vxlan: In EVPN mode, disable ARP/NDP learning

FRR populates the FDB via BGP EVPN, so kernel data-plane learning is
redundant and counterproductive.

Static ARP (IPv4) and NDP (IPv6) entries are added on startup of the
Instance and remove on shutdown.

FRR populates the FDB/neighbor table via control plane, and neigh_suppress
tells the kernel bridge to use that information instead of flooding.

This will vastly reduce BUM traffic with static ARP/NDP entries.

Author: wido

scripts/vm/network/vnet/modifyvxlan-evpn.sh

@@ -81,6 +81,8 @@ addVxlan() {
     bridge link show|grep ${VXLAN_BR}|awk '{print $2}'|grep "^${VXLAN_DEV}\$" > /dev/null
     if [[ $? -gt 0 ]]; then
         ip link set ${VXLAN_DEV} master ${VXLAN_BR}
+        bridge link set dev ${VXLAN_DEV} neigh_suppress on
+        bridge link set dev ${VXLAN_DEV} learning off
     fi
 }