net: Enable support for VRF with ipv4 multicast

Enable support for IPv4 multicast:
- similar to unicast the flow struct is updated to L3 master device
  if relevant prior to calling fib_rules_lookup. The table id is saved
  to the lookup arg so the rule action for ipmr can return the table
  associated with the device.

- ip_mr_forward needs to check for master device mismatch as well
  since the skb->dev is set to it

- allow multicast address on VRF device for Rx by checking for the
  daddr in the VRF device as well as the original ingress device

- on Tx need to drop to __mkroute_output when FIB lookup fails for
  multicast destination address.

- if CONFIG_IP_MROUTE_MULTIPLE_TABLES is enabled VRF driver creates
  IPMR FIB rules on first device create similar to FIB rules. In
  addition the VRF driver does not divert IPv4 multicast packets:
  it breaks on Tx since the fib lookup fails on the mcast address.

With this patch, ipmr forwarding and local rx/tx work.

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

1 files changed, 12 insertions, 1 deletions

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 51d71a70fbbe..f2fd13b07273 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -137,6 +137,9 @@ static int ipmr_fib_lookup(struct net *net, struct flowi4 *flp4,
 		.flags = FIB_LOOKUP_NOREF,
 	};
 
+	/* update flow if oif or iif point to device enslaved to l3mdev */
+	l3mdev_update_flow(net, flowi4_to_flowi(flp4));
+
 	err = fib_rules_lookup(net->ipv4.mr_rules_ops,
 			       flowi4_to_flowi(flp4), 0, &arg);
 	if (err < 0)
@@ -163,7 +166,9 @@ static int ipmr_rule_action(struct fib_rule *rule, struct flowi *flp,
 		return -EINVAL;
 	}
 
-	mrt = ipmr_get_table(rule->fr_net, rule->table);
+	arg->table = fib_rule_get_table(rule, arg);
+
+	mrt = ipmr_get_table(rule->fr_net, arg->table);
 	if (!mrt)
 		return -EAGAIN;
 	res->mrt = mrt;
@@ -1809,6 +1814,12 @@ static void ip_mr_forward(struct net *net, struct mr_table *mrt,
 
 	/* Wrong interface: drop packet and (maybe) send PIM assert. */
 	if (mrt->vif_table[vif].dev != skb->dev) {
+		struct net_device *mdev;
+
+		mdev = l3mdev_master_dev_rcu(mrt->vif_table[vif].dev);
+		if (mdev == skb->dev)
+			goto forward;
+
 		if (rt_is_output_route(skb_rtable(skb))) {
 			/* It is our own packet, looped back.
 			 * Very complicated situation...