Disappearing ARP in /proc/net/arp

[Jari Takkala]

We are running kernel 2.6.9-22.0.2.EL (CentOS 4) and a custom built
2.4.29 kernel on a few dozen Dell 850's. These are functioning as
firewall's and in some we publish a large number (greater than 75) ARP
entries using 'arp -Ds <IP> <iface> pub'.

I have noticed that one entry is intermittently missing from the output
of /proc/net/arp when we have greater than 10 published ARP entries.
This seems to be a display issue as the kernel continues to reply to ARP
who-has on the network (as confirmed with tcpdump). The entry which is
missing varies and seems to alternate between a fixed number of IP's
among the 75 or so ARP entries. I have not been able to find a bug-fix
for this in either the kernel source or on the mailing list.

To reproduce:

- Publish greater than 10 ARP entries.
- View output of 'arp -n' or 'cat /proc/net/arp'
	- Repeat until one published entry will be missing.

On average I have been able to repeat this problem within 1 minute by
comparing output from 'grep "0xc" /proc/net/arp' every 2 seconds.

Regards,

Jari
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