nd6_rtr.c

来自「eCos操作系统源码」· C语言 代码 · 共 2,371 行 · 第 1/5 页

			nd6log((LOG_INFO, "nd6_ra_input: mtu option "
			    "mtu=%d sent from %s; maxmtu unknown, "
			    "ignoring\n",
			    mtu, ip6_sprintf(&ip6->ip6_src)));
		}
	}

 skip:
	
	/*
	 * Source link layer address
	 */
    {
	char *lladdr = NULL;
	int lladdrlen = 0;
	
	if (ndopts.nd_opts_src_lladdr) {
		lladdr = (char *)(ndopts.nd_opts_src_lladdr + 1);
		lladdrlen = ndopts.nd_opts_src_lladdr->nd_opt_len << 3;
	}

	if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
		nd6log((LOG_INFO,
		    "nd6_ra_input: lladdrlen mismatch for %s "
		    "(if %d, RA packet %d)\n",
			ip6_sprintf(&saddr6), ifp->if_addrlen, lladdrlen - 2));
		goto bad;
	}

	nd6_cache_lladdr(ifp, &saddr6, lladdr, lladdrlen, ND_ROUTER_ADVERT, 0);

	/*
	 * Installing a link-layer address might change the state of the
	 * router's neighbor cache, which might also affect our on-link
	 * detection of adveritsed prefixes.
	 */
	pfxlist_onlink_check();
    }

 freeit:
	m_freem(m);
	return;

 bad:
	icmp6stat.icp6s_badra++;
	m_freem(m);
}

/*
 * default router list proccessing sub routines
 */

/* tell the change to user processes watching the routing socket. */
static void
nd6_rtmsg(cmd, rt)
	int cmd;
	struct rtentry *rt;
{
	struct rt_addrinfo info;

	bzero((caddr_t)&info, sizeof(info));
#if (defined(__bsdi__) && _BSDI_VERSION >= 199802) /* BSDI4 */
	/* maybe this is unnecessary */
	info.rti_flags = rt->rt_flags;
#endif
	info.rti_info[RTAX_DST] = rt_key(rt);
	info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
	info.rti_info[RTAX_NETMASK] = rt_mask(rt);
#if defined(__bsdi__) || (defined(__FreeBSD__) && __FreeBSD__ < 3)
	info.rti_info[RTAX_IFP] = rt->rt_ifp->if_addrlist->ifa_addr;
#else
	info.rti_info[RTAX_IFP] =
		(struct sockaddr *)TAILQ_FIRST(&rt->rt_ifp->if_addrlist);
#endif
	info.rti_info[RTAX_IFA] = rt->rt_ifa->ifa_addr;

	rt_missmsg(cmd, &info, rt->rt_flags, 0);
}

void
defrouter_addreq(new)
	struct nd_defrouter *new;
{
	struct sockaddr_in6 def, mask, gate;
	struct rtentry *newrt = NULL;
	int s;
	int error;

	Bzero(&def, sizeof(def));
	Bzero(&mask, sizeof(mask));
	Bzero(&gate, sizeof(gate));

	def.sin6_len = mask.sin6_len = gate.sin6_len
		= sizeof(struct sockaddr_in6);
	def.sin6_family = mask.sin6_family = gate.sin6_family = AF_INET6;
	gate.sin6_addr = new->rtaddr;

#ifdef __NetBSD__
	s = splsoftnet();
#else
	s = splnet();
#endif
	error = rtrequest(RTM_ADD, (struct sockaddr *)&def,
		(struct sockaddr *)&gate, (struct sockaddr *)&mask,
		RTF_GATEWAY, &newrt);
	if (newrt) {
		nd6_rtmsg(RTM_ADD, newrt); /* tell user process */
		newrt->rt_refcnt--;
	}
	if (error == 0)
		new->installed = 1;
	splx(s);
	return;
}

