drop_monitor: Expose tail drop counter

Previous patch made the length of the per-CPU skb drop list
configurable. Expose a counter that shows how many packets could not be
enqueued to this list.

This allows users determine the desired queue length.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/net_dropmon.h b/include/uapi/linux/net_dropmon.h
index 1d0bdb1..405b31c 100644 (file)
--- a/include/uapi/linux/net_dropmon.h
+++ b/include/uapi/linux/net_dropmon.h
@@ -56,6 +56,8 @@ enum {
        NET_DM_CMD_PACKET_ALERT,
        NET_DM_CMD_CONFIG_GET,
        NET_DM_CMD_CONFIG_NEW,
+       NET_DM_CMD_STATS_GET,
+       NET_DM_CMD_STATS_NEW,
        _NET_DM_CMD_MAX,
 };
 
@@ -80,6 +82,7 @@ enum net_dm_attr {
        NET_DM_ATTR_TRUNC_LEN,                  /* u32 */
        NET_DM_ATTR_ORIG_LEN,                   /* u32 */
        NET_DM_ATTR_QUEUE_LEN,                  /* u32 */
+       NET_DM_ATTR_STATS,                      /* nested */
 
        __NET_DM_ATTR_MAX,
        NET_DM_ATTR_MAX = __NET_DM_ATTR_MAX - 1
@@ -103,4 +106,11 @@ enum {
        NET_DM_ATTR_PORT_MAX = __NET_DM_ATTR_PORT_MAX - 1
 };
 
+enum {
+       NET_DM_ATTR_STATS_DROPPED,              /* u64 */
+
+       __NET_DM_ATTR_STATS_MAX,
+       NET_DM_ATTR_STATS_MAX = __NET_DM_ATTR_STATS_MAX - 1
+};
+
 #endif

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index eb3c34d..39e0949 100644 (file)
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -51,12 +51,18 @@ static int trace_state = TRACE_OFF;
  */
 static DEFINE_MUTEX(net_dm_mutex);
 
+struct net_dm_stats {
+       u64 dropped;
+       struct u64_stats_sync syncp;
+};
+
 struct per_cpu_dm_data {
        spinlock_t              lock;   /* Protects 'skb' and 'send_timer' */
        struct sk_buff          *skb;
        struct sk_buff_head     drop_queue;
        struct work_struct      dm_alert_work;
        struct timer_list       send_timer;
+       struct net_dm_stats     stats;
 };
 
 struct dm_hw_stat_delta {
@@ -300,6 +306,9 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
 
 unlock_free:
        spin_unlock_irqrestore(&data->drop_queue.lock, flags);
+       u64_stats_update_begin(&data->stats.syncp);
+       data->stats.dropped++;
+       u64_stats_update_end(&data->stats.syncp);
        consume_skb(nskb);
 }
 
@@ -732,6 +741,93 @@ free_msg:
        return rc;
 }
 
+static void net_dm_stats_read(struct net_dm_stats *stats)
+{
+       int cpu;
+
+       memset(stats, 0, sizeof(*stats));
+       for_each_possible_cpu(cpu) {
+               struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
+               struct net_dm_stats *cpu_stats = &data->stats;
+               unsigned int start;
+               u64 dropped;
+
+               do {
+                       start = u64_stats_fetch_begin_irq(&cpu_stats->syncp);
+                       dropped = cpu_stats->dropped;
+               } while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, start));
+
+               stats->dropped += dropped;
+       }
+}
+
+static int net_dm_stats_put(struct sk_buff *msg)
+{
+       struct net_dm_stats stats;
+       struct nlattr *attr;
+
+       net_dm_stats_read(&stats);
+
+       attr = nla_nest_start(msg, NET_DM_ATTR_STATS);
+       if (!attr)
+               return -EMSGSIZE;
+
+       if (nla_put_u64_64bit(msg, NET_DM_ATTR_STATS_DROPPED,
+                             stats.dropped, NET_DM_ATTR_PAD))
+               goto nla_put_failure;
+
+       nla_nest_end(msg, attr);
+
+       return 0;
+
+nla_put_failure:
+       nla_nest_cancel(msg, attr);
+       return -EMSGSIZE;
+}
+
+static int net_dm_stats_fill(struct sk_buff *msg, struct genl_info *info)
+{
+       void *hdr;
+       int rc;
+
+       hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
+                         &net_drop_monitor_family, 0, NET_DM_CMD_STATS_NEW);
+       if (!hdr)
+               return -EMSGSIZE;
+
+       rc = net_dm_stats_put(msg);
+       if (rc)
+               goto nla_put_failure;
+
+       genlmsg_end(msg, hdr);
+
+       return 0;
+
+nla_put_failure:
+       genlmsg_cancel(msg, hdr);
+       return -EMSGSIZE;
+}
+
+static int net_dm_cmd_stats_get(struct sk_buff *skb, struct genl_info *info)
+{
+       struct sk_buff *msg;
+       int rc;
+
+       msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+       if (!msg)
+               return -ENOMEM;
+
+       rc = net_dm_stats_fill(msg, info);
+       if (rc)
+               goto free_msg;
+
+       return genlmsg_reply(msg, info);
+
+free_msg:
+       nlmsg_free(msg);
+       return rc;
+}
+
 static int dropmon_net_event(struct notifier_block *ev_block,
                             unsigned long event, void *ptr)
 {
@@ -799,6 +895,10 @@ static const struct genl_ops dropmon_ops[] = {
                .cmd = NET_DM_CMD_CONFIG_GET,
                .doit = net_dm_cmd_config_get,
        },
+       {
+               .cmd = NET_DM_CMD_STATS_GET,
+               .doit = net_dm_cmd_stats_get,
+       },
 };
 
 static int net_dm_nl_pre_doit(const struct genl_ops *ops,
@@ -865,6 +965,7 @@ static int __init init_net_drop_monitor(void)
                data = &per_cpu(dm_cpu_data, cpu);
                spin_lock_init(&data->lock);
                skb_queue_head_init(&data->drop_queue);
+               u64_stats_init(&data->stats.syncp);
        }
 
        goto out;