ip6gre: add x-netns support

This patch allows to switch the netns when packet is encapsulated or
decapsulated. In other word, the encapsulated packet is received in a netns,
where the lookup is done to find the tunnel. Once the tunnel is found, the
packet is decapsulated and injecting into the corresponding interface which
stands to another netns.

When one of the two netns is removed, the tunnel is destroyed.
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_gre.c

@@ -72,6 +72,7 @@ struct ip6gre_net {
 };
 
 static struct rtnl_link_ops ip6gre_link_ops __read_mostly;
+static struct rtnl_link_ops ip6gre_tap_ops __read_mostly;
 static int ip6gre_tunnel_init(struct net_device *dev);
 static void ip6gre_tunnel_setup(struct net_device *dev);
 static void ip6gre_tunnel_link(struct ip6gre_net *ign, struct ip6_tnl *t);
@@ -353,10 +354,10 @@ static struct ip6_tnl *ip6gre_tunnel_locate(struct net *net,
 
 static void ip6gre_tunnel_uninit(struct net_device *dev)
 {
-	struct net *net = dev_net(dev);
-	struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
+	struct ip6_tnl *t = netdev_priv(dev);
+	struct ip6gre_net *ign = net_generic(t->net, ip6gre_net_id);
 
-	ip6gre_tunnel_unlink(ign, netdev_priv(dev));
+	ip6gre_tunnel_unlink(ign, t);
 	dev_put(dev);
 }
 
@@ -611,8 +612,8 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
 			 int encap_limit,
 			 __u32 *pmtu)
 {
-	struct net *net = dev_net(dev);
 	struct ip6_tnl *tunnel = netdev_priv(dev);
+	struct net *net = tunnel->net;
 	struct net_device *tdev;    /* Device to other host */
 	struct ipv6hdr  *ipv6h;     /* Our new IP header */
 	unsigned int max_headroom = 0; /* The extra header space needed */
@@ -979,7 +980,7 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu)
 		int strict = (ipv6_addr_type(&p->raddr) &
 			      (IPV6_ADDR_MULTICAST|IPV6_ADDR_LINKLOCAL));
 
-		struct rt6_info *rt = rt6_lookup(dev_net(dev),
+		struct rt6_info *rt = rt6_lookup(t->net,
 						 &p->raddr, &p->laddr,
 						 p->link, strict);
 
@@ -1063,13 +1064,12 @@ static int ip6gre_tunnel_ioctl(struct net_device *dev,
 	int err = 0;
 	struct ip6_tnl_parm2 p;
 	struct __ip6_tnl_parm p1;
-	struct ip6_tnl *t;
-	struct net *net = dev_net(dev);
+	struct ip6_tnl *t = netdev_priv(dev);
+	struct net *net = t->net;
 	struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
 
 	switch (cmd) {
 	case SIOCGETTUNNEL:
-		t = NULL;
 		if (dev == ign->fb_tunnel_dev) {
 			if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
 				err = -EFAULT;
@@ -1077,9 +1077,9 @@ static int ip6gre_tunnel_ioctl(struct net_device *dev,
 			}
 			ip6gre_tnl_parm_from_user(&p1, &p);
 			t = ip6gre_tunnel_locate(net, &p1, 0);
+			if (t == NULL)
+				t = netdev_priv(dev);
 		}
-		if (t == NULL)
-			t = netdev_priv(dev);
 		memset(&p, 0, sizeof(p));
 		ip6gre_tnl_parm_to_user(&p, &t->parms);
 		if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
@@ -1242,7 +1242,6 @@ static void ip6gre_tunnel_setup(struct net_device *dev)
 	dev->flags |= IFF_NOARP;
 	dev->iflink = 0;
 	dev->addr_len = sizeof(struct in6_addr);
-	dev->features |= NETIF_F_NETNS_LOCAL;
 	dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
 }
 
@@ -1297,11 +1296,17 @@ static struct inet6_protocol ip6gre_protocol __read_mostly = {
 	.flags       = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
 };
 
-static void ip6gre_destroy_tunnels(struct ip6gre_net *ign,
-	struct list_head *head)
+static void ip6gre_destroy_tunnels(struct net *net, struct list_head *head)
 {
+	struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
+	struct net_device *dev, *aux;
 	int prio;
 
+	for_each_netdev_safe(net, dev, aux)
+		if (dev->rtnl_link_ops == &ip6gre_link_ops ||
+		    dev->rtnl_link_ops == &ip6gre_tap_ops)
+			unregister_netdevice_queue(dev, head);
+
 	for (prio = 0; prio < 4; prio++) {
 		int h;
 		for (h = 0; h < HASH_SIZE; h++) {
@@ -1310,7 +1315,12 @@ static void ip6gre_destroy_tunnels(struct ip6gre_net *ign,
 			t = rtnl_dereference(ign->tunnels[prio][h]);
 
 			while (t != NULL) {
-				unregister_netdevice_queue(t->dev, head);
+				/* If dev is in the same netns, it has already
+				 * been added to the list by the previous loop.
+				 */
+				if (!net_eq(dev_net(t->dev), net))
+					unregister_netdevice_queue(t->dev,
+								   head);
 				t = rtnl_dereference(t->next);
 			}
 		}
@@ -1329,6 +1339,11 @@ static int __net_init ip6gre_init_net(struct net *net)
 		goto err_alloc_dev;
 	}
 	dev_net_set(ign->fb_tunnel_dev, net);
+	/* FB netdevice is special: we have one, and only one per netns.
+	 * Allowing to move it to another netns is clearly unsafe.
+	 */
+	ign->fb_tunnel_dev->features |= NETIF_F_NETNS_LOCAL;
+
 
 	ip6gre_fb_tunnel_init(ign->fb_tunnel_dev);
 	ign->fb_tunnel_dev->rtnl_link_ops = &ip6gre_link_ops;
@@ -1349,12 +1364,10 @@ static int __net_init ip6gre_init_net(struct net *net)
 
 static void __net_exit ip6gre_exit_net(struct net *net)
 {
-	struct ip6gre_net *ign;
 	LIST_HEAD(list);
 
-	ign = net_generic(net, ip6gre_net_id);
 	rtnl_lock();
-	ip6gre_destroy_tunnels(ign, &list);
+	ip6gre_destroy_tunnels(net, &list);
 	unregister_netdevice_many(&list);
 	rtnl_unlock();
 }
@@ -1531,15 +1544,14 @@ static int ip6gre_newlink(struct net *src_net, struct net_device *dev,
 static int ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
 			    struct nlattr *data[])
 {
-	struct ip6_tnl *t, *nt;
-	struct net *net = dev_net(dev);
+	struct ip6_tnl *t, *nt = netdev_priv(dev);
+	struct net *net = nt->net;
 	struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
 	struct __ip6_tnl_parm p;
 
 	if (dev == ign->fb_tunnel_dev)
 		return -EINVAL;
 
-	nt = netdev_priv(dev);
 	ip6gre_netlink_parms(data, &p);
 
 	t = ip6gre_tunnel_locate(net, &p, 0);