Subject: [RFC][PATCH 1/2] ipv4 multipath routing, bk head

From: Einar Lueck <[email-masked]>
Date: Wed, 22 Sep 2004 18:31:33 +0200

We propose the attached and the subsequent patch for an extension
of the existing multipath capabilities. These patches are partly
extended versions of patches posted last week as RFC. (Please
refer to the corresponding mails for details about their purpose).
There are the following changes and additions for which we hope
you have comments on:
* a _weighted_ random routing policiy utilizing the weights
configurable via "ip route" that allows to approximate many other policies
(e.g. round robin)
* a routing policy choosing routes with equal probability without
any state maintenance overhead(=> low delay)
* a simple round robin policy
* the extended behaviour is only optionally compiled in to allow for
the utilization of the old behaviour (as David Miller denoted: there
are scenarios/setups in which the old behaviour is more desirable
than the new behaviour)
* the ip_route_input lookup function does not consider more than
one alternative, only ip_route_output_key does (as Jamal denoted:
our extension makes primarily sense if one routes on a per
connection basis as we do in ip_route_output_key and not on a per
"packet" basis as we do in the ip forwarding case)
* an interface round robin policy that selects among relevant routes
in a way that tries to ensure an overall round robin among the
available _interfaces_ is achieved.

In addition to any opinions about the above mentioned changes we would
be very glad about any comments on the following issue:
Is it desirable to introduce modules for the policy implementations? We 
think
the weighted random policy is the most relevant one in this context as it
allows for the rough emulation of all other policies and considers the
weights configured via "ip route". Anyway,  the other policies are more
efficient than their emulated counterparts.  Up to now, as we are not sure,
wether more policies than weighted random are desired, one has to decide
via kernel configuration, which implementation should be utilized.

Further remarks on the organisation of the patch:
* the patch attached to this mail splits up ip_route_(input|output)_slow
(identical to the one posted last week as it still fits to bitkeeper head)
* the patch following in the subsequent mail encompasses the changes
mentioned above on the basis of the splitting patch

Regards,
Einar
diff -ruN linux-2.6.8.1/net/ipv4/route.c linux-2.6.8.1.split/net/ipv4/route.c
--- linux-2.6.8.1/net/ipv4/route.c	2004-09-10 10:24:12.000000000 +0200
+++ linux-2.6.8.1.split/net/ipv4/route.c	2004-09-14 09:38:49.000000000 +0200
@@ -104,6 +104,9 @@
 #include <linux/sysctl.h>
 #endif
 
+#define RT_FL_TOS(oldflp) \
+    ((u32)(oldflp->fl4_tos & (IPTOS_RT_MASK | RTO_ONLINK)))
+
 #define IP_MAX_MTU	0xFFF0
 
 #define RT_GC_TIMEOUT (300*HZ)
@@ -143,6 +146,7 @@
 static void		 ipv4_link_failure(struct sk_buff *skb);
 static void		 ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu);
 static int rt_garbage_collect(void);
+static inline int compare_keys(struct flowi *fl1, struct flowi *fl2);

 static struct dst_ops ipv4_dst_ops = {
@@ -1528,6 +1532,169 @@
 	return -EINVAL;
 }
 
