drop_monitor: Add packet alert mode

So far drop monitor supported only one alert mode in which a summary of
locations in which packets were recently dropped was sent to user space.

This alert mode is sufficient in order to understand that packets were
dropped, but lacks information to perform a more detailed analysis.

Add a new alert mode in which the dropped packet itself is passed to
user space along with metadata: The drop location (as program counter
and resolved symbol), ingress netdevice and drop timestamp. More
metadata can be added in the future.

To avoid performing expensive operations in the context in which
kfree_skb() is invoked (can be hard IRQ), the dropped skb is cloned and
queued on per-CPU skb drop list. Then, in process context the netlink
message is allocated, prepared and finally sent to user space.

The per-CPU skb drop list is limited to 1000 skbs to prevent exhausting
the system's memory. Subsequent patches will make this limit
configurable and also add a counter that indicates how many skbs were
tail dropped.

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

1 files changed, 27 insertions, 0 deletions

diff --git a/include/uapi/linux/net_dropmon.h b/include/uapi/linux/net_dropmon.h
index 0fecdedeb6ca..cfaaf75371b8 100644
--- a/include/uapi/linux/net_dropmon.h
+++ b/include/uapi/linux/net_dropmon.h
@@ -53,6 +53,7 @@ enum {
 	NET_DM_CMD_CONFIG,
 	NET_DM_CMD_START,
 	NET_DM_CMD_STOP,
+	NET_DM_CMD_PACKET_ALERT,
 	_NET_DM_CMD_MAX,
 };
 
@@ -63,12 +64,38 @@ enum {
  */
 #define NET_DM_GRP_ALERT 1
 
+enum net_dm_attr {
+	NET_DM_ATTR_UNSPEC,
+
+	NET_DM_ATTR_ALERT_MODE,			/* u8 */
+	NET_DM_ATTR_PC,				/* u64 */
+	NET_DM_ATTR_SYMBOL,			/* string */
+	NET_DM_ATTR_IN_PORT,			/* nested */
+	NET_DM_ATTR_TIMESTAMP,			/* struct timespec */
+	NET_DM_ATTR_PROTO,			/* u16 */
+	NET_DM_ATTR_PAYLOAD,			/* binary */
+	NET_DM_ATTR_PAD,
+
+	__NET_DM_ATTR_MAX,
+	NET_DM_ATTR_MAX = __NET_DM_ATTR_MAX - 1
+};
+
 /**
  * enum net_dm_alert_mode - Alert mode.
  * @NET_DM_ALERT_MODE_SUMMARY: A summary of recent drops is sent to user space.
+ * @NET_DM_ALERT_MODE_PACKET: Each dropped packet is sent to user space along
+ *                            with metadata.
  */
 enum net_dm_alert_mode {
 	NET_DM_ALERT_MODE_SUMMARY,
+	NET_DM_ALERT_MODE_PACKET,
+};
+
+enum {
+	NET_DM_ATTR_PORT_NETDEV_IFINDEX,	/* u32 */
+
+	__NET_DM_ATTR_PORT_MAX,
+	NET_DM_ATTR_PORT_MAX = __NET_DM_ATTR_PORT_MAX - 1
 };
 
 #endif