[ONOS] Compute path with Explicit path objects

Change-Id: Ib487688e15db7056283feef7720f610b2f59ad84
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceQueryPathCommand.java b/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceQueryPathCommand.java
index 09a396e..8994f47 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceQueryPathCommand.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceQueryPathCommand.java
@@ -24,10 +24,13 @@
 import org.onosproject.incubator.net.tunnel.Tunnel;
 import org.onosproject.incubator.net.tunnel.TunnelId;
 import org.onosproject.net.AnnotationKeys;
+import org.onosproject.pce.pceservice.ExplicitPathInfo;
 import org.onosproject.pce.pceservice.api.PceService;
 
 import org.slf4j.Logger;
 
+import java.util.List;
+
 /**
  * Supports quering PCE path.
  */
@@ -72,17 +75,28 @@
      * @param tunnel pce tunnel
      */
     void display(Tunnel tunnel) {
-        print("\npath-id            : %s \n" +
-                "source             : %s \n" +
-                "destination        : %s \n" +
-                "path-type          : %s \n" +
-                "symbolic-path-name : %s \n" +
+        List<ExplicitPathInfo> explicitPathInfoList = AbstractShellCommand.get(PceService.class)
+                .explicitPathInfoList(tunnel.tunnelName().value());
+
+        print("\npath-id                  : %s \n" +
+                "source                   : %s \n" +
+                "destination              : %s \n" +
+                "path-type                : %s \n" +
+                "symbolic-path-name       : %s \n" +
                 "constraints:            \n" +
-                "   cost            : %s \n" +
-                "   bandwidth       : %s",
+                "   cost                  : %s \n" +
+                "   bandwidth             : %s",
                 tunnel.tunnelId().id(), tunnel.path().src().deviceId().toString(),
                 tunnel.path().dst().deviceId().toString(),
                 tunnel.type().name(), tunnel.tunnelName(), tunnel.annotations().value(COST_TYPE),
                 tunnel.annotations().value(AnnotationKeys.BANDWIDTH));
+        if (explicitPathInfoList != null) {
+            for (ExplicitPathInfo e : explicitPathInfoList) {
+                print("explicitPathObjects      : \n" +
+                      "    type                 : %s \n" +
+                      "    value                : %s ",
+                      String.valueOf(e.type().type()), e.value().toString());
+            }
+        }
     }
 }
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceSetupPathCommand.java b/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceSetupPathCommand.java
index 7bd7970..6139004 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceSetupPathCommand.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/cli/PceSetupPathCommand.java
@@ -15,27 +15,35 @@
  */
 package org.onosproject.pce.cli;
 
+import static org.onosproject.net.Link.State.ACTIVE;
+import static org.onosproject.net.Link.Type.DIRECT;
 import static org.slf4j.LoggerFactory.getLogger;
 
 import java.util.Collection;
 import java.util.List;
 import java.util.LinkedList;
 
+import com.google.common.collect.Lists;
+
 import org.apache.karaf.shell.commands.Argument;
 import org.apache.karaf.shell.commands.Command;
 import org.apache.karaf.shell.commands.Option;
-
 import org.onlab.util.DataRateUnit;
 import org.onosproject.cli.AbstractShellCommand;
 import org.onosproject.incubator.net.tunnel.Tunnel;
 import org.onosproject.incubator.net.tunnel.TunnelService;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.DefaultLink;
 import org.onosproject.net.DeviceId;
+import org.onosproject.net.NetworkResource;
+import org.onosproject.net.PortNumber;
 import org.onosproject.net.intent.constraint.BandwidthConstraint;
 import org.onosproject.net.intent.Constraint;
+import org.onosproject.net.provider.ProviderId;
+import org.onosproject.pce.pceservice.ExplicitPathInfo;
 import org.onosproject.pce.pceservice.constraint.CostConstraint;
 import org.onosproject.pce.pceservice.LspType;
 import org.onosproject.pce.pceservice.api.PceService;
-
 import org.slf4j.Logger;
 
 /**
@@ -44,6 +52,16 @@
 @Command(scope = "onos", name = "pce-setup-path", description = "Supports creating pce path.")
 public class PceSetupPathCommand extends AbstractShellCommand {
     private final Logger log = getLogger(getClass());
+    public static final byte SUBTYPE_DEVICEID = 0;
+    public static final byte SUBTYPE_LINK = 1;
+    public static final byte SUBTYPE_INDEX = 1;
+    public static final byte TYPE_INDEX = 0;
+
+    public static final byte DEVICEID_INDEX = 2;
+    public static final byte SOURCE_DEVICEID_INDEX = 2;
+    public static final byte SOURCE_PORTNO_INDEX = 3;
+    public static final byte DESTINATION_DEVICEID_INDEX = 4;
+    public static final byte DESTINATION_PORTNO_INDEX = 5;
 
     @Argument(index = 0, name = "src", description = "source device.", required = true, multiValued = false)
     String src = null;
@@ -69,6 +87,19 @@
             + "Data rate unit is in BPS.", required = false, multiValued = false)
     double bandwidth = 0.0;
 
