src/main/java/net/onrc/onos/apps/segmentrouting/ECMPShortestPathGraph.java

package net.onrc.onos.apps.segmentrouting;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;

import net.onrc.onos.core.intent.Path;
import net.onrc.onos.core.topology.Link;
import net.onrc.onos.core.topology.LinkData;
import net.onrc.onos.core.topology.Switch;
import net.onrc.onos.core.util.Dpid;

import org.projectfloodlight.openflow.util.HexString;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This class creates bandwidth constrained breadth first tree and returns paths
 * from root switch to leaf switches which satisfies the bandwidth condition. If
 * bandwidth parameter is not specified, the normal breadth first tree will be
 * calculated. The paths are snapshot paths at the point of the class
 * instantiation.
 */
public class ECMPShortestPathGraph {
    LinkedList<Switch> switchQueue = new LinkedList<>();
    LinkedList<Integer> distanceQueue = new LinkedList<>();
    HashMap<Dpid, Integer> switchSearched = new HashMap<>();
    HashMap<Dpid, ArrayList<LinkData>> upstreamLinks = new HashMap<>();
    HashMap<Dpid, ArrayList<Path>> paths = new HashMap<>();
    HashMap<Integer, ArrayList<Switch>> distanceSwitchMap = new HashMap<>();
    Switch rootSwitch;
    private static final Logger log = LoggerFactory
            .getLogger(SegmentRoutingManager.class);

    /**
     * Constructor.
     *
     * @param rootSwitch root of the BFS tree
     */
    public ECMPShortestPathGraph(Switch rootSwitch) {
        this.rootSwitch = rootSwitch;
        calcECMPShortestPathGraph();
    }

    /**
     * Calculates the BFS tree using any provided constraints and Intents.
     */
    private void calcECMPShortestPathGraph() {
        switchQueue.add(rootSwitch);
        int currDistance = 0;
        distanceQueue.add(currDistance);
        switchSearched.put(rootSwitch.getDpid(),currDistance);
        while (!switchQueue.isEmpty()) {
            Switch sw = switchQueue.poll();
            Switch prevSw = null;
            currDistance = distanceQueue.poll();
            for (Link link : sw.getOutgoingLinks()) {
                Switch reachedSwitch = link.getDstPort().getSwitch();
                if ((prevSw != null) && (prevSw.getDpid().equals(reachedSwitch.getDpid())))
                {
                    /* Ignore LAG links between the same set of switches */
                	continue;
                }
                else
                {
                    prevSw = reachedSwitch;
                }

                Integer distance = switchSearched.get(reachedSwitch.getDpid());
                if ((distance != null) && (distance.intValue() < (currDistance+1))) {
                    continue;
                }
                if (distance == null){
                	/* First time visiting this switch node */
                    switchQueue.add(reachedSwitch);
                    distanceQueue.add(currDistance+1);
                    switchSearched.put(reachedSwitch.getDpid(),currDistance+1);

                    ArrayList<Switch> distanceSwArray = distanceSwitchMap.get(currDistance+1);
                    if (distanceSwArray == null)
                    {
                            distanceSwArray = new ArrayList<Switch>();
                            distanceSwArray.add(reachedSwitch);
                            distanceSwitchMap.put(currDistance+1, distanceSwArray);
                    }
                    else
                            distanceSwArray.add(reachedSwitch);
                }

                ArrayList<LinkData> upstreamLinkArray =
                		upstreamLinks.get(reachedSwitch.getDpid());
                if (upstreamLinkArray == null)
                {
                	upstreamLinkArray = new ArrayList<LinkData>();
                	upstreamLinkArray.add(new LinkData(link));
                	upstreamLinks.put(reachedSwitch.getDpid(), upstreamLinkArray);
                }
                else
                	/* ECMP links */
                	upstreamLinkArray.add(new LinkData(link));
            }
        }

        log.debug("ECMPShortestPathGraph:switchSearched for switch {} is {}",
                        HexString.toHexString(rootSwitch.getDpid().value()), switchSearched);
        log.debug("ECMPShortestPathGraph:upstreamLinks for switch {} is {}",
                        HexString.toHexString(rootSwitch.getDpid().value()), upstreamLinks);
        log.debug("ECMPShortestPathGraph:distanceSwitchMap for switch {} is {}",
                        HexString.toHexString(rootSwitch.getDpid().value()), distanceSwitchMap);
        /*
        for (Integer distance: distanceSwitchMap.keySet()){
                for (Switch sw: distanceSwitchMap.get(distance)){
                        ArrayList<Path> path = getPath(sw);
                        log.debug("ECMPShortestPathGraph:Paths in Pass{} from switch {} to switch {} is {}",
                                        distance,
                                        HexString.toHexString(rootSwitch.getDpid().value()),
                                        HexString.toHexString(sw.getDpid().value()), path);
                }
        }*/
    }

