[NETFILTER]: ip_tables: per-netns FILTER/MANGLE/RAW tables for real

Commit 9335f047fe61587ec82ff12fbb1220bcfdd32006 aka
"[NETFILTER]: ip_tables: per-netns FILTER, MANGLE, RAW"
added per-netns _view_ of iptables rules. They were shown to user, but
ignored by filtering code. Now that it's possible to at least ping loopback,
per-netns tables can affect filtering decisions.

netns is taken in case of
PRE_ROUTING, LOCAL_IN -- from in device,
POST_ROUTING, LOCAL_OUT -- from out device,
FORWARD -- from in device which should be equal to out device's netns.
This code is relatively new, so BUG_ON was plugged.

Wrappers were added to a) keep code the same from CONFIG_NET_NS=n users
(overwhelming majority), b) consolidate code in one place -- similar
changes will be done in ipv6 and arp netfilter code.

Signed-off-by: Alexey Dobriyan <[e-mail]>
Signed-off-by: Patrick McHardy <[e-mail]>

include/linux/netfilter.h

···
 #include <linux/types.h>
 #include <linux/skbuff.h>
 #include <linux/net.h>
+#include <linux/netdevice.h>
 #include <linux/if.h>
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <linux/wait.h>
 #include <linux/list.h>
+#include <net/net_namespace.h>
 #endif
 #include <linux/compiler.h>
 
···
 #define NF_MAX_HOOKS 8
 
 struct sk_buff;
-struct net_device;
 
 typedef unsigned int nf_hookfn(unsigned int hooknum,
 			       struct sk_buff *skb,
···
 #else
 static inline void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) {}
 #endif
+
+static inline struct net *nf_pre_routing_net(const struct net_device *in,
+					     const struct net_device *out)
+{
+#ifdef CONFIG_NET_NS
+	return in->nd_net;
+#else
+	return &init_net;
+#endif
+}
+
+static inline struct net *nf_local_in_net(const struct net_device *in,
+					  const struct net_device *out)
+{
+#ifdef CONFIG_NET_NS
+	return in->nd_net;
+#else
+	return &init_net;
+#endif
+}
+
+static inline struct net *nf_forward_net(const struct net_device *in,
+					 const struct net_device *out)
+{
+#ifdef CONFIG_NET_NS
+	BUG_ON(in->nd_net != out->nd_net);
+	return in->nd_net;
+#else
+	return &init_net;
+#endif
+}
+
+static inline struct net *nf_local_out_net(const struct net_device *in,
+					   const struct net_device *out)
+{
+#ifdef CONFIG_NET_NS
+	return out->nd_net;
+#else
+	return &init_net;
+#endif
+}
+
+static inline struct net *nf_post_routing_net(const struct net_device *in,
+					      const struct net_device *out)
+{
+#ifdef CONFIG_NET_NS
+	return out->nd_net;
+#else
+	return &init_net;
+#endif
+}
 
 #endif /*__KERNEL__*/
 #endif /*__LINUX_NETFILTER_H*/

net/ipv4/netfilter/iptable_filter.c

···
 
 /* The work comes in here from netfilter.c. */
 static unsigned int
+ipt_local_in_hook(unsigned int hook,
+		  struct sk_buff *skb,
+		  const struct net_device *in,
+		  const struct net_device *out,
+		  int (*okfn)(struct sk_buff *))
+{
+	return ipt_do_table(skb, hook, in, out,
+			    nf_local_in_net(in, out)->ipv4.iptable_filter);
+}
+
+static unsigned int
 ipt_hook(unsigned int hook,
 	 struct sk_buff *skb,
 	 const struct net_device *in,
 	 const struct net_device *out,
 	 int (*okfn)(struct sk_buff *))
 {
-	return ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_filter);
+	return ipt_do_table(skb, hook, in, out,
+			    nf_forward_net(in, out)->ipv4.iptable_filter);
 }
 
 static unsigned int
···
 		return NF_ACCEPT;
 	}
 
-	return ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_filter);
+	return ipt_do_table(skb, hook, in, out,
+			    nf_local_out_net(in, out)->ipv4.iptable_filter);
 }
 
