641 lines
26 KiB
ReStructuredText
641 lines
26 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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============
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Devlink Trap
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============
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Background
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==========
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Devices capable of offloading the kernel's datapath and perform functions such
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as bridging and routing must also be able to send specific packets to the
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kernel (i.e., the CPU) for processing.
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For example, a device acting as a multicast-aware bridge must be able to send
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IGMP membership reports to the kernel for processing by the bridge module.
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Without processing such packets, the bridge module could never populate its
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MDB.
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As another example, consider a device acting as router which has received an IP
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packet with a TTL of 1. Upon routing the packet the device must send it to the
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kernel so that it will route it as well and generate an ICMP Time Exceeded
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error datagram. Without letting the kernel route such packets itself, utilities
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such as ``traceroute`` could never work.
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The fundamental ability of sending certain packets to the kernel for processing
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is called "packet trapping".
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Overview
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========
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The ``devlink-trap`` mechanism allows capable device drivers to register their
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supported packet traps with ``devlink`` and report trapped packets to
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``devlink`` for further analysis.
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Upon receiving trapped packets, ``devlink`` will perform a per-trap packets and
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bytes accounting and potentially report the packet to user space via a netlink
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event along with all the provided metadata (e.g., trap reason, timestamp, input
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port). This is especially useful for drop traps (see :ref:`Trap-Types`)
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as it allows users to obtain further visibility into packet drops that would
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otherwise be invisible.
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The following diagram provides a general overview of ``devlink-trap``::
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Netlink event: Packet w/ metadata
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Or a summary of recent drops
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^
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Userspace |
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+---------------------------------------------------+
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Kernel |
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+-------+--------+
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| drop_monitor |
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+-------^--------+
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| Non-control traps
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+----+----+
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| | Kernel's Rx path
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| devlink | (non-drop traps)
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+----^----+ ^
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+-----------+
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+-------+-------+
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| Device driver |
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+-------^-------+
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Kernel |
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+---------------------------------------------------+
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Hardware |
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| Trapped packet
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+--+---+
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| ASIC |
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+------+
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.. _Trap-Types:
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Trap Types
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==========
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The ``devlink-trap`` mechanism supports the following packet trap types:
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* ``drop``: Trapped packets were dropped by the underlying device. Packets
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are only processed by ``devlink`` and not injected to the kernel's Rx path.
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The trap action (see :ref:`Trap-Actions`) can be changed.
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* ``exception``: Trapped packets were not forwarded as intended by the
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underlying device due to an exception (e.g., TTL error, missing neighbour
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entry) and trapped to the control plane for resolution. Packets are
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processed by ``devlink`` and injected to the kernel's Rx path. Changing the
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action of such traps is not allowed, as it can easily break the control
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plane.
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* ``control``: Trapped packets were trapped by the device because these are
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control packets required for the correct functioning of the control plane.
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For example, ARP request and IGMP query packets. Packets are injected to
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the kernel's Rx path, but not reported to the kernel's drop monitor.
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Changing the action of such traps is not allowed, as it can easily break
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the control plane.
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.. _Trap-Actions:
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Trap Actions
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============
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The ``devlink-trap`` mechanism supports the following packet trap actions:
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* ``trap``: The sole copy of the packet is sent to the CPU.
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* ``drop``: The packet is dropped by the underlying device and a copy is not
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sent to the CPU.
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* ``mirror``: The packet is forwarded by the underlying device and a copy is
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sent to the CPU.
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Generic Packet Traps
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====================
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Generic packet traps are used to describe traps that trap well-defined packets
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or packets that are trapped due to well-defined conditions (e.g., TTL error).
