Commit fb811395 authored by Rick Jones's avatar Rick Jones Committed by David S. Miller
Browse files

net: add explicit logging and stat for neighbour table overflow 



Add an explicit neighbour table overflow message (ratelimited) and
statistic to make diagnosing neighbour table overflows tractable in
the wild.

Diagnosing a neighbour table overflow can be quite difficult in the wild
because there is no explicit dmesg logged.  Callers to neighbour code
seem to use net_dbg_ratelimit when the neighbour call fails which means
the "base message" is not emitted and the callback suppressed messages
from the ratelimiting can end-up juxtaposed with unrelated messages.
Further, a forced garbage collection will increment a stat on each call
whether it was successful in freeing-up a table entry or not, so that
statistic is only a hint.  So, add a net_info_ratelimited message and
explicit statistic to the neighbour code.

Signed-off-by: default avatarRick Jones <rick.jones2@hp.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a7854037

include/net/neighbour.h

+1 −0
Original line number Diff line number Diff line
@@ -125,6 +125,7 @@ struct neigh_statistics { 
	unsigned long forced_gc_runs;	/* number of forced GC runs */



	unsigned long unres_discards;	/* number of unresolved drops */

	unsigned long table_fulls;      /* times even gc couldn't help */

};



#define NEIGH_CACHE_STAT_INC(tbl, field) this_cpu_inc((tbl)->stats->field)

include/uapi/linux/neighbour.h

+1 −0
Original line number Diff line number Diff line
@@ -106,6 +106,7 @@ struct ndt_stats { 
	__u64		ndts_rcv_probes_ucast;

	__u64		ndts_periodic_gc_runs;

	__u64		ndts_forced_gc_runs;

	__u64		ndts_table_fulls;

};



enum {

net/core/neighbour.c

+10 −4
Original line number Diff line number Diff line
@@ -274,9 +274,13 @@ static struct neighbour *neigh_alloc(struct neigh_table *tbl, struct net_device 
	    (entries >= tbl->gc_thresh2 &&

	     time_after(now, tbl->last_flush + 5 * HZ))) {

		if (!neigh_forced_gc(tbl) &&

		    entries >= tbl->gc_thresh3)

		    entries >= tbl->gc_thresh3) {

			net_info_ratelimited("%s: neighbor table overflow!\n",

					     tbl->id);

			NEIGH_CACHE_STAT_INC(tbl, table_fulls);

			goto out_entries;

		}

	}



	n = kzalloc(tbl->entry_size + dev->neigh_priv_len, GFP_ATOMIC);

	if (!n)
@@ -1849,6 +1853,7 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl, 
			ndst.ndts_rcv_probes_ucast	+= st->rcv_probes_ucast;

			ndst.ndts_periodic_gc_runs	+= st->periodic_gc_runs;

			ndst.ndts_forced_gc_runs	+= st->forced_gc_runs;

			ndst.ndts_table_fulls		+= st->table_fulls;

		}



		if (nla_put(skb, NDTA_STATS, sizeof(ndst), &ndst))
@@ -2717,12 +2722,12 @@ static int neigh_stat_seq_show(struct seq_file *seq, void *v) 
	struct neigh_statistics *st = v;



	if (v == SEQ_START_TOKEN) {

		seq_printf(seq, "entries  allocs destroys hash_grows  lookups hits  res_failed  rcv_probes_mcast rcv_probes_ucast  periodic_gc_runs forced_gc_runs unresolved_discards\n");

		seq_printf(seq, "entries  allocs destroys hash_grows  lookups hits  res_failed  rcv_probes_mcast rcv_probes_ucast  periodic_gc_runs forced_gc_runs unresolved_discards table_fulls\n");

		return 0;

	}



	seq_printf(seq, "%08x  %08lx %08lx %08lx  %08lx %08lx  %08lx  "

			"%08lx %08lx  %08lx %08lx %08lx\n",

			"%08lx %08lx  %08lx %08lx %08lx %08lx\n",

		   atomic_read(&tbl->entries),



		   st->allocs,
@@ -2739,7 +2744,8 @@ static int neigh_stat_seq_show(struct seq_file *seq, void *v) 


		   st->periodic_gc_runs,

		   st->forced_gc_runs,

		   st->unres_discards

		   st->unres_discards,

		   st->table_fulls

		   );



	return 0;

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