+
+static void ip_handle_martian_source(struct net_device *dev,
+				     struct in_device *in_dev,
+				     struct sk_buff *skb,
+				     u32 daddr,
+				     u32 saddr) 
+{
+	RT_CACHE_STAT_INC(in_martian_src);
+#ifdef CONFIG_IP_ROUTE_VERBOSE
+	if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit()) {
+		/*
+		 *	RFC1812 recommendation, if source is martian,
+		 *	the only hint is MAC header.
+		 */
+		printk(KERN_WARNING "martian source %u.%u.%u.%u from "
+			"%u.%u.%u.%u, on dev %s\n",
+			NIPQUAD(daddr), NIPQUAD(saddr), dev->name);
+		if (dev->hard_header_len) {
+			int i;
+			unsigned char *p = skb->mac.raw;
+			printk(KERN_WARNING "ll header: ");
+			for (i = 0; i < dev->hard_header_len; i++, p++) {
+				printk("%02x", *p);
+				if (i < (dev->hard_header_len - 1))
+					printk(":");
+			}
+			printk("\n");
+		}
+	}
+#endif
+}
+
+static inline int __mkroute_input(struct sk_buff *skb, 
+				  struct fib_result* res, 
+				  struct in_device *in_dev, 
+				  u32 daddr, u32 saddr, u32 tos, 
+				  struct rtable **result) 
+{
+
+	struct rtable *rth;
+	int err;
+	struct in_device *out_dev;
+	unsigned flags = 0;
+	u32 spec_dst, itag;
+
+	/* get a working reference to the output device */
+	out_dev = in_dev_get(FIB_RES_DEV(*res));
+	if (out_dev == NULL) {
+		if (net_ratelimit())
+			printk(KERN_CRIT "Bug in ip_route_input" \
+			       "_slow(). Please, report\n");
+		return -EINVAL;
+	}
+
+
+	err = fib_validate_source(saddr, daddr, tos, FIB_RES_OIF(*res), 
+				  in_dev->dev, &spec_dst, &itag);
+	if (err < 0) {
+		ip_handle_martian_source(in_dev->dev, in_dev, skb, daddr, 
+					 saddr);
+		
+		err = -EINVAL;
+		goto cleanup;
+	}
+
+	if (err)
+		flags |= RTCF_DIRECTSRC;
+
+	if (out_dev == in_dev && err && !(flags & (RTCF_NAT | RTCF_MASQ)) &&
+	    (IN_DEV_SHARED_MEDIA(out_dev) ||
+	     inet_addr_onlink(out_dev, saddr, FIB_RES_GW(*res))))
+		flags |= RTCF_DOREDIRECT;
+
+	if (skb->protocol != htons(ETH_P_IP)) {
+		/* Not IP (i.e. ARP). Do not create route, if it is
+		 * invalid for proxy arp. DNAT routes are always valid.
+		 */
+		if (out_dev == in_dev && !(flags & RTCF_DNAT)) {
+			err = -EINVAL;
+			goto cleanup;
+		}
+	}
+
+
+	rth = dst_alloc(&ipv4_dst_ops);
+	if (!rth) {
+		err = -ENOBUFS;
+		goto cleanup;
+	}
+
+	rth->u.dst.flags= DST_HOST;
+	if (in_dev->cnf.no_policy)
+		rth->u.dst.flags |= DST_NOPOLICY;
+	if (in_dev->cnf.no_xfrm)
+		rth->u.dst.flags |= DST_NOXFRM;
+	rth->fl.fl4_dst	= daddr;
+	rth->rt_dst	= daddr;
+	rth->fl.fl4_tos	= tos;
+#ifdef CONFIG_IP_ROUTE_FWMARK
+	rth->fl.fl4_fwmark= skb->nfmark;
+#endif
+	rth->fl.fl4_src	= saddr;
+	rth->rt_src	= saddr;
+	rth->rt_gateway	= daddr;
+	rth->rt_iif 	=
+		rth->fl.iif	= in_dev->dev->ifindex;
+	rth->u.dst.dev	= (out_dev)->dev;
+	dev_hold(rth->u.dst.dev);
+	rth->idev	= in_dev_get(rth->u.dst.dev);
+	rth->fl.oif 	= 0;
+	rth->rt_spec_dst= spec_dst;
+
+	rth->u.dst.input = ip_forward;
+	rth->u.dst.output = ip_output;
+
+	rt_set_nexthop(rth, res, itag);
+
+	rth->rt_flags = flags;
+
+	*result = rth;
+	err = 0;
+ cleanup:
+	/* release the working reference to the output device */
+	in_dev_put(out_dev);
+	return err;
+}						
+
+static inline int ip_mkroute_input_def(struct sk_buff *skb, 
+				       struct fib_result* res, 
+				       const struct flowi *fl,
+				       struct in_device *in_dev,
+				       u32 daddr, u32 saddr, u32 tos)
+{
+	struct rtable* rth;
+	int err;
+	unsigned hash;
+
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+	if (res->fi->fib_nhs > 1 && fl->oif == 0)
+		fib_select_multipath(fl, res);
+#endif
+
+	/* create a routing cache entry */
+	err = __mkroute_input( skb, res, in_dev, daddr, saddr, tos, &rth );
+	if ( err )
+		return err;
+	atomic_set(&rth->u.dst.__refcnt, 1);
+
+	/* put it into the cache */
+	hash = rt_hash_code(daddr, saddr ^ (fl->iif << 5), tos);
+	return rt_intern_hash(hash, rth, (struct rtable**)&skb->dst);	
+}
+
+static inline int ip_mkroute_input(struct sk_buff *skb, 
+				   struct fib_result* res, 
+				   const struct flowi *fl,
+				   struct in_device *in_dev,
+				   u32 daddr, u32 saddr, u32 tos)
+{
+	return ip_mkroute_input_def(skb, res, fl, in_dev, daddr, saddr, tos);
+}
+
+
 /*
  *	NOTE. We drop all the packets that has local source
  *	addresses, because every properly looped back packet
@@ -1539,11 +1706,10 @@
  */
 
