if_ether.c

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

	register u_char *desten;
	struct rtentry *rt0;
{
	register struct llinfo_arp *la;
	struct sockaddr_dl *sdl;

	if (m->m_flags & M_BCAST) {	/* broadcast */
		(void)memcpy(desten, etherbroadcastaddr, sizeof(etherbroadcastaddr));
		return (1);
	}
	if (m->m_flags & M_MCAST) {	/* multicast */
		ETHER_MAP_IP_MULTICAST(&SIN(dst)->sin_addr, desten);
		return(1);
	}
	if (rt)
		la = (struct llinfo_arp *)rt->rt_llinfo;
	else {
		la = arplookup(SIN(dst)->sin_addr.s_addr, 1, 0);
		if (la)
			rt = la->la_rt;
	}
	if (la == 0 || rt == 0) {
		log(LOG_DEBUG, "arpresolve: can't allocate llinfo for %s\n",
			inet_ntoa(SIN(dst)->sin_addr));
		m_freem(m);
		return (0);
	}
	sdl = SDL(rt->rt_gateway);
	/*
	 * Check the address family and length is valid, the address
	 * is resolved; otherwise, try to resolve.
	 */
	if ((rt->rt_expire == 0 || rt->rt_expire > rtems_bsdnet_seconds_since_boot()) &&
	    sdl->sdl_family == AF_LINK && sdl->sdl_alen != 0) {
		bcopy(LLADDR(sdl), desten, sdl->sdl_alen);
		return 1;
	}
	/*
	 * There is an arptab entry, but no ethernet address
	 * response yet.  Replace the held mbuf with this
	 * latest one.
	 */
	if (la->la_hold)
		m_freem(la->la_hold);
	la->la_hold = m;
	if (rt->rt_expire) {
		rt->rt_flags &= ~RTF_REJECT;
		if (la->la_asked == 0 || rt->rt_expire != rtems_bsdnet_seconds_since_boot()) {
			rt->rt_expire = rtems_bsdnet_seconds_since_boot();
			if (la->la_asked++ < arp_maxtries)
			    arprequest(ac,
			        &(SIN(rt->rt_ifa->ifa_addr)->sin_addr.s_addr),
				&(SIN(dst)->sin_addr.s_addr),
				ac->ac_enaddr);
			else {
				rt->rt_flags |= RTF_REJECT;
				rt->rt_expire += arpt_down;
				la->la_asked = 0;
			}

		}
	}
	return (0);
}

/*
 * Common length and type checks are done here,
 * then the protocol-specific routine is called.
 */
void
arpintr(void)
{
	register struct mbuf *m;
	register struct arphdr *ar;
	int s;

	while (arpintrq.ifq_head) {
		s = splimp();
		IF_DEQUEUE(&arpintrq, m);
		splx(s);
		if (m == 0 || (m->m_flags & M_PKTHDR) == 0)
			panic("arpintr");
		if (m->m_len >= sizeof(struct arphdr) &&
		    (ar = mtod(m, struct arphdr *)) &&
		    ntohs(ar->ar_hrd) == ARPHRD_ETHER &&
		    m->m_len >=
		      sizeof(struct arphdr) + 2 * ar->ar_hln + 2 * ar->ar_pln)

			    switch (ntohs(ar->ar_pro)) {

			    case ETHERTYPE_IP:
				    in_arpinput(m);
				    continue;
			    }
		m_freem(m);
	}
}

NETISR_SET(NETISR_ARP, arpintr);

/*
 * ARP for Internet protocols on 10 Mb/s Ethernet.
 * Algorithm is that given in RFC 826.
 * In addition, a sanity check is performed on the sender
 * protocol address, to catch impersonators.
 * We no longer handle negotiations for use of trailer protocol:
 * Formerly, ARP replied for protocol type ETHERTYPE_TRAIL sent
 * along with IP replies if we wanted trailers sent to us,
 * and also sent them in response to IP replies.
 * This allowed either end to announce the desire to receive
 * trailer packets.
 * We no longer reply to requests for ETHERTYPE_TRAIL protocol either,
 * but formerly didn't normally send requests.
 */
static void
in_arpinput(m)
	struct mbuf *m;
{
	register struct ether_arp *ea;
	register struct arpcom *ac = (struct arpcom *)m->m_pkthdr.rcvif;
	struct ether_header *eh;
	register struct llinfo_arp *la = 0;
	register struct rtentry *rt;
	struct in_ifaddr *ia, *maybe_ia = 0;
	struct sockaddr_dl *sdl;
	struct sockaddr sa;
	struct in_addr isaddr, itaddr, myaddr;
	int op;

