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ARP(3)                     Library Functions Manual                     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 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.

SEE ALSO
       ip(3), ipconfig(8)

SOURCE
       /sys/src/9/port/devarp.c



                                                                        ARP(3)