| File arp.c |
| |
Xinu path name net/arp.c |
/* arp.c - arp_init, arp_resolve, arp_in, arp_alloc, arp_ntoh, arp_hton */
#include
struct arpentry arpcache[ARP_SIZ]; /* ARP cache */
/*------------------------------------------------------------------------
* arp_init - Initialize ARP cache for an Ethernet interface
*------------------------------------------------------------------------
*/
void arp_init(void)
{
int32 i; /* ARP cache index */
for (i=1; iarstate == AR_FREE) {
continue;
}
if (arptr->arpaddr == nxthop) { /* Adddress is in cache */
break;
}
}
if (i < ARP_SIZ) { /* Entry was found */
/* If entry is resolved - handle and return */
if (arptr->arstate == AR_RESOLVED) {
memcpy(mac, arptr->arhaddr, ARP_HALEN);
restore(mask);
return OK;
}
/* Entry is already pending - return error because */
/* only one process can be waiting at a time */
if (arptr->arstate == AR_PENDING) {
restore(mask);
return SYSERR;
}
}
/* IP address not in cache - allocate a new cache entry and */
/* send an ARP request to obtain the answer */
slot = arp_alloc();
if (slot == SYSERR) {
restore(mask);
return SYSERR;
}
arptr = &arpcache[slot];
arptr->arstate = AR_PENDING;
arptr->arpaddr = nxthop;
arptr->arpid = currpid;
/* Hand-craft an ARP Request packet */
memcpy(apkt.arp_ethdst, NetData.ethbcast, ETH_ADDR_LEN);
memcpy(apkt.arp_ethsrc, NetData.ethucast, ETH_ADDR_LEN);
apkt.arp_ethtype = ETH_ARP; /* Packet type is ARP */
apkt.arp_htype = ARP_HTYPE; /* Hardware type is Ethernet */
apkt.arp_ptype = ARP_PTYPE; /* Protocol type is IP */
apkt.arp_hlen = 0xff & ARP_HALEN; /* Ethernet MAC size in bytes */
apkt.arp_plen = 0xff & ARP_PALEN; /* IP address size in bytes */
apkt.arp_op = 0xffff & ARP_OP_REQ;/* ARP type is Request */
memcpy(apkt.arp_sndha, NetData.ethucast, ARP_HALEN);
apkt.arp_sndpa = NetData.ipucast; /* IP address of interface */
memset(apkt.arp_tarha, '\0', ARP_HALEN); /* Target HA is unknown*/
apkt.arp_tarpa = nxthop; /* Target protocol address */
/* Convert ARP packet from host to net byte order */
arp_hton(&apkt);
/* Convert Ethernet header from host to net byte order */
eth_hton((struct netpacket *)&apkt);
/* Send the packet ARP_RETRY times and await response */
msg = recvclr();
for (i=0; iarstate = AR_FREE; /* Invalidate cache entry */
restore(mask);
return TIMEOUT;
}
/* Return hardware address */
memcpy(mac, arptr->arhaddr, ARP_HALEN);
restore(mask);
return OK;
}
/*------------------------------------------------------------------------
* arp_in - Handle an incoming ARP packet
*------------------------------------------------------------------------
*/
void arp_in (
struct arppacket *pktptr /* Ptr to incoming packet */
)
{
intmask mask; /* Saved interrupt mask */
struct arppacket apkt; /* Local packet buffer */
int32 slot; /* Slot in cache */
struct arpentry *arptr; /* Ptr to ARP cache entry */
bool8 found; /* Is the sender's address in */
/* the cache? */
/* Convert packet from network order to host order */
arp_ntoh(pktptr);
/* Verify ARP is for IPv4 and Ethernet */
if ( (pktptr->arp_htype != ARP_HTYPE) ||
(pktptr->arp_ptype != ARP_PTYPE) ) {
freebuf((char *)pktptr);
return;
}
/* Ensure only one process uses ARP at a time */
mask = disable();
/* Search cache for sender's IP address */
found = FALSE;
for (slot=0; slot < ARP_SIZ; slot++) {
arptr = &arpcache[slot];
/* Skip table entries that are unused */
if (arptr->arstate == AR_FREE) {
continue;
}
/* If sender's address matches, we've found it */
if (arptr->arpaddr == pktptr->arp_sndpa) {
found = TRUE;
break;
}
}
if (found) {
/* Update sender's hardware address */
memcpy(arptr->arhaddr, pktptr->arp_sndha, ARP_HALEN);
/* If a process was waiting, inform the process */
if (arptr->arstate == AR_PENDING) {
/* Mark resolved and notify waiting process */