+    @Option(name = "-e", aliases = "--explicitPathObjects", description = "List of strict and loose hopes"
+            + " explicitPathInfo format : Type/SubType/Value(DeviceId or Link info)\n" +
+            " If Value is Device : Type/SubType/deviceId\n" +
+            " If Value is Link : Type/SubType/SourceDeviceId/SourcePortNo/DestinationDeviceId/DestinationPortNo" +
+            "Type 0 - strict, 1 - loose \n" + "SubType 0 - deviceId, 1 - link \n",
+            required = false, multiValued = true)
+    String[] explicitPathInfoStrings;
+
+    //explicitPathInfo format : Type/SubType/Value(DeviceId or Link info)
+    //If Value is Device : Type/SubType/deviceId
+    //If Value is Link : Type/SubType/SourceDeviceId/SourcePortNo/DestinationDeviceId/DestinationPortNo
+    List<ExplicitPathInfo> explicitPathInfo = Lists.newLinkedList();
+
     @Override
     protected void execute() {
         log.info("executing pce-setup-path");
@@ -114,7 +145,50 @@
         CostConstraint.Type costType = CostConstraint.Type.values()[cost - 1];
         listConstrnt.add(CostConstraint.of(costType));
 
-        if (!service.setupPath(srcDevice, dstDevice, name, listConstrnt, lspType)) {
+        if (explicitPathInfoStrings != null)  {
+            for (String str : explicitPathInfoStrings) {
+                String[] splitted = str.split("/");
+                DeviceId deviceId;
+                NetworkResource res = null;
+                PortNumber portNo;
+                int explicitPathType = Integer.parseInt(splitted[TYPE_INDEX]);
+                if ((explicitPathType < 0) || (explicitPathType > 1)) {
+                    error("Explicit path validation failed");
+                    return;
+                }
+
+                //subtype 0 = deviceId, 1 = link
+                //subtype is required to store either as deviceId or Link
+                if (splitted[DEVICEID_INDEX] != null && Integer.parseInt(splitted[SUBTYPE_INDEX]) == SUBTYPE_DEVICEID) {
+                    res = DeviceId.deviceId(splitted[DEVICEID_INDEX]);
+                } else if (Integer.parseInt(splitted[SUBTYPE_INDEX]) == SUBTYPE_LINK
+                        && splitted[SOURCE_DEVICEID_INDEX] != null
+                        && splitted[SOURCE_PORTNO_INDEX] != null
+                        && splitted[DESTINATION_DEVICEID_INDEX] != null
+                        && splitted[DESTINATION_PORTNO_INDEX] != null) {
+
+                    deviceId = DeviceId.deviceId(splitted[SOURCE_DEVICEID_INDEX]);
+                    portNo = PortNumber.portNumber(splitted[SOURCE_PORTNO_INDEX]);
+                    ConnectPoint cpSrc = new ConnectPoint(deviceId, portNo);
+                    deviceId = DeviceId.deviceId(splitted[DESTINATION_DEVICEID_INDEX]);
+                    portNo = PortNumber.portNumber(splitted[DESTINATION_PORTNO_INDEX]);
+                    ConnectPoint cpDst = new ConnectPoint(deviceId, portNo);
+                    res = DefaultLink.builder()
+                            .providerId(ProviderId.NONE)
+                            .src(cpSrc)
+                            .dst(cpDst)
+                            .type(DIRECT)
+                            .state(ACTIVE)
+                            .build();
+                } else {
+                    error("Explicit path validation failed");
+                    return;
+                }
+                ExplicitPathInfo obj = new ExplicitPathInfo(ExplicitPathInfo.Type.values()[explicitPathType], res);
+                explicitPathInfo.add(obj);
+            }
+        }
+        if (!service.setupPath(srcDevice, dstDevice, name, listConstrnt, lspType, explicitPathInfo)) {
             error("Path creation failed.");
         }
     }
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/DefaultPcePath.java b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/DefaultPcePath.java
index 10acd0a..4c85fd7 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/DefaultPcePath.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/DefaultPcePath.java
@@ -18,8 +18,11 @@
 
 import static com.google.common.base.MoreObjects.toStringHelper;
 
+import java.util.Collection;
+import java.util.List;
 import java.util.Objects;
 
+import org.onlab.rest.BaseResource;
 import org.onlab.util.DataRateUnit;
 import org.onosproject.incubator.net.tunnel.Tunnel;
 import org.onosproject.incubator.net.tunnel.TunnelId;
@@ -39,6 +42,7 @@
     private String name; // symbolic-path-name
     private Constraint costConstraint; // cost constraint
     private Constraint bandwidthConstraint; // bandwidth constraint
+    private Collection<ExplicitPathInfo> explicitPathInfo; //list of explicit path info
 
     /**
      * Initializes PCE path attributes.
@@ -50,10 +54,11 @@
      * @param name symbolic-path-name
      * @param costConstrnt cost constraint
      * @param bandwidthConstrnt bandwidth constraint
+     * @param explicitPathInfo list of explicit path info
      */
     private DefaultPcePath(TunnelId id, String src, String dst, LspType lspType,
-                           String name, Constraint costConstrnt, Constraint bandwidthConstrnt) {
-
+                           String name, Constraint costConstrnt, Constraint bandwidthConstrnt,
+                           Collection<ExplicitPathInfo> explicitPathInfo) {
         this.id = id;
         this.source = src;
         this.destination = dst;
@@ -61,6 +66,7 @@
         this.name = name;
         this.costConstraint = costConstrnt;
         this.bandwidthConstraint = bandwidthConstrnt;
+        this.explicitPathInfo = explicitPathInfo;
     }
 
