ARP(3) Library Functions Manual ARP(3)
arp - Internet Address Resolution Protocol
bind -a #a /net/arp
The arp device provides the means by which the kernel resolves IP
addresses into Ethernet addresses. A cache is maintained by the arp
device to speed the process.
The ctl file controls the ARP cache maintained by the kernel. The
flush control message invalidates all entries in the cache. The delete
ipaddr control message invalidates a single cache entry. All IP
addresses passed to the system are in the canonical textual form
described in ip(2). The perm ipaddr control message makes an existing
cache entry permanent.
When the kernel boots, ipconfig sets up the IP stream and arpd opens
#a/arp/data (see ipconfig(8)). This establishes the ARP cache and
enables arpd to receive all ARP packets from the network, which it uses
to maintain the cache by writing the results of address resolution
requests back into the cache. The IP stream module uses the cache to
translate IP addresses.
Subsequent opens of the data file allow the contents of the cache to be
examined. Each cache entry consists of an IP address, an Ethernet
address, and the status of the entry. Entries may be invalid, perma-
nent, or temporary. Permanent entries will never be aged from the
cache. Temporary entries may be replaced by new addresses entered by
the ARP server.
The file stats reports the cache performance.