netfilter: netns: fix {ip,6}_route_me_harder() in netns

Take netns from skb->dst->dev. It should be safe because, they are called
from LOCAL_OUT hook where dst is valid (though, I'm not exactly sure about
IPVS and queueing packets to userspace).

[Patrick: its safe everywhere since they already expect skb->dst to be set]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/ipv4/netfilter.c

@@ -12,6 +12,7 @@
 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
 int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
 {
+	struct net *net = dev_net(skb->dst->dev);
 	const struct iphdr *iph = ip_hdr(skb);
 	struct rtable *rt;
 	struct flowi fl = {};
@@ -19,7 +20,7 @@ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
 	unsigned int hh_len;
 	unsigned int type;
 
-	type = inet_addr_type(&init_net, iph->saddr);
+	type = inet_addr_type(net, iph->saddr);
 	if (skb->sk && inet_sk(skb->sk)->transparent)
 		type = RTN_LOCAL;
 	if (addr_type == RTN_UNSPEC)
@@ -36,7 +37,7 @@ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
 		fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
 		fl.mark = skb->mark;
 		fl.flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
-		if (ip_route_output_key(&init_net, &rt, &fl) != 0)
+		if (ip_route_output_key(net, &rt, &fl) != 0)
 			return -1;
 
 		/* Drop old route. */
@@ -46,7 +47,7 @@ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
 		/* non-local src, find valid iif to satisfy
 		 * rp-filter when calling ip_route_input. */
 		fl.nl_u.ip4_u.daddr = iph->saddr;
-		if (ip_route_output_key(&init_net, &rt, &fl) != 0)
+		if (ip_route_output_key(net, &rt, &fl) != 0)
 			return -1;
 
 		odst = skb->dst;

net/ipv6/netfilter.c

@@ -23,7 +23,7 @@ int ip6_route_me_harder(struct sk_buff *skb)
 		    .saddr = iph->saddr, } },
 	};
 
-	dst = ip6_route_output(&init_net, skb->sk, &fl);
+	dst = ip6_route_output(dev_net(skb->dst->dev), skb->sk, &fl);
 
 #ifdef CONFIG_XFRM
 	if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&