     @Override
@@ -114,6 +120,11 @@
     }
 
     @Override
+    public Collection<ExplicitPathInfo> explicitPathInfo() {
+        return explicitPathInfo;
+    }
+
+    @Override
     public PcePath copy(PcePath path) {
         if (null != path.source()) {
             this.source = path.source();
@@ -138,7 +149,8 @@
 
     @Override
     public int hashCode() {
-        return Objects.hash(id, source, destination, lspType, name, costConstraint, bandwidthConstraint);
+        return Objects.hash(id, source, destination, lspType, name, costConstraint, bandwidthConstraint,
+                explicitPathInfo);
     }
 
     @Override
@@ -154,7 +166,8 @@
                     && Objects.equals(lspType, that.lspType)
                     && Objects.equals(name, that.name)
                     && Objects.equals(costConstraint, that.costConstraint)
-                    && Objects.equals(bandwidthConstraint, that.bandwidthConstraint);
+                    && Objects.equals(bandwidthConstraint, that.bandwidthConstraint)
+                    && Objects.equals(explicitPathInfo, that.explicitPathInfo);
         }
         return false;
     }
@@ -170,6 +183,7 @@
                 .add("name", name)
                 .add("costConstraint", costConstraint)
                 .add("bandwidthConstraint", bandwidthConstraint)
+                .add("explicitPathInfo", explicitPathInfo)
                 .toString();
     }
 
@@ -185,7 +199,7 @@
     /**
      * Builder class for pce path.
      */
-    public static final class Builder implements PcePath.Builder {
+    public static final class Builder extends BaseResource implements PcePath.Builder {
         private TunnelId id;
         private String source;
         private String destination;
@@ -193,6 +207,7 @@
         private String name;
         private Constraint costConstraint;
         private Constraint bandwidthConstraint;
+        private Collection<ExplicitPathInfo> explicitPathInfo;
 
         @Override
         public Builder id(String id) {
@@ -240,7 +255,13 @@
         }
 
         @Override
-        public Builder of(Tunnel tunnel) {
+        public Builder explicitPathInfo(Collection<ExplicitPathInfo> explicitPathInfo) {
+            this.explicitPathInfo = explicitPathInfo;
+            return this;
+        }
+
+        @Override
+        public Builder of(Tunnel tunnel, List<ExplicitPathInfo> explicitPathInfoList) {
             this.id = TunnelId.valueOf(tunnel.tunnelId().id());
             this.source = tunnel.path().src().deviceId().toString();
             this.destination = tunnel.path().dst().deviceId().toString();
@@ -264,13 +285,18 @@
                                                                   DataRateUnit.valueOf("BPS"));
             }
 
+            // Explicit Path
+            if (explicitPathInfoList != null) {
+                this.explicitPathInfo = explicitPathInfoList;
+            }
+
             return this;
         }
 
         @Override
         public PcePath build() {
             return new DefaultPcePath(id, source, destination, lspType, name,
-                                      costConstraint, bandwidthConstraint);
+                                      costConstraint, bandwidthConstraint, explicitPathInfo);
         }
     }
 }
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/ExplicitPathInfo.java b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/ExplicitPathInfo.java
new file mode 100644
index 0000000..52ef270
--- /dev/null
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/ExplicitPathInfo.java
@@ -0,0 +1,113 @@
+/*
+ * Copyright 2016-present 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.pce.pceservice;
+
+import org.onosproject.net.NetworkResource;
+
+import com.google.common.annotations.Beta;
+
+import java.util.Objects;
+
+/**
+ * Representation of explicit path info consists of contraints (strict / loose) to compute path.
+ */
+@Beta
+public final class ExplicitPathInfo {
+
+    private final Type type;
+
+    //Can be Link or DeviceId
+    private final NetworkResource value;
+
+    public enum Type {
+        /**
+         * Signifies that path includes strict node or link.
+         */
+        STRICT(0),
+
+        /**
+         * Signifies that path includes loose node or link.
+         */
+        LOOSE(1);
+
+        int value;
+
+        /**
+         * Assign val with the value as the type.
+         *
+         * @param val type
+         */
+        Type(int val) {
+            value = val;
+        }
+
+        /**
+         * Returns value of type.
+         *
+         * @return type
+         */
+        public byte type() {
+            return (byte) value;
+        }
+    }
+
+    /**
+     * Creates instance of explicit path object.
+     *
+     * @param type specifies whether strict or loose node/link
+     * @param value specifies deviceId or link
+     */
+    public ExplicitPathInfo(Type type, NetworkResource value) {
+        this.type = type;
+        this.value = value;
+    }
+
+    /**
+     * Returns explicit path type.
+     *
+     * @return explicit path type as strict/loose
+     */
+    public Type type() {
+        return type;
+    }
+
+    /**
+     * Returns deviceId or link.
+     *
+     * @return deviceId or link
+     */
+    public NetworkResource value() {
+        return value;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, value);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof ExplicitPathInfo) {
+            final ExplicitPathInfo other = (ExplicitPathInfo) obj;
+            return Objects.equals(this.type, other.type)
+                    && Objects.equals(this.value, other.value);
+        }
+        return false;
+    }
+}
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PceManager.java b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PceManager.java
index a4c2aa6..ecc1d72 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PceManager.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PceManager.java
@@ -48,9 +48,11 @@
 import org.onosproject.net.config.NetworkConfigService;
 import org.onosproject.net.DefaultAnnotations;
 import org.onosproject.net.DefaultAnnotations.Builder;
+import org.onosproject.net.DefaultPath;
 import org.onosproject.net.Device;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.Link;
+import org.onosproject.net.NetworkResource;
 import org.onosproject.net.Path;
 import org.onosproject.net.device.DeviceService;
 import org.onosproject.net.intent.Constraint;
@@ -86,6 +88,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
 
