xref: /csrg-svn/sys/netinet/if_ether.c (revision 18378)

/*	if_ether.c	6.7	85/03/18	*/

/*
 * Ethernet address resolution protocol.
 */

#include "param.h"
#include "systm.h"
#include "mbuf.h"
#include "socket.h"
#include "time.h"
#include "kernel.h"
#include "errno.h"
#include "ioctl.h"

#include "../net/if.h"
#include "in.h"
#include "in_systm.h"
#include "ip.h"
#include "if_ether.h"

#define	ARPTAB_BSIZ	5		/* bucket size */
#define	ARPTAB_NB	19		/* number of buckets */
#define	ARPTAB_SIZE	(ARPTAB_BSIZ * ARPTAB_NB)
struct	arptab arptab[ARPTAB_SIZE];
int	arptab_size = ARPTAB_SIZE;	/* for arp command */

#define	ARPTAB_HASH(a) \
	((short)((((a) >> 16) ^ (a)) & 0x7fff) % ARPTAB_NB)

#define	ARPTAB_LOOK(at,addr) { \
	register n; \
	at = &arptab[ARPTAB_HASH(addr) * ARPTAB_BSIZ]; \
	for (n = 0 ; n < ARPTAB_BSIZ ; n++,at++) \
		if (at->at_iaddr.s_addr == addr) \
			break; \
	if (n >= ARPTAB_BSIZ) \
		at = 0; }

int	arpt_age;		/* aging timer */

/* timer values */
#define	ARPT_AGE	(60*1)	/* aging timer, 1 min. */
#define	ARPT_KILLC	20	/* kill completed entry in 20 mins. */
#define	ARPT_KILLI	3	/* kill incomplete entry in 3 minutes */

struct ether_addr etherbroadcastaddr = {{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }};
extern struct ifnet loif;

/*
 * Local addresses in the range oldmap to infinity are
 * mapped according to the old mapping scheme.  That is,
 * mapping of Internet to Ethernet addresses is performed
 * by taking the high three bytes of the network interface's
 * address and the low three bytes of the local address part.
 * This only allows boards from the same manufacturer to
 * communicate unless the on-board address is overridden
 * (not possible in many manufacture's hardware).
 *
 * NB: setting oldmap to zero completely disables ARP
 *     (i.e. identical to setting IFF_NOARP with an ioctl).
 */
int	oldmap = 1024;

/*
 * Timeout routine.  Age arp_tab entries once a minute.
 */
arptimer()
{
	register struct arptab *at;
	register i;

	timeout(arptimer, (caddr_t)0, hz);
	if (++arpt_age > ARPT_AGE) {
		arpt_age = 0;
		at = &arptab[0];
		for (i = 0; i < ARPTAB_SIZE; i++, at++) {
			if (at->at_flags == 0 || (at->at_flags & ATF_PERM))
				continue;
			if (++at->at_timer < ((at->at_flags&ATF_COM) ?
			    ARPT_KILLC : ARPT_KILLI))
				continue;
			/* timer has expired, clear entry */
			arptfree(at);
		}
	}
}

/*
 * Broadcast an ARP packet, asking who has addr on interface ac.
 */
arpwhohas(ac, addr)
	register struct arpcom *ac;
	struct in_addr *addr;
{
	register struct mbuf *m;
	register struct ether_header *eh;
	register struct ether_arp *ea;
	struct sockaddr sa;

	if ((m = m_get(M_DONTWAIT, MT_DATA)) == NULL)
		return (1);
	m->m_len = sizeof *ea;
	m->m_off = MMAXOFF - m->m_len;
	ea = mtod(m, struct ether_arp *);
	eh = (struct ether_header *)sa.sa_data;
	bzero((caddr_t)ea, sizeof (*ea));
	eh->ether_dhost = etherbroadcastaddr;
	eh->ether_type = ETHERTYPE_ARP;		/* if_output will swap */
	ea->arp_hrd = htons(ARPHRD_ETHER);
	ea->arp_pro = htons(ETHERTYPE_IP);
	ea->arp_hln = sizeof arp_sha(ea);	/* hardware address length */
	ea->arp_pln = sizeof arp_spa(ea);	/* protocol address length */
	ea->arp_op = htons(ARPOP_REQUEST);
	arp_sha(ea) = ac->ac_enaddr;
	arp_spa(ea) = ac->ac_ipaddr;
	arp_tpa(ea) = *addr;
	sa.sa_family = AF_UNSPEC;
	return ((*ac->ac_if.if_output)(&ac->ac_if, m, &sa));
}

