net: ipv6: more places need LOOPBACK_IFINDEX for flowi6_iif

To properly match iif in ip rules we have to provide
LOOPBACK_IFINDEX in flowi6_iif, not 0. Some ip6mr_fib_lookup
and fib6_rule_lookup callers need such fix.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6mr.c

@@ -1633,7 +1633,7 @@ struct sock *mroute6_socket(struct net *net, struct sk_buff *skb)
 {
 	struct mr6_table *mrt;
 	struct flowi6 fl6 = {
-		.flowi6_iif	= skb->skb_iif,
+		.flowi6_iif	= skb->skb_iif ? : LOOPBACK_IFINDEX,
 		.flowi6_oif	= skb->dev->ifindex,
 		.flowi6_mark	= skb->mark,
 	};

net/ipv6/netfilter/ip6t_rpfilter.c

@@ -33,6 +33,7 @@ static bool rpfilter_lookup_reverse6(const struct sk_buff *skb,
 	struct ipv6hdr *iph = ipv6_hdr(skb);
 	bool ret = false;
 	struct flowi6 fl6 = {
+		.flowi6_iif = LOOPBACK_IFINDEX,
 		.flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
 		.flowi6_proto = iph->nexthdr,
 		.daddr = iph->saddr,

net/ipv6/route.c

@@ -1273,6 +1273,7 @@ void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark)
 	struct flowi6 fl6;
 
 	memset(&fl6, 0, sizeof(fl6));
+	fl6.flowi6_iif = LOOPBACK_IFINDEX;
 	fl6.flowi6_oif = oif;
 	fl6.flowi6_mark = mark;
 	fl6.daddr = iph->daddr;
@@ -1294,6 +1295,7 @@ void ip6_redirect_no_header(struct sk_buff *skb, struct net *net, int oif,
 	struct flowi6 fl6;
 
 	memset(&fl6, 0, sizeof(fl6));
+	fl6.flowi6_iif = LOOPBACK_IFINDEX;
 	fl6.flowi6_oif = oif;
 	fl6.flowi6_mark = mark;
 	fl6.daddr = msg->dest;