Re: Error reporting in Netlink (Re: Xtables2 Netlink spec)

[Patrick McHardy <kaber@trash.net>]

Am 16.12.2010 14:43, schrieb Thomas Graf:
> Thinking of netlink protocols in general and netfilter in specific,
> maintaining a list of reserved error codes for each subsystem/target/
> module will result in an unbearable pain if the error codes are not
> separated into individual namespaces for each module.
> 
> That would in turn require each module to define a unique number or
> some form of namespace resolution mechanism which does not help to keep
> things simple.
> 
> This is the main reason why I advocate the use of error strings.

I completely disagree. As I said previously, userspace has to have
knowledge of the kernel interpretation anyways.

We already have libc calls which define complex errors like:

stdtod(): if val == HUGE_VAL && errno == ERANGE: positive overflow

I see no reason why we can't define combination of attributes
and errno values for netlink messages.

Something like:

[IFLA_VLAN_ID] == NULL && errno == EINVAL: missing attribute
[IFLA_VLAN_LINK] && errno == ENODEV: lower link does not exist

and so on.