 import static org.onosproject.incubator.net.tunnel.Tunnel.State.INIT;
 import static org.onosproject.incubator.net.tunnel.Tunnel.State.UNSTABLE;
@@ -223,17 +226,196 @@
         if (pathService == null) {
             return ImmutableSet.of();
         }
+
         Set<Path> paths = pathService.getPaths(src, dst, weight(constraints));
+        log.info("paths in computePath ::" + paths);
         if (!paths.isEmpty()) {
             return paths;
         }
         return ImmutableSet.of();
     }
 
-    //[TODO:] handle requests in queue
+    //Computes the partial path from partial computed path to specified dst.
+    private List<Path> computePartialPath(List<Path> computedPath, DeviceId src, DeviceId dst,
+                                    List<Constraint> constraints) {
+        int size = computedPath.size();
+        Path path = null;
+        DeviceId deviceId = size == 0 ? src :
+                computedPath.get(size - 1).dst().deviceId();
+
+        Set<Path> tempComputePath = computePath(deviceId, dst, constraints);
+
+        if (tempComputePath.isEmpty()) {
+            return null;
+        }
+
+        //if path validation fails return null
+        //Validate computed path to avoid loop in the path
+        for (Path p : tempComputePath) {
+            if (pathValidation(computedPath, p)) {
+                path = p;
+                break;
+            }
+        }
+        if (path == null) {
+            return null;
+        }
+
+        //Store the partial path result in a list
+        computedPath.add(path);
+        return computedPath;
+    }
+
+    private List<DeviceId> createListOfDeviceIds(List<? extends NetworkResource> list) {
+        List<Link> links = new LinkedList<>();
+        if (!list.isEmpty() && list.iterator().next() instanceof Path) {
+            for (Path path : (List<Path>) list) {
+                links.addAll(path.links());
+            }
+        } else if (!list.isEmpty() && list.iterator().next() instanceof Link) {
+            links.addAll((List<Link>) list);
+        }
+
+        //List of devices for new path computed
+        DeviceId source = null;
+        DeviceId destination = null;
+        List<DeviceId> devList = new LinkedList<>();
+
+        for (Link l : links) {
+            if (!devList.contains(l.src().deviceId())) {
+                devList.add(l.src().deviceId());
+            }
+            if (!devList.contains(l.dst().deviceId())) {
+                devList.add(l.dst().deviceId());
+            }
+        }
+
+        return devList;
+    }
+
+    //To dectect loops in the path i.e if the partial paths has intersection node avoid it.
+    private boolean pathValidation(List<Path> partialPath, Path path) {
+
+        //List of devices in new path computed
+        List<DeviceId> newPartialPathDevList;
+        newPartialPathDevList = createListOfDeviceIds(path.links());
+
+        //List of devices in partial computed path
+        List<DeviceId> partialComputedPathDevList;
+        partialComputedPathDevList = createListOfDeviceIds(partialPath);
+
+        for (DeviceId deviceId : newPartialPathDevList) {
+            for (DeviceId devId : partialComputedPathDevList) {
+                if (!newPartialPathDevList.get(0).equals(deviceId) &&
+                        !partialComputedPathDevList.get(partialComputedPathDevList.size() - 1).equals(devId)
+                        && deviceId.equals(devId)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    //Returns final computed explicit path (list of partial computed paths).
+    private List<Path> computeExplicitPath(List<ExplicitPathInfo> explicitPathInfo, DeviceId src, DeviceId dst,
+            List<Constraint> constraints) {
+        List<Path> finalComputedPath = new LinkedList<>();
+        for (ExplicitPathInfo info : explicitPathInfo) {
+            /*
+             * If explicit path object is LOOSE,
+             * 1) If specified as DeviceId (node) :
+             * If it is source , compute from source to destination (partial computation not required),
+             * otherwise compute from specified source to specified device
+             * 2) If specified as Link :
+             * Compute partial path from source to link's source , if path exists compute from link's source to dst
+             */
+            if (info.type().equals(ExplicitPathInfo.Type.LOOSE)) {
+                if (info.value() instanceof DeviceId) {
+                    // If deviceId is source no need to compute
+                    if (!(info.value()).equals(src)) {
+                        log.debug("computeExplicitPath :: Loose , device");
+                        finalComputedPath = computePartialPath(finalComputedPath, src, (DeviceId) info.value(),
+                                constraints);
+                        log.debug("finalComputedPath in computeExplicitPath ::" + finalComputedPath);
+                    }
+
+                } else if (info.value() instanceof Link) {
+                    if ((((Link) info.value()).src().deviceId().equals(src))
+                            || (!finalComputedPath.isEmpty()
+                            && finalComputedPath.get(finalComputedPath.size() - 1).dst().deviceId().equals(
+                                    ((Link) info.value()).src().deviceId()))) {
+
+                        finalComputedPath = computePartialPath(finalComputedPath, src, ((Link) info.value()).dst()
+                                .deviceId(), constraints);
+                    } else {
+
+                        finalComputedPath = computePartialPath(finalComputedPath, src, ((Link) info.value()).src()
+                                .deviceId(), constraints) != null ? computePartialPath(finalComputedPath, src,
+                                ((Link) info.value()).dst().deviceId(), constraints) : null;
+                    }
+                }
+                /*
+                 * If explicit path object is STRICT,
+                 * 1) If specified as DeviceId (node) :
+                 * Check whether partial computed path has reachable to strict specified node orde
+                 * strict node is the source, if no set path as null else do nothing
+                 * 2) If specified as Link :
+                 * Check whether partial computed path has reachable to strict link's src, if yes compute
+                 * path from strict link's src to link's dst (to include specified link)
+                 */
+            } else if (info.type().equals(ExplicitPathInfo.Type.STRICT)) {
+                if (info.value() instanceof DeviceId) {
+                    log.debug("computeExplicitPath :: Strict , device");
+                    if (!(!finalComputedPath.isEmpty() && finalComputedPath.get(finalComputedPath.size() - 1).dst()
+                            .deviceId().equals(info.value()))
+                            && !info.value().equals(src)) {
+                        finalComputedPath = null;
+                    }
+
+                } else if (info.value() instanceof Link) {
+                    log.info("computeExplicitPath :: Strict");
+                    finalComputedPath = ((Link) info.value()).src().deviceId().equals(src)
+                            || !finalComputedPath.isEmpty()
+                            && finalComputedPath.get(finalComputedPath.size() - 1).dst().deviceId()
+                                    .equals(((Link) info.value()).src().deviceId()) ? computePartialPath(
+                            finalComputedPath, src, ((Link) info.value()).dst().deviceId(), constraints) : null;
+
+                    //Log.info("computeExplicitPath :: (Link) info.value() " + (Link) info.value());
+                    //Log.info("computeExplicitPath :: finalComputedPath " + finalComputedPath);
+
+                    if (finalComputedPath != null && !finalComputedPath.get(finalComputedPath.size() - 1).links()
+                            .contains((Link) info.value())) {
+                        finalComputedPath = null;
+                    }
+                }
+            }
+            if (finalComputedPath == null) {
+                return null;
+            }
+        }
+        // Destination is not reached in Partial computed path then compute till destination
+        if (finalComputedPath.isEmpty() || !finalComputedPath.isEmpty()
+                && !finalComputedPath.get(finalComputedPath.size() - 1).dst().deviceId().equals(dst)) {
+
+            finalComputedPath = computePartialPath(finalComputedPath, src, dst, constraints);
+            if (finalComputedPath == null) {
+                return null;
+            }
+        }
+
+        return finalComputedPath;
+    }
+
     @Override
     public boolean setupPath(DeviceId src, DeviceId dst, String tunnelName, List<Constraint> constraints,
                              LspType lspType) {
+        return setupPath(src, dst, tunnelName, constraints, lspType, null);
+    }
+
+    //[TODO:] handle requests in queue
+    @Override
+    public boolean setupPath(DeviceId src, DeviceId dst, String tunnelName, List<Constraint> constraints,
+                             LspType lspType, List<ExplicitPathInfo> explicitPathInfo) {
         checkNotNull(src);
         checkNotNull(dst);
         checkNotNull(tunnelName);
@@ -245,7 +427,7 @@
 
