Monitoring the IPv4 Neighbor Table

[Jim Murphy]

Hi,

I am trying to use a netlink socket to monitor the RTM_XXXNEIGH 
messages. When I make a direct request for messages via:

req.nlh.nlmsg_type = RTM_GETNEIGH

I get the neighbor table as expected.

However, I don't get subsequent updates to the neighbor table as ARP 
entries are added and aged.

This differs from the link, address and route entries, for which I get 
updates whenever these objects are configured.

Note, I have set the the socket to bind on all nl_groups.

I suspect the issue might be that arp entries are not a result of 
configuration to the kernel via the routing socket and hence there are 
no associated RTNETLINK messages created.

Assuming this is the case, short of actually opening up a raw socket to 
receive all ARP packets (as seems to be the technique used by 
iproute2-2.6.25/misc/arpd.c) and implementing my own ARP cache, is there 
some mechanism available to monitor the state of the neighbor table in 
the kernel (sort of the obvious, inefficient and untimely method of 
polling)?

Thanks,

Jim
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