *
   4  * Copyright (C) 2009 Neil Horman <nhorman@tuxdriver.com>
   5  */
   6
   7 #include <linux/netdevice.h>
   8 #include <linux/etherdevice.h>
   9 #include <linux/string.h>
  10 #include <linux/if_arp.h>
  11 #include <linux/inetdevice.h>
  12 #include <linux/inet.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/netpoll.h>
  15 #include <linux/sched.h>
  16 #include <linux/delay.h>
  17 #include <linux/types.h>
  18 #include <linux/workqueue.h>
  19 #include <linux/netlink.h>
  20 #include <linux/net_dropmon.h>
  21 #include <linux/percpu.h>
  22 #include <linux/timer.h>
  23 #include <linux/bitops.h>
  24 #include <net/genetlink.h>
  25
  26 #include <trace/skb.h>
  27
  28 #include <asm/unaligned.h>
  29
  30 #define TRACE_ON 1
  31 #define TRACE_OFF 0
  32
  33 static void send_dm_alert(struct work_struct *unused);
  34
  35
  36 /*
  37  * Globals, our netlink socket pointer
  38  * and the work handle that will send up
  39  * netlink alerts
  40  */
  41 struct sock *dm_sock;
  42
  43 struct per_cpu_dm_data {
  44         struct work_struct dm_alert_work;
  45         struct sk_buff *skb;
  46         atomic_t dm_hit_count;
  47         struct timer_list send_timer;
  48 };
  49
  50 static struct genl_family net_drop_monitor_family = {
  51         .id             = GENL_ID_GENERATE,
  52         .hdrsize        = 0,
  53         .name           = "NET_DM",
  54         .version        = 1,
  55         .maxattr        = NET_DM_CMD_MAX,
  56 };
  57
  58 static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);
  59
  60 static int dm_hit_limit = 64;
  61 static int dm_delay = 1;
  62
  63
  64 static void reset_per_cpu_data(struct per_cpu_dm_data *data)
  65 {
  66         size_t al;
  67         struct net_dm_alert_msg *msg;
  68
  69         al = sizeof(struct net_dm_alert_msg);
  70         al += dm_hit_limit * sizeof(struct net_dm_drop_point);
  71         data->skb = genlmsg_new(al, GFP_KERNEL);
  72         genlmsg_put(data->skb, 0, 0, &net_drop_monitor_family,
  73                         0, NET_DM_CMD_ALERT);
  74         msg = __nla_reserve_nohdr(data->skb, sizeof(struct net_dm_alert_msg));
  75         memset(msg, 0, al);
  76         atomic_set(&data->dm_hit_count, dm_hit_limit);
  77 }
  78
  79 static void send_dm_alert(struct work_struct *unused)
  80 {
  81         struct sk_buff *skb;
  82         struct per_cpu_dm_data *data = &__get_cpu_var(dm_cpu_data);
  83
  84         /*
  85          * Grab the skb we're about to send
  86          */
  87         skb = data->skb;
  88
  89         /*
  90          * Replace it with a new one
  91          */
  92         reset_per_cpu_data(data);
  93
  94         /*
  95          * Ship it!
