[ONOS] BGP Selection Algo and Test

Change-Id: I9d9e8c699dea46fde07b7cba526b3c7fd1f3bd34

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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.
+ */
+package org.onosproject.bgp.controller.impl;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.ListIterator;
+
+import org.onosproject.bgpio.protocol.linkstate.PathAttrNlriDetailsLocalRib;
+import org.onosproject.bgpio.types.AsPath;
+import org.onosproject.bgpio.types.BgpValueType;
+import org.onosproject.bgpio.types.LocalPref;
+import org.onosproject.bgpio.types.Med;
+import org.onosproject.bgpio.types.Origin;
+import org.onosproject.bgpio.types.Origin.ORIGINTYPE;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implementation of BGP best path Selection process.
+ */
+public final class BgpSelectionAlgo implements Comparator<PathAttrNlriDetailsLocalRib> {
+    private static final Logger log = LoggerFactory.getLogger(BgpSelectionAlgo.class);
+    LocalPref obj1LocPref = null;
+    AsPath obj1Aspath = null;
+    Origin obj1Origin = null;
+    Med obj1Med = null;
+    LocalPref obj2LocPref = null;
+    AsPath obj2Aspath = null;
+    Origin obj2Origin = null;
+    Med obj2Med = null;
+
+    @Override
+    public int compare(PathAttrNlriDetailsLocalRib pathNlriDetails1, PathAttrNlriDetailsLocalRib pathNlriDetails2) {
+        if (pathNlriDetails1 == null) {
+            return -1;
+        }
+        if (pathNlriDetails2 == null) {
+            return 1;
+        }
+        if (pathNlriDetails1.equals(pathNlriDetails2)) {
+            return 0;
+        }
+
+        List<BgpValueType> o1 = pathNlriDetails1.localRibNlridetails().pathAttributes();
+        List<BgpValueType> o2 = pathNlriDetails2.localRibNlridetails().pathAttributes();
+        ListIterator<BgpValueType> listIteratorObj1 = o1.listIterator();
+        ListIterator<BgpValueType> listIteratorObj2 = o2.listIterator();
+        storeAttr(listIteratorObj1, listIteratorObj2);
+
+        // prefer attribute with higher local preference
+        if (obj1LocPref != null || obj2LocPref != null && (obj1LocPref != null && !obj1LocPref.equals(obj2LocPref))) {
+            return compareLocalPref(obj1LocPref, obj2LocPref);
+        }
+
+        // prefer attribute with shortest Aspath
+        if (!obj1Aspath.equals(obj2Aspath)) {
+            Integer obj1Size = countASSize(obj1Aspath);
+            Integer obj2Size = countASSize(obj2Aspath);
+            if (obj1Size != obj2Size) {
+                return compareAsPath(obj1Size, obj2Size);
+            }
+        }
+
+        // prefer attribute with lowest origin type
+        if (!obj1Origin.equals(obj2Origin)) {
+            return compareOrigin(obj1Origin, obj2Origin);
+        }
+
+        // prefer attribute with lowest MED
+        if (obj1Med != null || obj2Med != null && (obj1Med != null && !obj1Med.equals(obj2Med))) {
+            return compareMed(obj1Med, obj2Med);
+        }
+
+        if ((pathNlriDetails1 != null || pathNlriDetails2 != null) && (pathNlriDetails1 != null && !pathNlriDetails1
+                        .equals(pathNlriDetails2))) {
+            return comparePeerDetails(pathNlriDetails1, pathNlriDetails2);
+        }
+        return 0;
+    }
+
+    /**
+     * Compares local preference of two objects and returns object with higher preference.
+     *
+     * @param obj1LocPref local preference object1
+     * @param obj2LocPref local preference object2
+     * @return object with higher preference
+     */
+    int compareLocalPref(LocalPref obj1LocPref, LocalPref obj2LocPref) {
+            return ((Integer) (obj1LocPref.localPref())).compareTo((Integer) (obj2LocPref.localPref()));
+    }
+
+    /**
+     * Compares AsPath of two objects and returns object with shortest AsPath.
+     *
+     * @param obj1Size object1 AS count
+     * @param obj2Size object2 AS count
+     * @return
+     */
+    int compareAsPath(Integer obj1Size, Integer obj2Size) {
+            return obj1Size.compareTo(obj2Size);
+    }
+
+    /**
+     * Compare Origin of two objects and returns object with lowest origin value.
+     *
+     * @param obj1Origin Origin object1
+     * @param obj2Origin Origin object1
+     * @return object with lowest origin value
+     */
+    int compareOrigin(Origin obj1Origin, Origin obj2Origin) {
+        if (obj1Origin.origin() == ORIGINTYPE.IGP) {
+            return 1;
+        }
+        if (obj2Origin.origin() == ORIGINTYPE.IGP) {
+            return -1;
+        }
+        if (obj1Origin.origin() == ORIGINTYPE.EGP) {
+            return 1;
+        } else {
+            return -1;
+        }
+    }
+
+    /**
+     * Compare Med of two objects and returns object with lowestMed value.
