Re: 100% CPU load when generating traffic to destination network that nexthop is not reachable
flat view
From: Julian Anastasov <ja@ssi.bg>
Date: 2017-08-16 07:42:15
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Hello, On Tue, 15 Aug 2017, Eric Dumazet wrote:
It must be possible to add a fast path without locks. (say if jiffies has not changed before last state change)
New day - new idea. Something like this? But it has bug: without checking neigh->dead under lock we don't have the right to access neigh->parms, it can be destroyed immediately by neigh_release->neigh_destroy->neigh_parms_put-> neigh_parms_destroy->kfree. Not sure, may be kfree_rcu can help for this...
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 9816df2..f52763c 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h@@ -428,10 +428,10 @@ static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb) { unsigned long now = jiffies; - if (neigh->used != now) - neigh->used = now; if (!(neigh->nud_state&(NUD_CONNECTED|NUD_DELAY|NUD_PROBE))) return __neigh_event_send(neigh, skb); + if (neigh->used != now) + neigh->used = now; return 0; }
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 16a1a4c..52a8718 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c@@ -991,8 +991,18 @@ static void neigh_timer_handler(unsigned long arg) int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb) { - int rc; bool immediate_probe = false; + unsigned long now = jiffies; + int rc; + + if (neigh->used != now) { + neigh->used = now; + } else if (neigh->nud_state == NUD_INCOMPLETE && + (!skb || neigh->arp_queue_len_bytes + skb->truesize > + NEIGH_VAR(neigh->parms, QUEUE_LEN_BYTES))) { + kfree_skb(skb); + return 1; + } write_lock_bh(&neigh->lock);
@@ -1005,7 +1015,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb) if (!(neigh->nud_state & (NUD_STALE | NUD_INCOMPLETE))) { if (NEIGH_VAR(neigh->parms, MCAST_PROBES) + NEIGH_VAR(neigh->parms, APP_PROBES)) { - unsigned long next, now = jiffies; + unsigned long next; atomic_set(&neigh->probes, NEIGH_VAR(neigh->parms, UCAST_PROBES));
Regards