Allow TAP instances to be interfaces

- Cannot have LCP, Address or Sub-Interface
- Cannot be PHY
- Cannot be Bond member
- Can be target of L2XC
- Can be member of Bridge
- interface.mtu must be the same as tap.host.mtu

Add YAML tests for common mistakes. This unblocks taps becoming members
of a bridgedomain, and allowing a very cool feature: slowpath networking!

config/interface.py

@@ -19,6 +19,7 @@ import config.vxlan_tunnel as vxlan_tunnel
 import config.lcp as lcp
 import config.address as address
 import config.mac as mac
+import config.tap as tap
 
 def get_qinx_parent_by_name(yaml, ifname):
     """ Returns the sub-interface which matches a QinAD or QinQ outer tag, or None,None
@@ -280,6 +281,8 @@ def is_phy(yaml, ifname):
         return False
     if vxlan_tunnel.is_vxlan_tunnel(yaml, ifname):
         return False
+    if tap.is_tap(yaml, ifname):
+        return False
     return True
 
 
@@ -434,6 +437,26 @@ def validate_interfaces(yaml):
         iface_lcp = get_lcp(yaml, ifname)
         iface_address = has_address(yaml, ifname)
 
+        if ifname.startswith('tap'):
+            tap_ifname, tap_iface = tap.get_by_name(yaml, ifname)
+            if not tap_iface:
+                msgs.append("interface %s is a TAP but does not exist in taps" % (ifname))
+                result = False
+            elif 'mtu' in tap_iface['host']:
+                host_mtu = tap_iface['host']['mtu']
+                if host_mtu != iface_mtu:
+                    msgs.append("interface %s is a TAP so its MTU %d must match host MTU %d" % (ifname, host_mtu, iface_mtu))
+                    result = False
+            if iface_address:
+                msgs.append("interface %s is a TAP so it cannot have an address" % (ifname))
+                result = False
+            if iface_lcp:
+                msgs.append("interface %s is a TAP so it cannot have an LCP" % (ifname))
+                result = False
+            if has_sub(yaml, ifname):
+                msgs.append("interface %s is a TAP so it cannot have sub-interfaces" % (ifname))
+                result = False
+
         if is_l2(yaml, ifname) and iface_lcp:
             msgs.append("interface %s is in L2 mode but has LCP name %s" % (ifname, iface_lcp))
             result = False

example.yaml

@@ -69,6 +69,9 @@ interfaces:
   vxlan_tunnel1:
     mtu: 2000
 
+  tap101:
+    mtu: 1500
+
 loopbacks:
   loop0:
     lcp: "lo0"
@@ -78,6 +81,11 @@ loopbacks:
     mtu: 2000
     mac: 02:de:ad:01:be:ef
     addresses: [ 10.0.1.1/24, 2001:db8:1::1/64 ]
+  loop11:
+    lcp: "bvi11"
+    mtu: 1500
+    mac: 02:de:ad:11:be:ef
+    addresses: [ 10.0.2.1/24, 2001:db8:2::1/64 ]
 
 bridgedomains:
   bd1:
@@ -86,9 +94,26 @@ bridgedomains:
     interfaces: [ BondEthernet0.500, BondEthernet0.501, HundredGigabitEthernet12/0/1, vxlan_tunnel1 ]
   bd11:
     mtu: 1500
+    bvi: loop11
+    interfaces: [ tap101 ]
 
 vxlan_tunnels:
   vxlan_tunnel1:
     local: 192.0.2.1
     remote: 192.0.2.2
     vni: 101
+
+taps:
+  tap100:
+    host:
+      name: vpp-tap100
+      mac: 00:01:02:03:04:05
+      mtu: 9216
+      bridge: br0
+    rx-ring-size: 256
+    tx-ring-size: 256
+  tap101:
+    host:
+      name: vpp-tap101
+      mtu: 1500
+      bridge: br1

unittest/yaml/error-tap6.yaml

@@ -0,0 +1,26 @@
+test:
+  description: "TAP interfaces cannot have LCP, address or sub-interfaces. MTU must match tap.host.mtu"
+  errors:
+    expected:
+     - "interface .* is a TAP so its MTU .* must match host MTU .*"
+     - "interface .* is a TAP so it cannot have an address"
+     - "interface .* is a TAP so it cannot have an LCP"
+     - "interface .* is a TAP so it cannot have sub-interfaces"
+    count: 4
+---
+interfaces:
+  tap0:
+    addresses: [ 10.0.0.1/24 ]
+    lcp: "mytap"
+    mtu: 9216
+    sub-interfaces:
+      100:
+        description: "TAP is not allowed to have a sub"
+taps:
+  tap0:
+    host:
+      mac: 02:00:00:00:00:00
+      name: vpp-tap0
+      mtu: 1500
+      bridge: vpp-br0
+      namespace: vpp-test