if_ether.c

早期freebsd实现

 * set one up and broadcast a request for the IP address.
 * Hold onto this mbuf and resend it once the address
 * is finally resolved.  A return value of 1 indicates
 * that desten has been filled in and the packet should be sent
 * normally; a 0 return indicates that the packet has been
 * taken over here, either now or for later transmission.
 */
int
arpresolve(ac, rt, m, dst, desten)
	register struct arpcom *ac;
	register struct rtentry *rt;
	struct mbuf *m;
	register struct sockaddr *dst;
	register u_char *desten;
{
	register struct llinfo_arp *la;
	struct sockaddr_dl *sdl;

	if (m->m_flags & M_BCAST) {	/* broadcast */
		bcopy((caddr_t)etherbroadcastaddr, (caddr_t)desten,
		    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 {
		if (la = arplookup(SIN(dst)->sin_addr.s_addr, 1, 0))
			rt = la->la_rt;
	}
	if (la == 0 || rt == 0) {
		log(LOG_DEBUG, "arpresolve: can't allocate llinfo");
		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 > time.tv_sec) &&
	    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 != time.tv_sec) {
			rt->rt_expire = time.tv_sec;
			if (la->la_asked++ < arp_maxtries)
				arpwhohas(ac, &(SIN(dst)->sin_addr));
			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()
{
	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:
			    case ETHERTYPE_IPTRAILERS:
				    in_arpinput(m);
				    continue;
			    }
		m_freem(m);
	}
}

/*
 * 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);
	bcopy((caddr_t)ea->arp_spa, (caddr_t)&isaddr, sizeof (isaddr));
	bcopy((caddr_t)ea->arp_tpa, (caddr_t)&itaddr, 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)
		goto out;
	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)))
		goto out;	/* it's from me, ignore it. */
	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 %x!\n",
		    ntohl(isaddr.s_addr));
		goto out;
	}
	if (isaddr.s_addr == myaddr.s_addr) {
		log(LOG_ERR,
		   "duplicate IP address %x!! sent from ethernet address: %s\n",
		   ntohl(isaddr.s_addr), ether_sprintf(ea->arp_sha));
		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 info overwritten for %x by %s\n",
			    isaddr.s_addr, ether_sprintf(ea->arp_sha));
		bcopy((caddr_t)ea->arp_sha, LLADDR(sdl),
			    sdl->sdl_alen = sizeof(ea->arp_sha));
		if (rt->rt_expire)
			rt->rt_expire = time.tv_sec + 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) {
	out:
		m_freem(m);
		return;
	}
	if (itaddr.s_addr == myaddr.s_addr) {
		/* I am the target */
		bcopy((caddr_t)ea->arp_sha, (caddr_t)ea->arp_tha,
		    sizeof(ea->arp_sha));
		bcopy((caddr_t)ac->ac_enaddr, (caddr_t)ea->arp_sha,
		    sizeof(ea->arp_sha));
	} else {
		la = arplookup(itaddr.s_addr, 0, SIN_PROXY);
		if (la == NULL)
			goto out;
		rt = la->la_rt;
		bcopy((caddr_t)ea->arp_sha, (caddr_t)ea->arp_tha,
		    sizeof(ea->arp_sha));
		sdl = SDL(rt->rt_gateway);
		bcopy(LLADDR(sdl), (caddr_t)ea->arp_sha, sizeof(ea->arp_sha));
	}

	bcopy((caddr_t)ea->arp_spa, (caddr_t)ea->arp_tpa, sizeof(ea->arp_spa));
	bcopy((caddr_t)&itaddr, (caddr_t)ea->arp_spa, 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;
	bcopy((caddr_t)ea->arp_tha, (caddr_t)eh->ether_dhost,
	    sizeof(eh->ether_dhost));
	eh->ether_type = 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 };

	sin.sin_addr.s_addr = addr;
	sin.sin_other = proxy ? SIN_PROXY : 0;
	rt = rtalloc1((struct sockaddr *)&sin, create);
	if (rt == 0)
		return (0);
	rt->rt_refcnt--;
	if ((rt->rt_flags & RTF_GATEWAY) || (rt->rt_flags & RTF_LLINFO) == 0 ||
	    rt->rt_gateway->sa_family != AF_LINK) {
		if (create)
			log(LOG_DEBUG, "arptnew failed on %x\n", ntohl(addr));
		return (0);
	}
	return ((struct llinfo_arp *)rt->rt_llinfo);
}

int
arpioctl(cmd, data)
	int cmd;
	caddr_t data;
{
	return (EOPNOTSUPP);
}