         if (srcDevice == null || dstDevice == null) {
             // Device is not known.
-            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType));
+            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType, explicitPathInfo));
             return false;
         }
 
@@ -255,7 +437,7 @@
 
         if (srcLsrId == null || dstLsrId == null) {
             // LSR id is not known.
-            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType));
+            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType, explicitPathInfo));
             return false;
         }
 
@@ -263,7 +445,7 @@
         DeviceCapability cfg = netCfgService.getConfig(DeviceId.deviceId(srcLsrId), DeviceCapability.class);
         if (cfg == null) {
             log.debug("No session to ingress.");
-            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType));
+            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType, explicitPathInfo));
             return false;
         }
 
@@ -299,12 +481,30 @@
             constraints = new LinkedList<>();
             constraints.add(CapabilityConstraint.of(CapabilityType.valueOf(lspType.name())));
         }
+        Set<Path> computedPathSet = Sets.newLinkedHashSet();
 
-        Set<Path> computedPathSet = computePath(src, dst, constraints);
+        if (explicitPathInfo != null && !explicitPathInfo.isEmpty()) {
+            List<Path> finalComputedPath = computeExplicitPath(explicitPathInfo, src, dst, constraints);
+            if (finalComputedPath == null) {
+                return false;
+            }
+
+            pceStore.tunnelNameExplicitPathInfoMap(tunnelName, explicitPathInfo);
+            List<Link> links = new LinkedList<>();
+            double totalCost = 0;
+            // Add all partial computed paths
+            for (Path path : finalComputedPath) {
+                links.addAll(path.links());
+                totalCost = totalCost + path.cost();
+            }
+            computedPathSet.add(new DefaultPath(finalComputedPath.iterator().next().providerId(), links, totalCost));
+        } else {
+            computedPathSet = computePath(src, dst, constraints);
+        }
 
