net: ipv6: put host and anycast routes on device with address

One nagging difference between ipv4 and ipv6 is host routes for ipv6
addresses are installed using the loopback device or VRF / L3 Master
device. e.g.,

    2001:db8:1::/120 dev veth0 proto kernel metric 256 pref medium
    local 2001:db8:1::1 dev lo table local proto kernel metric 0 pref medium

Using the loopback device is convenient -- necessary for local tx, but
has some nasty side effects, most notably setting the 'lo' device down
causes all host routes for all local IPv6 address to be removed from the
FIB and completely breaks IPv6 networking across all interfaces.

This patch puts FIB entries for IPv6 routes against the device. This
simplifies the routes in the FIB, for example by making dst->dev and
rt6i_idev->dev the same (a future patch can look at removing the device
reference taken for rt6i_idev for FIB entries).

When copies are made on FIB lookups, the cloned route has dst->dev
set to loopback (or the L3 master device). This is needed for the
local Tx of packets to local addresses.

With fib entries allocated against the real network device, the addrconf
code that reinserts host routes on admin up of 'lo' is no longer needed.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 34 insertions, 12 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index bec12ae3e6b7..9b02064c3335 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -958,10 +958,34 @@ int ip6_ins_rt(struct rt6_info *rt)
 	return __ip6_ins_rt(rt, &info, &mxc, NULL);
 }
 
+/* called with rcu_lock held */
+static struct net_device *ip6_rt_get_dev_rcu(struct rt6_info *rt)
+{
+	struct net_device *dev = rt->dst.dev;
+
+	if (rt->rt6i_flags & RTF_LOCAL) {
+		/* for copies of local routes, dst->dev needs to be the
+		 * device if it is a master device, the master device if
+		 * device is enslaved, and the loopback as the default
+		 */
+		if (netif_is_l3_slave(dev) &&
+		    !rt6_need_strict(&rt->rt6i_dst.addr))
+			dev = l3mdev_master_dev_rcu(dev);
+		else if (!netif_is_l3_master(dev))
+			dev = dev_net(dev)->loopback_dev;
+		/* last case is netif_is_l3_master(dev) is true in which
+		 * case we want dev returned to be dev
+		 */
+	}
+
+	return dev;
+}
+
 static struct rt6_info *ip6_rt_cache_alloc(struct rt6_info *ort,
 					   const struct in6_addr *daddr,
 					   const struct in6_addr *saddr)
 {
+	struct net_device *dev;
 	struct rt6_info *rt;
 
 	/*
@@ -971,8 +995,10 @@ static struct rt6_info *ip6_rt_cache_alloc(struct rt6_info *ort,
 	if (ort->rt6i_flags & (RTF_CACHE | RTF_PCPU))
 		ort = (struct rt6_info *)ort->dst.from;
 
-	rt = __ip6_dst_alloc(dev_net(ort->dst.dev), ort->dst.dev, 0);
-
+	rcu_read_lock();
+	dev = ip6_rt_get_dev_rcu(ort);
+	rt = __ip6_dst_alloc(dev_net(dev), dev, 0);
+	rcu_read_unlock();
 	if (!rt)
 		return NULL;
 
@@ -1000,11 +1026,13 @@ static struct rt6_info *ip6_rt_cache_alloc(struct rt6_info *ort,
 
 static struct rt6_info *ip6_rt_pcpu_alloc(struct rt6_info *rt)
 {
+	struct net_device *dev;
 	struct rt6_info *pcpu_rt;
 
-	pcpu_rt = __ip6_dst_alloc(dev_net(rt->dst.dev),
-				  rt->dst.dev, rt->dst.flags);
-
+	rcu_read_lock();
+	dev = ip6_rt_get_dev_rcu(rt);
+	pcpu_rt = __ip6_dst_alloc(dev_net(dev), dev, rt->dst.flags);
+	rcu_read_unlock();
 	if (!pcpu_rt)
 		return NULL;
 	ip6_rt_copy_init(pcpu_rt, rt);
@@ -2688,15 +2716,9 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev,
 {
 	u32 tb_id;
 	struct net *net = dev_net(idev->dev);
-	struct net_device *dev = net->loopback_dev;
+	struct net_device *dev = idev->dev;
 	struct rt6_info *rt;
 
-	/* use L3 Master device as loopback for host routes if device
-	 * is enslaved and address is not link local or multicast
-	 */
-	if (!rt6_need_strict(addr))
-		dev = l3mdev_master_dev_rcu(idev->dev) ? : dev;
-
 	rt = ip6_dst_alloc(net, dev, DST_NOCOUNT);
 	if (!rt)
 		return ERR_PTR(-ENOMEM);