Since commit ce6cb8113c84 ("tools: ynl-gen: individually free previous
values on double set"), specifying the "multi-attr" property raises an
error unless the "nested-attributes" property is specified as well:

  File "tools/net/ynl/./pyynl/ynl_gen_c.py", line 1147, in _load_nested_sets
    child = self.pure_nested_structs.get(nested)
                                         ^^^^^^
  UnboundLocalError: cannot access local variable 'nested' where it is not associated with a value

This appears to be a bug since there are existing specs which omit
"nested-attributes" on "multi-attr" attributes.  Also, according to
Documentation/userspace-api/netlink/specs.rst, multi-attr "is the
recommended way of implementing arrays (no extra nesting)", suggesting
that nesting should even be avoided in favor of multi-attr.

Fix the indentation of the if-block introduced by the commit to avoid
the error.

Fixes: ce6cb8113c84 ("tools: ynl-gen: individually free previous values on double set")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://patch.msgid.link/d6b58684b7e5bfb628f7313e6893d0097904e1d1.1746940107.git.lukas@wunner.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Fix a crash in the ethtool YNL implementation when Hardware Clock information
is not present in the response. This ensures graceful handling of devices or
drivers that do not provide this optional field. e.g.

  Traceback (most recent call last):
    File "/net/tools/net/ynl/pyynl/./ethtool.py", line 438, in <module>
      main()
      ~~~~^^
    File "/net/tools/net/ynl/pyynl/./ethtool.py", line 341, in main
      print(f'PTP Hardware Clock: {tsinfo["phc-index"]}')
                                   ~~~~~~^^^^^^^^^^^^^
  KeyError: 'phc-index'

Fixes: f3d07b02b2b8 ("tools: ynl: ethtool testing tool")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508035414.82974-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Strings from the kernel are guaranteed to be null terminated and
ynl_attr_validate() checks for this. But it doesn't check if the string
has a len of 0, which would cause problems when trying to access
data[len - 1]. Fix this by checking that len is positive.

Signed-off-by: David Wei <dw@davidwei.uk>
Link: https://patch.msgid.link/20250503043050.861238-1-dw@davidwei.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

ArrayNest AKA indexed-array support currently skips inner type
validation. We count the attributes and then we parse them,
make sure we call validate, too. Otherwise buggy / unexpected
kernel response may lead to crashes.

Fixes: be5bea1cc0bf ("net: add basic C code generators for Netlink")
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250414211851.602096-5-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

When user calls request_attrA_set() multiple times (for the same
attribute), and attrA is of type which allocates memory -
we try to free the previously associated values. For array
types (including multi-attr) we have only freed the array,
but the array may have contained pointers.

Refactor the code generation for free attr and reuse the generated
lines in setters to flush out the previous state. Since setters
are static inlines in the header we need to add forward declarations
for the free helpers of pure nested structs. Track which types get
used by arrays and include the right forwad declarations.

At least ethtool string set and bit set would not be freed without
this. Tho, admittedly, overriding already set attribute twice is likely
a very very rare thing to do.

Fixes: be5bea1cc0bf ("net: add basic C code generators for Netlink")
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250414211851.602096-4-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

The "function writing helper" tries to put local variables
between prototype and the opening bracket. Clearly wrong,
but up until now nothing actually uses it to write local
vars so it wasn't noticed.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250414211851.602096-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

The codegen tries to follow the "old" C style and declare loop
iterators at the start of the block / function. Only nested
request handling breaks this style, so adjust it.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250414211851.602096-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add a rudimentary YNL spec for nl80211 that covers get-wiphy,
get-interface and get-protocol-features.

./tools/net/ynl/pyynl/cli.py --family nl80211 \
    --do get-protocol-features
{'protocol-features': {'split-wiphy-dump'}}

./tools/net/ynl/pyynl/cli.py --family nl80211 \
    --dump get-wiphy --json '{ "split-wiphy-dump": true }'

./tools/net/ynl/pyynl/cli.py --family nl80211 \
    --dump get-interface

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Link: https://patch.msgid.link/20250211120127.84858-11-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Extend ynl-gen-c.py with support for indexed-array that has a scalar
sub-type.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250211120127.84858-8-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Turn attribute names with leading digits into valid C names by
prepending an underscore, e.g. 5ghz -> _5ghz

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250211120127.84858-7-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>