From: Theo Buehler <tb@theobuehler.org>
Subject: Re: bgpd: compare scopeid for nexthops -- aka I hate IPv6
To: tech@openbsd.org
Date: Wed, 13 May 2026 16:03:39 +0200

On Wed, May 13, 2026 at 03:59:11PM +0200, Claudio Jeker wrote:
> I hate IPv6 and especially scope ids.
> 
> Add missing scope_id checks in nexthop_cmp() since we now do allow
> link-local nexthops in some cases.
> 
> There is probably more missing but this is one step.

almost ok.

> -- 
> :wq Claudio
> 
> Index: rde_rib.c
> ===================================================================
> RCS file: /cvs/src/usr.sbin/bgpd/rde_rib.c,v
> diff -u -p -r1.292 rde_rib.c
> --- rde_rib.c	7 May 2026 11:21:24 -0000	1.292
> +++ rde_rib.c	13 May 2026 13:55:32 -0000
> @@ -1469,6 +1469,7 @@ static inline int
>  nexthop_cmp(struct nexthop *na, struct nexthop *nb)
>  {
>  	struct bgpd_addr	*a, *b;
> +	int r;
>  
>  	if (na == nb)
>  		return (0);
> @@ -1491,7 +1492,16 @@ nexthop_cmp(struct nexthop *na, struct n
>  			return (-1);
>  		return (0);
>  	case AID_INET6:
> -		return (memcmp(&a->v6, &b->v6, sizeof(struct in6_addr)));
> +		r = memcmp(&a->v6, &b->v6, sizeof(struct in6_addr));
> +		if (r != 0)
> +			return r;
> +		if (IN6_IS_ADDR_LINKLOCAL(&a->v6)) {
> +			if (a->scope_id > b->scope_id)
> +				return (1);
> +			if (a->scope_id < b->scope_id)
> +				return (1);

This wants to be
				return (-1);


> +		}
> +		return (0);
>  	default:
>  		fatalx("nexthop_cmp: %s is unsupported", aid2str(a->aid));
>  	}
>