/* Add a route to a given interface as default */
static void
defrouter_addifreq(ifp)
	struct ifnet *ifp;
{
	struct sockaddr_in6 def, mask;
	struct ifaddr *ifa;
	struct rtentry *newrt = NULL;
	int error, flags;
#if (defined(__bsdi__) && _BSDI_VERSION >= 199802)
	struct rt_addrinfo info;
#endif

	/* remove one if we have already installed one */
	if (nd6_defif_installed)
		defrouter_delifreq();

	bzero(&def, sizeof(def));
	bzero(&mask, sizeof(mask));

	def.sin6_len = mask.sin6_len = sizeof(struct sockaddr_in6);
	def.sin6_family = mask.sin6_family = AF_INET6;

	/*
	 * Search for an ifaddr beloging to the specified interface.
	 * XXX: An IPv6 address are required to be assigned on the interface.
	 */
	if ((ifa = ifaof_ifpforaddr((struct sockaddr *)&def, ifp)) == NULL) {
		nd6log((LOG_ERR,	/* better error? */
		    "defrouter_addifreq: failed to find an ifaddr "
		    "to install a route to interface %s\n",
		    if_name(ifp)));
		return;
	}

	flags = ifa->ifa_flags;
#if (defined(__bsdi__) && _BSDI_VERSION >= 199802)
	bzero(&info, sizeof(info));
	info.rti_info[RTAX_DST] = (struct sockaddr *)&def;
	info.rti_info[RTAX_GATEWAY] = (struct sockaddr *)ifa->ifa_addr;
	info.rti_info[RTAX_NETMASK] = (struct sockaddr *)&mask;
	info.rti_info[RTAX_IFA] = (struct sockaddr *)ifa->ifa_addr;
	info.rti_flags = flags;
	error = rtrequest1(RTM_ADD, &info, &newrt);
#else
	error = rtrequest(RTM_ADD, (struct sockaddr *)&def, ifa->ifa_addr,
			  (struct sockaddr *)&mask, flags, &newrt);
#endif
	if (error != 0) {
		nd6log((LOG_ERR,
		    "defrouter_addifreq: failed to install a route to "
		    "interface %s (errno = %d)\n",
		    if_name(ifp), error));

		if (newrt)	/* maybe unnecessary, but do it for safety */
			newrt->rt_refcnt--;
	} else {
		if (newrt) {
			nd6_rtmsg(RTM_ADD, newrt);
			newrt->rt_refcnt--;
		}
	}

	nd6_defif_installed = ifa;
	IFAREF(ifa);
}

/* Remove a default route points to interface */
static void
defrouter_delifreq()
{
	struct sockaddr_in6 def, mask;
	struct rtentry *oldrt = NULL;

	if (!nd6_defif_installed)
		return;

	Bzero(&def, sizeof(def));
	Bzero(&mask, sizeof(mask));

	def.sin6_len = mask.sin6_len = sizeof(struct sockaddr_in6);
	def.sin6_family = mask.sin6_family = AF_INET6;

	rtrequest(RTM_DELETE, (struct sockaddr *)&def,
	    (struct sockaddr *)nd6_defif_installed->ifa_addr,
	    (struct sockaddr *)&mask, RTF_GATEWAY, &oldrt);
	if (oldrt) {
		nd6_rtmsg(RTM_DELETE, oldrt);
		if (oldrt->rt_refcnt <= 0) {
			/*
			 * XXX: borrowed from the RTM_DELETE case of
			 * rtrequest().
			 */
			oldrt->rt_refcnt++;
			rtfree(oldrt);
		}
	}

	IFAFREE(nd6_defif_installed);
	nd6_defif_installed = NULL;
}

struct nd_defrouter *
defrouter_lookup(addr, ifp)
	struct in6_addr *addr;
	struct ifnet *ifp;
{
	struct nd_defrouter *dr;

	for (dr = TAILQ_FIRST(&nd_defrouter); dr;
	     dr = TAILQ_NEXT(dr, dr_entry)) {
		if (dr->ifp == ifp && IN6_ARE_ADDR_EQUAL(addr, &dr->rtaddr))
			return(dr);
	}

	return(NULL);		/* search failed */
}

void
defrtrlist_del(dr)
	struct nd_defrouter *dr;
{
	struct nd_defrouter *deldr = NULL;
	struct nd_prefix *pr;

