Commit 7e980569 authored by Jiri Benc's avatar Jiri Benc Committed by David S. Miller
Browse files

ipv6: router reachability probing 



RFC 4191 states in 3.5:

   When a host avoids using any non-reachable router X and instead sends
   a data packet to another router Y, and the host would have used
   router X if router X were reachable, then the host SHOULD probe each
   such router X's reachability by sending a single Neighbor
   Solicitation to that router's address.  A host MUST NOT probe a
   router's reachability in the absence of useful traffic that the host
   would have sent to the router if it were reachable.  In any case,
   these probes MUST be rate-limited to no more than one per minute per
   router.

Currently, when the neighbour corresponding to a router falls into
NUD_FAILED, it's never considered again. Introduce a new rt6_nud_state
value, RT6_NUD_FAIL_PROBE, which suggests the route should not be used but
should be probed with a single NS. The probe is ratelimited by the existing
code. To better distinguish meanings of the failure values, rename
RT6_NUD_FAIL_SOFT to RT6_NUD_FAIL_DO_RR.

Signed-off-by: default avatarJiri Benc <jbenc@redhat.com>
Acked-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e4772668

include/net/neighbour.h

+1 −0
Original line number Diff line number Diff line
@@ -252,6 +252,7 @@ static inline struct neighbour *neigh_create(struct neigh_table *tbl, 
void neigh_destroy(struct neighbour *neigh);

int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb);

int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, u32 flags);

void __neigh_set_probe_once(struct neighbour *neigh);

void neigh_changeaddr(struct neigh_table *tbl, struct net_device *dev);

int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev);

int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb);

net/core/neighbour.c

+15 −0
Original line number Diff line number Diff line
@@ -1238,6 +1238,21 @@ out: 
}

EXPORT_SYMBOL(neigh_update);



/* Update the neigh to listen temporarily for probe responses, even if it is

 * in a NUD_FAILED state. The caller has to hold neigh->lock for writing.

 */

void __neigh_set_probe_once(struct neighbour *neigh)

{

	neigh->updated = jiffies;

	if (!(neigh->nud_state & NUD_FAILED))

		return;

	neigh->nud_state = NUD_PROBE;

	atomic_set(&neigh->probes, NEIGH_VAR(neigh->parms, UCAST_PROBES));

	neigh_add_timer(neigh,

			jiffies + NEIGH_VAR(neigh->parms, RETRANS_TIME));

}

EXPORT_SYMBOL(__neigh_set_probe_once);



struct neighbour *neigh_event_ns(struct neigh_table *tbl,

				 u8 *lladdr, void *saddr,

				 struct net_device *dev)

net/ipv6/route.c

+10 −6
Original line number Diff line number Diff line
@@ -66,8 +66,9 @@ 
#endif



enum rt6_nud_state {

	RT6_NUD_FAIL_HARD = -2,

	RT6_NUD_FAIL_SOFT = -1,

	RT6_NUD_FAIL_HARD = -3,

	RT6_NUD_FAIL_PROBE = -2,

	RT6_NUD_FAIL_DO_RR = -1,

	RT6_NUD_SUCCEED = 1

};
@@ -521,7 +522,7 @@ static void rt6_probe(struct rt6_info *rt) 
		work = kmalloc(sizeof(*work), GFP_ATOMIC);



		if (neigh && work)

			neigh->updated = jiffies;

			__neigh_set_probe_once(neigh);



		if (neigh)

			write_unlock(&neigh->lock);
@@ -577,11 +578,13 @@ static inline enum rt6_nud_state rt6_check_neigh(struct rt6_info *rt) 
#ifdef CONFIG_IPV6_ROUTER_PREF

		else if (!(neigh->nud_state & NUD_FAILED))

			ret = RT6_NUD_SUCCEED;

		else

			ret = RT6_NUD_FAIL_PROBE;

#endif

		read_unlock(&neigh->lock);

	} else {

		ret = IS_ENABLED(CONFIG_IPV6_ROUTER_PREF) ?

		      RT6_NUD_SUCCEED : RT6_NUD_FAIL_SOFT;

		      RT6_NUD_SUCCEED : RT6_NUD_FAIL_DO_RR;

	}

	rcu_read_unlock_bh();
@@ -618,16 +621,17 @@ static struct rt6_info *find_match(struct rt6_info *rt, int oif, int strict, 
		goto out;



	m = rt6_score_route(rt, oif, strict);

	if (m == RT6_NUD_FAIL_SOFT) {

	if (m == RT6_NUD_FAIL_DO_RR) {

		match_do_rr = true;

		m = 0; /* lowest valid score */

	} else if (m < 0) {

	} else if (m == RT6_NUD_FAIL_HARD) {

		goto out;

	}



	if (strict & RT6_LOOKUP_F_REACHABLE)

		rt6_probe(rt);



	/* note that m can be RT6_NUD_FAIL_PROBE at this point */

	if (m > *mpri) {

		*do_rr = match_do_rr;

		*mpri = m;

CRA Git | Maintained and supported by SUSTech CRA and CCSE