 static int ip_route_input_slow(struct sk_buff *skb, u32 daddr, u32 saddr,
-			u8 tos, struct net_device *dev)
+			       u8 tos, struct net_device *dev)
 {
 	struct fib_result res;
 	struct in_device *in_dev = in_dev_get(dev);
-	struct in_device *out_dev = NULL;
 	struct flowi fl = { .nl_u = { .ip4_u =
 				      { .daddr = daddr,
 					.saddr = saddr,
@@ -1567,8 +1733,6 @@
 	if (!in_dev)
 		goto out;
 
-	hash = rt_hash_code(daddr, saddr ^ (fl.iif << 5), tos);
-
 	/* Check for the most weird martians, which can be not detected
 	   by fib_lookup.
 	 */
@@ -1621,79 +1785,14 @@
 	if (res.type != RTN_UNICAST)
 		goto martian_destination;
 
-#ifdef CONFIG_IP_ROUTE_MULTIPATH
-	if (res.fi->fib_nhs > 1 && fl.oif == 0)
-		fib_select_multipath(&fl, &res);
-#endif
-	out_dev = in_dev_get(FIB_RES_DEV(res));
-	if (out_dev == NULL) {
-		if (net_ratelimit())
-			printk(KERN_CRIT "Bug in ip_route_input_slow(). "
-					 "Please, report\n");
-		goto e_inval;
-	}
-
-	err = fib_validate_source(saddr, daddr, tos, FIB_RES_OIF(res), dev,
-				  &spec_dst, &itag);
-	if (err < 0)
-		goto martian_source;
-
-	if (err)
-		flags |= RTCF_DIRECTSRC;
-
-	if (out_dev == in_dev && err && !(flags & (RTCF_NAT | RTCF_MASQ)) &&
-	    (IN_DEV_SHARED_MEDIA(out_dev) ||
-	     inet_addr_onlink(out_dev, saddr, FIB_RES_GW(res))))
-		flags |= RTCF_DOREDIRECT;
-
-	if (skb->protocol != htons(ETH_P_IP)) {
-		/* Not IP (i.e. ARP). Do not create route, if it is
-		 * invalid for proxy arp. DNAT routes are always valid.
-		 */
-		if (out_dev == in_dev && !(flags & RTCF_DNAT))
-			goto e_inval;
-	}
-
-	rth = dst_alloc(&ipv4_dst_ops);
-	if (!rth)
+	err = ip_mkroute_input(skb, &res, &fl, in_dev, daddr, saddr, tos);
+	if ( err == -ENOBUFS )
 		goto e_nobufs;
-
-	atomic_set(&rth->u.dst.__refcnt, 1);
-	rth->u.dst.flags= DST_HOST;
-	if (in_dev->cnf.no_policy)
-		rth->u.dst.flags |= DST_NOPOLICY;
-	if (in_dev->cnf.no_xfrm)
-		rth->u.dst.flags |= DST_NOXFRM;
-	rth->fl.fl4_dst	= daddr;
-	rth->rt_dst	= daddr;
-	rth->fl.fl4_tos	= tos;
-#ifdef CONFIG_IP_ROUTE_FWMARK
-	rth->fl.fl4_fwmark= skb->nfmark;
-#endif
-	rth->fl.fl4_src	= saddr;
-	rth->rt_src	= saddr;
-	rth->rt_gateway	= daddr;
-	rth->rt_iif 	=
-	rth->fl.iif	= dev->ifindex;
-	rth->u.dst.dev	= out_dev->dev;
-	dev_hold(rth->u.dst.dev);
-	rth->idev	= in_dev_get(rth->u.dst.dev);
-	rth->fl.oif 	= 0;
-	rth->rt_spec_dst= spec_dst;
-
-	rth->u.dst.input = ip_forward;
-	rth->u.dst.output = ip_output;
-
-	rt_set_nexthop(rth, &res, itag);
-
-	rth->rt_flags = flags;
-
-intern:
-	err = rt_intern_hash(hash, rth, (struct rtable**)&skb->dst);
+	if ( err == -EINVAL )
+		goto e_inval;
+	
 done:
 	in_dev_put(in_dev);
-	if (out_dev)
-		in_dev_put(out_dev);
 	if (free_res)
 		fib_res_put(&res);
 out:	return err;
@@ -1753,7 +1852,9 @@
 		rth->rt_flags 	&= ~RTCF_LOCAL;
 	}
 	rth->rt_type	= res.type;
-	goto intern;
+	hash = rt_hash_code(daddr, saddr ^ (fl.iif << 5), tos);
+	err = rt_intern_hash(hash, rth, (struct rtable**)&skb->dst);
+	goto done;
 
