diff --git a/include/net/flow.h b/include/net/flow.h
index 64fd24836650b7ea14a5c6ba8278066bbb21bf0d..8109a159d1b3ba5ced3aa6d2bc10b9f01d274520 100644
--- a/include/net/flow.h
+++ b/include/net/flow.h
@@ -11,6 +11,14 @@
 #include <linux/in6.h>
 #include <linux/atomic.h>
 
+/*
+ * ifindex generation is per-net namespace, and loopback is
+ * always the 1st device in ns (see net_dev_init), thus any
+ * loopback device should get ifindex 1
+ */
+
+#define LOOPBACK_IFINDEX	1
+
 struct flowi_common {
 	int	flowic_oif;
 	int	flowic_iif;
@@ -80,7 +88,7 @@ static inline void flowi4_init_output(struct flowi4 *fl4, int oif,
 				      __be16 dport, __be16 sport)
 {
 	fl4->flowi4_oif = oif;
-	fl4->flowi4_iif = 0;
+	fl4->flowi4_iif = LOOPBACK_IFINDEX;
 	fl4->flowi4_mark = mark;
 	fl4->flowi4_tos = tos;
 	fl4->flowi4_scope = scope;
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 79387f73f87585101ff44f548c5db299ae0b574c..5f9eb260990f6507d61f42d2463d45455346e812 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -9,6 +9,7 @@
 #include <linux/list.h>
 #include <linux/sysctl.h>
 
+#include <net/flow.h>
 #include <net/netns/core.h>
 #include <net/netns/mib.h>
 #include <net/netns/unix.h>
@@ -131,14 +132,6 @@ struct net {
 	atomic_t		fnhe_genid;
 };
 
-/*
- * ifindex generation is per-net namespace, and loopback is
- * always the 1st device in ns (see net_dev_init), thus any
- * loopback device should get ifindex 1
- */
-
-#define LOOPBACK_IFINDEX	1
-
 #include <linux/seq_file_net.h>
 
 /* Init's network namespace */
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 1a629f870274de3c1b70910ec5285f7baae139eb..255aa9946fe785a2577fbdb23560288599c1ba0a 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -250,7 +250,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
 	bool dev_match;
 
 	fl4.flowi4_oif = 0;
-	fl4.flowi4_iif = oif;
+	fl4.flowi4_iif = oif ? : LOOPBACK_IFINDEX;
 	fl4.daddr = src;
 	fl4.saddr = dst;
 	fl4.flowi4_tos = tos;
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index b53f0bf84dcaba3fd2767dd734add99d05db9fa6..8a043f03c88ecbb418b5466953abefd54c50b1d0 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -631,6 +631,7 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
 				.daddr = nh->nh_gw,
 				.flowi4_scope = cfg->fc_scope + 1,
 				.flowi4_oif = nh->nh_oif,
+				.flowi4_iif = LOOPBACK_IFINDEX,
 			};
 
 			/* It is not necessary, but requires a bit of thinking */
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 28863570dd60557ca27d8c73c7590b926c7dcf57..d84dc8d4c916e7f50260a2b29df5d79f4adb4c1e 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -455,7 +455,7 @@ static netdev_tx_t reg_vif_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct mr_table *mrt;
 	struct flowi4 fl4 = {
 		.flowi4_oif	= dev->ifindex,
-		.flowi4_iif	= skb->skb_iif,
+		.flowi4_iif	= skb->skb_iif ? : LOOPBACK_IFINDEX,
 		.flowi4_mark	= skb->mark,
 	};
 	int err;
diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c
index c49dcd0284a06c6bb4b4e6787af5888289ba50f3..4bfaedf9b34e5248aa6f8133e2c3bb0e555062e9 100644
--- a/net/ipv4/netfilter/ipt_rpfilter.c
+++ b/net/ipv4/netfilter/ipt_rpfilter.c
@@ -89,11 +89,8 @@ static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	if (ipv4_is_multicast(iph->daddr)) {
 		if (ipv4_is_zeronet(iph->saddr))
 			return ipv4_is_local_multicast(iph->daddr) ^ invert;
-		flow.flowi4_iif = 0;
-	} else {
-		flow.flowi4_iif = LOOPBACK_IFINDEX;
 	}
-
+	flow.flowi4_iif = LOOPBACK_IFINDEX;
 	flow.daddr = iph->saddr;
 	flow.saddr = rpfilter_get_saddr(iph->daddr);
 	flow.flowi4_oif = 0;
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 1485aafcad59f3eb1510253f631f567279d952d9..db1e0da871f40a2284d67bd48c0f21d772b923f3 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1700,8 +1700,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 
 	if (res.type == RTN_LOCAL) {
 		err = fib_validate_source(skb, saddr, daddr, tos,
-					  LOOPBACK_IFINDEX,
-					  dev, in_dev, &itag);
+					  0, dev, in_dev, &itag);
 		if (err < 0)
 			goto martian_source_keep_err;
 		goto local_input;
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 8737400af0a095cac6666112cb8dcd4d60518823..8659067da28e8a8557af6f4109fc52056ccdee1b 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -700,7 +700,7 @@ static netdev_tx_t reg_vif_xmit(struct sk_buff *skb,
 	struct mr6_table *mrt;
 	struct flowi6 fl6 = {
 		.flowi6_oif	= dev->ifindex,
-		.flowi6_iif	= skb->skb_iif,
+		.flowi6_iif	= skb->skb_iif ? : LOOPBACK_IFINDEX,
 		.flowi6_mark	= skb->mark,
 	};
 	int err;