route.c

GNU Hurd 源代码

work_done:
	expire += ip_rt_gc_min_interval;
	if (expire > ip_rt_gc_timeout ||
	    atomic_read(&ipv4_dst_ops.entries) < ipv4_dst_ops.gc_thresh)
		expire = ip_rt_gc_timeout;
#if RT_CACHE_DEBUG >= 2
	printk(KERN_DEBUG "expire++ %u %d %d %d\n", expire, atomic_read(&ipv4_dst_ops.entries), goal, rover);
#endif
	return 0;
}

static int rt_intern_hash(unsigned hash, struct rtable * rt, struct rtable ** rp)
{
	struct rtable	*rth, **rthp;
	unsigned long	now = jiffies;
	int attempts = !in_interrupt();

restart:
	start_bh_atomic();

	rthp = &rt_hash_table[hash];

	while ((rth = *rthp) != NULL) {
		if (memcmp(&rth->key, &rt->key, sizeof(rt->key)) == 0) {
			/* Put it first */
			*rthp = rth->u.rt_next;
			rth->u.rt_next = rt_hash_table[hash];
			rt_hash_table[hash] = rth;

			atomic_inc(&rth->u.dst.refcnt);
			atomic_inc(&rth->u.dst.use);
			rth->u.dst.lastuse = now;
			end_bh_atomic();

			rt_drop(rt);
			*rp = rth;
			return 0;
		}

		rthp = &rth->u.rt_next;
	}

	/* Try to bind route to arp only if it is output
	   route or unicast forwarding path.
	 */
	if (rt->rt_type == RTN_UNICAST || rt->key.iif == 0) {
		if (!arp_bind_neighbour(&rt->u.dst)) {
			end_bh_atomic();

			/* Neighbour tables are full and nothing
			   can be released. Try to shrink route cache,
			   it is most likely it holds some neighbour records.
			 */
			if (attempts-- > 0) {
				int saved_elasticity = ip_rt_gc_elasticity;
				int saved_int = ip_rt_gc_min_interval;
				ip_rt_gc_elasticity = 1;
				ip_rt_gc_min_interval = 0;
				rt_garbage_collect();
				ip_rt_gc_min_interval = saved_int;
				ip_rt_gc_elasticity = saved_elasticity;
				goto restart;
			}

			rt_drop(rt);
			if (net_ratelimit())
				printk("neighbour table overflow\n");
			return -ENOBUFS;
		}
	}

	rt->u.rt_next = rt_hash_table[hash];
#if RT_CACHE_DEBUG >= 2
	if (rt->u.rt_next) {
		struct rtable * trt;
		printk("rt_cache @%02x: %08x", hash, rt->rt_dst);
		for (trt=rt->u.rt_next; trt; trt=trt->u.rt_next)
			printk(" . %08x", trt->rt_dst);
		printk("\n");
	}
#endif
	rt_hash_table[hash] = rt;
	end_bh_atomic();
	*rp = rt;
	return 0;
}

static void rt_del(unsigned hash, struct rtable *rt)
{
	struct rtable **rthp;

	start_bh_atomic();
	ip_rt_put(rt);
	for (rthp = &rt_hash_table[hash]; *rthp; rthp = &(*rthp)->u.rt_next) {
		if (*rthp == rt) {
			*rthp = rt->u.rt_next;
			rt_free(rt);
			break;
		}
	}
	end_bh_atomic();
}

void ip_rt_redirect(u32 old_gw, u32 daddr, u32 new_gw,
		    u32 saddr, u8 tos, struct device *dev)
{
	int i, k;
	struct in_device *in_dev = dev->ip_ptr;
	struct rtable *rth, **rthp;
	u32  skeys[2] = { saddr, 0 };
	int  ikeys[2] = { dev->ifindex, 0 };

	tos &= IPTOS_TOS_MASK;

	if (!in_dev)
		return;

	if (new_gw == old_gw || !IN_DEV_RX_REDIRECTS(in_dev)
	    || MULTICAST(new_gw) || BADCLASS(new_gw) || ZERONET(new_gw))
		goto reject_redirect;

	if (!IN_DEV_SHARED_MEDIA(in_dev)) {
		if (!inet_addr_onlink(in_dev, new_gw, old_gw))
			goto reject_redirect;
		if (IN_DEV_SEC_REDIRECTS(in_dev) && ip_fib_check_default(new_gw, dev))
			goto reject_redirect;
	} else {
		if (inet_addr_type(new_gw) != RTN_UNICAST)
			goto reject_redirect;
	}

