diff -ur v2.6.11-before-nf_reroute/linux/include/linux/netfilter_ipv4/ip_nat.h linux/include/linux/netfilter_ipv4/ip_nat.h
--- v2.6.11-before-nf_reroute/linux/include/linux/netfilter_ipv4/ip_nat.h	2005-03-03 10:17:23.000000000 +0200
+++ linux/include/linux/netfilter_ipv4/ip_nat.h	2005-03-03 15:17:10.157526296 +0200
@@ -68,6 +68,13 @@
 
 struct ip_conntrack;
 
+/* Call input routing for SNAT-ed traffic */
+extern unsigned int ip_nat_route_input(unsigned int hooknum,
+				       struct sk_buff **pskb,
+				       const struct net_device *in,
+				       const struct net_device *out,
+				       int (*okfn)(struct sk_buff *));
+
 /* Set up the info structure to map into this range. */
 extern unsigned int ip_nat_setup_info(struct ip_conntrack *conntrack,
 				      const struct ip_nat_range *range,
diff -ur v2.6.11-before-nf_reroute/linux/include/net/flow.h linux/include/net/flow.h
--- v2.6.11-before-nf_reroute/linux/include/net/flow.h	2004-04-04 09:43:36.000000000 +0300
+++ linux/include/net/flow.h	2005-03-03 15:16:40.777992664 +0200
@@ -19,6 +19,8 @@
 			__u32			daddr;
 			__u32			saddr;
 			__u32			fwmark;
+			__u32			lsrc;
+			__u32			gw;
 			__u8			tos;
 			__u8			scope;
 		} ip4_u;
@@ -46,6 +48,8 @@
 #define fl4_dst		nl_u.ip4_u.daddr
 #define fl4_src		nl_u.ip4_u.saddr
 #define fl4_fwmark	nl_u.ip4_u.fwmark
+#define fl4_lsrc	nl_u.ip4_u.lsrc
+#define fl4_gw		nl_u.ip4_u.gw
 #define fl4_tos		nl_u.ip4_u.tos
 #define fl4_scope	nl_u.ip4_u.scope
 
diff -ur v2.6.11-before-nf_reroute/linux/include/net/route.h linux/include/net/route.h
--- v2.6.11-before-nf_reroute/linux/include/net/route.h	2005-03-03 10:17:23.000000000 +0200
+++ linux/include/net/route.h	2005-03-03 15:16:40.778992512 +0200
@@ -119,6 +119,7 @@
 extern int		ip_route_output_key(struct rtable **, struct flowi *flp);
 extern int		ip_route_output_flow(struct rtable **rp, struct flowi *flp, struct sock *sk, int flags);
 extern int		ip_route_input(struct sk_buff*, u32 dst, u32 src, u8 tos, struct net_device *devin);
+extern int		ip_route_input_lookup(struct sk_buff*, u32 dst, u32 src, u8 tos, struct net_device *devin, u32 lsrc);
 extern unsigned short	ip_rt_frag_needed(struct iphdr *iph, unsigned short new_mtu);
 extern void		ip_rt_send_redirect(struct sk_buff *skb);
 
diff -ur v2.6.11-before-nf_reroute/linux/net/ipv4/fib_semantics.c linux/net/ipv4/fib_semantics.c
--- v2.6.11-before-nf_reroute/linux/net/ipv4/fib_semantics.c	2005-03-03 15:05:51.000000000 +0200
+++ linux/net/ipv4/fib_semantics.c	2005-03-03 15:17:58.876119944 +0200
@@ -331,6 +331,9 @@
 	for (nhsel = 0, nh = fi->fib_nh; nhsel < fi->fib_nhs; nh++, nhsel++) {
 		if (flp->oif && flp->oif != nh->nh_oif)
 			continue;
+		if (flp->fl4_gw && flp->fl4_gw != nh->nh_gw && nh->nh_gw &&
+		    nh->nh_scope == RT_SCOPE_LINK)
+			continue;
 		if (nh->nh_flags & RTNH_F_DEAD)
 			continue;
 
