docs: netlink: add NLMSG_DONE message format for doit actions

In case NLMSG_DONE message is sent as a reply to doit action, multiple
kernel implementation do not send anything else than struct nlmsg

docs: netlink: add NLMSG_DONE message format for doit actions

In case NLMSG_DONE message is sent as a reply to doit action, multiple
kernel implementation do not send anything else than struct nlmsghdr.
Add this note to the Netlink intro documentation.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20231201180154.864007-1-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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doc/netlink: Fix missing classic_netlink doc reference

Add missing cross-reference label for classic_netlink.

Fixes: 2db8abf0b455 ("doc/netlink: Document the netlink-raw schema extensions")
Signed-

doc/netlink: Fix missing classic_netlink doc reference

Add missing cross-reference label for classic_netlink.

Fixes: 2db8abf0b455 ("doc/netlink: Document the netlink-raw schema extensions")
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20230829085539.36354-1-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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Documentation: Fix typos

Fix typos in Documentation.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20230814212822.193684-4-helgaas@kernel.org
Signed-off-by: Jon

Documentation: Fix typos

Fix typos in Documentation.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20230814212822.193684-4-helgaas@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

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docs: netlink: clarify the historical baggage of Netlink flags

nlmsg_flags are full of historical baggage, inconsistencies and
strangeness. Try to document it more thoroughly. Explain the meaning
of

docs: netlink: clarify the historical baggage of Netlink flags

nlmsg_flags are full of historical baggage, inconsistencies and
strangeness. Try to document it more thoroughly. Explain the meaning
of the ECHO flag (and while at it clarify the comment in the uAPI).
Handwave a little about the NEW request flags and how they make
sense on the surface but cater to really old paradigm before commands
were a thing.

I will add more notes on how to make use of ECHO and discouragement
for reuse of flags to the kernel-side documentation.

Link: https://lore.kernel.org/r/20220927212306.823862-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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netlink: add support for ext_ack missing attributes

There is currently no way to report via extack in a structured way
that an attribute is missing. This leads to families resorting to
string messag

netlink: add support for ext_ack missing attributes

There is currently no way to report via extack in a structured way
that an attribute is missing. This leads to families resorting to
string messages.

Add a pair of attributes - @offset and @type for machine-readable
way of reporting missing attributes. The @offset points to the
nest which should have contained the attribute, @type is the
expected nla_type. The offset will be skipped if the attribute
is missing at the message level rather than inside a nest.

User space should be able to figure out which attribute enum
(AKA attribute space AKA attribute set) the nest pointed to by
@offset is using.

Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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docs: netlink: basic introduction to Netlink

Provide a bit of a brain dump of netlink related information
as documentation. Hopefully this will be useful to people
trying to navigate implementing YA

docs: netlink: basic introduction to Netlink

Provide a bit of a brain dump of netlink related information
as documentation. Hopefully this will be useful to people
trying to navigate implementing YAML based parsing in languages
we won't be able to help with.

I started writing this doc while trying to figure out what
it'd take to widen the applicability of YAML to good old rtnl,
but the doc grew beyond that as it usually happens.

In all honesty a lot of this information is new to me as I usually
follow the "copy an existing example, drink to forget" process
of writing netlink user space, so reviews will be much appreciated.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20220819200221.422801-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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