From 7e9805696428113e34625a65a30dbc62cb78acc5 Mon Sep 17 00:00:00 2001 From: Jiri Benc Date: Wed, 11 Dec 2013 13:48:20 +0100 Subject: [PATCH] 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 Acked-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- include/net/neighbour.h | 1 + net/core/neighbour.c | 15 +++++++++++++++ net/ipv6/route.c | 16 ++++++++++------ 3 files changed, 26 insertions(+), 6 deletions(-) diff --git a/include/net/neighbour.h b/include/net/neighbour.h index 41b1ce6c96a8..4c09bd23b832 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -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); diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 8be82a7f0e0f..bf6f404c04aa 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -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) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index ddb9d41c8eea..a1a57523b158 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -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; -- 2.34.1