Re: [RFC PATCH] iproute2: Add flag to indicate extended dump info

[Stephen Hemminger <shemminger@vyatta.com>]

On Fri, 10 Feb 2012 07:18:05 -0800
Greg Rose <gregory.v.rose@intel.com> wrote:

> Add flag to the ip link dump command to indicate to the kernel that
> the application is requesting the extended interface information such
> as VFs.  The kernel will take this flag as an implicit indication that
> the application has allocated a 16K or larger buffer, which is what
> the 'ip' command in fact does.
> 
> Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
> ---
> 
>  include/linux/netlink.h |    1 +
>  lib/libnetlink.c        |    2 +-
>  2 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/netlink.h b/include/linux/netlink.h
> index 5c4f087..f913797 100644
> --- a/include/linux/netlink.h
> +++ b/include/linux/netlink.h
> @@ -59,6 +59,7 @@ struct nlmsghdr {
>  #define NLM_F_MATCH	0x200	/* return all matching	*/
>  #define NLM_F_ATOMIC	0x400	/* atomic GET		*/
>  #define NLM_F_DUMP	(NLM_F_ROOT|NLM_F_MATCH)
> +#define NLM_F_EXT	0x800   /* Get extended interface info such as VFs */
>  
>  /* Modifiers to NEW request */
>  #define NLM_F_REPLACE	0x100	/* Override existing		*/
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index c581e11..f29da3d 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -99,7 +99,7 @@ int rtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
>  	memset(&req, 0, sizeof(req));
>  	req.nlh.nlmsg_len = sizeof(req);
>  	req.nlh.nlmsg_type = type;
> -	req.nlh.nlmsg_flags = NLM_F_DUMP|NLM_F_REQUEST;
> +	req.nlh.nlmsg_flags = NLM_F_DUMP|NLM_F_REQUEST|NLM_F_EXT;
>  	req.nlh.nlmsg_pid = 0;
>  	req.nlh.nlmsg_seq = rth->dump = ++rth->seq;
>  	req.g.rtgen_family = family;
> 

Make sure and test backwards compatibility with older kernels.
It should be fine as long as the flag is ignored now.