 no_route:
 	RT_CACHE_STAT_INC(in_no_route);
@@ -1781,30 +1882,7 @@
 	goto done;
 
 martian_source:
-
-	RT_CACHE_STAT_INC(in_martian_src);
-#ifdef CONFIG_IP_ROUTE_VERBOSE
-	if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit()) {
-		/*
-		 *	RFC1812 recommendation, if source is martian,
-		 *	the only hint is MAC header.
-		 */
-		printk(KERN_WARNING "martian source %u.%u.%u.%u from "
-			"%u.%u.%u.%u, on dev %s\n",
-			NIPQUAD(daddr), NIPQUAD(saddr), dev->name);
-		if (dev->hard_header_len) {
-			int i;
-			unsigned char *p = skb->mac.raw;
-			printk(KERN_WARNING "ll header: ");
-			for (i = 0; i < dev->hard_header_len; i++, p++) {
-				printk("%02x", *p);
-				if (i < (dev->hard_header_len - 1))
-					printk(":");
-			}
-			printk("\n");
-		}
-	}
-#endif
+	ip_handle_martian_source(dev, in_dev, skb, daddr, saddr);
 	goto e_inval;
 }
 
@@ -1875,13 +1953,166 @@
 	return ip_route_input_slow(skb, daddr, saddr, tos, dev);
 }
 
