Add TAP syntax/semantic validator

config/tap.py

@@ -0,0 +1,101 @@
+#
+# Copyright (c) 2022 Pim van Pelt
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#     http://www.apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+import logging
+import config.mac as mac
+
+def get_taps(yaml):
+    """ Return a list of all taps. """
+    ret = []
+    if 'taps' in yaml:
+        for ifname, iface in yaml['taps'].items():
+            ret.append(ifname)
+    return ret
+
+
+def get_by_name(yaml, ifname):
+    """ Return the tap by name, if it exists. Return None otherwise. """
+    try:
+        if ifname in yaml['taps']:
+            return ifname, yaml['taps'][ifname]
+    except:
+        pass
+    return None, None
+
+
+def is_tap(yaml, ifname):
+    """ Returns True if the interface name is an existing tap in the config.
+        The TAP has to be explicitly named in the configuration, and notably
+        a TAP belonging to a Linux Control Plane (LCP) will return False.
+    """
+    ifname, iface = get_by_name(yaml, ifname)
+    return not iface == None
+
+
+def is_host_name_unique(yaml, hostname):
+    """ Returns True if there is at most one occurence of the given ifname amonst all host-names of TAPs. """
+    if not 'taps' in yaml:
+        return True
+    host_names = []
+    for tap_ifname, tap_iface in yaml['taps'].items():
+        host_names.append(tap_iface['host']['name'])
+    return host_names.count(hostname) < 2
+
+
+def validate_taps(yaml):
+    result = True
+    msgs = []
+    logger = logging.getLogger('vppcfg.config')
+    logger.addHandler(logging.NullHandler())
+
+    if not 'taps' in yaml:
+        return result, msgs
+
+    for ifname, iface in yaml['taps'].items():
+        logger.debug("tap %s" % iface)
+        instance = int(ifname[3:])
+
+        ## NOTE(pim): 1024 is not off-by-one, tap1024 is precisely the highest permissible id
+        if instance > 1024:
+            msgs.append("tap %s has instance %d which is too large" % (ifname, instance))
+            result = False
+
+        if not is_host_name_unique(yaml, iface['host']['name']):
+            msgs.append("tap %s does not have a unique host name %s" % (ifname, iface['host']['name']))
+            result = False
+
+        if 'rx-ring-size' in iface:
+            n = iface['rx-ring-size']
+            if n & (n-1) != 0:
+                msgs.append("tap %s rx-ring-size must be a power of two" % (ifname))
+                result = False
+
+        if 'tx-ring-size' in iface:
+            n = iface['tx-ring-size']
+            if n & (n-1) != 0:
+                msgs.append("tap %s tx-ring-size must be a power of two" % (ifname))
+                result = False
+
+        if 'namespace-create' in iface['host'] and iface['host']['namespace-create'] and not 'namespace' in iface['host']:
+            msgs.append("tap %s namespace-create can only be set if namespace is set" % (ifname))
+            result = False
+
+        if 'bridge-create' in iface['host'] and iface['host']['bridge-create'] and not 'bridge' in iface['host']:
+            msgs.append("tap %s bridge-create can only be set if bridge is set" % (ifname))
+            result = False
+
+        if 'mac' in iface['host'] and mac.is_multicast(iface['host']['mac']):
+            msgs.append("tap %s host MAC address %s cannot be multicast" % (ifname, iface['host']['mac']))
+            result = False
+
+    return result, msgs