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Such traps can be shared by multiple device drivers and their description must
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be added to the following table:
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.. list-table:: List of Generic Packet Traps
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:widths: 5 5 90
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* - Name
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- Type
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- Description
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* - ``source_mac_is_multicast``
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- ``drop``
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- Traps incoming packets that the device decided to drop because of a
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multicast source MAC
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* - ``vlan_tag_mismatch``
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- ``drop``
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- Traps incoming packets that the device decided to drop in case of VLAN
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tag mismatch: The ingress bridge port is not configured with a PVID and
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the packet is untagged or prio-tagged
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* - ``ingress_vlan_filter``
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- ``drop``
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- Traps incoming packets that the device decided to drop in case they are
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tagged with a VLAN that is not configured on the ingress bridge port
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* - ``ingress_spanning_tree_filter``
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- ``drop``
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- Traps incoming packets that the device decided to drop in case the STP
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state of the ingress bridge port is not "forwarding"
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* - ``port_list_is_empty``
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- ``drop``
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- Traps packets that the device decided to drop in case they need to be
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flooded (e.g., unknown unicast, unregistered multicast) and there are
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no ports the packets should be flooded to
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* - ``port_loopback_filter``
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- ``drop``
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- Traps packets that the device decided to drop in case after layer 2
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forwarding the only port from which they should be transmitted through
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is the port from which they were received
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* - ``blackhole_route``
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- ``drop``
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- Traps packets that the device decided to drop in case they hit a
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blackhole route
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* - ``ttl_value_is_too_small``
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- ``exception``
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- Traps unicast packets that should be forwarded by the device whose TTL
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was decremented to 0 or less
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* - ``tail_drop``
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- ``drop``
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- Traps packets that the device decided to drop because they could not be
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enqueued to a transmission queue which is full
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* - ``non_ip``
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- ``drop``
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- Traps packets that the device decided to drop because they need to
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undergo a layer 3 lookup, but are not IP or MPLS packets
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* - ``uc_dip_over_mc_dmac``
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- ``drop``
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- Traps packets that the device decided to drop because they need to be
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routed and they have a unicast destination IP and a multicast destination
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MAC
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* - ``dip_is_loopback_address``
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- ``drop``
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- Traps packets that the device decided to drop because they need to be
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routed and their destination IP is the loopback address (i.e., 127.0.0.0/8
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and ::1/128)
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* - ``sip_is_mc``
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- ``drop``
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- Traps packets that the device decided to drop because they need to be
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routed and their source IP is multicast (i.e., 224.0.0.0/8 and ff::/8)
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* - ``sip_is_loopback_address``
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- ``drop``
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- Traps packets that the device decided to drop because they need to be
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routed and their source IP is the loopback address (i.e., 127.0.0.0/8 and ::1/128)
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* - ``ip_header_corrupted``
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- ``drop``
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- Traps packets that the device decided to drop because they need to be
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routed and their IP header is corrupted: wrong checksum, wrong IP version
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or too short Internet Header Length (IHL)
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* - ``ipv4_sip_is_limited_bc``
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- ``drop``
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- Traps packets that the device decided to drop because they need to be
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routed and their source IP is limited broadcast (i.e., 255.255.255.255/32)
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* - ``ipv6_mc_dip_reserved_scope``
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- ``drop``
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- Traps IPv6 packets that the device decided to drop because they need to
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be routed and their IPv6 multicast destination IP has a reserved scope
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(i.e., ffx0::/16)
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* - ``ipv6_mc_dip_interface_local_scope``
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- ``drop``
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- Traps IPv6 packets that the device decided to drop because they need to
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be routed and their IPv6 multicast destination IP has an interface-local scope
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(i.e., ffx1::/16)
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* - ``mtu_value_is_too_small``
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- ``exception``
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- Traps packets that should have been routed by the device, but were bigger
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than the MTU of the egress interface
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* - ``unresolved_neigh``
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- ``exception``
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- Traps packets that did not have a matching IP neighbour after routing
