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Date: Mon, 12 May 2014 14:37:20 -0400 (EDT) From: David Miller <davem@...emloft.net> To: duanj.fnst@...fujitsu.com Cc: hannes@...essinduktion.org, netdev@...r.kernel.org, jbenc@...hat.com Subject: Re: [PATCH v2] neigh: set nud_state to NUD_INCOMPLETE when probing router reachability From: Duan Jiong <duanj.fnst@...fujitsu.com> Date: Mon, 12 May 2014 11:26:10 +0800 > 于 2014年05月12日 06:04, Hannes Frederic Sowa 写道: >> On Thu, May 8, 2014, at 22:16, Duan Jiong wrote: >>> >>> Since commit 7e98056964("ipv6: router reachability probing"), a router falls >>> into NUD_FAILED will be probed. >>> >>> Now if function rt6_select() selects a router which neighbour state is NUD_FAILED, >>> and at the same time function rt6_probe() changes the neighbour state to NUD_PROBE, >>> then function dst_neigh_output() can directly send packets, but actually the >>> neighbour still is unreachable. If we set nud_state to NUD_INCOMPLETE instead >>> NUD_PROBE, packets will not be sent out until the neihbour is reachable. >>> >>> In addition, because the route should be probes with a single NS, so we must >>> set neigh->probes to neigh_max_probes(), then the neigh timer timeout and function >>> neigh_timer_handler() will not send other NS Messages. >>> >>> Signed-off-by: Duan Jiong <duanj.fnst@...fujitsu.com> >>> --- >>> Changes from v1: >>> *modify changelog to explain in detail why use neigh_max_probes(). >>> >>> net/core/neighbour.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/net/core/neighbour.c b/net/core/neighbour.c >>> index 8f8a96e..32d872e 100644 >>> --- a/net/core/neighbour.c >>> +++ b/net/core/neighbour.c >>> @@ -1248,8 +1248,8 @@ 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->nud_state = NUD_INCOMPLETE; >>> + atomic_set(&neigh->probes, neigh_max_probes(neigh)); >> >> Wouldn't it be better if we neigh_suspect the neighbour and leaving the state in NUD_PROBE? We call down to ->output in case neighbour is in NUD_PROBE state, so we must just disable connected 'fast-path'. >> > > You can look into neigh_event_send() called in neigh_resolve_output(), and if neigh->nud_state > still is NUD_PROBE, the neigh_event_send() will return 0, so the packet will still be sent out > without probe. > > So, using neigh_suspect is not a good idea. If you set it to NUD_INCOMPLETE however, neigh_event_send() is going to add the packet to the neigh's ARP queue and return '1'. Is that really what you want to happen in this case? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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