/*
 * Resolve an IP address into an ethernet address.  If success,
 * desten is filled in and 1 is returned.  If there is no entry
 * in arptab, set one up and broadcast a request
 * for the IP address;  return 0.  Hold onto this mbuf and
 * resend it once the address is finally resolved.
 *
 * We do some (conservative) locking here at splimp, since
 * arptab is also altered from input interrupt service (ecintr/ilintr
 * calls arpinput when ETHERTYPE_ARP packets come in).
 */
arpresolve(ac, m, destip, desten)
	register struct arpcom *ac;
	struct mbuf *m;
	register struct in_addr *destip;
	register struct ether_addr *desten;
{
	register struct arptab *at;
	register struct ifnet *ifp;
	register int i;
	struct sockaddr_in sin;
	int s, lna;

	if (in_broadcast(*destip)) {	/* broadcast address */
		*desten = etherbroadcastaddr;
		return (1);
	}
	lna = in_lnaof(*destip);
	ifp = &ac->ac_if;
	/* if for us, then use software loopback driver */
	if (destip->s_addr == ac->ac_ipaddr.s_addr &&
	    (loif.if_flags & IFF_UP)) {
		sin.sin_family = AF_INET;
		sin.sin_addr = *destip;
		(void) looutput(&loif, m, (struct sockaddr *)&sin);
		/*
		 * We really don't want to indicate failure,
		 * but the packet has already been sent and freed.
		 */
		return (0);
	}
	s = splimp();
	ARPTAB_LOOK(at, destip->s_addr);
	if (at == 0) {			/* not found */
		if ((ifp->if_flags & IFF_NOARP) || lna >= oldmap) {
			*desten = ac->ac_enaddr;
			desten->ether_addr_octet[3] = (lna >> 16) & 0x7f;
			desten->ether_addr_octet[4] = (lna >> 8) & 0xff;
			desten->ether_addr_octet[5] = lna & 0xff;
			splx(s);
			return (1);
		} else {
			at = arptnew(destip);
			at->at_hold = m;
			arpwhohas(ac, destip);
			splx(s);
			return (0);
		}
	}
	at->at_timer = 0;		/* restart the timer */
	if (at->at_flags & ATF_COM) {	/* entry IS complete */
		*desten = at->at_enaddr;
		splx(s);
		return (1);
	}
	/*
	 * There is an arptab entry, but no ethernet address
	 * response yet.  Replace the held mbuf with this
	 * latest one.
	 */
	if (at->at_hold)
		m_freem(at->at_hold);
	at->at_hold = m;
	arpwhohas(ac, destip);		/* ask again */
	splx(s);
	return (0);
}

/*
 * Called from 10 Mb/s Ethernet interrupt handlers
 * when ether packet type ETHERTYPE_ARP
 * is received.  Algorithm is that given in RFC 826.
 * In addition, a sanity check is performed on the sender
 * protocol address, to catch impersonators.
 */
arpinput(ac, m)
	register struct arpcom *ac;
	struct mbuf *m;
{
	register struct ether_arp *ea;
	struct ether_header *eh;
	register struct arptab *at = 0;  /* same as "merge" flag */
	struct sockaddr_in sin;
	struct sockaddr sa;
	struct mbuf *mhold;
	struct in_addr isaddr,itaddr,myaddr;

	if (m->m_len < sizeof *ea)
		goto out;
	if (ac->ac_if.if_flags & IFF_NOARP)
		goto out;
	myaddr = ac->ac_ipaddr;
	ea = mtod(m, struct ether_arp *);
	if (ntohs(ea->arp_pro) != ETHERTYPE_IP)
		goto out;
	isaddr = arp_spa(ea);
	itaddr = arp_tpa(ea);
	if (!bcmp((caddr_t)&arp_sha(ea), (caddr_t)&ac->ac_enaddr,
	  sizeof (ac->ac_enaddr)))
		goto out;	/* it's from me, ignore it. */
	if (isaddr.s_addr == myaddr.s_addr) {
		printf("duplicate IP address!! sent from ethernet address: ");
		printf("%x %x %x %x %x %x\n", ea->arp_xsha[0], ea->arp_xsha[1],
			ea->arp_xsha[2], ea->arp_xsha[3],
			ea->arp_xsha[4], ea->arp_xsha[5]);
		itaddr = myaddr;
		if (ntohs(ea->arp_op) == ARPOP_REQUEST)
			goto reply;
		goto out;
	}
	ARPTAB_LOOK(at, isaddr.s_addr);
	if (at) {		/* XXX ? - can overwrite ATF_PERM */
		at->at_enaddr = arp_sha(ea);
		at->at_flags |= ATF_COM;
		if (at->at_hold) {
			mhold = at->at_hold;
			at->at_hold = 0;
			sin.sin_family = AF_INET;
			sin.sin_addr = isaddr;
			(*ac->ac_if.if_output)(&ac->ac_if,
			    mhold, (struct sockaddr *)&sin);
		}
	} else if (itaddr.s_addr == myaddr.s_addr) {
		/* ensure we have a table entry */
		at = arptnew(&isaddr);
		at->at_enaddr = arp_sha(ea);
		at->at_flags |= ATF_COM;
	}
	if (ntohs(ea->arp_op) != ARPOP_REQUEST)
		goto out;
	ARPTAB_LOOK(at, itaddr.s_addr);
	if (at == NULL) {
		if (itaddr.s_addr != myaddr.s_addr)
			goto out;	/* if I am not the target */
		at = arptnew(&myaddr);
		at->at_enaddr = ac->ac_enaddr;
		at->at_flags |= ATF_COM;
	}
	if (itaddr.s_addr != myaddr.s_addr && (at->at_flags & ATF_PUBL) == 0)
		goto out;

