ipv4, fib: pass LOOPBACK_IFINDEX instead of 0 to flowi4_iif

As suggested by Julian:

	Simply, flowi4_iif must not contain 0, it does not
	look logical to ignore all ip rules with specified iif.

because in fib_rule_match() we do:

        if (rule->iifindex && (rule->iifindex != fl->flowi_iif))
                goto out;

flowi4_iif should be LOOPBACK_IFINDEX by default.

We need to move LOOPBACK_IFINDEX to include/net/flow.h:

1) It is mostly used by flowi_iif

2) Fix the following compile error if we use it in flow.h
by the patches latter:

In file included from include/linux/netfilter.h:277:0,
                 from include/net/netns/netfilter.h:5,
                 from include/net/net_namespace.h:21,
                 from include/linux/netdevice.h:43,
                 from include/linux/icmpv6.h:12,
                 from include/linux/ipv6.h:61,
                 from include/net/ipv6.h:16,
                 from include/linux/sunrpc/clnt.h:27,
                 from include/linux/nfs_fs.h:30,
                 from init/do_mounts.c:32:
include/net/flow.h: In function ‘flowi4_init_output’:
include/net/flow.h:84:32: error: ‘LOOPBACK_IFINDEX’ undeclared (first use in this function)

[Backport of net-next 6a662719c9868b3d6c7d26b3a085f0cd3cc15e64]

Change-Id: Ib7a0a08d78c03800488afa1b2c170cb70e34cfd9
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>

7 files changed, 15 insertions, 16 deletions

diff --git a/include/net/flow.h b/include/net/flow.h
index c91e2aae3..1426681f7 100644
--- a/include/net/flow.h
+++ b/include/net/flow.h
@@ -12,6 +12,14 @@
 #include <linux/atomic.h>
 #include <linux/uidgid.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;
@@ -85,7 +93,7 @@ static inline void flowi4_init_output(struct flowi4 *fl4, int oif,
 				      kuid_t uid)
 {
 	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 f4f12e845..0faaed2e2 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>
@@ -122,14 +123,6 @@ struct net {
 	atomic_t		rt_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 4f3295ad5..f31866e9a 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 bc773a10d..d00d8f965 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -629,6 +629,7 @@ 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 a429ac69a..91941b0b6 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -454,7 +454,7 @@ 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 c49dcd028..4bfaedf9b 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/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 8344f6863..4147716a9 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -701,7 +701,7 @@ 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;