	/*
	 * Flush all the routing table entries that use the router
	 * as a next hop.
	 */
	if (!ip6_forwarding && ip6_accept_rtadv) {
		/* above is a good condition? */
		rt6_flush(&dr->rtaddr, dr->ifp);
	}

	if (dr->installed) {
		deldr = dr;
		defrouter_delreq(dr);
	}
	TAILQ_REMOVE(&nd_defrouter, dr, dr_entry);

	/*
	 * Also delete all the pointers to the router in each prefix lists.
	 */
	for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
		struct nd_pfxrouter *pfxrtr;
		if ((pfxrtr = pfxrtr_lookup(pr, dr)) != NULL)
			pfxrtr_del(pfxrtr);
	}
	pfxlist_onlink_check();

	/*
	 * If the router is the primary one, choose a new one.
	 * Note that defrouter_select() will remove the current gateway
	 * from the routing table.
	 */
	if (deldr)
		defrouter_select();

	free(dr, M_IP6NDP);
}

/*
 * Remove the default route for a given router.
 * This is just a subroutine function for defrouter_select(), and should
 * not be called from anywhere else.
 */
static void
defrouter_delreq(dr)
	struct nd_defrouter *dr;
{
	struct sockaddr_in6 def, mask, gw;
	struct rtentry *oldrt = NULL;

	Bzero(&def, sizeof(def));
	Bzero(&mask, sizeof(mask));
	Bzero(&gw, sizeof(gw));

	def.sin6_len = mask.sin6_len = gw.sin6_len =
	    sizeof(struct sockaddr_in6);
	def.sin6_family = mask.sin6_family = gw.sin6_family = AF_INET6;
	if (dr)
		gw.sin6_addr = dr->rtaddr;

	rtrequest(RTM_DELETE, (struct sockaddr *)&def,
	    dr ? (struct sockaddr *)&gw : NULL,
	    (struct sockaddr *)&mask, RTF_GATEWAY, &oldrt);
	if (oldrt) {
		nd6_rtmsg(RTM_DELETE, oldrt);
		if (oldrt->rt_refcnt <= 0) {
			/*
			 * XXX: borrowed from the RTM_DELETE case of
			 * rtrequest().
			 */
			oldrt->rt_refcnt++;
			rtfree(oldrt);
		}
	}

	if (dr)
		dr->installed = 0;
}

/*
 * remove all default routes from default router list
 */
void
defrouter_reset()
{
	struct nd_defrouter *dr;

	for (dr = TAILQ_FIRST(&nd_defrouter); dr;
	     dr = TAILQ_NEXT(dr, dr_entry))
		defrouter_delreq(dr);
	defrouter_delifreq();

	/*
	 * XXX should we also nuke any default routers in the kernel, by 
	 * going through them by rtalloc1()?
	 */
}

/*
 * Default Router Selection according to Section 6.3.6 of RFC 2461 and
 * draft-ietf-ipngwg-router-selection:
 * 1) Routers that are reachable or probably reachable should be preferred.
 *    If we have more than one (probably) reachable router, prefer ones
 *    with the highest router preference.
 * 2) When no routers on the list are known to be reachable or
 *    probably reachable, routers SHOULD be selected in a round-robin
 *    fashion, regardless of router preference values.
 * 3) If the Default Router List is empty, assume that all
 *    destinations are on-link.
 *
 * We assume nd_defrouter is sorted by router preference value.
 * Since the code below covers both with and without router preference cases,
 * we do not need to classify the cases by ifdef.
 *
 * At this moment, we do not try to install more than one default router,
 * even when the multipath routing is available, because we're not sure about
 * the benefits for stub hosts comparing to the risk of making the code
 * complicated and the possibility of introducing bugs.
 */
void
defrouter_select()
{
#ifdef __NetBSD__
	int s = splsoftnet();
#else
	int s = splnet();
#endif
	struct nd_defrouter *dr, *selected_dr = NULL, *installed_dr = NULL;
	struct rtentry *rt = NULL;
	struct llinfo_nd6 *ln = NULL;