@@ -936,8 +939,12 @@
 				for_nexthops(fi) {
 					if (nh->nh_flags&RTNH_F_DEAD)
 						continue;
-					if (!flp->oif || flp->oif == nh->nh_oif)
-						break;
+					if (flp->oif && flp->oif != nh->nh_oif)
+						continue;
+					if (flp->fl4_gw && flp->fl4_gw != nh->nh_gw &&
+					    nh->nh_gw && nh->nh_scope == RT_SCOPE_LINK)
+						continue;
+					break;
 				}
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 				if (nhsel < fi->fib_nhs) {
@@ -1377,6 +1384,9 @@
 		change_nexthops(fi) {
 			if (flp->oif != nh->nh_oif)
 				continue;
+			if (flp->fl4_gw && flp->fl4_gw != nh->nh_gw &&
+			    nh->nh_gw && nh->nh_scope == RT_SCOPE_LINK)
+				continue;
 			if (!(nh->nh_flags&RTNH_F_BADSTATE)) {
 				if (nh->nh_power > w) {
 					w = nh->nh_power;
@@ -1435,11 +1445,14 @@
 
 	for_nexthops(fi) {
 		if (!(nh->nh_flags&RTNH_F_DEAD)) {
-			if (!flp->oif || flp->oif == nh->nh_oif) {
-				spin_unlock_bh(&fib_multipath_lock);
-				res->nh_sel = nhsel;
-				return;
-			}
+			if (flp->oif && flp->oif != nh->nh_oif)
+				continue;
+			if (flp->fl4_gw && flp->fl4_gw != nh->nh_gw &&
+			    nh->nh_gw && nh->nh_scope == RT_SCOPE_LINK)
+				continue;
+			spin_unlock_bh(&fib_multipath_lock);
+			res->nh_sel = nhsel;
+			return;
 		}
 	} endfor_nexthops(fi);
 
diff -ur v2.6.11-before-nf_reroute/linux/net/ipv4/netfilter/ip_nat_core.c linux/net/ipv4/netfilter/ip_nat_core.c
--- v2.6.11-before-nf_reroute/linux/net/ipv4/netfilter/ip_nat_core.c	2005-03-03 10:17:23.000000000 +0200
+++ linux/net/ipv4/netfilter/ip_nat_core.c	2005-03-03 16:05:03.797666592 +0200
@@ -505,6 +505,52 @@
 	synchronize_net();
 }
 
+unsigned int
+ip_nat_route_input(unsigned int hooknum,
+		struct sk_buff **pskb,
+		const struct net_device *in,
+		const struct net_device *out,
+		int (*okfn)(struct sk_buff *))
+{
+	struct sk_buff *skb = *pskb;
+	struct iphdr *iph;
+	struct ip_conntrack *conn;
+	enum ip_conntrack_info ctinfo;
+	enum ip_conntrack_dir dir;
+	unsigned long statusbit;
+	u32 saddr;
+
+	if (!(conn = ip_conntrack_get(skb, &ctinfo)))
+		return NF_ACCEPT;
+
+	if (!(conn->status & IPS_NAT_DONE_MASK))
+		return NF_ACCEPT;
+	dir = CTINFO2DIR(ctinfo);
+	statusbit = IPS_SRC_NAT;
+	if (dir == IP_CT_DIR_REPLY)
+		statusbit ^= IPS_NAT_MASK;
+	if (!(conn->status & statusbit))
+		return NF_ACCEPT;
+
+	if (skb->dst)
+		return NF_ACCEPT;
+
+	if (skb->len < sizeof(struct iphdr))
+		return NF_ACCEPT;
+
+	/* use daddr in other direction as masquerade address (lsrc) */
+	iph = skb->nh.iph;
+	saddr = conn->tuplehash[!dir].tuple.dst.ip;
+	if (saddr == iph->saddr)
+		return NF_ACCEPT;
+
+	if (ip_route_input_lookup(skb, iph->daddr, iph->saddr, iph->tos,
+	    skb->dev, saddr))
+		return NF_DROP;
+
+	return NF_ACCEPT;
+}
+
 int __init ip_nat_init(void)
 {
 	size_t i;
diff -ur v2.6.11-before-nf_reroute/linux/net/ipv4/netfilter/ip_nat_standalone.c linux/net/ipv4/netfilter/ip_nat_standalone.c
--- v2.6.11-before-nf_reroute/linux/net/ipv4/netfilter/ip_nat_standalone.c	2005-03-03 10:17:23.000000000 +0200
+++ linux/net/ipv4/netfilter/ip_nat_standalone.c	2005-03-03 15:16:42.846678176 +0200
@@ -241,6 +241,14 @@
 	.priority	= NF_IP_PRI_NAT_DST,
 };
 
