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Johannes Berg d07dcf9aad netlink: add infrastructure to expose policies to userspace
Add, and use in generic netlink, helpers to dump out a netlink
policy to userspace, including all the range validation data,
nested policies etc.

This lets userspace discover what the kernel understands.

For families/commands other than generic netlink, the helpers
need to be used directly in an appropriate command, or we can
add some infrastructure (a new netlink family) that those can
register their policies with for introspection. I'm not that
familiar with non-generic netlink, so that's left out for now.

The data exposed to userspace also includes min and max length
for binary/string data, I've done that instead of letting the
userspace tools figure out whether min/max is intended based
on the type so that we can extend this later in the kernel, we
might want to just use the range data for example.

Because of this, I opted to not directly expose the NLA_*
values, even if some of them are already exposed via BPF, as
with min/max length we don't need to have different types here
for NLA_BINARY/NLA_MIN_LEN/NLA_EXACT_LEN, we just make them
all NL_ATTR_TYPE_BINARY with min/max length optionally set.

Similarly, we don't really need NLA_MSECS, and perhaps can
remove it in the future - but not if we encode it into the
userspace API now. It gets mapped to NL_ATTR_TYPE_U64 here.

Note that the exposing here corresponds to the strict policy
interpretation, and NLA_UNSPEC items are omitted entirely.
To get those, change them to NLA_MIN_LEN which behaves in
exactly the same way, but is exposed.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-04-30 17:51:42 -07:00
arch ARM: dts: qcom: ipq4019: add MDIO node 2020-04-30 12:11:14 -07:00
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Documentation tcp: add hrtimer slack to sack compression 2020-04-30 13:24:01 -07:00
drivers net: dsa: b53: Remove is_static argument to b53_read_op() 2020-04-30 17:43:29 -07:00
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include netlink: add infrastructure to expose policies to userspace 2020-04-30 17:51:42 -07:00
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kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-04-25 20:18:53 -07:00
lib netlink: factor out policy range helpers 2020-04-30 17:51:42 -07:00
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net netlink: add infrastructure to expose policies to userspace 2020-04-30 17:51:42 -07:00
samples docs: networking: convert pktgen.txt to ReST 2020-04-30 12:56:37 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-04-25 20:18:53 -07:00
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tools docs: networking: convert filter.txt to ReST 2020-04-28 14:39:46 -07:00
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MAINTAINERS docs: networking: convert sctp.txt to ReST 2020-04-30 12:56:38 -07:00
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