	/*
	 * This function should be called only when acting as an autoconfigured
	 * host.  Although the remaining part of this function is not effective
	 * if the node is not an autoconfigured host, we explicitly exclude
	 * such cases here for safety.
	 */
	if (ip6_forwarding || !ip6_accept_rtadv) {
		nd6log((LOG_WARNING,
		    "defrouter_select: called unexpectedly (forwarding=%d, "
		    "accept_rtadv=%d)\n", ip6_forwarding, ip6_accept_rtadv));
		splx(s);
		return;
	}

	/*
	 * Let's handle easy case (3) first:
	 * If default router list is empty, we should probably install
	 * an interface route and assume that all destinations are on-link.
	 */
	if (!TAILQ_FIRST(&nd_defrouter)) {
		/*
		 * XXX: The specification does not say this mechanism should
		 * be restricted to hosts, but this would be not useful
		 * (even harmful) for routers.
		 * This test is meaningless due to a test at the beginning of
		 * the function, but we intentionally keep it to make the note
		 * clear.
		 */
		if (!ip6_forwarding) {
			if (nd6_defifp) {
				/*
				 * Install a route to the default interface
				 * as default route.
				 */
				defrouter_addifreq(nd6_defifp);
			} else {
				/*
				 * purge the existing route.
				 * XXX: is this really correct?
				 */
				defrouter_delifreq();
				nd6log((LOG_INFO, "defrouter_select: "
				    "there's no default router and no default"
				    " interface\n"));
			}
		}
		splx(s);
		return;
	}

	/*
	 * If we have a default route for the default interface, delete it.
	 * Note that the existence of the route is checked in the delete
	 * function.
	 */
	defrouter_delifreq();

	/*
	 * Search for a (probably) reachable router from the list.
	 * We just pick up the first reachable one (if any), assuming that
	 * the ordering rule of the list described in defrtrlist_update().
	 */
	for (dr = TAILQ_FIRST(&nd_defrouter); dr;
	     dr = TAILQ_NEXT(dr, dr_entry)) {
		if (!selected_dr &&
		    (rt = nd6_lookup(&dr->rtaddr, 0, dr->ifp)) &&
		    (ln = (struct llinfo_nd6 *)rt->rt_llinfo) &&
		    ND6_IS_LLINFO_PROBREACH(ln)) {
			selected_dr = dr;
		}

		if (dr->installed && !installed_dr)
			installed_dr = dr;
		else if (dr->installed && installed_dr) {
			/* this should not happen.  warn for diagnosis. */
			log(LOG_ERR, "defrouter_select: more than one router"
			    " is installed\n");
		}
	}
	/*
	 * If none of the default routers was found to be reachable,
	 * round-robin the list regardless of preference.
	 * Otherwise, if we have an installed router, check if the selected
	 * (reachable) router should really be preferred to the installed one.
	 * We only prefer the new router when the old one is not reachable
	 * or when the new one has a really higher preference value.
	 */
	if (!selected_dr) {
		if (!installed_dr || !TAILQ_NEXT(installed_dr, dr_entry))
			selected_dr = TAILQ_FIRST(&nd_defrouter);
		else
 			selected_dr = TAILQ_NEXT(installed_dr, dr_entry);
	} else if (installed_dr &&
		   (rt = nd6_lookup(&installed_dr->rtaddr, 0,
				    installed_dr->ifp)) &&
		   (ln = (struct llinfo_nd6 *)rt->rt_llinfo) &&
		   ND6_IS_LLINFO_PROBREACH(ln) &&
		   rtpref(selected_dr) <= rtpref(installed_dr)) {
			selected_dr = installed_dr;
	}

	/*
	 * If the selected router is different than the installed one,
	 * remove the installed router and install the selected one.
	 * Note that the selected router is never NULL here.
	 */