1.\" $NetBSD: arp.9,v 1.25 2010/05/14 18:52:53 joerg Exp $ 2.\" 3.\" Copyright (c) 1997 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Ignatios Souvatzis. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.\" 31.Dd March 3, 1997 32.Dt ARP 9 33.Os 34.Sh NAME 35.Nm arp , 36.Nm arp_ifinit , 37.Nm arpresolve , 38.Nm arpintr 39.Nd externally visible ARP functions 40.Sh SYNOPSIS 41.In netinet/if_inarp.h 42.Ft void 43.Fn arp_ifinit "struct ifnet *ifp" "struct ifaddr *ifa" 44.Ft int 45.Fn arpresolve "struct ifnet *ifp" "struct rtentry *rt" "struct mbuf *m" "struct sockaddr *dst" "u_char *desten" 46.Ft void 47.Fn arpintr 48.Sh DESCRIPTION 49The 50.Nm 51functions provide the interface between the 52.Nm 53module and the network drivers which need 54.Nm 55functionality. 56Such drivers must request the 57.Ar arp 58attribute in their "files" declaration. 59.Bl -tag -width "arp_ifinit()" 60.It Fn arp_ifinit 61Sets up the 62.Nm 63specific fields in 64.Fa ifa . 65Additionally, it sends out a gratuitous 66.Nm 67request on 68.Fa ifp , 69so that other machines are warned that we have a (new) address and 70duplicate addresses can be detected. 71.Pp 72You must call this in your drivers' ioctl function when you get a 73SIOCSIFADDR request with an AF_INET address family. 74.It Fn arpresolve 75is called by network output functions to resolve an IPv4 address. 76If no 77.Fa rt 78is given, a new one is looked up or created. 79If the passed or found 80.Fa rt 81does not contain a valid gateway link level address, a pointer to the packet 82in 83.Fa m 84is stored in the route entry, possibly replacing older stored packets, and an 85.Nm 86request is sent instead. 87When an 88.Nm 89reply is received, the last held packet is send. 90Otherwise, the looked up address is returned and written into the storage 91.Fa desten 92points to. 93.Fn arpresolve 94returns 1, if a valid address was stored to 95.Fa desten , 96and the packet can be sent immediately. 97Else a 0 is returned. 98.It Fn arpintr 99When an 100.Nm 101packet is received, the network driver (class) input interrupt handler queues 102the packet on the arpintrq queue, and requests an 103.Fn arpintr 104soft interrupt callback. 105.Fn arpintr 106dequeues the packets, performs sanity checks and calls (for IPv4 107.Nm 108packets, which are the only ones supported currently) the 109.Fn in_arpinput 110function. 111.Fn in_arpinput 112either generates a reply to request packets, and adds the sender address 113translation to the routing table, if a matching route entry is found. 114If the route entry contained a pointer to a held packet, that packet is 115sent. 116.El 117.Sh SEE ALSO 118.Xr ether_ifattach 9 119.\" .Xr fddi_ifattach 9 , 120.\" .Xr arc_ifattach 9 121.Pp 122Plummer, D., "RFC826", An Ethernet Address Resolution Protocol. 123.Sh STANDARDS 124RFC 826 125.Sh HISTORY 126Rewritten to support other than Ethernet link level addresses in 127.Nx 1.3 . 128.Sh AUTHORS 129.An UCB CSRG 130(original implementation) 131.An Ignatios Souvatzis 132(support for non-Ethernet) 133.Sh CODE REFERENCES 134The ARP code is implemented in 135.Pa sys/net/if_arp.h , 136.Pa sys/netinet/if_inarp.h 137and 138.Pa sys/netinet/if_arp.c . 139