Re: [PATCH libmnl] examples: genl: fix wrong attribute size

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Sep 15, 2025 at 02:40:30PM +0200, Florian Westphal wrote:
> This example no longer works on more recent kernels:
> 
> genl-family-get
> error: Invalid argument
> 
> dmesg says:
> netlink: 'genl-family-get': attribute type 1 has an invalid length.
> 
> Fix this and also zero out the reserved field in the genl header,
> while not validated yet for dumps this could change.
> 
> Reported-by: Divyanshu Rathore <Divyanshu.Rathore@bmwtechworks.in>
> Signed-off-by: Florian Westphal <fw@strlen.de>

Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>

> ---
>  I will push this out later today.
> 
>  examples/genl/genl-family-get.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/examples/genl/genl-family-get.c b/examples/genl/genl-family-get.c
> index ba8de122094c..0c2006755e30 100644
> --- a/examples/genl/genl-family-get.c
> +++ b/examples/genl/genl-family-get.c
> @@ -199,8 +199,9 @@ int main(int argc, char *argv[])
>  	genl = mnl_nlmsg_put_extra_header(nlh, sizeof(struct genlmsghdr));
>  	genl->cmd = CTRL_CMD_GETFAMILY;
>  	genl->version = 1;
> +	genl->reserved = 0;
>  
> -	mnl_attr_put_u32(nlh, CTRL_ATTR_FAMILY_ID, GENL_ID_CTRL);
> +	mnl_attr_put_u16(nlh, CTRL_ATTR_FAMILY_ID, GENL_ID_CTRL);
>  	if (argc >= 2)
>  		mnl_attr_put_strz(nlh, CTRL_ATTR_FAMILY_NAME, argv[1]);
>  	else
> -- 
> 2.51.0
> 
>