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 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, 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