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,
const struct
rtentry *rt,
struct mbuf
*m,
const struct sockaddr
*dst,
void *desten,
size_t destlen);
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" declaration.
-
-
- arp_ifinit()
- Sets up the arp specific fields in
ifa. Additionally, it sends out a gratuitous
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 currently) 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.
CODE REFERENCES
The ARP code is implemented in
sys/net/if_arp.h,
sys/netinet/if_inarp.h and
sys/netinet/if_arp.c.
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)