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* - ``mc_reverse_path_forwarding``
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- ``exception``
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- Traps multicast IP packets that failed reverse-path forwarding (RPF)
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check during multicast routing
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* - ``reject_route``
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- ``exception``
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- Traps packets that hit reject routes (i.e., "unreachable", "prohibit")
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* - ``ipv4_lpm_miss``
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- ``exception``
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- Traps unicast IPv4 packets that did not match any route
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* - ``ipv6_lpm_miss``
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- ``exception``
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- Traps unicast IPv6 packets that did not match any route
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* - ``non_routable_packet``
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- ``drop``
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- Traps packets that the device decided to drop because they are not
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supposed to be routed. For example, IGMP queries can be flooded by the
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device in layer 2 and reach the router. Such packets should not be
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routed and instead dropped
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* - ``decap_error``
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- ``exception``
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- Traps NVE and IPinIP packets that the device decided to drop because of
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failure during decapsulation (e.g., packet being too short, reserved
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bits set in VXLAN header)
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* - ``overlay_smac_is_mc``
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- ``drop``
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- Traps NVE packets that the device decided to drop because their overlay
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source MAC is multicast
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* - ``ingress_flow_action_drop``
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- ``drop``
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- Traps packets dropped during processing of ingress flow action drop
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* - ``egress_flow_action_drop``
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- ``drop``
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- Traps packets dropped during processing of egress flow action drop
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* - ``stp``
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- ``control``
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- Traps STP packets
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* - ``lacp``
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- ``control``
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- Traps LACP packets
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* - ``lldp``
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- ``control``
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- Traps LLDP packets
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* - ``igmp_query``
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- ``control``
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- Traps IGMP Membership Query packets
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* - ``igmp_v1_report``
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- ``control``
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- Traps IGMP Version 1 Membership Report packets
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* - ``igmp_v2_report``
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- ``control``
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- Traps IGMP Version 2 Membership Report packets
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* - ``igmp_v3_report``
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- ``control``
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- Traps IGMP Version 3 Membership Report packets
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* - ``igmp_v2_leave``
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- ``control``
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- Traps IGMP Version 2 Leave Group packets
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* - ``mld_query``
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- ``control``
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- Traps MLD Multicast Listener Query packets
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* - ``mld_v1_report``
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- ``control``
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- Traps MLD Version 1 Multicast Listener Report packets
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* - ``mld_v2_report``
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- ``control``
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- Traps MLD Version 2 Multicast Listener Report packets
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* - ``mld_v1_done``
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- ``control``
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- Traps MLD Version 1 Multicast Listener Done packets
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* - ``ipv4_dhcp``
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- ``control``
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- Traps IPv4 DHCP packets
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* - ``ipv6_dhcp``
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- ``control``
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- Traps IPv6 DHCP packets
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* - ``arp_request``
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- ``control``
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- Traps ARP request packets
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* - ``arp_response``
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- ``control``
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- Traps ARP response packets
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* - ``arp_overlay``
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- ``control``
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- Traps NVE-decapsulated ARP packets that reached the overlay network.
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This is required, for example, when the address that needs to be
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resolved is a local address
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* - ``ipv6_neigh_solicit``
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- ``control``
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- Traps IPv6 Neighbour Solicitation packets
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* - ``ipv6_neigh_advert``
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- ``control``
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- Traps IPv6 Neighbour Advertisement packets
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* - ``ipv4_bfd``
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- ``control``
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- Traps IPv4 BFD packets
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* - ``ipv6_bfd``
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- ``control``
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- Traps IPv6 BFD packets
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* - ``ipv4_ospf``
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- ``control``
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- Traps IPv4 OSPF packets
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* - ``ipv6_ospf``
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- ``control``
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- Traps IPv6 OSPF packets
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* - ``ipv4_bgp``