arptr->arstate = AR_RESOLVED;
send(arptr->arpid, OK);
}
}
/* For an ARP reply, processing is complete */
if (pktptr->arp_op == ARP_OP_RPLY) {
freebuf((char *)pktptr);
restore(mask);
return;
}
/* The following is for an ARP request packet: if the local */
/* machine is not the target or the local IP address is not */
/* yet known, ignore the request (i.e., processing is complete)*/
if ((!NetData.ipvalid) ||
(pktptr->arp_tarpa != NetData.ipucast)) {
freebuf((char *)pktptr);
restore(mask);
return;
}
/* Request has been sent to the local machine's address. So, */
/* add sender's info to cache, if not already present */
if (!found) {
slot = arp_alloc();
if (slot == SYSERR) { /* Cache is full */
kprintf("ARP cache overflow on interface\n");
freebuf((char *)pktptr);
restore(mask);
return;
}
arptr = &arpcache[slot];
arptr->arpaddr = pktptr->arp_sndpa;
memcpy(arptr->arhaddr, pktptr->arp_sndha, ARP_HALEN);
arptr->arstate = AR_RESOLVED;
}
/* Hand-craft an ARP reply packet and send back to requester */
memcpy(apkt.arp_ethdst, pktptr->arp_sndha, ARP_HALEN);
memcpy(apkt.arp_ethsrc, NetData.ethucast, ARP_HALEN);
apkt.arp_ethtype= ETH_ARP; /* Frame carries ARP */
apkt.arp_htype = ARP_HTYPE; /* Hardware is Ethernet */
apkt.arp_ptype = ARP_PTYPE; /* Protocol is IP */
apkt.arp_hlen = ARP_HALEN; /* Ethernet address size*/
apkt.arp_plen = ARP_PALEN; /* IP address size */
apkt.arp_op = ARP_OP_RPLY; /* Type is Reply */
/* Insert local Ethernet and IP address in sender fields */
memcpy(apkt.arp_sndha, NetData.ethucast, ARP_HALEN);
apkt.arp_sndpa = NetData.ipucast;
/* Copy target Ethernet and IP addresses from request packet */
memcpy(apkt.arp_tarha, pktptr->arp_sndha, ARP_HALEN);
apkt.arp_tarpa = pktptr->arp_sndpa;
/* Convert ARP packet from host to network byte order */
arp_hton(&apkt);
/* Convert the Ethernet header to network byte order */
eth_hton((struct netpacket *)&apkt);
/* Send the reply */
write(ETHER0, (char *)&apkt, sizeof(struct arppacket));
freebuf((char *)pktptr);
restore(mask);
return;
}
/*------------------------------------------------------------------------
* arp_alloc - Find a free slot or kick out an entry to create one
*------------------------------------------------------------------------
*/
int32 arp_alloc ()
{
int32 slot; /* Slot in ARP cache */
/* Search for a free slot */
for (slot=0; slot < ARP_SIZ; slot++) {
if (arpcache[slot].arstate == AR_FREE) {
memset((char *)&arpcache[slot],
NULLCH, sizeof(struct arpentry));
return slot;
}
}
/* Search for a resolved entry */
for (slot=0; slot < ARP_SIZ; slot++) {
if (arpcache[slot].arstate == AR_RESOLVED) {
memset((char *)&arpcache[slot],
NULLCH, sizeof(struct arpentry));
return slot;
}
}
/* At this point, all slots are pending (should not happen) */
kprintf("ARP cache size exceeded\n");
return SYSERR;
}
/*------------------------------------------------------------------------
* arp_ntoh - Convert ARP packet fields from net to host byte order
*------------------------------------------------------------------------
*/
void arp_ntoh(
struct arppacket *pktptr
)
{
pktptr->arp_htype = ntohs(pktptr->arp_htype);
pktptr->arp_ptype = ntohs(pktptr->arp_ptype);
pktptr->arp_op = ntohs(pktptr->arp_op);
pktptr->arp_sndpa = ntohl(pktptr->arp_sndpa);
pktptr->arp_tarpa = ntohl(pktptr->arp_tarpa);
}
/*------------------------------------------------------------------------
* arp_hton - Convert ARP packet fields from host to net byte order
*------------------------------------------------------------------------
*/
void arp_hton(
struct arppacket *pktptr
)
{
pktptr->arp_htype = htons(pktptr->arp_htype);
pktptr->arp_ptype = htons(pktptr->arp_ptype);
pktptr->arp_op = htons(pktptr->arp_op);
pktptr->arp_sndpa = htonl(pktptr->arp_sndpa);
pktptr->arp_tarpa = htonl(pktptr->arp_tarpa);
}