Network Drop Monitor: Adding drop monitor implementation & Netlink protocol

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

 include/linux/net_dropmon.h |   56 +++++++++
 net/core/drop_monitor.c     |  263 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 319 insertions(+)
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 263 insertions, 0 deletions

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
new file mode 100644
index 000000000000..9fd0dc3cca99
--- /dev/null
+++ b/net/core/drop_monitor.c
@@ -0,0 +1,263 @@
+/*
+ * Monitoring code for network dropped packet alerts
+ *
+ * Copyright (C) 2009 Neil Horman <nhorman@tuxdriver.com>
+ */
+
+#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 <net/genetlink.h>
+
+#include <trace/skb.h>
+
+#include <asm/unaligned.h>
+
+#define TRACE_ON 1
+#define TRACE_OFF 0
+
+static void send_dm_alert(struct work_struct *unused);
+
+
+/*
+ * Globals, our netlink socket pointer
+ * and the work handle that will send up
+ * netlink alerts
+ */
+struct sock *dm_sock;
+
+struct per_cpu_dm_data {
+        struct work_struct dm_alert_work;
+        struct sk_buff *skb;
+        atomic_t dm_hit_count;
+        struct timer_list send_timer;
+};
+
+static struct genl_family net_drop_monitor_family = {
+        .id             = GENL_ID_GENERATE,
+        .hdrsize        = 0,
+        .name           = "NET_DM",
+        .version        = 1,
+        .maxattr        = NET_DM_CMD_MAX,
+};
+
+static DEFINE_PER_CPU(struct per_cpu_dm_data, dm_cpu_data);
+
+static int dm_hit_limit = 64;
+static int dm_delay = 1;
+
+
+static void reset_per_cpu_data(struct per_cpu_dm_data *data)
+{
+        size_t al;
+        struct net_dm_alert_msg *msg;
+
+        al = sizeof(struct net_dm_alert_msg);
+        al += dm_hit_limit * sizeof(struct net_dm_drop_point);
+        data->skb = genlmsg_new(al, GFP_KERNEL);
+        genlmsg_put(data->skb, 0, 0, &net_drop_monitor_family,
+                        0, NET_DM_CMD_ALERT);
+        msg = __nla_reserve_nohdr(data->skb, sizeof(struct net_dm_alert_msg));
+        memset(msg, 0, al);
+        atomic_set(&data->dm_hit_count, dm_hit_limit);
+}
+
+static void send_dm_alert(struct work_struct *unused)
+{
+        struct sk_buff *skb;
+        struct per_cpu_dm_data *data = &__get_cpu_var(dm_cpu_data);
+
+        /*
+         * Grab the skb we're about to send
+         */
+        skb = data->skb;
+
+        /*
+         * Replace it with a new one
+         */
+        reset_per_cpu_data(data);
+
+        /*
+         * Ship it!
+         */
+        genlmsg_multicast(skb, 0, NET_DM_GRP_ALERT, GFP_KERNEL);
+
+}
+
+/*
+ * This is the timer function to delay the sending of an alert
+ * in the event that more drops will arrive during the
+ * hysteresis period.  Note that it operates under the timer interrupt
+ * so we don't need to disable preemption here
+ */
+static void sched_send_work(unsigned long unused)
+{
+        struct per_cpu_dm_data *data =  &__get_cpu_var(dm_cpu_data);
+
+        schedule_work(&data->dm_alert_work);
+}
+
+static void trace_kfree_skb_hit(struct sk_buff *skb, void *location)
+{
+        struct net_dm_alert_msg *msg;
+        struct nlmsghdr *nlh;
+        int i;
+        struct per_cpu_dm_data *data = &__get_cpu_var(dm_cpu_data);
+
+
+        if (!atomic_add_unless(&data->dm_hit_count, -1, 0)) {
+                /*
+                 * we're already at zero, discard this hit
+                 */
+                goto out;
+        }
+
+        nlh = (struct nlmsghdr *)data->skb->data;
+        msg = genlmsg_data(nlmsg_data(nlh));
+        for (i = 0; i < msg->entries; i++) {
+                if (!memcmp(&location, msg->points[i].pc, sizeof(void *))) {
+                        msg->points[i].count++;
+                        goto out;
+                }
+        }
+
+        /*
+         * We need to create a new entry
+         */
+        __nla_reserve_nohdr(data->skb, 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_on(&data->send_timer, smp_processor_id());
+        }
+
+out:
+        return;
+}
+
+static int set_all_monitor_traces(int state)
+{
+        int rc = 0;
+
+        switch (state) {
+        case TRACE_ON:
+                rc |= register_trace_kfree_skb(trace_kfree_skb_hit);
+                break;
+        case TRACE_OFF:
+                rc |= unregister_trace_kfree_skb(trace_kfree_skb_hit);
+
+                tracepoint_synchronize_unregister();
+                break;
+        default:
+                rc = 1;
+                break;
+        }
+
+        if (rc)
+                return -EINPROGRESS;
+        return rc;
+}
+
+
+static int net_dm_cmd_config(struct sk_buff *skb,
+                        struct genl_info *info)
+{
+        return -ENOTSUPP;
+}
+
+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);
+                break;
+        case NET_DM_CMD_STOP:
+                return set_all_monitor_traces(TRACE_OFF);
+                break;
+        }
+
+        return -ENOTSUPP;
+}
+
+
+static 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 int __init init_net_drop_monitor(void)
+{
+        int cpu;
+        int rc, i, ret;
+        struct per_cpu_dm_data *data;
+        printk(KERN_INFO "Initalizing network drop monitor service\n");
+
+        if (sizeof(void *) > 8) {
+                printk(KERN_ERR "Unable to store program counters on this arch, Drop monitor failed\n");
+                return -ENOSPC;
+        }
+
+        if (genl_register_family(&net_drop_monitor_family) < 0) {
+                printk(KERN_ERR "Could not create drop monitor netlink family\n");
+                return -EFAULT;
+        }
+
+        rc = -EFAULT;
+
+        for (i = 0; i < ARRAY_SIZE(dropmon_ops); i++) {
+                ret = genl_register_ops(&net_drop_monitor_family,
+                                        &dropmon_ops[i]);
+                if (ret) {
+                        printk(KERN_CRIT "failed to register operation %d\n",
+                                dropmon_ops[i].cmd);
+                        goto out_unreg;
+                }
+        }
+
+        rc = 0;
+
+        for_each_present_cpu(cpu) {
+                data = &per_cpu(dm_cpu_data, cpu);
+                reset_per_cpu_data(data);
+                INIT_WORK(&data->dm_alert_work, send_dm_alert);
+                init_timer(&data->send_timer);
+                data->send_timer.data = cpu;
+                data->send_timer.function = sched_send_work;
+        }
+        goto out;
+
+out_unreg:
+        genl_unregister_family(&net_drop_monitor_family);
+out:
+        return rc;
+}
+
+late_initcall(init_net_drop_monitor);