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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: Jiri Benc <jbenc@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jiri Benc 2013-12-11 13:48:20 +01:00 committed by David S. Miller
parent e477266838
commit 7e98056964
3 changed files with 26 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/neighbour.h
View File

@ -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);

15
net/core/neighbour.c
View File

@ -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)

16
net/ipv6/route.c
View File

@ -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;