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diff --git a/Documentation/networking/devlink-trap.rst b/Documentation/networking/devlink-trap.rst deleted file mode 100644 index 03311849bfb1..000000000000 --- a/Documentation/networking/devlink-trap.rst +++ /dev/null @@ -1,270 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -============ -Devlink Trap -============ - -Background -========== - -Devices capable of offloading the kernel's datapath and perform functions such -as bridging and routing must also be able to send specific packets to the -kernel (i.e., the CPU) for processing. - -For example, a device acting as a multicast-aware bridge must be able to send -IGMP membership reports to the kernel for processing by the bridge module. -Without processing such packets, the bridge module could never populate its -MDB. - -As another example, consider a device acting as router which has received an IP -packet with a TTL of 1. Upon routing the packet the device must send it to the -kernel so that it will route it as well and generate an ICMP Time Exceeded -error datagram. Without letting the kernel route such packets itself, utilities -such as ``traceroute`` could never work. - -The fundamental ability of sending certain packets to the kernel for processing -is called "packet trapping". - -Overview -======== - -The ``devlink-trap`` mechanism allows capable device drivers to register their -supported packet traps with ``devlink`` and report trapped packets to -``devlink`` for further analysis. - -Upon receiving trapped packets, ``devlink`` will perform a per-trap packets and -bytes accounting and potentially report the packet to user space via a netlink -event along with all the provided metadata (e.g., trap reason, timestamp, input -port). This is especially useful for drop traps (see :ref:`Trap-Types`) -as it allows users to obtain further visibility into packet drops that would -otherwise be invisible. - -The following diagram provides a general overview of ``devlink-trap``:: - - Netlink event: Packet w/ metadata - Or a summary of recent drops - ^ - | - Userspace | - +---------------------------------------------------+ - Kernel | - | - +-------+--------+ - | | - | drop_monitor | - | | - +-------^--------+ - | - | - | - +----+----+ - | | Kernel's Rx path - | devlink | (non-drop traps) - | | - +----^----+ ^ - | | - +-----------+ - | - +-------+-------+ - | | - | Device driver | - | | - +-------^-------+ - Kernel | - +---------------------------------------------------+ - Hardware | - | Trapped packet - | - +--+---+ - | | - | ASIC | - | | - +------+ - -.. _Trap-Types: - -Trap Types -========== - -The ``devlink-trap`` mechanism supports the following packet trap types: - - * ``drop``: Trapped packets were dropped by the underlying device. Packets - are only processed by ``devlink`` and not injected to the kernel's Rx path. - The trap action (see :ref:`Trap-Actions`) can be changed. - * ``exception``: Trapped packets were not forwarded as intended by the - underlying device due to an exception (e.g., TTL error, missing neighbour - entry) and trapped to the control plane for resolution. Packets are - 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. - -.. _Trap-Actions: - -Trap Actions -============ - -The ``devlink-trap`` mechanism supports the following packet trap actions: - - * ``trap``: The sole copy of the packet is sent to the CPU. - * ``drop``: The packet is dropped by the underlying device and a copy is not - sent to the CPU. - -Generic Packet Traps -==================== - -Generic packet traps are used to describe traps that trap well-defined packets -or packets that are trapped due to well-defined conditions (e.g., TTL error). -Such traps can be shared by multiple device drivers and their description must -be added to the following table: - -.. list-table:: List of Generic Packet Traps - :widths: 5 5 90 - - * - Name - - Type - - Description - * - ``source_mac_is_multicast`` - - ``drop`` - - Traps incoming packets that the device decided to drop because of a - multicast source MAC - * - ``vlan_tag_mismatch`` - - ``drop`` - - Traps incoming packets that the device decided to drop in case of VLAN - tag mismatch: The ingress bridge port is not configured with a PVID and - the packet is untagged or prio-tagged - * - ``ingress_vlan_filter`` - - ``drop`` - - Traps incoming packets that the device decided to drop in case they are - tagged with a VLAN that is not configured on the ingress bridge port - * - ``ingress_spanning_tree_filter`` - - ``drop`` - - Traps incoming packets that the device decided to drop in case the STP - state of the ingress bridge port is not "forwarding" - * - ``port_list_is_empty`` - - ``drop`` - - Traps packets that the device decided to drop in case they need to be - flooded (e.g., unknown unicast, unregistered multicast) and there are - no ports the packets should be flooded to - * - ``port_loopback_filter`` - - ``drop`` - - Traps packets that the device decided to drop in case after layer 2 - forwarding the only port from which they should be transmitted through - is the port from which they were received - * - ``blackhole_route`` - - ``drop`` - - Traps packets that the device decided to drop in case they hit a - blackhole route - * - ``ttl_value_is_too_small`` - - ``exception`` - - Traps unicast packets that should be forwarded by the device whose TTL - was decremented to 0 or less - * - ``tail_drop`` - - ``drop`` - - Traps packets that the device decided to drop because they could not be - enqueued to a transmission queue which is full - * - ``non_ip`` - - ``drop`` - - Traps packets that the device decided to drop because they need to - undergo a layer 3 lookup, but are not IP or MPLS packets - * - ``uc_dip_over_mc_dmac`` - - ``drop`` - - Traps packets that the device decided to drop because they need to be - routed and they have a unicast destination IP and a multicast destination - MAC - * - ``dip_is_loopback_address`` - - ``drop`` - - Traps packets that the device decided to drop because they need to be - routed and their destination IP is the loopback address (i.e., 127.0.0.0/8 - and ::1/128) - * - ``sip_is_mc`` - - ``drop`` - - Traps packets that the device decided to drop because they need to be - routed and their source IP is multicast (i.e., 224.0.0.0/8 and ff::/8) - * - ``sip_is_loopback_address`` - - ``drop`` - - Traps packets that the device decided to drop because they need to be - routed and their source IP is the loopback address (i.e., 127.0.0.0/8 and ::1/128) - * - ``ip_header_corrupted`` - - ``drop`` - - Traps packets that the device decided to drop because they need to be - routed and their IP header is corrupted: wrong checksum, wrong IP version - or too short Internet Header Length (IHL) - * - ``ipv4_sip_is_limited_bc`` - - ``drop`` - - Traps packets that the device decided to drop because they need to be - routed and their source IP is limited broadcast (i.e., 255.255.255.255/32) - * - ``ipv6_mc_dip_reserved_scope`` - - ``drop`` - - Traps IPv6 packets that the device decided to drop because they need to - be routed and their IPv6 multicast destination IP has a reserved scope - (i.e., ffx0::/16) - * - ``ipv6_mc_dip_interface_local_scope`` - - ``drop`` - - 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 -============================ - -Device drivers can register driver-specific packet traps, but these must be -clearly documented. Such traps can correspond to device-specific exceptions and -help debug packet drops caused by these exceptions. The following list includes -links to the description of driver-specific traps registered by various device -drivers: - - * :doc:`devlink-trap-netdevsim` - -Generic Packet Trap Groups -========================== - -Generic packet trap groups are used to aggregate logically related packet -traps. These groups allow the user to batch operations such as setting the trap -action of all member traps. In addition, ``devlink-trap`` can report aggregated -per-group packets and bytes statistics, in case per-trap statistics are too -narrow. The description of these groups must be added to the following table: - -.. list-table:: List of Generic Packet Trap Groups - :widths: 10 90 - - * - Name - - Description - * - ``l2_drops`` - - Contains packet traps for packets that were dropped by the device during - layer 2 forwarding (i.e., bridge) - * - ``l3_drops`` - - Contains packet traps for packets that were dropped by the device or hit - an exception (e.g., TTL error) during layer 3 forwarding - * - ``buffer_drops`` - - Contains packet traps for packets that were dropped by the device due to - an enqueue decision - -Testing -======= - -See ``tools/testing/selftests/drivers/net/netdevsim/devlink_trap.sh`` for a -test covering the core infrastructure. Test cases should be added for any new -functionality. - -Device drivers should focus their tests on device-specific functionality, such -as the triggering of supported packet traps. |