	for (i=0; i<2; i++) {
		for (k=0; k<2; k++) {
			unsigned hash = rt_hash_code(daddr, skeys[i]^(ikeys[k]<<5), tos);

			rthp=&rt_hash_table[hash];

			while ( (rth = *rthp) != NULL) {
				struct rtable *rt;

				if (rth->key.dst != daddr ||
				    rth->key.src != skeys[i] ||
				    rth->key.tos != tos ||
				    rth->key.oif != ikeys[k] ||
				    rth->key.iif != 0) {
					rthp = &rth->u.rt_next;
					continue;
				}

				if (rth->rt_dst != daddr ||
				    rth->rt_src != saddr ||
				    rth->u.dst.error ||
				    rth->rt_gateway != old_gw ||
				    rth->u.dst.dev != dev)
					break;

				dst_clone(&rth->u.dst);

				rt = dst_alloc(sizeof(struct rtable), &ipv4_dst_ops);
				if (rt == NULL) {
					ip_rt_put(rth);
					return;
				}

				/*
				 * Copy all the information.
				 */
				*rt = *rth;
				atomic_set(&rt->u.dst.refcnt, 1);
				atomic_set(&rt->u.dst.use, 1);
				rt->u.dst.lastuse = jiffies;
				rt->u.dst.neighbour = NULL;
				rt->u.dst.hh = NULL;
				rt->u.dst.obsolete = 0;

				rt->rt_flags |= RTCF_REDIRECTED;

				/* Gateway is different ... */
				rt->rt_gateway = new_gw;

				/* Redirect received -> path was valid */
				dst_confirm(&rth->u.dst);

				if (!arp_bind_neighbour(&rt->u.dst) ||
				    !(rt->u.dst.neighbour->nud_state&NUD_VALID)) {
					if (rt->u.dst.neighbour)
						neigh_event_send(rt->u.dst.neighbour, NULL);
					ip_rt_put(rth);
					rt_drop(rt);
					break;
				}

				rt_del(hash, rth);

				if (!rt_intern_hash(hash, rt, &rt))
					ip_rt_put(rt);
				break;
			}
		}
	}
	return;

reject_redirect:
#ifdef CONFIG_IP_ROUTE_VERBOSE
	if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit())
		printk(KERN_INFO "Redirect from %X/%s to %X ignored."
		       "Path = %X -> %X, tos %02x\n",
		       ntohl(old_gw), dev->name, ntohl(new_gw),
		       ntohl(saddr), ntohl(daddr), tos);
#else
	; /* Do nothing.  */
#endif
}

static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)
{
	struct rtable *rt = (struct rtable*)dst;

	if (rt != NULL) {
		if (dst->obsolete) {
			ip_rt_put(rt);
			return NULL;
		}
		if ((rt->rt_flags&RTCF_REDIRECTED) || rt->u.dst.expires) {
			unsigned hash = rt_hash_code(rt->key.dst, rt->key.src^(rt->key.oif<<5), rt->key.tos);
#if RT_CACHE_DEBUG >= 1
			printk(KERN_DEBUG "ip_rt_advice: redirect to %d.%d.%d.%d/%02x dropped\n", NIPQUAD(rt->rt_dst), rt->key.tos);
#endif
			rt_del(hash, rt);
			return NULL;
		}
	}
	return dst;
}

/*
 * Algorithm:
 *	1. The first ip_rt_redirect_number redirects are sent
 *	   with exponential backoff, then we stop sending them at all,
 *	   assuming that the host ignores our redirects.
 *	2. If we did not see packets requiring redirects
 *	   during ip_rt_redirect_silence, we assume that the host
 *	   forgot redirected route and start to send redirects again.
 *
 * This algorithm is much cheaper and more intelligent than dumb load limiting
 * in icmp.c.
 *
 * NOTE. Do not forget to inhibit load limiting for redirects (redundant)
 * and "frag. need" (breaks PMTU discovery) in icmp.c.
 */

void ip_rt_send_redirect(struct sk_buff *skb)
{
	struct rtable *rt = (struct rtable*)skb->dst;
	struct in_device *in_dev = (struct in_device*)rt->u.dst.dev->ip_ptr;

	if (!in_dev || !IN_DEV_TX_REDIRECTS(in_dev))
		return;

	/* No redirected packets during ip_rt_redirect_silence;
	 * reset the algorithm.
	 */
	if (jiffies - rt->u.dst.rate_last > ip_rt_redirect_silence)
		rt->u.dst.rate_tokens = 0;

