From: Florian Obser <florian@openbsd.org>
Subject: Re: carp: embed scope-id when sending NA
To: YASUOKA Masahiko <yasuoka@openbsd.org>
Cc: tech@openbsd.org
Date: Thu, 05 Dec 2024 18:36:34 +0100

This reads OK to me.

(I don't have a carp setup at the moment).

On 2024-12-05 12:26 +09, YASUOKA Masahiko <yasuoka@openbsd.org> wrote:
> Hi,
>
> My colleague noticed that all unsolicited NAs when carp becomes master
> are ignored by the received hosts.  This is because the source address
> is ::1.
>
>   20:32:08.676523 00:50:56:xx:xx:xx 33:33:00:00:00:01 86dd 86: ::1 > ff02::1: icmp6: neighbor adv: tgt is xxxx:xxxx:bb5e:1823::1:250
>
> We must embed a scope-id to the destination when calling
> nd6_na_output().  Also the route the "ff02:1" is not RTF_UP at that
> time.  We need to wait until if state change task is completed.
>
>
> comments? ok?
>
> Embed scope-id when sending NA.  Also, do it when the link state is
> up because the route entry to the mutlicast is not ready yet when the
> carp becomes master.
>
> Index: sys/netinet/ip_carp.c
> ===================================================================
> RCS file: /disk/cvs/openbsd/src/sys/netinet/ip_carp.c,v
> diff -u -p -r1.363 ip_carp.c
> --- sys/netinet/ip_carp.c	14 Jul 2024 18:53:39 -0000	1.363
> +++ sys/netinet/ip_carp.c	5 Dec 2024 03:19:34 -0000
> @@ -138,6 +138,7 @@ struct carp_softc {
>  	struct ip_moptions sc_imo;
>  #ifdef INET6
>  	struct ip6_moptions sc_im6o;
> +	struct task sc_itask;
>  #endif /* INET6 */
>  
>  	SRPL_ENTRY(carp_softc) sc_list;
> @@ -171,6 +172,9 @@ struct carp_softc {
>  	u_int32_t sc_lsmask;		/* load sharing mask */
>  	int sc_lscount;			/* # load sharing interfaces (max 32) */
>  	int sc_delayed_arp;		/* delayed ARP request countdown */
> +#ifdef INET6
> +	int sc_send_na;			/* send NA when link state up */
> +#endif /* INET6 */
>  	int sc_realmac;			/* using real mac */
>  
>  	struct in_addr sc_peer;
> @@ -250,6 +254,7 @@ int	carp_join_multicast(struct carp_soft
>  void	carp_send_na(struct carp_softc *);
>  int	carp_set_addr6(struct carp_softc *, struct sockaddr_in6 *);
>  int	carp_join_multicast6(struct carp_softc *);
> +void	carp_if_linkstate(void *);
>  #endif
>  int	carp_clone_create(struct if_clone *, int);
>  int	carp_clone_destroy(struct ifnet *);
> @@ -811,6 +816,9 @@ carp_clone_create(struct if_clone *ifc, 
>  	task_set(&sc->sc_atask, carp_addr_updated, sc);
>  	task_set(&sc->sc_ltask, carp_carpdev_state, sc);
>  	task_set(&sc->sc_dtask, carpdetach, sc);
> +#ifdef INET6
> +	task_set(&sc->sc_itask, carp_if_linkstate, sc);
> +#endif /* INET6 */
>  
>  	sc->sc_suppress = 0;
>  	sc->sc_advbase = CARP_DFLTINTV;
> @@ -843,6 +851,9 @@ carp_clone_create(struct if_clone *ifc, 
>  
>  	/* Hook carp_addr_updated to cope with address and route changes. */
>  	if_addrhook_add(&sc->sc_if, &sc->sc_atask);
> +#ifdef INET6
> +	if_linkstatehook_add(&sc->sc_if, &sc->sc_itask);
> +#endif /* INET6 */
>  
>  	return (0);
>  }
> @@ -894,6 +905,9 @@ carp_clone_destroy(struct ifnet *ifp)
>  	struct carp_softc *sc = ifp->if_softc;
>  
>  	if_addrhook_del(&sc->sc_if, &sc->sc_atask);
> +#ifdef INET6
> +	if_linkstatehook_del(&sc->sc_if, &sc->sc_itask);
> +#endif /* INET6 */
>  
>  	NET_LOCK();
>  	carpdetach(sc);
> @@ -1285,13 +1299,13 @@ void
>  carp_send_na(struct carp_softc *sc)
>  {
>  	struct ifaddr *ifa;
> -	struct in6_addr *in6;
> -	static struct in6_addr mcast = IN6ADDR_LINKLOCAL_ALLNODES_INIT;
> +	struct in6_addr *in6, mcast = IN6ADDR_LINKLOCAL_ALLNODES_INIT;
>  	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
>  	int flags = ND_NA_FLAG_OVERRIDE;
>  
>  	if (i_am_router)
>  		flags |= ND_NA_FLAG_ROUTER;
> +	mcast.s6_addr16[1] = htons(sc->sc_if.if_index);
>  
>  	TAILQ_FOREACH(ifa, &sc->sc_if.if_addrlist, ifa_list) {
>  
> @@ -1534,7 +1548,8 @@ carp_master_down(struct carp_vhost_entry
>  			/* Schedule a delayed ARP to deal w/ some L3 switches */
>  			sc->sc_delayed_arp = 2;
>  #ifdef INET6
> -			carp_send_na(sc);
> +			/* routing entry is not ready yet.  do it later */
> +			sc->sc_send_na = 1;
>  #endif /* INET6 */
>  		}
>  		carp_setrun(vhe, 0);
> @@ -1955,6 +1970,17 @@ carp_join_multicast6(struct carp_softc *
>  	return (0);
>  }
>  
> +void
> +carp_if_linkstate(void *v)
> +{
> +	struct carp_softc *sc = v;
> +
> +	if (sc->sc_send_na) {
> +		if (sc->sc_if.if_link_state == LINK_STATE_UP)
> +			carp_send_na(sc);
> +		sc->sc_send_na = 0;
> +	}
> +}
>  #endif /* INET6 */
>  
>  int
>

-- 
In my defence, I have been left unsupervised.