+/* Before routing, route before mangling */
+static struct nf_hook_ops ip_nat_inr_ops = {
+	.hook		= ip_nat_route_input,
+	.pf		= PF_INET,
+	.hooknum	= NF_IP_PRE_ROUTING,
+	.priority	= NF_IP_PRI_LAST-1,
+};
+
 /* After packet filtering, change source */
 static struct nf_hook_ops ip_nat_out_ops = {
 	.hook		= ip_nat_out,
@@ -291,10 +299,15 @@
 		printk("ip_nat_init: can't register in hook.\n");
 		goto cleanup_nat;
 	}
+	ret = nf_register_hook(&ip_nat_inr_ops);
+	if (ret < 0) {
+		printk("ip_nat_init: can't register inr hook.\n");
+		goto cleanup_inops;
+	}
 	ret = nf_register_hook(&ip_nat_out_ops);
 	if (ret < 0) {
 		printk("ip_nat_init: can't register out hook.\n");
-		goto cleanup_inops;
+		goto cleanup_inrops;
 	}
 	ret = nf_register_hook(&ip_nat_local_out_ops);
 	if (ret < 0) {
@@ -314,6 +327,8 @@
 	nf_unregister_hook(&ip_nat_local_out_ops);
  cleanup_outops:
 	nf_unregister_hook(&ip_nat_out_ops);
+ cleanup_inrops:
+	nf_unregister_hook(&ip_nat_inr_ops);
  cleanup_inops:
 	nf_unregister_hook(&ip_nat_in_ops);
  cleanup_nat:
diff -ur v2.6.11-before-nf_reroute/linux/net/ipv4/netfilter/ipt_MASQUERADE.c linux/net/ipv4/netfilter/ipt_MASQUERADE.c
--- v2.6.11-before-nf_reroute/linux/net/ipv4/netfilter/ipt_MASQUERADE.c	2005-03-03 10:17:23.000000000 +0200
+++ linux/net/ipv4/netfilter/ipt_MASQUERADE.c	2005-03-03 15:16:42.847678024 +0200
@@ -96,13 +96,31 @@
 	                    || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
 
 	mr = targinfo;
-	rt = (struct rtable *)(*pskb)->dst;
-	newsrc = inet_select_addr(out, rt->rt_gateway, RT_SCOPE_UNIVERSE);
-	if (!newsrc) {
-		printk("MASQUERADE: %s ate my IP address\n", out->name);
-		return NF_DROP;
+
+	{
+		struct flowi fl = { .nl_u = { .ip4_u =
+					      { .daddr = (*pskb)->nh.iph->daddr,
+						.tos = (RT_TOS((*pskb)->nh.iph->tos) |
+							RTO_CONN),
+						.gw = ((struct rtable *) (*pskb)->dst)->rt_gateway,
+#ifdef CONFIG_IP_ROUTE_FWMARK
+						.fwmark = (*pskb)->nfmark
+#endif
+					      } },
+				    .oif = out->ifindex };
+		if (ip_route_output_key(&rt, &fl) != 0) {
+			/* Funky routing can do this. */
+			if (net_ratelimit())
+				printk("MASQUERADE:"
+				       " No route: Rusty's brain broke!\n");
+			return NF_DROP;
+		}
 	}
 
+	newsrc = rt->rt_src;
+	DEBUGP("newsrc = %u.%u.%u.%u\n", NIPQUAD(newsrc));
+	ip_rt_put(rt);
+
 	WRITE_LOCK(&masq_lock);
 	ct->nat.masq_index = out->ifindex;
 	WRITE_UNLOCK(&masq_lock);
diff -ur v2.6.11-before-nf_reroute/linux/net/ipv4/route.c linux/net/ipv4/route.c
--- v2.6.11-before-nf_reroute/linux/net/ipv4/route.c	2005-03-03 15:05:51.000000000 +0200
+++ linux/net/ipv4/route.c	2005-03-03 15:16:42.849677720 +0200
@@ -1061,6 +1061,7 @@
 
 				/* Gateway is different ... */
 				rt->rt_gateway		= new_gw;
+				if (rt->fl.fl4_gw) rt->fl.fl4_gw = new_gw;
 
