vxlan: advertise netns of vxlan dev in fdb msg

Netlink FDB messages are sent in the link netns. The header of these messages
contains the ifindex (ndm_ifindex) of the netdevice, but this ifindex is
unusable in case of x-netns vxlan.
I named the new attribute NDA_NDM_IFINDEX_NETNSID, to avoid confusion with
NDA_IFINDEX.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -339,6 +339,11 @@ static int vxlan_fdb_info(struct sk_buff *skb, struct vxlan_dev *vxlan,
 	ndm->ndm_flags = fdb->flags;
 	ndm->ndm_type = RTN_UNICAST;
 
+	if (!net_eq(dev_net(vxlan->dev), vxlan->net) &&
+	    nla_put_s32(skb, NDA_NDM_IFINDEX_NETNSID,
+			peernet2id(vxlan->net, dev_net(vxlan->dev))))
+		goto nla_put_failure;
+
 	if (send_eth && nla_put(skb, NDA_LLADDR, ETH_ALEN, &fdb->eth_addr))
 		goto nla_put_failure;
 

include/uapi/linux/neighbour.h

@@ -25,6 +25,7 @@ enum {
 	NDA_VNI,
 	NDA_IFINDEX,
 	NDA_MASTER,
+	NDA_NDM_IFINDEX_NETNSID,
 	__NDA_MAX
 };
 

net/core/net_namespace.c

@@ -202,6 +202,7 @@ int peernet2id(struct net *net, struct net *peer)
 
 	return id >= 0 ? id : NETNSA_NSID_NOT_ASSIGNED;
 }
+EXPORT_SYMBOL(peernet2id);
 
 struct net *get_net_ns_by_id(struct net *net, int id)
 {