         // NO-PATH
         if (computedPathSet.isEmpty()) {
-            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType));
+            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType, explicitPathInfo));
             return false;
         }
 
@@ -339,14 +539,15 @@
         if (bwConstraintValue != 0) {
             consumerId = reserveBandwidth(computedPath, bwConstraintValue, null);
             if (consumerId == null) {
-                pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType));
+                pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints,
+                        lspType, explicitPathInfo));
                 return false;
             }
         }
 
         TunnelId tunnelId = tunnelService.setupTunnel(appId, src, tunnel, computedPath);
         if (tunnelId == null) {
-            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType));
+            pceStore.addFailedPathInfo(new PcePathInfo(src, dst, tunnelName, constraints, lspType, explicitPathInfo));
             if (consumerId != null) {
                 resourceService.release(consumerId);
             }
@@ -363,7 +564,7 @@
     @Override
     public boolean updatePath(TunnelId tunnelId, List<Constraint> constraints) {
         checkNotNull(tunnelId);
-        Set<Path> computedPathSet = null;
+        Set<Path> computedPathSet = Sets.newLinkedHashSet();
         Tunnel tunnel = tunnelService.queryTunnel(tunnelId);
 
         if (tunnel == null) {
@@ -441,8 +642,30 @@
             constraints.add(costConstraint);
         }
 
-        computedPathSet = computePath(links.get(0).src().deviceId(), links.get(links.size() - 1).dst().deviceId(),
-                                      constraints);
+        List<ExplicitPathInfo> explicitPathInfo = pceStore
+                .getTunnelNameExplicitPathInfoMap(tunnel.tunnelName().value());
+        if (explicitPathInfo != null) {
+            List<Path> finalComputedPath = computeExplicitPath(explicitPathInfo,
+                    tunnel.path().src().deviceId(), tunnel.path().dst().deviceId(),
+                    constraints);
+
+            if (finalComputedPath == null) {
+                return false;
+            }
+
+            List<Link> totalLinks = new LinkedList<>();
+            double totalCost = 0;
+            //Add all partial computed paths
+            for (Path path : finalComputedPath) {
+                totalLinks.addAll(path.links());
+                totalCost = totalCost + path.cost();
+            }
+            computedPathSet.add(new DefaultPath(finalComputedPath.iterator().next().providerId(),
+                    totalLinks, totalCost));
+        } else {
+            computedPathSet = computePath(tunnel.path().src().deviceId(), tunnel.path().dst().deviceId(),
+                    constraints);
+        }
 
         // NO-PATH
         if (computedPathSet.isEmpty()) {
@@ -636,7 +859,8 @@
                 // then PCInitiate (Remove)
                 pceStore.addFailedPathInfo(new PcePathInfo(tunnel.path().src().deviceId(), tunnel
                         .path().dst().deviceId(), tunnel.tunnelName().value(), constraintList,
-                        LspType.valueOf(tunnel.annotations().value(LSP_SIG_TYPE))));
+                        LspType.valueOf(tunnel.annotations().value(LSP_SIG_TYPE)),
+                         pceStore.getTunnelNameExplicitPathInfoMap(tunnel.tunnelName().value())));
                 //Release that tunnel calling PCInitiate
                 releasePath(tunnel.tunnelId());
             }
@@ -832,7 +1056,9 @@
                     List<Link> links = tunnel.path().links();
                     pceStore.addFailedPathInfo(new PcePathInfo(links.get(0).src().deviceId(),
                                                                   links.get(links.size() - 1).dst().deviceId(),
-                                                                  tunnel.tunnelName().value(), constraints, lspType));
+                                                                  tunnel.tunnelName().value(), constraints, lspType,
+                                                                  pceStore.getTunnelNameExplicitPathInfoMap(tunnel
+                                                                          .tunnelName().value())));
                 }
 
                 break;
@@ -861,6 +1087,11 @@
         }
     }
 
+    @Override
+    public List<ExplicitPathInfo> explicitPathInfoList(String tunnelName) {
+        return pceStore.getTunnelNameExplicitPathInfoMap(tunnelName);
+    }
+
     //Computes path from tunnel store and also path failed to setup.
     private void callForOptimization() {
         //Recompute the LSPs which it was delegated [LSPs stored in PCE store (failed paths)]
@@ -880,7 +1111,7 @@
          */
         if (mastershipService.isLocalMaster(failedPathInfo.src())) {
             if (setupPath(failedPathInfo.src(), failedPathInfo.dst(), failedPathInfo.name(),
-                    failedPathInfo.constraints(), failedPathInfo.lspType())) {
+                    failedPathInfo.constraints(), failedPathInfo.lspType(), failedPathInfo.explicitPathInfo())) {
                 // If computation is success remove that path
                 pceStore.removeFailedPathInfo(failedPathInfo);
                 return true;
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PcePath.java b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PcePath.java
index 807b233..4886b97 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PcePath.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/PcePath.java
@@ -19,7 +19,9 @@
 import org.onosproject.incubator.net.tunnel.Tunnel;
 import org.onosproject.incubator.net.tunnel.TunnelId;
 import org.onosproject.net.intent.Constraint;
-import org.onosproject.pce.pceservice.DefaultPcePath.Builder;
+
+import java.util.Collection;
+import java.util.List;
 
