From: Ido Schimmel <idosch@mellanox.com>
Date: Fri, 29 May 2020 21:36:40 +0300
Subject: devlink: Add 'control' trap type
Patch-mainline: v5.8-rc1
Git-commit: 30a4e9a29ab9aadfe6c5386ae4aa396b1d2556c2
References: bsc#1176774

This type is used for traps that trap control packets such as ARP
request and IGMP query to the CPU.

Do not report such packets to the kernel's drop monitor as they were not
dropped by the device no encountered an exception during forwarding.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 Documentation/networking/devlink/devlink-trap.rst |    8 +++++++-
 include/uapi/linux/devlink.h                      |    6 ++++++
 net/core/devlink.c                                |    7 +++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

--- a/Documentation/networking/devlink/devlink-trap.rst
+++ b/Documentation/networking/devlink/devlink-trap.rst
@@ -55,7 +55,7 @@ The following diagram provides a general
                           |                |
                           +-------^--------+
                                   |
-                                  |
+                                  | Non-control traps
                                   |
                              +----+----+
                              |         |      Kernel's Rx path
@@ -97,6 +97,12 @@ The ``devlink-trap`` mechanism supports
     processed by ``devlink`` and injected to the kernel's Rx path. Changing the
     action of such traps is not allowed, as it can easily break the control
     plane.
+  * ``control``: Trapped packets were trapped by the device because these are
+    control packets required for the correct functioning of the control plane.
+    For example, ARP request and IGMP query packets. Packets are injected to
+    the kernel's Rx path, but not reported to the kernel's drop monitor.
+    Changing the action of such traps is not allowed, as it can easily break
+    the control plane.
 
 .. _Trap-Actions:
 
--- a/include/uapi/linux/devlink.h
+++ b/include/uapi/linux/devlink.h
@@ -250,10 +250,16 @@ enum devlink_trap_action {
  *                               control plane for resolution. Trapped packets
  *                               are processed by devlink and injected to
  *                               the kernel's Rx path.
+ * @DEVLINK_TRAP_TYPE_CONTROL: Packet was trapped because it is required for
+ *                             the correct functioning of the control plane.
+ *                             For example, an ARP request packet. Trapped
+ *                             packets are injected to the kernel's Rx path,
+ *                             but not reported to drop monitor.
  */
 enum devlink_trap_type {
 	DEVLINK_TRAP_TYPE_DROP,
 	DEVLINK_TRAP_TYPE_EXCEPTION,
+	DEVLINK_TRAP_TYPE_CONTROL,
 };
 
 enum {
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -8795,6 +8795,13 @@ void devlink_trap_report(struct devlink
 	devlink_trap_stats_update(trap_item->stats, skb->len);
 	devlink_trap_stats_update(trap_item->group_item->stats, skb->len);
 
+	/* Control packets were not dropped by the device or encountered an
+	 * exception during forwarding and therefore should not be reported to
+	 * the kernel's drop monitor.
+	 */
+	if (trap_item->trap->type == DEVLINK_TRAP_TYPE_CONTROL)
+		return;
+
 	devlink_trap_report_metadata_fill(&hw_metadata, trap_item,
 					  in_devlink_port, fa_cookie);
 	net_dm_hw_report(skb, &hw_metadata);