  96          */
  97         genlmsg_multicast(skb, 0, NET_DM_GRP_ALERT, GFP_KERNEL);
  98
  99 }
 100
 101 /*
 102  * This is the timer function to delay the sending of an alert
 103  * in the event that more drops will arrive during the
 104  * hysteresis period.  Note that it operates under the timer interrupt
 105  * so we don't need to disable preemption here
 106  */
 107 static void sched_send_work(unsigned long unused)
 108 {
 109         struct per_cpu_dm_data *data =  &__get_cpu_var(dm_cpu_data);
 110
 111         schedule_work(&data->dm_alert_work);
 112 }
 113
 114 static void trace_kfree_skb_hit(struct sk_buff *skb, void *location)
 115 {
 116         struct net_dm_alert_msg *msg;
 117         struct nlmsghdr *nlh;
 118         int i;
 119         struct per_cpu_dm_data *data = &__get_cpu_var(dm_cpu_data);
 120
 121
 122         if (!atomic_add_unless(&data->dm_hit_count, -1, 0)) {
 123                 /*
 124                  * we're already at zero, discard this hit
 125                  */
 126                 goto out;
 127         }
 128
 129         nlh = (struct nlmsghdr *)data->skb->data;
 130         msg = genlmsg_data(nlmsg_data(nlh));
 131         for (i = 0; i < msg->entries; i++) {
 132                 if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) {
 133                         msg->points[i].count++;
 134                         goto out;
 135                 }
 136         }
 137
 138         /*
 139          * We need to create a new entry
 140          */
 141         __nla_reserve_nohdr(data->skb, sizeof(struct net_dm_drop_point));
 142         memcpy(msg->points[msg->entries].pc, &location, sizeof(void *));
 143         msg->points[msg->entries].count = 1;
 144         msg->entries++;
 145
 146         if (!timer_pending(&data->send_timer)) {
 147                 data->send_timer.expires = jiffies + dm_delay * HZ;
 148                 add_timer_on(&data->send_timer, smp_processor_id());
 149         }
 150
 151 out:
 152         return;
 153 }
 154
 155 static int set_all_monitor_traces(int state)
 156 {
 157         int rc = 0;
 158
 159         switch (state) {
 160         case TRACE_ON:
 161                 rc |= register_trace_kfree_skb(trace_kfree_skb_hit);
 162                 break;
 163         case TRACE_OFF:
 164                 rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit);
 165
 166                 tracepoint_synchronize_unregister();
 167                 break;
 168         default:
 169                 rc = 1;
 170                 break;
 171         }
 172
 173         if (rc)
 174                 return -EINPROGRESS;
 175         return rc;
 176 }
 177
 178
 179 static int net_dm_cmd_config(struct sk_buff *skb,
 180                         struct genl_info *info)
 181 {
 182         return -ENOTSUPP;
 183 }
 184
 185 static int net_dm_cmd_trace(struct sk_buff *skb,
 186                         struct genl_info *info)
 187 {
 188         switch (info->genlhdr->cmd) {
 189         case NET_DM_CMD_START:
 190                 return set_all_monitor_traces(TRACE_ON);
 191                 break;
 192         case NET_DM_CMD_STOP:
 193                 return set_all_monitor_traces(TRACE_OFF);
 194                 break;
 195         }
 196
 197         return -ENOTSUPP;
 198 }
 199
 200
 201 static struct genl_ops dropmon_ops[] = {
 202         {
 203                 .cmd = NET_DM_CMD_CONFIG,
 204                 .doit = net_dm_cmd_config,
 205         },
 206         {
 207                 .cmd = NET_DM_CMD_START,
 208                 .doit = net_dm_cmd_trace,
 209         },
 210         {
 211                 .cmd = NET_DM_CMD_STOP,
 212                 .doit = net_dm_cmd_trace,
 213         },
 214 };
 215
 216 static int __init init_net_drop_monitor(void)
 217 {
 218         int cpu;
 219         int rc, i, ret;
 220         struct per_cpu_dm_data *data;
 221         printk(KERN_INFO "Initalizing network drop monitor service\n");
 222
 223         if (sizeof(void *) > 8) {
 224                 printk(KERN_ERR "Unable to store program counters on this arch, Drop monitor failed\n");
 225                 return -ENOSPC;
 226         }
 227
 228         if (genl_register_family(&net_drop_monitor_family) < 0) {
 229                 printk(KERN_ERR "Could not create drop monitor netlink family\n");
 230                 return -EFAULT;
 231         }
 232
 233         rc = -EFAULT;
 234
 235         for (i = 0; i < ARRAY_SIZE(dropmon_ops); i++) {
 236                 ret = genl_register_ops(&net_drop_monitor_family,
 237                                         &dropmon_ops[i]);
 238                 if (ret) {
 239                         printk(KERN_CRIT "failed to register operation %d\n",
 240                                 dropmon_ops[i].cmd);
 241                         goto out_unreg;
 242                 }
 243         }
 244
 245         rc = 0;
 246
 247         for_each_present_cpu(cpu) {
 248                 data = &per_cpu(dm_cpu_data, cpu);
 249                 reset_per_cpu_data(data);
 250                 INIT_WORK(&data->dm_alert_work, send_dm_alert);
 251                 init_timer(&data->send_timer);
 252                 data->send_timer.data = cpu;
 253                 data->send_timer.function = sched_send_work;
 254         }
 255         goto out;
 256
 257 out_unreg:
 258         genl_unregister_family(&net_drop_monitor_family);
 259 out:
 260         return rc;
 261 }
 262
 263 late_initcall(init_net_drop_monitor);