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NetBSD 6.1.5 - man page for arp (netbsd section 9)

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ARP(9)				  BSD Kernel Developer's Manual 			   ARP(9)

NAME
     arp, arp_ifinit, arpresolve, arpintr -- externally visible ARP functions

SYNOPSIS
     #include <netinet/if_inarp.h>

     void
     arp_ifinit(struct ifnet *ifp, struct ifaddr *ifa);

     int
     arpresolve(struct ifnet *ifp, struct rtentry *rt, struct mbuf *m, struct sockaddr *dst,
	 u_char *desten);

     void
     arpintr();

DESCRIPTION
     The arp functions provide the interface between the arp module and the network drivers which
     need arp functionality.  Such drivers must request the arp attribute in their "files" decla-
     ration.

     arp_ifinit()  Sets up the arp specific fields in ifa.  Additionally, it sends out a gratu-
		   itous arp request on ifp, so that other machines are warned that we have a
		   (new) address and duplicate addresses can be detected.

		   You must call this in your drivers' ioctl function when you get a SIOCSIFADDR
		   request with an AF_INET address family.

     arpresolve()  is called by network output functions to resolve an IPv4 address.  If no rt is
		   given, a new one is looked up or created.  If the passed or found rt does not
		   contain a valid gateway link level address, a pointer to the packet in m is
		   stored in the route entry, possibly replacing older stored packets, and an arp
		   request is sent instead.  When an arp reply is received, the last held packet
		   is send.  Otherwise, the looked up address is returned and written into the
		   storage desten points to.  arpresolve() returns 1, if a valid address was
		   stored to desten, and the packet can be sent immediately.  Else a 0 is
		   returned.

     arpintr()	   When an arp packet is received, the network driver (class) input interrupt
		   handler queues the packet on the arpintrq queue, and requests an arpintr()
		   soft interrupt callback.  arpintr() dequeues the packets, performs sanity
		   checks and calls (for IPv4 arp packets, which are the only ones supported cur-
		   rently) the in_arpinput() function.	in_arpinput() either generates a reply to
		   request packets, and adds the sender address translation to the routing table,
		   if a matching route entry is found.	If the route entry contained a pointer to
		   a held packet, that packet is sent.

SEE ALSO
     ether_ifattach(9)

     Plummer, D., "RFC826", An Ethernet Address Resolution Protocol.

STANDARDS
     RFC 826

HISTORY
     Rewritten to support other than Ethernet link level addresses in NetBSD 1.3.

AUTHORS
     UCB CSRG (original implementation)
     Ignatios Souvatzis (support for non-Ethernet)

CODE REFERENCES
     The ARP code is implemented in sys/net/if_arp.h, sys/netinet/if_inarp.h and
     sys/netinet/if_arp.c.

BSD					  March 3, 1997 				      BSD
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