cregit-Linux how code gets into the kernel

Release 4.8 net/core/drop_monitor.c

Directory: net/core
 * Monitoring code for network dropped packet alerts
 * Copyright (C) 2009 Neil Horman <>

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/string.h>
#include <linux/if_arp.h>
#include <linux/inetdevice.h>
#include <linux/inet.h>
#include <linux/interrupt.h>
#include <linux/netpoll.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/types.h>
#include <linux/workqueue.h>
#include <linux/netlink.h>
#include <linux/net_dropmon.h>
#include <linux/percpu.h>
#include <linux/timer.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <net/genetlink.h>
#include <net/netevent.h>

#include <trace/events/skb.h>
#include <trace/events/napi.h>

#include <asm/unaligned.h>

#define TRACE_ON 1

#define TRACE_OFF 0

 * Globals, our netlink socket pointer
 * and the work handle that will send up
 * netlink alerts

static int trace_state = TRACE_OFF;
static DEFINE_MUTEX(trace_state_mutex);

struct per_cpu_dm_data {
spinlock_t		lock;
struct sk_buff		*skb;
struct work_struct	dm_alert_work;
struct timer_list	send_timer;

struct dm_hw_stat_delta {
struct net_device *dev;
unsigned long last_rx;
struct list_head list;
struct rcu_head rcu;
unsigned long last_drop_val;

static struct genl_family net_drop_monitor_family = {
	.id             = GENL_ID_GENERATE,
	.hdrsize        = 0,
	.name           = "NET_DM",
	.version        = 2,

static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);

static int dm_hit_limit = 64;

static int dm_delay = 1;

static unsigned long dm_hw_check_delta = 2*HZ;
static LIST_HEAD(hw_stats_list);

static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data) { size_t al; struct net_dm_alert_msg *msg; struct nlattr *nla; struct sk_buff *skb; unsigned long flags; al = sizeof(struct net_dm_alert_msg); al += dm_hit_limit * sizeof(struct net_dm_drop_point); al += sizeof(struct nlattr); skb = genlmsg_new(al, GFP_KERNEL); if (skb) { genlmsg_put(skb, 0, 0, &net_drop_monitor_family, 0, NET_DM_CMD_ALERT); nla = nla_reserve(skb, NLA_UNSPEC, sizeof(struct net_dm_alert_msg)); msg = nla_data(nla); memset(msg, 0, al); } else { mod_timer(&data->send_timer, jiffies + HZ / 10); } spin_lock_irqsave(&data->lock, flags); swap(data->skb, skb); spin_unlock_irqrestore(&data->lock, flags); return skb; }


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static struct genl_multicast_group dropmon_mcgrps[] = { { .name = "events", }, };
static void send_dm_alert(struct work_struct *work) { struct sk_buff *skb; struct per_cpu_dm_data *data; data = container_of(work, struct per_cpu_dm_data, dm_alert_work); skb = reset_per_cpu_data(data); if (skb) genlmsg_multicast(&net_drop_monitor_family, skb, 0, 0, GFP_KERNEL); }


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/* * This is the timer function to delay the sending of an alert * in the event that more drops will arrive during the * hysteresis period. */
static void sched_send_work(unsigned long _data) { struct per_cpu_dm_data *data = (struct per_cpu_dm_data *)_data; schedule_work(&data->dm_alert_work); }


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static void trace_drop_common(struct sk_buff *skb, void *location) { struct net_dm_alert_msg *msg; struct nlmsghdr *nlh; struct nlattr *nla; int i; struct sk_buff *dskb; struct per_cpu_dm_data *data; unsigned long flags; local_irq_save(flags); data = this_cpu_ptr(&dm_cpu_data); spin_lock(&data->lock); dskb = data->skb; if (!dskb) goto out; nlh = (struct nlmsghdr *)dskb->data; nla = genlmsg_data(nlmsg_data(nlh)); msg = nla_data(nla); for (i = 0; i < msg->entries; i++) { if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) { msg->points[i].count++; goto out; } } if (msg->entries == dm_hit_limit) goto out; /* * We need to create a new entry */ __nla_reserve_nohdr(dskb, sizeof(struct net_dm_drop_point)); nla->nla_len += NLA_ALIGN(sizeof(struct net_dm_drop_point)); memcpy(msg->points[msg->entries].pc, &location, sizeof(void *)); msg->points[msg->entries].count = 1; msg->entries++; if (!timer_pending(&data->send_timer)) { data->send_timer.expires = jiffies + dm_delay * HZ; add_timer(&data->send_timer); } out: spin_unlock_irqrestore(&data->lock, flags); }


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static void trace_kfree_skb_hit(void *ignore, struct sk_buff *skb, void *location) { trace_drop_common(skb, location); }


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static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi, int work, int budget) { struct dm_hw_stat_delta *new_stat; /* * Don't check napi structures with no associated device */ if (!napi->dev) return; rcu_read_lock(); list_for_each_entry_rcu(new_stat, &hw_stats_list, list) { /* * only add a note to our monitor buffer if: * 1) this is the dev we received on * 2) its after the last_rx delta * 3) our rx_dropped count has gone up */ if ((new_stat->dev == napi->dev) && (time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) && (napi->dev->stats.rx_dropped != new_stat->last_drop_val)) { trace_drop_common(NULL, NULL); new_stat->last_drop_val = napi->dev->stats.rx_dropped; new_stat->last_rx = jiffies; break; } } rcu_read_unlock(); }


