On 17-07-24 07:18 AM, Jiri Pirko wrote:

Mon, Jul 24, 2017 at 03:35:43AM CEST, jhs@mojatatu.com wrote:

quoted

From: Jamal Hadi Salim <jhs@mojatatu.com>

Generic bitflags attribute content sent to the kernel by user.
With this type the user can either set or unset a flag in the
kernel.

The nla_value is a bitmap that defines the values being set
The nla_selector is a bitmask that defines which value is legit.

A check is made to ensure the rules that a kernel subsystem always
conforms to bitflags the kernel already knows about. i.e
if the user tries to set a bit flag that is not understood then
the _it will be rejected_.

In the most basic form, the user specifies the attribute policy as:
[ATTR_GOO] = { .type = NLA_BITFIELD_32, .validation_data = &myvalidflags },

where myvalidflags is the bit mask of the flags the kernel understands.

If the user _does not_ provide myvalidflags then the attribute will
also be rejected.

Examples:
nla_value = 0x0, and nla_selector = 0x1
implies we are selecting bit 1 and we want to set its value to 0.

nla_value = 0x2, and nla_selector = 0x2
implies we are selecting bit 2 and we want to set its value to 1.

Oh, 2 more things:

[...]

;-> ok will do that next opportunity (probably at 30K feet).

cheers,
jamal