+static inline int __mkroute_output(struct rtable **result,
+				   struct fib_result* res, 
+				   const struct flowi *fl,
+				   const struct flowi *oldflp, 
+				   struct net_device *dev_out, 
+				   unsigned flags) 
+{
+	struct rtable *rth;
+	struct in_device *in_dev;
+	u32 tos = RT_FL_TOS(oldflp);
+	int err = 0;
+
+	if (LOOPBACK(fl->fl4_src) && !(dev_out->flags&IFF_LOOPBACK))
+		return -EINVAL;
+
+	if (fl->fl4_dst == 0xFFFFFFFF)
+		res->type = RTN_BROADCAST;
+	else if (MULTICAST(fl->fl4_dst))
+		res->type = RTN_MULTICAST;
+	else if (BADCLASS(fl->fl4_dst) || ZERONET(fl->fl4_dst))
+		return -EINVAL;
+
+	if (dev_out->flags & IFF_LOOPBACK)
+		flags |= RTCF_LOCAL;
+
+	/* get work reference to inet device */
+	in_dev = in_dev_get(dev_out);
+	if (!in_dev)
+		return -EINVAL;
+
+	if (res->type == RTN_BROADCAST) {
+		flags |= RTCF_BROADCAST | RTCF_LOCAL;
+		if (res->fi) {
+			fib_info_put(res->fi);
+			res->fi = NULL;
+		}
+	} else if (res->type == RTN_MULTICAST) {
+		flags |= RTCF_MULTICAST|RTCF_LOCAL;
+		if (!ip_check_mc(in_dev, oldflp->fl4_dst, oldflp->fl4_src, 
+				 oldflp->proto))
+			flags &= ~RTCF_LOCAL;
+		/* If multicast route do not exist use
+		   default one, but do not gateway in this case.
+		   Yes, it is hack.
+		 */
+		if (res->fi && res->prefixlen < 4) {
+			fib_info_put(res->fi);
+			res->fi = NULL;
+		}
+	}
+
+
+	rth = dst_alloc(&ipv4_dst_ops);
+	if (!rth) {
+		err = -ENOBUFS;
+		goto cleanup;
+	}		
+
+	rth->u.dst.flags= DST_HOST;
+	if (in_dev->cnf.no_xfrm)
+		rth->u.dst.flags |= DST_NOXFRM;
+	if (in_dev->cnf.no_policy)
+		rth->u.dst.flags |= DST_NOPOLICY;
+
+	rth->fl.fl4_dst	= oldflp->fl4_dst;
+	rth->fl.fl4_tos	= tos;
+	rth->fl.fl4_src	= oldflp->fl4_src;
+	rth->fl.oif	= oldflp->oif;
+#ifdef CONFIG_IP_ROUTE_FWMARK
+	rth->fl.fl4_fwmark= oldflp->fl4_fwmark;
+#endif
+	rth->rt_dst	= fl->fl4_dst;
+	rth->rt_src	= fl->fl4_src;
+	rth->rt_iif	= oldflp->oif ? : dev_out->ifindex;
+	/* get references to the devices that are to be hold by the routing 
+	   cache entry */
+	rth->u.dst.dev	= dev_out;
+	dev_hold(dev_out);
+	rth->idev	= in_dev_get(dev_out);
+	rth->rt_gateway = fl->fl4_dst;
+	rth->rt_spec_dst= fl->fl4_src;
+
+	rth->u.dst.output=ip_output;
+
+	RT_CACHE_STAT_INC(out_slow_tot);
+
+	if (flags & RTCF_LOCAL) {
+		rth->u.dst.input = ip_local_deliver;
+		rth->rt_spec_dst = fl->fl4_dst;
+	}
+	if (flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
+		rth->rt_spec_dst = fl->fl4_src;
+		if (flags & RTCF_LOCAL && 
+		    !(dev_out->flags & IFF_LOOPBACK)) {
+			rth->u.dst.output = ip_mc_output;
+			RT_CACHE_STAT_INC(out_slow_mc);
+		}
+#ifdef CONFIG_IP_MROUTE
+		if (res->type == RTN_MULTICAST) {
+			if (IN_DEV_MFORWARD(in_dev) &&
+			    !LOCAL_MCAST(oldflp->fl4_dst)) {
+				rth->u.dst.input = ip_mr_input;
+				rth->u.dst.output = ip_mc_output;
+			}
+		}
+#endif
+	}
+
+	rt_set_nexthop(rth, res, 0);
+
+	rth->rt_flags = flags;
+
+	*result = rth;
+ cleanup:
+	/* release work reference to inet device */
+	in_dev_put(in_dev);
+
+	return err;
+}
+
+static inline int ip_mkroute_output_def(struct rtable **rp,
+					struct fib_result* res,
+					const struct flowi *fl,
+					const struct flowi *oldflp,
+					struct net_device *dev_out,
+					unsigned flags)
+{
+	struct rtable *rth;
+	int err = __mkroute_output(&rth, res, fl, oldflp, dev_out, flags);
+	unsigned hash;
+	if ( err == 0 ) {
+		u32 tos = RT_FL_TOS(oldflp);
+
+		atomic_set(&rth->u.dst.__refcnt, 1);
+		
+		hash = rt_hash_code(oldflp->fl4_dst, 
+				    oldflp->fl4_src ^ (oldflp->oif << 5), tos);
+		err = rt_intern_hash(hash, rth, rp);
+	}
+	
+	return err;
+}
+
+static inline int ip_mkroute_output(struct rtable** rp,
+				    struct fib_result* res,
+				    const struct flowi *fl,
+				    const struct flowi *oldflp,
+				    struct net_device *dev_out,
+				    unsigned flags)
+{
+	return ip_mkroute_output_def(rp, res, fl, oldflp, dev_out, flags);
+}
+
 /*
  * Major route resolver routine.
  */
 
 static int ip_route_output_slow(struct rtable **rp, const struct flowi *oldflp)
 {
-	u32 tos	= oldflp->fl4_tos & (IPTOS_RT_MASK | RTO_ONLINK);
+	u32 tos	= RT_FL_TOS(oldflp);
 	struct flowi fl = { .nl_u = { .ip4_u =
 				      { .daddr = oldflp->fl4_dst,
 					.saddr = oldflp->fl4_src,
@@ -1897,10 +2128,7 @@
 			    .oif = oldflp->oif };
 	struct fib_result res;
 	unsigned flags = 0;
-	struct rtable *rth;
 	struct net_device *dev_out = NULL;
-	struct in_device *in_dev = NULL;
-	unsigned hash;
 	int free_res = 0;
 	int err;
 
@@ -2060,116 +2288,13 @@
 	fl.oif = dev_out->ifindex;
 
 make_route:
-	if (LOOPBACK(fl.fl4_src) && !(dev_out->flags&IFF_LOOPBACK))
-		goto e_inval;
+	err = ip_mkroute_output(rp, &res, &fl, oldflp, dev_out, flags);
 
