vxlan: support fdb and learning in COLLECT_METADATA mode

Vxlan COLLECT_METADATA mode today solves the per-vni netdev scalability problem in l3 networks. It expects all forwarding information to be present in dst_metadata. This patch series enhances collect metadata mode to include the case where only vni is present in dst_metadata, and the vxlan driver can then use the rest of the forwarding information datbase to make forwarding decisions. There is no change to default COLLECT_METADATA behaviour. These changes only apply to COLLECT_METADATA when used with the bridging use-case with a special dst_metadata tunnel info flag (eg: where vxlan device is part of a bridge). For all this to work, the vxlan driver will need to now support a single fdb table hashed by mac + vni. This series essentially makes this happen. use-case and workflow: vxlan collect metadata device participates in bridging vlan to vn-segments. Bridge driver above the vxlan device, sends the vni corresponding to the vlan in the dst_metadata. vxlan driver will lookup forwarding database with (mac + vni) for the required remote destination information to forward the packet. Changes introduced by this patch: - allow learning and forwarding database state in vxlan netdev in COLLECT_METADATA mode. Current behaviour is not changed by default. tunnel info flag IP_TUNNEL_INFO_BRIDGE is used to support the new bridge friendly mode. - A single fdb table hashed by (mac, vni) to allow fdb entries with multiple vnis in the same fdb table - rx path already has the vni - tx path expects a vni in the packet with dst_metadata - prior to this series, fdb remote_dsts carried remote vni and the vxlan device carrying the fdb table represented the source vni. With the vxlan device now representing multiple vnis, this patch adds a src vni attribute to the fdb entry. The remote vni already uses NDA_VNI attribute. This patch introduces NDA_SRC_VNI netlink attribute to represent the src vni in a multi vni fdb table. iproute2 example (patched and pruned iproute2 output to just show relevant fdb entries): example shows same host mac learnt on two vni's. before (netdev per vni): $bridge fdb show | grep "00:02:00:00:00:03" 00:02:00:00:00:03 dev vxlan1001 dst 12.0.0.8 self 00:02:00:00:00:03 dev vxlan1000 dst 12.0.0.8 self after this patch with collect metadata in bridged mode (single netdev): $bridge fdb show | grep "00:02:00:00:00:03" 00:02:00:00:00:03 dev vxlan0 src_vni 1001 dst 12.0.0.8 self 00:02:00:00:00:03 dev vxlan0 src_vni 1000 dst 12.0.0.8 self

RPRoopa Prabhu committed 9 years ago