	/* Too many ignored redirects; do not send anything
	 * set u.dst.rate_last to the last seen redirected packet.
	 */
	if (rt->u.dst.rate_tokens >= ip_rt_redirect_number) {
		rt->u.dst.rate_last = jiffies;
		return;
	}

	/* Check for load limit; set rate_last to the latest sent
	 * redirect.
	 */
	if (jiffies - rt->u.dst.rate_last > (ip_rt_redirect_load<<rt->u.dst.rate_tokens)) {
		icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, rt->rt_gateway);
		rt->u.dst.rate_last = jiffies;
		++rt->u.dst.rate_tokens;
#ifdef CONFIG_IP_ROUTE_VERBOSE
		if (IN_DEV_LOG_MARTIANS(in_dev) &&
		    rt->u.dst.rate_tokens == ip_rt_redirect_number && net_ratelimit())
			printk(KERN_WARNING "host %08x/if%d ignores redirects for %08x to %08x.\n",
			       rt->rt_src, rt->rt_iif, rt->rt_dst, rt->rt_gateway);
#endif
	}
}

static int ip_error(struct sk_buff *skb)
{
	struct rtable *rt = (struct rtable*)skb->dst;
	unsigned long now;
	int code;

	switch (rt->u.dst.error) {
	case EINVAL:
	default:
		kfree_skb(skb);
		return 0;
	case EHOSTUNREACH:
		code = ICMP_HOST_UNREACH;
		break;
	case ENETUNREACH:
		code = ICMP_NET_UNREACH;
		break;
	case EACCES:
		code = ICMP_PKT_FILTERED;
		break;
	}

	now = jiffies;
	if ((rt->u.dst.rate_tokens += (now - rt->u.dst.rate_last)) > ip_rt_error_burst)
		rt->u.dst.rate_tokens = ip_rt_error_burst;
	rt->u.dst.rate_last = now;
	if (rt->u.dst.rate_tokens >= ip_rt_error_cost) {
		rt->u.dst.rate_tokens -= ip_rt_error_cost;
		icmp_send(skb, ICMP_DEST_UNREACH, code, 0);
	}

	kfree_skb(skb);
	return 0;
} 

/*
 *	The last two values are not from the RFC but
 *	are needed for AMPRnet AX.25 paths.
 */

static unsigned short mtu_plateau[] =
{32000, 17914, 8166, 4352, 2002, 1492, 576, 296, 216, 128 };

static __inline__ unsigned short guess_mtu(unsigned short old_mtu)
{
	int i;
	
	for (i = 0; i < sizeof(mtu_plateau)/sizeof(mtu_plateau[0]); i++)
		if (old_mtu > mtu_plateau[i])
			return mtu_plateau[i];
	return 68;
}

unsigned short ip_rt_frag_needed(struct iphdr *iph, unsigned short new_mtu)
{
	int i;
	unsigned short old_mtu = ntohs(iph->tot_len);
	struct rtable *rth;
	u32  skeys[2] = { iph->saddr, 0, };
	u32  daddr = iph->daddr;
	u8   tos = iph->tos & IPTOS_TOS_MASK;
	unsigned short est_mtu = 0;

	if (ipv4_config.no_pmtu_disc)
		return 0;

	for (i=0; i<2; i++) {
		unsigned hash = rt_hash_code(daddr, skeys[i], tos);

		for (rth = rt_hash_table[hash]; rth; rth = rth->u.rt_next) {
			if (rth->key.dst == daddr &&
			    rth->key.src == skeys[i] &&
			    rth->rt_dst == daddr &&
			    rth->rt_src == iph->saddr &&
			    rth->key.tos == tos &&
			    rth->key.iif == 0 &&
			    !(rth->u.dst.mxlock&(1<<RTAX_MTU))) {
				unsigned short mtu = new_mtu;

				if (new_mtu < 68 || new_mtu >= old_mtu) {

					/* BSD 4.2 compatibility hack :-( */
					if (mtu == 0 && old_mtu >= rth->u.dst.pmtu &&
					    old_mtu >= 68 + (iph->ihl<<2))
						old_mtu -= iph->ihl<<2;

					mtu = guess_mtu(old_mtu);
				}
				if (mtu <= rth->u.dst.pmtu) {
					if (mtu < rth->u.dst.pmtu) { 
						dst_confirm(&rth->u.dst);
						rth->u.dst.pmtu = mtu;
						dst_set_expires(&rth->u.dst, ip_rt_mtu_expires);
					}
					est_mtu = mtu;
				}
			}
		}
	}
	return est_mtu ? : new_mtu;
}

void ip_rt_update_pmtu(struct dst_entry *dst, unsigned mtu)
{
	if (dst->pmtu > mtu && mtu >= 68 &&
	    !(dst->mxlock&(1<<RTAX_MTU))) {
		dst->pmtu = mtu;
		dst_set_expires(dst, ip_rt_mtu_expires);
	}
}

static struct dst_entry * ipv4_dst_check(struct dst_entry * dst, u32 cookie)
{
	dst_release(dst);
	return NULL;
}

static struct dst_entry * ipv4_dst_reroute(struct dst_entry * dst,
					   struct sk_buff *skb)
{
	return NULL;
}

static void ipv4_link_failure(struct sk_buff *skb)
{
	struct rtable *rt;

