Re: [PATCH] ipv6: check per-interface proxy_ndp in forwarding and NA paths

[Hangbin Liu]

On Fri, Sep 18, 2026 at 12:14:05PM -0300, Adriano Cordova wrote:
> proxy_ndp can be enabled per interface, with net.ipv6.conf.all.proxy_ndp
> as a global default. ndisc_recv_ns() checks both, but ip6_forward() and
> ndisc_recv_na() check only the global value. With the per-interface proxy
> ndp set and the global one left at 0, the router answers proxy NS but
> does not pass NDP messages to the proxied target.
> 
> Check both values at these two sites, as ndisc_recv_ns() already does.
> 
> Fixes: fbea49e1e240 ("[IPV6] NDISC: Add proxy_ndp sysctl.")
> Signed-off-by: Adriano Cordova <adrianox@xxxxxxxxx>
> ---
>  net/ipv6/ip6_output.c | 4 ++--
>  net/ipv6/ndisc.c      | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index 550965058991..738fa46a892a 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -581,8 +581,8 @@ int ip6_forward(struct sk_buff *skb)
>  		return -ETIMEDOUT;
>  	}
>  
> -	/* XXX: idev->cnf.proxy_ndp? */
> -	if (READ_ONCE(net->ipv6.devconf_all->proxy_ndp) &&
> +	if ((READ_ONCE(net->ipv6.devconf_all->proxy_ndp) ||
> +	     (idev && READ_ONCE(idev->cnf.proxy_ndp))) &&
>  	    pneigh_lookup(&nd_tbl, net, &hdr->daddr, skb->dev)) {
>  		int proxied = ip6_forward_proxy_check(skb);
>  
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index 75515fd99383..f787082069b7 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -1097,9 +1097,9 @@ static enum skb_drop_reason ndisc_recv_na(struct sk_buff *skb)
>  		 */
>  		if (lladdr && !memcmp(lladdr, dev->dev_addr, dev->addr_len) &&
>  		    READ_ONCE(net->ipv6.devconf_all->forwarding) &&
> -		    READ_ONCE(net->ipv6.devconf_all->proxy_ndp) &&
> +		    (READ_ONCE(net->ipv6.devconf_all->proxy_ndp) ||
> +		     (idev && READ_ONCE(idev->cnf.proxy_ndp))) &&
>  		    pneigh_lookup(&nd_tbl, net, &msg->target, dev)) {
> -			/* XXX: idev->cnf.proxy_ndp */
>  			goto out;
>  		}
>  
> -- 
> 2.51.0
> 

LGTM

Reviewed-by: Hangbin Liu <liuhangbin@xxxxxxxxxx>