 				/* Redirect received -> path was valid */
 				dst_confirm(&rth->u.dst);
@@ -1497,6 +1498,7 @@
 	rth->fl.fl4_fwmark= skb->nfmark;
 #endif
 	rth->fl.fl4_src	= saddr;
+	rth->fl.fl4_lsrc = 0;
 	rth->rt_src	= saddr;
 #ifdef CONFIG_NET_CLS_ROUTE
 	rth->u.dst.tclassid = itag;
@@ -1507,6 +1509,7 @@
 	dev_hold(rth->u.dst.dev);
 	rth->idev	= in_dev_get(rth->u.dst.dev);
 	rth->fl.oif	= 0;
+	rth->fl.fl4_gw	= 0;
 	rth->rt_gateway	= daddr;
 	rth->rt_spec_dst= spec_dst;
 	rth->rt_type	= RTN_MULTICAST;
@@ -1546,21 +1549,21 @@
  */
 
 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, u32 lsrc)
 {
 	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,
+					.saddr = lsrc? : saddr,
 					.tos = tos,
 					.scope = RT_SCOPE_UNIVERSE,
 #ifdef CONFIG_IP_ROUTE_FWMARK
 					.fwmark = skb->nfmark
 #endif
 				      } },
-			    .iif = dev->ifindex };
+			    .iif = lsrc? loopback_dev.ifindex : dev->ifindex };
 	unsigned	flags = 0;
 	u32		itag = 0;
 	struct rtable * rth;
@@ -1574,7 +1577,7 @@
 	if (!in_dev)
 		goto out;
 
-	hash = rt_hash_code(daddr, saddr ^ (fl.iif << 5), tos);
+	hash = rt_hash_code(daddr, saddr ^ (dev->ifindex << 5), tos);
 
 	/* Check for the most weird martians, which can be not detected
 	   by fib_lookup.
@@ -1595,6 +1598,12 @@
 	if (BADCLASS(daddr) || ZERONET(daddr) || LOOPBACK(daddr))
 		goto martian_destination;
 
+	if (lsrc) {
+		if (MULTICAST(lsrc) || BADCLASS(lsrc) ||
+		    ZERONET(lsrc) || LOOPBACK(lsrc))
+			goto e_inval;
+	}
+
 	/*
 	 *	Now we are ready to route packet.
 	 */
@@ -1604,6 +1613,10 @@
 		goto no_route;
 	}
 	free_res = 1;
+	if (lsrc && res.type != RTN_UNICAST && res.type != RTN_NAT)
+		goto e_inval;
+	fl.iif = dev->ifindex;
+	fl.fl4_src = saddr;
 
 	RT_CACHE_STAT_INC(in_slow_tot);
 
@@ -1650,6 +1663,7 @@
 		flags |= RTCF_DIRECTSRC;
 
 	if (out_dev == in_dev && err && !(flags & (RTCF_NAT | RTCF_MASQ)) &&
+	    !lsrc &&
 	    (IN_DEV_SHARED_MEDIA(out_dev) ||
 	     inet_addr_onlink(out_dev, saddr, FIB_RES_GW(res))))
 		flags |= RTCF_DOREDIRECT;
@@ -1680,6 +1694,7 @@
 #endif
 	rth->fl.fl4_src	= saddr;
 	rth->rt_src	= saddr;
+	rth->fl.fl4_lsrc	= lsrc;
 	rth->rt_gateway	= daddr;
 	rth->rt_iif 	=
 	rth->fl.iif	= dev->ifindex;
@@ -1687,6 +1702,7 @@
 	dev_hold(rth->u.dst.dev);
 	rth->idev	= in_dev_get(rth->u.dst.dev);
 	rth->fl.oif 	= 0;
+	rth->fl.fl4_gw	= 0;
 	rth->rt_spec_dst= spec_dst;
 
 	rth->u.dst.input = ip_forward;
@@ -1709,6 +1725,8 @@
 brd_input:
 	if (skb->protocol != htons(ETH_P_IP))
 		goto e_inval;
+	if (lsrc)
+		goto e_inval;
 
 	if (ZERONET(saddr))
 		spec_dst = inet_select_addr(dev, 0, RT_SCOPE_LINK);
@@ -1751,6 +1769,7 @@
 	rth->u.dst.dev	= &loopback_dev;
 	dev_hold(rth->u.dst.dev);
 	rth->idev	= in_dev_get(rth->u.dst.dev);
+	rth->fl.fl4_gw	= 0;
 	rth->rt_gateway	= daddr;
 	rth->rt_spec_dst= spec_dst;
 	rth->u.dst.input= ip_local_deliver;
@@ -1816,8 +1835,9 @@
 	goto e_inval;
 }
 
