Performance: Neighbour table overflow

[Rajasekhar Inguva]

Hi All,
I have observed that when the ARP cache is full , any further networking
apps fail with error "Neighbour table overflow" until a timer expires and
the cache is cleared. Below is a detailed re-creation scenario....

1) Set  /proc/sys/net/ipv4/neigh/default/gc_thresh1,2,3  to values 2
2) ping one_neighbour ( arp cache now has this entry )
3) ping another_neighbour ( arp cache has now 2 entries )
4) ping third_neighbour

    Neighbour table overflow
    Ping: No buffer space available

Until the timer expires and the arp cache gets cleared , no further network
connections succeed.

IMHO, in situations wherein stale entries do exist in the cache and the
cache is full, then one should not wait for a timer expiry but remove a few
entries asap.

I get a feeling it might violate some rfc's , but i am not really sure....

Any feedback ?

Regards,

Raj