Missing generic netlink controller operations

Missing generic netlink controller operations

[Collin]

While messing around with libnl and netlink I noticed that despite existing in an enum in linux/genetlink.h, the CTRL_CMD_{NEW,DEL,GET}OPS operations (and in fact, all operations except for CTRL_CMD_{NEWFAMILY,DELFAMILY,NEWMCAST_GRP,DELMCAST_GRP}) are unimplemented, and have been around, untouched, since the introduction of the generic netlink family. Is there a reason these exist without implementation, or has it simply not been done?

Re: Missing generic netlink controller operations

[Randy Dunlap]

[change linux-netdev@ to netdev@]

On 11/16/22 19:54, Collin wrote:
> While messing around with libnl and netlink I noticed that despite existing in an enum in linux/genetlink.h, the CTRL_CMD_{NEW,DEL,GET}OPS operations (and in fact, all operations except for CTRL_CMD_{NEWFAMILY,DELFAMILY,NEWMCAST_GRP,DELMCAST_GRP}) are unimplemented, and have been around, untouched, since the introduction of the generic netlink family. Is there a reason these exist without implementation, or has it simply not been done?

-- 
~Randy

Re: Missing generic netlink controller operations

[Jakub Kicinski]

On Thu, 17 Nov 2022 08:38:40 -0800 Randy Dunlap wrote:
> [change linux-netdev@ to netdev@]
> 
> On 11/16/22 19:54, Collin wrote:
> > While messing around with libnl and netlink I noticed that despite
> > existing in an enum in linux/genetlink.h, the
> > CTRL_CMD_{NEW,DEL,GET}OPS operations (and in fact, all operations
> > except for
> > CTRL_CMD_{NEWFAMILY,DELFAMILY,NEWMCAST_GRP,DELMCAST_GRP}) are
> > unimplemented, and have been around, untouched, since the
> > introduction of the generic netlink family. Is there a reason these
> > exist without implementation, or has it simply not been done?  

Only CTRL_CMD_GETMCAST_GRP was never used AFAIU, it was likely added
to maintain the triplet cadence (NEW,DEL,GET); probably cargo cult /
inspired by the classic netlink / rtnl.

Ops used to be more dynamic, and separately registered, I think.
Which found no real life use, so that option was dropped and now
all ops must be statically defined for the family at family
registration time.