-	if (fl.fl4_dst == 0xFFFFFFFF)
-		res.type = RTN_BROADCAST;
-	else if (MULTICAST(fl.fl4_dst))
-		res.type = RTN_MULTICAST;
-	else if (BADCLASS(fl.fl4_dst) || ZERONET(fl.fl4_dst))
-		goto e_inval;
-
-	if (dev_out->flags & IFF_LOOPBACK)
-		flags |= RTCF_LOCAL;
-
-	in_dev = in_dev_get(dev_out);
-	if (!in_dev)
-		goto e_inval;
-
-	if (res.type == RTN_BROADCAST) {
-		flags |= RTCF_BROADCAST | RTCF_LOCAL;
-		if (res.fi) {
-			fib_info_put(res.fi);
-			res.fi = NULL;
-		}
-	} else if (res.type == RTN_MULTICAST) {
-		flags |= RTCF_MULTICAST|RTCF_LOCAL;
-		if (!ip_check_mc(in_dev, oldflp->fl4_dst, oldflp->fl4_src, oldflp->proto))
-			flags &= ~RTCF_LOCAL;
-		/* If multicast route do not exist use
-		   default one, but do not gateway in this case.
-		   Yes, it is hack.
-		 */
-		if (res.fi && res.prefixlen < 4) {
-			fib_info_put(res.fi);
-			res.fi = NULL;
-		}
-	}
-
-	rth = dst_alloc(&ipv4_dst_ops);
-	if (!rth)
-		goto e_nobufs;
-
-	atomic_set(&rth->u.dst.__refcnt, 1);
-	rth->u.dst.flags= DST_HOST;
-	if (in_dev->cnf.no_xfrm)
-		rth->u.dst.flags |= DST_NOXFRM;
-	if (in_dev->cnf.no_policy)
-		rth->u.dst.flags |= DST_NOPOLICY;
-	rth->fl.fl4_dst	= oldflp->fl4_dst;
-	rth->fl.fl4_tos	= tos;
-	rth->fl.fl4_src	= oldflp->fl4_src;
-	rth->fl.oif	= oldflp->oif;
-#ifdef CONFIG_IP_ROUTE_FWMARK
-	rth->fl.fl4_fwmark= oldflp->fl4_fwmark;
-#endif
-	rth->rt_dst	= fl.fl4_dst;
-	rth->rt_src	= fl.fl4_src;
-	rth->rt_iif	= oldflp->oif ? : dev_out->ifindex;
-	rth->u.dst.dev	= dev_out;
-	dev_hold(dev_out);
-	rth->idev	= in_dev_get(dev_out);
-	rth->rt_gateway = fl.fl4_dst;
-	rth->rt_spec_dst= fl.fl4_src;
-
-	rth->u.dst.output=ip_output;
-
-	RT_CACHE_STAT_INC(out_slow_tot);
-
-	if (flags & RTCF_LOCAL) {
-		rth->u.dst.input = ip_local_deliver;
-		rth->rt_spec_dst = fl.fl4_dst;
-	}
-	if (flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
-		rth->rt_spec_dst = fl.fl4_src;
-		if (flags & RTCF_LOCAL && !(dev_out->flags & IFF_LOOPBACK)) {
-			rth->u.dst.output = ip_mc_output;
-			RT_CACHE_STAT_INC(out_slow_mc);
-		}
-#ifdef CONFIG_IP_MROUTE
-		if (res.type == RTN_MULTICAST) {
-			if (IN_DEV_MFORWARD(in_dev) &&
-			    !LOCAL_MCAST(oldflp->fl4_dst)) {
-				rth->u.dst.input = ip_mr_input;
-				rth->u.dst.output = ip_mc_output;
-			}
-		}
-#endif
-	}
-
-	rt_set_nexthop(rth, &res, 0);
-	
-
-	rth->rt_flags = flags;
-
-	hash = rt_hash_code(oldflp->fl4_dst, oldflp->fl4_src ^ (oldflp->oif << 5), tos);
-	err = rt_intern_hash(hash, rth, rp);
-done:
 	if (free_res)
 		fib_res_put(&res);
 	if (dev_out)
 		dev_put(dev_out);
-	if (in_dev)
-		in_dev_put(in_dev);
 out:	return err;
-
-e_inval:
-	err = -EINVAL;
-	goto done;
-e_nobufs:
-	err = -ENOBUFS;
-	goto done;
 }
 
 int __ip_route_output_key(struct rtable **rp, const struct flowi *flp)