> 2. Description
> --------------
> The default values of some properties may not be known a priori
> to dladm. For example, the default MTU of ethernet links is
> 1500 bytes, whereas that for InfiniBand is 2044, and the value can
> vary for tunnel links. In these cases, dladm will have to send
> a system call to the driver to obtain the default value of the property.
> Also, the "reset-linkprop" command will have to notify the driver
> that the value of the property must be reset to the default value for
> that driver.
>
> This feature is achieved by sending a DLDIOC{SET, GET}PROP ioctl
> to the driver with the pr_flags set to DLD_DEFAULT. The driver
> may then recognize the DLD_DEFAULT flag and return the default value
> for the property (in the case of a GETPROP), or reset the property
> to the default value (for SETPROP).
This all seems reasonable for what's proposed, but I wonder how it might
be extended to handle an additional case that's come up in another thread.
In particular, ndd currently allows one to effectively change the default
value, which can be handy when e.g. the set of objects that need to be
tweaked is dynamic or large. Clearly, some thought is needed to figure
out how to express this via dladm(1M) (a new "-d" option to set-prop?),
but leaving that aside, I'd think that SETPROP with DLD_DEFAULT would be
the logical way to pass that information down into the framework -- so I'm
not sure the semantics proposed above are optimal.
--
meem