	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);

	rt = (struct rtable *) skb->dst;
	if (rt)
		dst_set_expires(&rt->u.dst, 0);
}

static int ip_rt_bug(struct sk_buff *skb)
{
	printk(KERN_DEBUG "ip_rt_bug: %08x -> %08x, %s\n", skb->nh.iph->saddr,
	       skb->nh.iph->daddr, skb->dev ? skb->dev->name : "?");
	kfree_skb(skb);
	return 0;
}

/*
   We do not cache source address of outgoing interface,
   because it is used only by IP RR, TS and SRR options,
   so that it out of fast path.

   BTW remember: "addr" is allowed to be not aligned
   in IP options!
 */

void ip_rt_get_source(u8 *addr, struct rtable *rt)
{
	u32 src;
	struct fib_result res;

	if (rt->key.iif == 0)
		src = rt->rt_src;
	else if (fib_lookup(&rt->key, &res) == 0 && res.type != RTN_NAT)
		src = FIB_RES_PREFSRC(res);
	else
		src = inet_select_addr(rt->u.dst.dev, rt->rt_gateway, RT_SCOPE_UNIVERSE);
	memcpy(addr, &src, 4);
}

#ifdef CONFIG_NET_CLS_ROUTE
static void set_class_tag(struct rtable *rt, u32 tag)
{
	if (!(rt->u.dst.tclassid&0xFFFF))
		rt->u.dst.tclassid |= tag&0xFFFF;
	if (!(rt->u.dst.tclassid&0xFFFF0000))
		rt->u.dst.tclassid |= tag&0xFFFF0000;
}
#endif

static void rt_set_nexthop(struct rtable *rt, struct fib_result *res, u32 itag)
{
	struct fib_info *fi = res->fi;

	if (fi) {
		if (FIB_RES_GW(*res) && FIB_RES_NH(*res).nh_scope == RT_SCOPE_LINK)
			rt->rt_gateway = FIB_RES_GW(*res);
		rt->u.dst.mxlock = fi->fib_metrics[RTAX_LOCK-1];
		rt->u.dst.pmtu = fi->fib_mtu;
		if (fi->fib_mtu == 0) {
			rt->u.dst.pmtu = rt->u.dst.dev->mtu;
			if (rt->u.dst.pmtu > IP_MAX_MTU)
				rt->u.dst.pmtu = IP_MAX_MTU;
			if (rt->u.dst.pmtu < 68)
				rt->u.dst.pmtu = 68;
			if (rt->u.dst.mxlock&(1<<RTAX_MTU) &&
			    rt->rt_gateway != rt->rt_dst &&
			    rt->u.dst.pmtu > 576)
				rt->u.dst.pmtu = 576;
		}
		rt->u.dst.window= fi->fib_window ? : 0;
		rt->u.dst.rtt	= fi->fib_rtt ? : TCP_TIMEOUT_INIT;
#ifdef CONFIG_NET_CLS_ROUTE
		rt->u.dst.tclassid = FIB_RES_NH(*res).nh_tclassid;
#endif
	} else {
		rt->u.dst.pmtu	= rt->u.dst.dev->mtu;
		if (rt->u.dst.pmtu > IP_MAX_MTU)
			rt->u.dst.pmtu = IP_MAX_MTU;
		if (rt->u.dst.pmtu < 68)
			rt->u.dst.pmtu = 68;
		rt->u.dst.window= 0;
		rt->u.dst.rtt	= TCP_TIMEOUT_INIT;
	}
#ifdef CONFIG_NET_CLS_ROUTE
#ifdef CONFIG_IP_MULTIPLE_TABLES
	set_class_tag(rt, fib_rules_tclass(res));
#endif
	set_class_tag(rt, itag);
#endif
        rt->rt_type = res->type;
}

static int
ip_route_input_mc(struct sk_buff *skb, u32 daddr, u32 saddr,
		  u8 tos, struct device *dev, int our)
{
	unsigned hash;