mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-06 08:46:46 +00:00
937d6eefc7
- Various kerneldoc script enhancements.
- More RST conversions; those are slowing down as we run out of things to
convert, but we're a ways from done still.
- Dan's "maintainer profile entry" work landed at last. Now we just need
to get maintainers to fill in the profiles...
- A reworking of the parallel build setup to work better with a variety of
systems (and to not take over huge systems entirely in particular).
- The MAINTAINERS file is now converted to RST during the build.
Hopefully nobody ever tries to print this thing, or they will need to
load a lot of paper.
- A script and documentation making it easy for maintainers to add Link:
tags at commit time.
Also included is the removal of a bunch of spurious CR characters.
-----BEGIN PGP SIGNATURE-----
iQFDBAABCAAtFiEEIw+MvkEiF49krdp9F0NaE2wMflgFAl3j5B0PHGNvcmJldEBs
d24ubmV0AAoJEBdDWhNsDH5YtBcH/jIN2cO8/0YW2rjVT+1G6ytSdFUKx5WJ/lpf
5uBeCvuCeYhtCB6+BgnXvjykJ7jDW11/NJNjWqz/gsvD5l5FJK1rXarI/oz2Klyi
kcPtDmBF/ki4wz9qXzEpa0vg8LXdjeys50S1vE75qCzxZoPP7YjuRbPnLrlIJukv
JbDVi4p9kxgeHfRB4+BHOe5rFwA3mMmaxKNIX34Y+UUO2KZ0g/yUi1bAaQwQAdt+
PsORmkVQ8Puh3K9xRIr7dYlcWBlBiPqzYdvDgTVxSjrxdK6wjYjSgVk2VjC5MBUN
mTSTWgyfsIcD/76/s8tq7ZRl2fw+SkCSkFo79Rb/hJwDTb7Vnng=
=LPBr
-----END PGP SIGNATURE-----
Merge tag 'docs-5.5a' of git://git.lwn.net/linux
Pull Documentation updates from Jonathan Corbet:
"Here are the main documentation changes for 5.5:
- Various kerneldoc script enhancements.
- More RST conversions; those are slowing down as we run out of
things to convert, but we're a ways from done still.
- Dan's "maintainer profile entry" work landed at last. Now we just
need to get maintainers to fill in the profiles...
- A reworking of the parallel build setup to work better with a
variety of systems (and to not take over huge systems entirely in
particular).
- The MAINTAINERS file is now converted to RST during the build.
Hopefully nobody ever tries to print this thing, or they will need
to load a lot of paper.
- A script and documentation making it easy for maintainers to add
Link: tags at commit time.
Also included is the removal of a bunch of spurious CR characters"
* tag 'docs-5.5a' of git://git.lwn.net/linux: (91 commits)
docs: remove a bunch of stray CRs
docs: fix up the maintainer profile document
libnvdimm, MAINTAINERS: Maintainer Entry Profile
Maintainer Handbook: Maintainer Entry Profile
MAINTAINERS: Reclaim the P: tag for Maintainer Entry Profile
docs, parallelism: Rearrange how jobserver reservations are made
docs, parallelism: Do not leak blocking mode to other readers
docs, parallelism: Fix failure path and add comment
Documentation: Remove bootmem_debug from kernel-parameters.txt
Documentation: security: core.rst: fix warnings
Documentation/process/howto/kokr: Update for 4.x -> 5.x versioning
Documentation/translation: Use Korean for Korean translation title
docs/memory-barriers.txt: Remove remaining references to mmiowb()
docs/memory-barriers.txt/kokr: Update I/O section to be clearer about CPU vs thread
docs/memory-barriers.txt/kokr: Fix style, spacing and grammar in I/O section
Documentation/kokr: Kill all references to mmiowb()
docs/memory-barriers.txt/kokr: Rewrite "KERNEL I/O BARRIER EFFECTS" section
docs: Add initial documentation for devfreq
Documentation: Document how to get links with git am
docs: Add request_irq() documentation
...
270 lines
11 KiB
ReStructuredText
270 lines
11 KiB
ReStructuredText
.. 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.
|