Re: [PATCH net-next v2] net: ipv6: seg6: report lwtunnel setup errors via extack

[Hangbin Liu <hangbin.liu@linux.dev>]

On Tue, Sep 22, 2026 at 11:08:33AM +0200, Gabriel Goller wrote:
> seg6_build_state() rejected invalid configurations with a generic -EINVAL, so
> "ip route add ... encap seg6 ..." always reported "Invalid argument".
> 
> Attach an extack message to each of them. The checks themselves and their return
> values are unchanged.
> 
> Signed-off-by: Gabriel Goller <g.goller@proxmox.com>
> ---
> 
> v2 (https://lore.kernel.org/netdev/20260918153544.1178884-1-g.goller@proxmox.com/):
>  * dropped tests
> 
>  net/ipv6/seg6_iptunnel.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
> index 61c6a27bf202..e7f75970e26e 100644
> --- a/net/ipv6/seg6_iptunnel.c
> +++ b/net/ipv6/seg6_iptunnel.c
> @@ -756,8 +756,12 @@ static int seg6_build_state(struct net *net, struct nlattr *nla,
>  	struct seg6_lwt *slwt;
>  	int err;
>  
> -	if (family != AF_INET && family != AF_INET6)
> +	if (family != AF_INET && family != AF_INET6) {
> +		NL_SET_ERR_MSG(
> +			extack,
> +			"unsupported address family for SRv6 encapsulation");
>  		return -EINVAL;
> +	}
>  
>  	err = nla_parse_nested_deprecated(tb, SEG6_IPTUNNEL_MAX, nla,
>  					  seg6_iptunnel_policy, extack);
> @@ -765,8 +769,10 @@ static int seg6_build_state(struct net *net, struct nlattr *nla,
>  	if (err < 0)
>  		return err;
>  
> -	if (!tb[SEG6_IPTUNNEL_SRH])
> +	if (!tb[SEG6_IPTUNNEL_SRH]) {
> +		NL_SET_ERR_MSG(extack, "missing SRv6 SRH attribute");

I think we can use NL_SET_ERR_MSG_ATTR.

Thanks
Hangbin