 static struct nf_hook_ops ipt_ops[] __read_mostly = {
 	{
-		.hook		= ipt_hook,
+		.hook		= ipt_local_in_hook,
 		.owner		= THIS_MODULE,
 		.pf		= PF_INET,
 		.hooknum	= NF_INET_LOCAL_IN,

net/ipv4/netfilter/iptable_mangle.c

···
 
 /* The work comes in here from netfilter.c. */
 static unsigned int
-ipt_route_hook(unsigned int hook,
+ipt_pre_routing_hook(unsigned int hook,
+		     struct sk_buff *skb,
+		     const struct net_device *in,
+		     const struct net_device *out,
+		     int (*okfn)(struct sk_buff *))
+{
+	return ipt_do_table(skb, hook, in, out,
+			    nf_pre_routing_net(in, out)->ipv4.iptable_mangle);
+}
+
+static unsigned int
+ipt_post_routing_hook(unsigned int hook,
+		      struct sk_buff *skb,
+		      const struct net_device *in,
+		      const struct net_device *out,
+		      int (*okfn)(struct sk_buff *))
+{
+	return ipt_do_table(skb, hook, in, out,
+			    nf_post_routing_net(in, out)->ipv4.iptable_mangle);
+}
+
+static unsigned int
+ipt_local_in_hook(unsigned int hook,
+		  struct sk_buff *skb,
+		  const struct net_device *in,
+		  const struct net_device *out,
+		  int (*okfn)(struct sk_buff *))
+{
+	return ipt_do_table(skb, hook, in, out,
+			    nf_local_in_net(in, out)->ipv4.iptable_mangle);
+}
+
+static unsigned int
+ipt_forward_hook(unsigned int hook,
 	 struct sk_buff *skb,
 	 const struct net_device *in,
 	 const struct net_device *out,
 	 int (*okfn)(struct sk_buff *))
 {
-	return ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_mangle);
+	return ipt_do_table(skb, hook, in, out,
+			    nf_forward_net(in, out)->ipv4.iptable_mangle);
 }
 
 static unsigned int
···
 	daddr = iph->daddr;
 	tos = iph->tos;
 
-	ret = ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_mangle);
+	ret = ipt_do_table(skb, hook, in, out,
+			   nf_local_out_net(in, out)->ipv4.iptable_mangle);
 	/* Reroute for ANY change. */
 	if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE) {
 		iph = ip_hdr(skb);
···
 
 static struct nf_hook_ops ipt_ops[] __read_mostly = {
 	{
-		.hook		= ipt_route_hook,
+		.hook		= ipt_pre_routing_hook,
 		.owner		= THIS_MODULE,
 		.pf		= PF_INET,
 		.hooknum	= NF_INET_PRE_ROUTING,
 		.priority	= NF_IP_PRI_MANGLE,
 	},
 	{
-		.hook		= ipt_route_hook,
+		.hook		= ipt_local_in_hook,
 		.owner		= THIS_MODULE,
 		.pf		= PF_INET,
 		.hooknum	= NF_INET_LOCAL_IN,
 		.priority	= NF_IP_PRI_MANGLE,
 	},
 	{
-		.hook		= ipt_route_hook,
+		.hook		= ipt_forward_hook,
 		.owner		= THIS_MODULE,
 		.pf		= PF_INET,
 		.hooknum	= NF_INET_FORWARD,
···
 		.priority	= NF_IP_PRI_MANGLE,
 	},
 	{
-		.hook		= ipt_route_hook,
+		.hook		= ipt_post_routing_hook,
 		.owner		= THIS_MODULE,
 		.pf		= PF_INET,
 		.hooknum	= NF_INET_POST_ROUTING,

net/ipv4/netfilter/iptable_raw.c

···
 	 const struct net_device *out,
 	 int (*okfn)(struct sk_buff *))
 {
-	return ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_raw);
+	return ipt_do_table(skb, hook, in, out,
+			    nf_pre_routing_net(in, out)->ipv4.iptable_raw);
 }
 
 static unsigned int
···
 			       "packet.\n");
 		return NF_ACCEPT;
 	}
-	return ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_raw);
+	return ipt_do_table(skb, hook, in, out,
+			    nf_local_out_net(in, out)->ipv4.iptable_raw);
 }
 
 /* 'raw' is the very first table. */