    private void getDFSPaths(Dpid dstSwitchDpid, Path path, ArrayList<Path> paths) {
        Dpid rootSwitchDpid = rootSwitch.getDpid();
        for (LinkData upstreamLink : upstreamLinks.get(dstSwitchDpid)) {
        	/* Deep clone the path object */
            Path sofarPath = new Path();
            if (!path.isEmpty())
            	sofarPath.addAll(path.subList(0, path.size()));
            sofarPath.add(upstreamLink);
            if (upstreamLink.getSrc().getDpid().equals(rootSwitchDpid))
            {
                    paths.add(sofarPath);
                    return;
            }
            else
                    getDFSPaths(upstreamLink.getSrc().getDpid(),sofarPath, paths);
        }
    }

    /**
     * Return the computed ECMP paths from the root switch to a given switch
     * in the network
     *
     * @param targetSwitch the target switch
     * @return the list of ECMP Paths from the root switch to the target switch
     */
    public ArrayList<Path> getECMPPaths(Switch targetSwitch) {
        ArrayList<Path> pathArray = paths.get(targetSwitch.getDpid());
        if (pathArray == null && switchSearched.containsKey(
                targetSwitch.getDpid())) {
            pathArray = new ArrayList<>();
            Path path = new Path();
            Dpid sw = targetSwitch.getDpid();
            getDFSPaths(sw, path, pathArray);
            paths.put(targetSwitch.getDpid(), pathArray);
        }
        return pathArray;
    }

    /**
     * Return the complete info of the computed ECMP paths for each switch
     * learned in multiple iterations from the root switch
     *
     * @return the hash table of Switches learned in multiple Dijkstra
     * iterations and corresponding ECMP paths to it from the root switch
     */
    public HashMap<Integer, HashMap<Switch,
                ArrayList<Path>>> getCompleteLearnedSwitchesAndPaths() {

        HashMap<Integer, HashMap<Switch, ArrayList<Path>>> pathGraph = new
                        HashMap<Integer, HashMap<Switch, ArrayList<Path>>>();

        for (Integer itrIndx : distanceSwitchMap.keySet()) {
            HashMap<Switch, ArrayList<Path>> swMap = new
                            HashMap<Switch, ArrayList<Path>>();
            for (Switch sw : distanceSwitchMap.get(itrIndx)) {
                swMap.put(sw, getECMPPaths(sw));
            }
            pathGraph.put(itrIndx, swMap);
        }

        return pathGraph;
    }

    /**
     * Return the complete info of the computed ECMP paths for each switch
     * learned in multiple iterations from the root switch in the form of
     * {
     * Iteration1,
     *              Switch<> via {Switch<>, Switch<>}
     *              Switch<> via {Switch<>, Switch<>}
     * Iteration2,
     *              Switch<> via {Switch<>, Switch<>, Switch<>}
     *                           {Switch<>, Switch<>, Switch<>}
     *              Switch<> via {Switch<>, Switch<>, Switch<>}
     * }
     *
     * @return the hash table of Switches learned in multiple Dijkstra
     * iterations and corresponding ECMP paths in terms of Switches to be
     * traversed to it from the root switch
     */
    public HashMap<Integer, HashMap<Switch,
                ArrayList<ArrayList<Dpid>>>> getAllLearnedSwitchesAndVia() {

        HashMap<Integer, HashMap<Switch, ArrayList<ArrayList<Dpid>>>>
            switchViaMap = new HashMap();

        for (Integer itrIndx : distanceSwitchMap.keySet()) {
            HashMap<Switch, ArrayList<ArrayList<Dpid>>> swMap = new HashMap();

            for (Switch sw : distanceSwitchMap.get(itrIndx)) {
                ArrayList<ArrayList<Dpid>> swViaArray = new ArrayList<>();
                for (Path path:getECMPPaths(sw)){
                    ArrayList<Dpid> swVia = new ArrayList<>();
                    for (LinkData link:path.subList(0, path.size())){
                        if (link.getSrc().getDpid().equals(rootSwitch.getDpid())){
                            /* No need to add the root switch again in
                             * the Via list
                             */
                            continue;
                        }
                        swVia.add(link.getSrc().getDpid());
                    }
                    swViaArray.add(swVia);
                }
                swMap.put(sw, swViaArray);
            }
            switchViaMap.put(itrIndx, swMap);
        }
        return switchViaMap;
    }
}