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static int set_all_monitor_traces(int state) { int rc = 0; struct dm_hw_stat_delta *new_stat = NULL; struct dm_hw_stat_delta *temp; mutex_lock(&trace_state_mutex); if (state == trace_state) { rc = -EAGAIN; goto out_unlock; } switch (state) { case TRACE_ON: if (!try_module_get(THIS_MODULE)) { rc = -ENODEV; break; } rc |= register_trace_kfree_skb(trace_kfree_skb_hit, NULL); rc |= register_trace_napi_poll(trace_napi_poll_hit, NULL); break; case TRACE_OFF: rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL); rc |= unregister_trace_napi_poll(trace_napi_poll_hit, NULL); tracepoint_synchronize_unregister(); /* * Clean the device list */ list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) { if (new_stat->dev == NULL) { list_del_rcu(&new_stat->list); kfree_rcu(new_stat, rcu); } } module_put(THIS_MODULE); break; default: rc = 1; break; } if (!rc) trace_state = state; else rc = -EINPROGRESS; out_unlock: mutex_unlock(&trace_state_mutex); return rc; }


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static int net_dm_cmd_config(struct sk_buff *skb, struct genl_info *info) { return -ENOTSUPP; }


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static int net_dm_cmd_trace(struct sk_buff *skb, struct genl_info *info) { switch (info->genlhdr->cmd) { case NET_DM_CMD_START: return set_all_monitor_traces(TRACE_ON); case NET_DM_CMD_STOP: return set_all_monitor_traces(TRACE_OFF); } return -ENOTSUPP; }


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static int dropmon_net_event(struct notifier_block *ev_block, unsigned long event, void *ptr) { struct net_device *dev = netdev_notifier_info_to_dev(ptr); struct dm_hw_stat_delta *new_stat = NULL; struct dm_hw_stat_delta *tmp; switch (event) { case NETDEV_REGISTER: new_stat = kzalloc(sizeof(struct dm_hw_stat_delta), GFP_KERNEL); if (!new_stat) goto out; new_stat->dev = dev; new_stat->last_rx = jiffies; mutex_lock(&trace_state_mutex); list_add_rcu(&new_stat->list, &hw_stats_list); mutex_unlock(&trace_state_mutex); break; case NETDEV_UNREGISTER: mutex_lock(&trace_state_mutex); list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) { if (new_stat->dev == dev) { new_stat->dev = NULL; if (trace_state == TRACE_OFF) { list_del_rcu(&new_stat->list); kfree_rcu(new_stat, rcu); break; } } } mutex_unlock(&trace_state_mutex); break; } out: return NOTIFY_DONE; }


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static const struct genl_ops dropmon_ops[] = { { .cmd = NET_DM_CMD_CONFIG, .doit = net_dm_cmd_config, }, { .cmd = NET_DM_CMD_START, .doit = net_dm_cmd_trace, }, { .cmd = NET_DM_CMD_STOP, .doit = net_dm_cmd_trace, }, }; static struct notifier_block dropmon_net_notifier = { .notifier_call = dropmon_net_event };
static int __init init_net_drop_monitor(void) { struct per_cpu_dm_data *data; int cpu, rc; pr_info("Initializing network drop monitor service\n"); if (sizeof(void *) > 8) { pr_err("Unable to store program counters on this arch, Drop monitor failed\n"); return -ENOSPC; } rc = genl_register_family_with_ops_groups(&net_drop_monitor_family, dropmon_ops, dropmon_mcgrps); if (rc) { pr_err("Could not create drop monitor netlink family\n"); return rc; } WARN_ON(net_drop_monitor_family.mcgrp_offset != NET_DM_GRP_ALERT); rc = register_netdevice_notifier(&dropmon_net_notifier); if (rc < 0) { pr_crit("Failed to register netdevice notifier\n"); goto out_unreg; } rc = 0; for_each_possible_cpu(cpu) { data = &per_cpu(dm_cpu_data, cpu); INIT_WORK(&data->dm_alert_work, send_dm_alert); init_timer(&data->send_timer); data-> = (unsigned long)data; data->send_timer.function = sched_send_work; spin_lock_init(&data->lock); reset_per_cpu_data(data); } goto out; out_unreg: genl_unregister_family(&net_drop_monitor_family); out: return rc; }


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static void exit_net_drop_monitor(void) { struct per_cpu_dm_data *data; int cpu; BUG_ON(unregister_netdevice_notifier(&dropmon_net_notifier)); /* * Because of the module_get/put we do in the trace state change path * we are guarnateed not to have any current users when we get here * all we need to do is make sure that we don't have any running timers * or pending schedule calls */ for_each_possible_cpu(cpu) { data = &per_cpu(dm_cpu_data, cpu); del_timer_sync(&data->send_timer); cancel_work_sync(&data->dm_alert_work); /* * At this point, we should have exclusive access * to this struct and can free the skb inside it */ kfree_skb(data->skb); } BUG_ON(genl_unregister_family(&net_drop_monitor_family)); }


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module_init(init_net_drop_monitor); module_exit(exit_net_drop_monitor); MODULE_LICENSE("GPL v2"); MODULE_AUTHOR("Neil Horman <>"); MODULE_ALIAS_GENL_FAMILY("NET_DM");

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Directory: net/core
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