+     *
+     * @param obj1Med Med object1
+     * @param obj2Med Med object2
+     * @return returns object with lowestMed value
+     */
+    int compareMed(Med obj1Med, Med obj2Med) {
+        return ((Integer) (obj2Med.med())).compareTo((Integer) (obj1Med.med()));
+    }
+
+    /**
+     * Compares EBGP over IBGP, BGP identifier value and peer address.
+     *
+     * @param pathNlriDetails1 PathAttrNlriDetailsLocalRib object1
+     * @param pathNlriDetails2 PathAttrNlriDetailsLocalRib object2
+     * @return object which as EBGP over IBGP, lowest BGP identifier value and lowest peer address
+     */
+    int comparePeerDetails(PathAttrNlriDetailsLocalRib pathNlriDetails1, PathAttrNlriDetailsLocalRib pathNlriDetails2) {
+        // consider EBGP over IBGP
+        if (pathNlriDetails1.isLocalRibIbgpSession() != pathNlriDetails2.isLocalRibIbgpSession()) {
+            if (pathNlriDetails1 == null || pathNlriDetails1.isLocalRibIbgpSession()) {
+                return -1;
+            }
+            if (pathNlriDetails2 == null || pathNlriDetails2.isLocalRibIbgpSession()) {
+                return 1;
+            }
+        }
+        // prefer lowest BGP identifier value.
+        if (pathNlriDetails1.localRibIdentifier() != pathNlriDetails2.localRibIdentifier()) {
+            return ((Integer) pathNlriDetails2.localRibIdentifier())
+                    .compareTo(pathNlriDetails1.localRibIdentifier());
+        }
+        //prefer lowest peer address
+        if (pathNlriDetails1.localRibIpAddress() != pathNlriDetails2.localRibIpAddress()) {
+            return pathNlriDetails2.localRibIpAddress().compareTo(pathNlriDetails1.localRibIpAddress());
+        }
+        return 0;
+    }
+
+    /**
+     * Returns ASes count of AsPath attribute , if AS_SET is present then count as 1.
+     *
+     * @param aspath object of AsPath
+     * @return count of ASes
+     */
+    Integer countASSize(AsPath aspath) {
+        boolean isASSet = false;
+        int count = 0;
+        if (!aspath.asPathSet().isEmpty()) {
+            isASSet = true;
+        }
+        if (!aspath.asPathSeq().isEmpty()) {
+            count = aspath.asPathSeq().size();
+        }
+        return isASSet ? ++count : count;
+    }
+
+    /**
+     * Stores BGP basic attributes of two objects.
+     *
+     * @param listIteratorObj1 list iterator of object1
+     * @param listIteratorObj2 list iterator of object2
+     */
+    void storeAttr(ListIterator<BgpValueType> listIteratorObj1, ListIterator<BgpValueType> listIteratorObj2) {
+         while (listIteratorObj1.hasNext()) {
+             BgpValueType pathAttributeObj1 = listIteratorObj1.next();
+             switch (pathAttributeObj1.getType()) {
+             case LocalPref.LOCAL_PREF_TYPE:
+                 obj1LocPref = (LocalPref) pathAttributeObj1;
+                 break;
+             case AsPath.ASPATH_TYPE:
+                 obj1Aspath = (AsPath) pathAttributeObj1;
+                 break;
+             case Origin.ORIGIN_TYPE:
+                 obj1Origin = (Origin) pathAttributeObj1;
+                 break;
+             case Med.MED_TYPE:
+                 obj1Med = (Med) pathAttributeObj1;
+                 break;
+             default:
+                 log.debug("Got other type, Not required: " + pathAttributeObj1.getType());
+             }
+         }
+         while (listIteratorObj2.hasNext()) {
+             BgpValueType pathAttributeObj2 = listIteratorObj2.next();
+             switch (pathAttributeObj2.getType()) {
+             case LocalPref.LOCAL_PREF_TYPE:
+                 obj2LocPref = (LocalPref) pathAttributeObj2;
+                 break;
+             case AsPath.ASPATH_TYPE:
+                 obj2Aspath = (AsPath) pathAttributeObj2;
+                 break;
+             case Origin.ORIGIN_TYPE:
+                 obj2Origin = (Origin) pathAttributeObj2;
+                 break;
+             case Med.MED_TYPE:
+                 obj2Med = (Med) pathAttributeObj2;
+                 break;
+             default:
+                 log.debug("Got other type, Not required: " + pathAttributeObj2.getType());
+             }
+        }
+    }
+}
\ No newline at end of file