	ea = mtod(m, struct ether_arp *);
	op = ntohs(ea->arp_op);
	(void)memcpy(&isaddr, ea->arp_spa, sizeof (isaddr));
	(void)memcpy(&itaddr, ea->arp_tpa, sizeof (itaddr));
	for (ia = in_ifaddr; ia; ia = ia->ia_next)
		if (ia->ia_ifp == &ac->ac_if) {
			maybe_ia = ia;
			if ((itaddr.s_addr == ia->ia_addr.sin_addr.s_addr) ||
			     (isaddr.s_addr == ia->ia_addr.sin_addr.s_addr))
				break;
		}
	if (maybe_ia == 0) {
		m_freem(m);
		return;
	}
	myaddr = ia ? ia->ia_addr.sin_addr : maybe_ia->ia_addr.sin_addr;
	if (!bcmp((caddr_t)ea->arp_sha, (caddr_t)ac->ac_enaddr,
	    sizeof (ea->arp_sha))) {
		m_freem(m);	/* it's from me, ignore it. */
		return;
	}
	if (!bcmp((caddr_t)ea->arp_sha, (caddr_t)etherbroadcastaddr,
	    sizeof (ea->arp_sha))) {
		log(LOG_ERR,
		    "arp: ether address is broadcast for IP address %s!\n",
		    inet_ntoa(isaddr));
		m_freem(m);
		return;
	}
	if (isaddr.s_addr == myaddr.s_addr) {
		log(LOG_ERR,
		   "arp: %6D is using my IP address %s!\n",
		   ea->arp_sha, ":", inet_ntoa(isaddr));
		itaddr = myaddr;
		goto reply;
	}
	la = arplookup(isaddr.s_addr, itaddr.s_addr == myaddr.s_addr, 0);
	if (la && (rt = la->la_rt) && (sdl = SDL(rt->rt_gateway))) {
		if (sdl->sdl_alen &&
		    bcmp((caddr_t)ea->arp_sha, LLADDR(sdl), sdl->sdl_alen))
			log(LOG_INFO, "arp: %s moved from %6D to %6D\n",
			    inet_ntoa(isaddr), (u_char *)LLADDR(sdl), ":",
			    ea->arp_sha, ":");
		(void)memcpy(LLADDR(sdl), ea->arp_sha, sizeof(ea->arp_sha));
		sdl->sdl_alen = sizeof(ea->arp_sha);
		if (rt->rt_expire)
			rt->rt_expire = rtems_bsdnet_seconds_since_boot() + arpt_keep;
		rt->rt_flags &= ~RTF_REJECT;
		la->la_asked = 0;
		if (la->la_hold) {
			(*ac->ac_if.if_output)(&ac->ac_if, la->la_hold,
				rt_key(rt), rt);
			la->la_hold = 0;
		}
	}
reply:
	if (op != ARPOP_REQUEST) {
		m_freem(m);
		return;
	}
	if (itaddr.s_addr == myaddr.s_addr) {
		/* I am the target */
		(void)memcpy(ea->arp_tha, ea->arp_sha, sizeof(ea->arp_sha));
		(void)memcpy(ea->arp_sha, ac->ac_enaddr, sizeof(ea->arp_sha));
	} else {
		la = arplookup(itaddr.s_addr, 0, SIN_PROXY);
		if (la == NULL) {
			struct sockaddr_in sin;

			if (!arp_proxyall) {
				m_freem(m);
				return;
			}

			bzero(&sin, sizeof sin);
			sin.sin_family = AF_INET;
			sin.sin_len = sizeof sin;
			sin.sin_addr = itaddr;