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- ``control``
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- Traps IPv4 BGP packets
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* - ``ipv6_bgp``
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- ``control``
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- Traps IPv6 BGP packets
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* - ``ipv4_vrrp``
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- ``control``
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- Traps IPv4 VRRP packets
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* - ``ipv6_vrrp``
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- ``control``
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- Traps IPv6 VRRP packets
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* - ``ipv4_pim``
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- ``control``
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- Traps IPv4 PIM packets
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* - ``ipv6_pim``
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- ``control``
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- Traps IPv6 PIM packets
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* - ``uc_loopback``
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- ``control``
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- Traps unicast packets that need to be routed through the same layer 3
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interface from which they were received. Such packets are routed by the
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kernel, but also cause it to potentially generate ICMP redirect packets
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* - ``local_route``
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- ``control``
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- Traps unicast packets that hit a local route and need to be locally
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delivered
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* - ``external_route``
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- ``control``
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- Traps packets that should be routed through an external interface (e.g.,
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management interface) that does not belong to the same device (e.g.,
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switch ASIC) as the ingress interface
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* - ``ipv6_uc_dip_link_local_scope``
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- ``control``
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- Traps unicast IPv6 packets that need to be routed and have a destination
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IP address with a link-local scope (i.e., fe80::/10). The trap allows
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device drivers to avoid programming link-local routes, but still receive
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packets for local delivery
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* - ``ipv6_dip_all_nodes``
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- ``control``
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- Traps IPv6 packets that their destination IP address is the "All Nodes
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Address" (i.e., ff02::1)
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* - ``ipv6_dip_all_routers``
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- ``control``
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- Traps IPv6 packets that their destination IP address is the "All Routers
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Address" (i.e., ff02::2)
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* - ``ipv6_router_solicit``
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- ``control``
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- Traps IPv6 Router Solicitation packets
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* - ``ipv6_router_advert``
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- ``control``
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- Traps IPv6 Router Advertisement packets
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* - ``ipv6_redirect``
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- ``control``
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- Traps IPv6 Redirect Message packets
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* - ``ipv4_router_alert``
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- ``control``
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- Traps IPv4 packets that need to be routed and include the Router Alert
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option. Such packets need to be locally delivered to raw sockets that
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have the IP_ROUTER_ALERT socket option set
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* - ``ipv6_router_alert``
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- ``control``
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- Traps IPv6 packets that need to be routed and include the Router Alert
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option in their Hop-by-Hop extension header. Such packets need to be
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locally delivered to raw sockets that have the IPV6_ROUTER_ALERT socket
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option set
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* - ``ptp_event``
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- ``control``
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- Traps PTP time-critical event messages (Sync, Delay_req, Pdelay_Req and
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Pdelay_Resp)
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* - ``ptp_general``
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- ``control``
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- Traps PTP general messages (Announce, Follow_Up, Delay_Resp,
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Pdelay_Resp_Follow_Up, management and signaling)
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* - ``flow_action_sample``
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- ``control``
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- Traps packets sampled during processing of flow action sample (e.g., via
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tc's sample action)
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* - ``flow_action_trap``
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- ``control``
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- Traps packets logged during processing of flow action trap (e.g., via
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tc's trap action)
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* - ``early_drop``
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- ``drop``
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- Traps packets dropped due to the RED (Random Early Detection) algorithm
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(i.e., early drops)
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* - ``vxlan_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the VXLAN header parsing which
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might be because of packet truncation or the I flag is not set.
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* - ``llc_snap_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the LLC+SNAP header parsing
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* - ``vlan_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the VLAN header parsing. Could
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include unexpected packet truncation.
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* - ``pppoe_ppp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the PPPoE+PPP header parsing.
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This could include finding a session ID of 0xFFFF (which is reserved and
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not for use), a PPPoE length which is larger than the frame received or
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any common error on this type of header
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* - ``mpls_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the MPLS header parsing which
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could include unexpected header truncation