 /**
  * Abstraction of an entity which provides functionalities of pce path.
@@ -97,6 +99,13 @@
     Constraint bandwidthConstraint();
 
     /**
+     * Returns the list of explicit path objects.
+     *
+     * @return list of explicit path objects
+     */
+    Collection<ExplicitPathInfo> explicitPathInfo();
+
+    /**
      * Copies only non-null or non-zero member variables.
      *
      * @param id path-id
@@ -169,9 +178,18 @@
          * Copies tunnel information to local.
          *
          * @param tunnel pcc tunnel
+         * @param explicitPathInfoList list of explicit path objects info
          * @return object of pce-path
          */
-        Builder of(Tunnel tunnel);
+        Builder of(Tunnel tunnel, List<ExplicitPathInfo> explicitPathInfoList);
+
+        /**
+         * Returns the builder object of ExplicitPathInfo.
+         *
+         * @param explicitPathInfo list of explicit path obj
+         * @return builder object of ExplicitPathInfo
+         */
+        Builder explicitPathInfo(Collection<ExplicitPathInfo> explicitPathInfo);
 
         /**
          * Builds object of pce path.
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/api/PceService.java b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/api/PceService.java
index f2d3622..fdfdb73 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/api/PceService.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pceservice/api/PceService.java
@@ -19,6 +19,7 @@
 
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.intent.Constraint;
+import org.onosproject.pce.pceservice.ExplicitPathInfo;
 import org.onosproject.pce.pceservice.LspType;
 import org.onosproject.incubator.net.tunnel.Tunnel;
 import org.onosproject.incubator.net.tunnel.TunnelId;
@@ -42,6 +43,20 @@
     boolean setupPath(DeviceId src, DeviceId dst, String tunnelName, List<Constraint> constraints, LspType lspType);
 
     /**
+     * Creates new path based on constraints and LSP type.
+     *
+     * @param src source device
+     * @param dst destination device
+     * @param tunnelName name of the tunnel
+     * @param constraints list of constraints to be applied on path
+     * @param lspType type of path to be setup
+     * @param explicitPathInfo list of explicit path info
+     * @return false on failure and true on successful path creation
+     */
+    boolean setupPath(DeviceId src, DeviceId dst, String tunnelName, List<Constraint> constraints, LspType lspType,
+                      List<ExplicitPathInfo> explicitPathInfo);
+
+    /**
      * Updates an existing path.
      *
      * @param tunnelId tunnel identifier
@@ -72,4 +87,12 @@
      * @return tunnel if path exists, otherwise null
      */
     Tunnel queryPath(TunnelId tunnelId);
+
+    /**
+     * Returns list of explicit path info.
+     *
+     * @param tunnelName tunnel name
+     * @return list of explicit path info
+     */
+    List<ExplicitPathInfo> explicitPathInfoList(String tunnelName);
 }
\ No newline at end of file
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/DistributedPceStore.java b/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/DistributedPceStore.java
index 9b2941f..001f74b 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/DistributedPceStore.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/DistributedPceStore.java
@@ -19,6 +19,7 @@
 
 import com.google.common.collect.ImmutableSet;
 
+import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
@@ -33,6 +34,7 @@
 import org.onosproject.incubator.net.tunnel.TunnelId;
 import org.onosproject.net.intent.constraint.BandwidthConstraint;
 import org.onosproject.net.resource.ResourceConsumer;
+import org.onosproject.pce.pceservice.ExplicitPathInfo;
 import org.onosproject.pce.pceservice.constraint.CapabilityConstraint;
 import org.onosproject.pce.pceservice.constraint.CostConstraint;
 import org.onosproject.pce.pceservice.TunnelConsumerId;
@@ -69,9 +71,14 @@
     // List of Failed path info
     private DistributedSet<PcePathInfo> failedPathSet;
 
+    // Maintains tunnel name mapped to explicit path info
+    private ConsistentMap<String, List<ExplicitPathInfo>> tunnelNameExplicitPathInfoMap;
+
     private static final Serializer SERIALIZER = Serializer
             .using(new KryoNamespace.Builder().register(KryoNamespaces.API)
                     .register(PcePathInfo.class)
+                    .register(ExplicitPathInfo.class)
+                    .register(ExplicitPathInfo.Type.class)
                     .register(CostConstraint.class)
                     .register(CostConstraint.Type.class)
                     .register(BandwidthConstraint.class)
@@ -99,6 +106,16 @@
                 .build()
                 .asDistributedSet();
 
+        tunnelNameExplicitPathInfoMap = storageService.<String, List<ExplicitPathInfo>>consistentMapBuilder()
+                .withName("onos-pce-explicitpathinfo")
+                .withSerializer(Serializer.using(
+                        new KryoNamespace.Builder()
+                                .register(KryoNamespaces.API)
+                                .register(ExplicitPathInfo.class)
+                                .register(ExplicitPathInfo.Type.class)
+                                .build()))
+                .build();
+
         log.info("Started");
     }
 