reply:
	arp_tha(ea) = arp_sha(ea);
	arp_tpa(ea) = arp_spa(ea);
	arp_sha(ea) = at->at_enaddr;
	arp_spa(ea) = itaddr;
	ea->arp_op = htons(ARPOP_REPLY);
	eh = (struct ether_header *)sa.sa_data;
	eh->ether_dhost = arp_tha(ea);
	eh->ether_type = ETHERTYPE_ARP;
	sa.sa_family = AF_UNSPEC;
	(*ac->ac_if.if_output)(&ac->ac_if, m, &sa);
	return;
out:
	m_freem(m);
	return;
}

/*
 * Free an arptab entry.
 */
arptfree(at)
	register struct arptab *at;
{
	int s = splimp();

	if (at->at_hold)
		m_freem(at->at_hold);
	at->at_hold = 0;
	at->at_timer = at->at_flags = 0;
	at->at_iaddr.s_addr = 0;
	splx(s);
}

/*
 * Enter a new address in arptab, pushing out the oldest entry
 * from the bucket if there is no room.
 * This always succeeds since no bucket can be completely filled
 * with permanent entries (except from arpioctl when testing whether
 * another permanent entry).
 */
struct arptab *
arptnew(addr)
	struct in_addr *addr;
{
	register n;
	int oldest = 0;
	register struct arptab *at, *ato = NULL;
	static int first = 1;

	if (first) {
		first = 0;
		timeout(arptimer, (caddr_t)0, hz);
	}
	at = &arptab[ARPTAB_HASH(addr->s_addr) * ARPTAB_BSIZ];
	for (n = 0 ; n < ARPTAB_BSIZ ; n++,at++) {
		if (at->at_flags == 0)
			goto out;	 /* found an empty entry */
		if (at->at_flags & ATF_PERM)
			continue;
		if (at->at_timer > oldest) {
			oldest = at->at_timer;
			ato = at;
		}
	}
	if (ato == NULL)
		return(NULL);
	at = ato;
	arptfree(at);
out:
	at->at_iaddr = *addr;
	at->at_flags = ATF_INUSE;
	return (at);
}

arpioctl(cmd, data)
	int cmd;
	caddr_t data;
{
	register struct arpreq *ar = (struct arpreq *)data;
	register struct arptab *at;
	register struct sockaddr_in *sin;
	int s;

	if (ar->arp_pa.sa_family != AF_INET ||
	    ar->arp_ha.sa_family != AF_UNSPEC)
		return (EAFNOSUPPORT);
	sin = (struct sockaddr_in *)&ar->arp_pa;
	s = splimp();
	ARPTAB_LOOK(at, sin->sin_addr.s_addr);
	if (at == NULL) {		/* not found */
		if (cmd != SIOCSARP) {
			splx(s);
			return (ENXIO);
		}
		if (ifa_ifwithnet(&ar->arp_pa) == NULL) {
			splx(s);
			return (ENETUNREACH);
		}
	}
	switch (cmd) {

	case SIOCSARP:		/* set entry */
		if (at == NULL) {
			at = arptnew(&sin->sin_addr);
			if (ar->arp_flags & ATF_PERM) {
			/* never make all entries in a bucket permanent */
				register struct arptab *tat;

				/* try to re-allocate */
				tat = arptnew(&sin->sin_addr);
				if (tat == NULL) {
					arptfree(at);
					splx(s);
					return (EADDRNOTAVAIL);
				}
				arptfree(tat);
			}
		}
		at->at_enaddr = *(struct ether_addr *)ar->arp_ha.sa_data;
		at->at_flags = ATF_COM | ATF_INUSE |
			(ar->arp_flags & (ATF_PERM|ATF_PUBL));
		at->at_timer = 0;
		break;

	case SIOCDARP:		/* delete entry */
		arptfree(at);
		break;

	case SIOCGARP:		/* get entry */
		*(struct ether_addr *)ar->arp_ha.sa_data = at->at_enaddr;
		ar->arp_flags = at->at_flags;
		break;
	}
	splx(s);
	return (0);
}