			rt = rtalloc1((struct sockaddr *)&sin, 0, 0UL);
			if (!rt) {
				m_freem(m);
				return;
			}
			/*
			 * Don't send proxies for nodes on the same interface
			 * as this one came out of, or we'll get into a fight
			 * over who claims what Ether address.
			 */
			if (rt->rt_ifp == &ac->ac_if) {
				rtfree(rt);
				m_freem(m);
				return;
			}
			(void)memcpy(ea->arp_tha, ea->arp_sha, sizeof(ea->arp_sha));
			(void)memcpy(ea->arp_sha, ac->ac_enaddr, sizeof(ea->arp_sha));
			rtfree(rt);
#ifdef DEBUG_PROXY
			printf("arp: proxying for %s\n",
			       inet_ntoa(itaddr));
#endif
		} else {
			rt = la->la_rt;
			(void)memcpy(ea->arp_tha, ea->arp_sha, sizeof(ea->arp_sha));
			sdl = SDL(rt->rt_gateway);
			(void)memcpy(ea->arp_sha, LLADDR(sdl), sizeof(ea->arp_sha));
		}
	}

	(void)memcpy(ea->arp_tpa, ea->arp_spa, sizeof(ea->arp_spa));
	(void)memcpy(ea->arp_spa, &itaddr, sizeof(ea->arp_spa));
	ea->arp_op = htons(ARPOP_REPLY);
	ea->arp_pro = htons(ETHERTYPE_IP); /* let's be sure! */
	eh = (struct ether_header *)sa.sa_data;
	(void)memcpy(eh->ether_dhost, ea->arp_tha, sizeof(eh->ether_dhost));
	eh->ether_type = htons(ETHERTYPE_ARP);
	sa.sa_family = AF_UNSPEC;
	sa.sa_len = sizeof(sa);
	(*ac->ac_if.if_output)(&ac->ac_if, m, &sa, (struct rtentry *)0);
	return;
}

/*
 * Free an arp entry.
 */
static void
arptfree(la)
	register struct llinfo_arp *la;
{
	register struct rtentry *rt = la->la_rt;
	register struct sockaddr_dl *sdl;
	if (rt == 0)
		panic("arptfree");
	if (rt->rt_refcnt > 0 && (sdl = SDL(rt->rt_gateway)) &&
	    sdl->sdl_family == AF_LINK) {
		sdl->sdl_alen = 0;
		la->la_asked = 0;
		rt->rt_flags &= ~RTF_REJECT;
		return;
	}
	rtrequest(RTM_DELETE, rt_key(rt), (struct sockaddr *)0, rt_mask(rt),
			0, (struct rtentry **)0);
}
/*
 * Lookup or enter a new address in arptab.
 */
static struct llinfo_arp *
arplookup(addr, create, proxy)
	u_long addr;
	int create, proxy;
{
	register struct rtentry *rt;
	static struct sockaddr_inarp sin = {sizeof(sin), AF_INET };
	const char *why = 0;

	sin.sin_addr.s_addr = addr;
	sin.sin_other = proxy ? SIN_PROXY : 0;
	rt = rtalloc1((struct sockaddr *)&sin, create, 0UL);
	if (rt == 0)
		return (0);
	rt->rt_refcnt--;

	if (rt->rt_flags & RTF_GATEWAY)
		why = "host is not on local network";
	else if ((rt->rt_flags & RTF_LLINFO) == 0)
		why = "could not allocate llinfo";
	else if (rt->rt_gateway->sa_family != AF_LINK)
		why = "gateway route is not ours";

	if (why && create) {
		log(LOG_DEBUG, "arplookup %s failed: %s\n",
		    inet_ntoa(sin.sin_addr), why);
		return 0;
	} else if (why) {
		return 0;
	}
	return ((struct llinfo_arp *)rt->rt_llinfo);
}

void
arp_ifinit(ac, ifa)
	struct arpcom *ac;
	struct ifaddr *ifa;
{
	if (ntohl(IA_SIN(ifa)->sin_addr.s_addr) != INADDR_ANY)
		arprequest(ac, &(IA_SIN(ifa)->sin_addr.s_addr),
			       &(IA_SIN(ifa)->sin_addr.s_addr), ac->ac_enaddr);
	ifa->ifa_rtrequest = arp_rtrequest;
	ifa->ifa_flags |= RTF_CLONING;
}