@@ -181,4 +198,21 @@
         }
         return true;
     }
+
+    @Override
+    public boolean tunnelNameExplicitPathInfoMap(String tunnelName, List<ExplicitPathInfo> explicitPathInfo) {
+        checkNotNull(tunnelName);
+        checkNotNull(explicitPathInfo);
+        return tunnelNameExplicitPathInfoMap.put(tunnelName, explicitPathInfo) != null ? true : false;
+    }
+
+    @Override
+    public List<ExplicitPathInfo> getTunnelNameExplicitPathInfoMap(String tunnelName) {
+        checkNotNull(tunnelName);
+        if (tunnelNameExplicitPathInfoMap.get(tunnelName) != null) {
+            return tunnelNameExplicitPathInfoMap.get(tunnelName).value();
+        }
+        return null;
+    }
+
 }
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/PcePathInfo.java b/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/PcePathInfo.java
index 3b7b47e..6497e36 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/PcePathInfo.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/PcePathInfo.java
@@ -22,6 +22,7 @@
 
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.intent.Constraint;
+import org.onosproject.pce.pceservice.ExplicitPathInfo;
 import org.onosproject.pce.pceservice.LspType;
 
 /**
@@ -40,6 +41,8 @@
 
     private LspType lspType; // lsp type
 
+    private List<ExplicitPathInfo> explicitPathInfo; //Explicit path info to compute explicit path
+
     /**
      * Initialization of member variables.
      *
@@ -48,17 +51,20 @@
      * @param name tunnel name
      * @param constraints list of constraints
      * @param lspType lsp type
+     * @param explicitPathInfo explicit path info
      */
     public PcePathInfo(DeviceId src,
                     DeviceId dst,
                     String name,
                     List<Constraint> constraints,
-                    LspType lspType) {
+                    LspType lspType,
+                    List<ExplicitPathInfo> explicitPathInfo) {
        this.src = src;
        this.dst = dst;
        this.name = name;
        this.constraints = constraints;
        this.lspType = lspType;
+       this.explicitPathInfo = explicitPathInfo;
     }
 
     /**
@@ -70,6 +76,7 @@
        this.name = null;
        this.constraints = null;
        this.lspType = null;
+       this.explicitPathInfo = null;
     }
 
     /**
@@ -162,9 +169,27 @@
         this.lspType = lspType;
     }
 
+    /**
+     * Returns list of explicit path info.
+     *
+     * @return list of explicit path info
+     */
+    public List<ExplicitPathInfo> explicitPathInfo() {
+        return explicitPathInfo;
+    }
+
+    /**
+     * Sets list of explicit path info.
+     *
+     * @param explicitPathInfo list of explicit path info
+     */
+    public void explicitPathInfo(List<ExplicitPathInfo> explicitPathInfo) {
+        this.explicitPathInfo = explicitPathInfo;
+    }
+
     @Override
     public int hashCode() {
-        return Objects.hash(src, dst, name, constraints, lspType);
+        return Objects.hash(src, dst, name, constraints, lspType, explicitPathInfo);
     }
 
     @Override
@@ -178,7 +203,8 @@
                     Objects.equals(this.dst, other.dst) &&
                     Objects.equals(this.name, other.name) &&
                     Objects.equals(this.constraints, other.constraints) &&
-                    Objects.equals(this.lspType, other.lspType);
+                    Objects.equals(this.lspType, other.lspType) &&
+                    Objects.equals(this.explicitPathInfo, other.explicitPathInfo);
         }
         return false;
     }
@@ -187,11 +213,12 @@
     public String toString() {
         return MoreObjects.toStringHelper(getClass())
                 .omitNullValues()
-                .add("Source", src.toString())
-                .add("Destination", dst.toString())
-                .add("Name", name.toString())
-                .add("Constraints", constraints.toString())
-                .add("LspType", lspType.toString())
+                .add("Source", src)
+                .add("Destination", dst)
+                .add("Name", name)
+                .add("Constraints", constraints)
+                .add("explicitPathInfo", explicitPathInfo)
+                .add("LspType", lspType)
                 .toString();
     }
 }
diff --git a/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/api/PceStore.java b/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/api/PceStore.java
index 3fdef15..0a7fa94 100644
--- a/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/api/PceStore.java
+++ b/apps/pce/app/src/main/java/org/onosproject/pce/pcestore/api/PceStore.java
@@ -15,8 +15,11 @@
  */
 package org.onosproject.pce.pcestore.api;
 
+import java.util.List;
+
 import org.onosproject.incubator.net.tunnel.TunnelId;
 import org.onosproject.net.resource.ResourceConsumer;
+import org.onosproject.pce.pceservice.ExplicitPathInfo;
 import org.onosproject.pce.pcestore.PcePathInfo;
 
 import java.util.Map;
@@ -107,4 +110,21 @@
      * @return success or failure
      */
     boolean removeFailedPathInfo(PcePathInfo failedPathInfo);
+
+    /**
+     * Adds explicit path info to the map with corresponding tunnel name.
+     *
+     * @param tunnelName tunnel name as key
+     * @param explicitPathInfo list of explicit path objects
+     * @return whether it is added to map
+     */
+    boolean tunnelNameExplicitPathInfoMap(String tunnelName, List<ExplicitPathInfo> explicitPathInfo);
+
+    /**
+     * Gets explicit path info based on tunnel name.
+     *
+     * @param tunnelName tunnel name as key
+     * @return list of explicit path info
+     */
+    List<ExplicitPathInfo> getTunnelNameExplicitPathInfoMap(String tunnelName);
 }