ARP(3) ARP(3)
NAME
arp - Internet Address Resolution Protocol
SYNOPSIS
bind -a #a /net/arp
/net/arp/ctl
/net/arp/data
/net/arp/stats
DESCRIPTION
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 ker-
nel. 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, permanent, 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.
SEE ALSO
ip(3), ipconfig(8)
SOURCE
/sys/src/9/port/devarp.c