-int ip_route_input(struct sk_buff *skb, u32 daddr, u32 saddr,
-		   u8 tos, struct net_device *dev)
+static inline int
+ip_route_input_cached(struct sk_buff *skb, u32 daddr, u32 saddr,
+		      u8 tos, struct net_device *dev, u32 lsrc)
 {
 	struct rtable * rth;
 	unsigned	hash;
@@ -1832,6 +1852,7 @@
 		if (rth->fl.fl4_dst == daddr &&
 		    rth->fl.fl4_src == saddr &&
 		    rth->fl.iif == iif &&
+		    rth->fl.fl4_lsrc == lsrc &&
 		    rth->fl.oif == 0 &&
 #ifdef CONFIG_IP_ROUTE_FWMARK
 		    rth->fl.fl4_fwmark == skb->nfmark &&
@@ -1880,9 +1901,21 @@
 		rcu_read_unlock();
 		return -EINVAL;
 	}
-	return ip_route_input_slow(skb, daddr, saddr, tos, dev);
+	return ip_route_input_slow(skb, daddr, saddr, tos, dev, lsrc);
 }
 
+int ip_route_input(struct sk_buff *skb, u32 daddr, u32 saddr,
+		   u8 tos, struct net_device *dev)
+{
+	return ip_route_input_cached(skb, daddr, saddr, tos, dev, 0);
+}
+
+int ip_route_input_lookup(struct sk_buff *skb, u32 daddr, u32 saddr,
+			  u8 tos, struct net_device *dev, u32 lsrc)
+{
+	return ip_route_input_cached(skb, daddr, saddr, tos, dev, lsrc);
+}
+ 
 /*
  * Major route resolver routine.
  */
@@ -1893,6 +1926,7 @@
 	struct flowi fl = { .nl_u = { .ip4_u =
 				      { .daddr = oldflp->fl4_dst,
 					.saddr = oldflp->fl4_src,
+					.gw = oldflp->fl4_gw,
 					.tos = tos & IPTOS_RT_MASK,
 					.scope = ((tos & RTO_ONLINK) ?
 						  RT_SCOPE_LINK :
@@ -1996,6 +2030,7 @@
 		dev_out = &loopback_dev;
 		dev_hold(dev_out);
 		fl.oif = loopback_dev.ifindex;
+		fl.fl4_gw = 0;
 		res.type = RTN_LOCAL;
 		flags |= RTCF_LOCAL;
 		goto make_route;
@@ -2043,6 +2078,7 @@
 		dev_out = &loopback_dev;
 		dev_hold(dev_out);
 		fl.oif = dev_out->ifindex;
+		fl.fl4_gw = 0;
 		if (res.fi)
 			fib_info_put(res.fi);
 		res.fi = NULL;
@@ -2118,6 +2154,7 @@
 	rth->fl.fl4_tos	= tos;
 	rth->fl.fl4_src	= oldflp->fl4_src;
 	rth->fl.oif	= oldflp->oif;
+	rth->fl.fl4_gw	= oldflp->fl4_gw;
 #ifdef CONFIG_IP_ROUTE_FWMARK
 	rth->fl.fl4_fwmark= oldflp->fl4_fwmark;
 #endif
@@ -2193,6 +2230,7 @@
 		    rth->fl.fl4_src == flp->fl4_src &&
 		    rth->fl.iif == 0 &&
 		    rth->fl.oif == flp->oif &&
+		    rth->fl.fl4_gw == flp->fl4_gw &&
 #ifdef CONFIG_IP_ROUTE_FWMARK
 		    rth->fl.fl4_fwmark == flp->fl4_fwmark &&
 #endif
@@ -2825,3 +2863,4 @@
 EXPORT_SYMBOL(__ip_select_ident);
 EXPORT_SYMBOL(ip_route_input);
 EXPORT_SYMBOL(ip_route_output_key);
+EXPORT_SYMBOL(ip_route_input_lookup);
