ip: Path MTU

Type: feature

Support setting the MTU for a peer on an interface. The minimum value of
the path and interface MTU is used at forwarding time.

the path MTU is specified for a given peer, by address and table-ID.
In the forwarding plane the MTU is enfored either:
 1 - if the peer is attached, then the MTU is set on the peer's
adjacency
 2 - if the peer is not attached, it is remote, then a DPO is added to
the peer's FIB entry to perform the necessary fragmentation.

Signed-off-by: Neale Ranns <neale@graphiant.com>
Change-Id: I8b9ea6a07868b50e97e2561f18d9335407dea7ae

test/vpp_ip.py

@@ -181,3 +181,49 @@ class VppIpPuntRedirect(VppObject):
         if self.get_vpp_config():
             return True
         return False
+
+
+class VppIpPathMtu(VppObject):
+    def __init__(self, test, nh, pmtu, table_id=0):
+        self._test = test
+        self.nh = nh
+        self.pmtu = pmtu
+        self.table_id = table_id
+
+    def add_vpp_config(self):
+        self._test.vapi.ip_path_mtu_update(pmtu={'nh': self.nh,
+                                                 'table_id': self.table_id,
+                                                 'path_mtu': self.pmtu})
+        self._test.registry.register(self, self._test.logger)
+        return self
+
+    def modify(self, pmtu):
+        self.pmtu = pmtu
+        self._test.vapi.ip_path_mtu_update(pmtu={'nh': self.nh,
+                                                 'table_id': self.table_id,
+                                                 'path_mtu': self.pmtu})
+        return self
+
+    def remove_vpp_config(self):
+        self._test.vapi.ip_path_mtu_update(pmtu={'nh': self.nh,
+                                                 'table_id': self.table_id,
+                                                 'path_mtu': 0})
+
+    def query_vpp_config(self):
+        ds = list(self._test.vapi.vpp.details_iter(
+            self._test.vapi.ip_path_mtu_get))
+
+        for d in ds:
+            if self.nh == str(d.pmtu.nh) \
+               and self.table_id == d.pmtu.table_id \
+               and self.pmtu == d.pmtu.path_mtu:
+                return True
+        return False
+
+    def object_id(self):
+        return ("ip-path-mtu-%d-%s-%d" % (self.table_id,
+                                          self.nh,
+                                          self.pmtu))
+
+    def __str__(self):
+        return self.object_id()