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* - ``arp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the ARP header parsing
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* - ``ip_1_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the first IP header parsing.
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This packet trap could include packets which do not pass an IP checksum
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check, a header length check (a minimum of 20 bytes), which might suffer
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from packet truncation thus the total length field exceeds the received
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packet length etc
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* - ``ip_n_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the parsing of the last IP
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header (the inner one in case of an IP over IP tunnel). The same common
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error checking is performed here as for the ip_1_parsing trap
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* - ``gre_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the GRE header parsing
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* - ``udp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the UDP header parsing.
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This packet trap could include checksum errorrs, an improper UDP
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length detected (smaller than 8 bytes) or detection of header
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truncation.
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* - ``tcp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the TCP header parsing.
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This could include TCP checksum errors, improper combination of SYN, FIN
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and/or RESET etc.
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* - ``ipsec_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the IPSEC header parsing
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* - ``sctp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the SCTP header parsing.
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This would mean that port number 0 was used or that the header is
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truncated.
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* - ``dccp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the DCCP header parsing
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* - ``gtp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the GTP header parsing
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* - ``esp_parsing``
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- ``drop``
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- Traps packets dropped due to an error in the ESP header parsing
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* - ``blackhole_nexthop``
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- ``drop``
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- Traps packets that the device decided to drop in case they hit a
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blackhole nexthop
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* - ``dmac_filter``
|
|
- ``drop``
|
|
- Traps incoming packets that the device decided to drop because
|
|
the destination MAC is not configured in the MAC table and
|
|
the interface is not in promiscuous mode
|
|
* - ``eapol``
|
|
- ``control``
|
|
- Traps "Extensible Authentication Protocol over LAN" (EAPOL) packets
|
|
specified in IEEE 802.1X
|
|
* - ``locked_port``
|
|
- ``drop``
|
|
- Traps packets that the device decided to drop because they failed the
|
|
locked bridge port check. That is, packets that were received via a
|
|
locked port and whose {SMAC, VID} does not correspond to an FDB entry
|
|
pointing to the port
|
|
|
|
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:
|
|
|
|
* Documentation/networking/devlink/netdevsim.rst
|
|
* Documentation/networking/devlink/mlxsw.rst
|
|
* Documentation/networking/devlink/prestera.rst
|
|
|
|
.. _Generic-Packet-Trap-Groups:
|
|
|
|
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 during
|
|
layer 3 forwarding
|
|
* - ``l3_exceptions``
|
|
- Contains packet traps for packets that 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
|
|
* - ``tunnel_drops``
|
|
- Contains packet traps for packets that were dropped by the device during
|
|
tunnel encapsulation / decapsulation
|
|
* - ``acl_drops``
|
|
- Contains packet traps for packets that were dropped by the device during
|
|
ACL processing
|
|
* - ``stp``
|
|
- Contains packet traps for STP packets
|
|
* - ``lacp``
|
|
- Contains packet traps for LACP packets
|
|
* - ``lldp``
|
|
- Contains packet traps for LLDP packets
|
|
* - ``mc_snooping``
|
|
- Contains packet traps for IGMP and MLD packets required for multicast
|
|
snooping
|
|
* - ``dhcp``
|
|
- Contains packet traps for DHCP packets
|
|
* - ``neigh_discovery``
|
|
- Contains packet traps for neighbour discovery packets (e.g., ARP, IPv6
|
|
ND)
|
|
* - ``bfd``
|
|
- Contains packet traps for BFD packets
|
|
* - ``ospf``
|
|
- Contains packet traps for OSPF packets
|
|
* - ``bgp``
|
|
- Contains packet traps for BGP packets
|
|
* - ``vrrp``
|
|
- Contains packet traps for VRRP packets
|
|
* - ``pim``
|
|
- Contains packet traps for PIM packets
|
|
* - ``uc_loopback``
|
|
- Contains a packet trap for unicast loopback packets (i.e.,
|
|
``uc_loopback``). This trap is singled-out because in cases such as
|
|
one-armed router it will be constantly triggered. To limit the impact on
|
|
the CPU usage, a packet trap policer with a low rate can be bound to the
|
|
group without affecting other traps
|
|
* - ``local_delivery``
|
|
- Contains packet traps for packets that should be locally delivered after
|
|
routing, but do not match more specific packet traps (e.g.,
|
|
``ipv4_bgp``)
|
|
* - ``external_delivery``
|
|
- Contains packet traps for packets that should be routed through an
|
|
external interface (e.g., management interface) that does not belong to
|
|
the same device (e.g., switch ASIC) as the ingress interface
|
|
* - ``ipv6``
|
|
- Contains packet traps for various IPv6 control packets (e.g., Router
|
|
Advertisements)
|
|
* - ``ptp_event``
|
|
- Contains packet traps for PTP time-critical event messages (Sync,
|
|
Delay_req, Pdelay_Req and Pdelay_Resp)
|
|
* - ``ptp_general``
|
|
- Contains packet traps for PTP general messages (Announce, Follow_Up,
|
|
Delay_Resp, Pdelay_Resp_Follow_Up, management and signaling)
|
|
* - ``acl_sample``
|
|
- Contains packet traps for packets that were sampled by the device during
|
|
ACL processing
|
|
* - ``acl_trap``
|
|
- Contains packet traps for packets that were trapped (logged) by the
|
|
device during ACL processing
|
|
* - ``parser_error_drops``
|
|
- Contains packet traps for packets that were marked by the device during
|
|
parsing as erroneous
|
|
* - ``eapol``
|
|
- Contains packet traps for "Extensible Authentication Protocol over LAN"
|
|
(EAPOL) packets specified in IEEE 802.1X
|
|
|
|
Packet Trap Policers
|
|
====================
|
|
|
|
As previously explained, the underlying device can trap certain packets to the
|
|
CPU for processing. In most cases, the underlying device is capable of handling
|
|
packet rates that are several orders of magnitude higher compared to those that
|
|
can be handled by the CPU.
|
|
|
|
Therefore, in order to prevent the underlying device from overwhelming the CPU,
|
|
devices usually include packet trap policers that are able to police the
|
|
trapped packets to rates that can be handled by the CPU.
|
|
|
|
The ``devlink-trap`` mechanism allows capable device drivers to register their
|
|
supported packet trap policers with ``devlink``. The device driver can choose
|
|
to associate these policers with supported packet trap groups (see
|
|
:ref:`Generic-Packet-Trap-Groups`) during its initialization, thereby exposing
|
|
its default control plane policy to user space.
|
|
|
|
Device drivers should allow user space to change the parameters of the policers
|
|
(e.g., rate, burst size) as well as the association between the policers and
|
|
trap groups by implementing the relevant callbacks.
|
|
|
|
If possible, device drivers should implement a callback that allows user space
|
|
to retrieve the number of packets that were dropped by the policer because its
|
|
configured policy was violated.
|
|
|
|
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.
|