devlink: Add layer 3 generic packet exception traps

Add layer 3 generic packet exception traps that can report trapped
packets and documentation of the traps.

Unlike drop traps, these exception traps also need to inject the packet
to the kernel's receive path. For example, a packet that was trapped due
to unreachable neighbour need to be injected into the kernel so that it
will trigger an ARP request or a neighbour solicitation message.

Signed-off-by: Amit Cohen <amitc@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/devlink-trap.rst

@@ -203,6 +203,26 @@ be added to the following table:
      - Traps IPv6 packets that the device decided to drop because they need to
        be routed and their IPv6 multicast destination IP has an interface-local scope
        (i.e., ffx1::/16)
+   * - ``mtu_value_is_too_small``
+     - ``exception``
+     - Traps packets that should have been routed by the device, but were bigger
+       than the MTU of the egress interface
+   * - ``unresolved_neigh``
+     - ``exception``
+     - Traps packets that did not have a matching IP neighbour after routing
+   * - ``mc_reverse_path_forwarding``
+     - ``exception``
+     - Traps multicast IP packets that failed reverse-path forwarding (RPF)
+       check during multicast routing
+   * - ``reject_route``
+     - ``exception``
+     - Traps packets that hit reject routes (i.e., "unreachable", "prohibit")
+   * - ``ipv4_lpm_miss``
+     - ``exception``
+     - Traps unicast IPv4 packets that did not match any route
+   * - ``ipv6_lpm_miss``
+     - ``exception``
+     - Traps unicast IPv6 packets that did not match any route
 
 Driver-specific Packet Traps
 ============================

include/net/devlink.h

@@ -578,6 +578,12 @@ enum devlink_trap_generic_id {
 	DEVLINK_TRAP_GENERIC_ID_IPV4_SIP_BC,
 	DEVLINK_TRAP_GENERIC_ID_IPV6_MC_DIP_RESERVED_SCOPE,
 	DEVLINK_TRAP_GENERIC_ID_IPV6_MC_DIP_INTERFACE_LOCAL_SCOPE,
+	DEVLINK_TRAP_GENERIC_ID_MTU_ERROR,
+	DEVLINK_TRAP_GENERIC_ID_UNRESOLVED_NEIGH,
+	DEVLINK_TRAP_GENERIC_ID_RPF,
+	DEVLINK_TRAP_GENERIC_ID_REJECT_ROUTE,
+	DEVLINK_TRAP_GENERIC_ID_IPV4_LPM_UNICAST_MISS,
+	DEVLINK_TRAP_GENERIC_ID_IPV6_LPM_UNICAST_MISS,
 
 	/* Add new generic trap IDs above */
 	__DEVLINK_TRAP_GENERIC_ID_MAX,
@@ -634,6 +640,18 @@ enum devlink_trap_group_generic_id {
 	"ipv6_mc_dip_reserved_scope"
 #define DEVLINK_TRAP_GENERIC_NAME_IPV6_MC_DIP_INTERFACE_LOCAL_SCOPE \
 	"ipv6_mc_dip_interface_local_scope"
+#define DEVLINK_TRAP_GENERIC_NAME_MTU_ERROR \
+	"mtu_value_is_too_small"
+#define DEVLINK_TRAP_GENERIC_NAME_UNRESOLVED_NEIGH \
+	"unresolved_neigh"
+#define DEVLINK_TRAP_GENERIC_NAME_RPF \
+	"mc_reverse_path_forwarding"
+#define DEVLINK_TRAP_GENERIC_NAME_REJECT_ROUTE \
+	"reject_route"
+#define DEVLINK_TRAP_GENERIC_NAME_IPV4_LPM_UNICAST_MISS \
+	"ipv4_lpm_miss"
+#define DEVLINK_TRAP_GENERIC_NAME_IPV6_LPM_UNICAST_MISS \
+	"ipv6_lpm_miss"
 
 #define DEVLINK_TRAP_GROUP_GENERIC_NAME_L2_DROPS \
 	"l2_drops"

net/core/devlink.c

@@ -7611,6 +7611,12 @@ static const struct devlink_trap devlink_trap_generic[] = {
 	DEVLINK_TRAP(IPV4_SIP_BC, DROP),
 	DEVLINK_TRAP(IPV6_MC_DIP_RESERVED_SCOPE, DROP),
 	DEVLINK_TRAP(IPV6_MC_DIP_INTERFACE_LOCAL_SCOPE, DROP),
+	DEVLINK_TRAP(MTU_ERROR, EXCEPTION),
+	DEVLINK_TRAP(UNRESOLVED_NEIGH, EXCEPTION),
+	DEVLINK_TRAP(RPF, EXCEPTION),
+	DEVLINK_TRAP(REJECT_ROUTE, EXCEPTION),
+	DEVLINK_TRAP(IPV4_LPM_UNICAST_MISS, EXCEPTION),
+	DEVLINK_TRAP(IPV6_LPM_UNICAST_MISS, EXCEPTION),
 };
 
 #define DEVLINK_TRAP_GROUP(_id)						      \