Examples with BoolExpr com.microsoft.z3.BoolExpr used on opensource projects

Example 61 with BoolExpr

use of com.microsoft.z3.BoolExpr in project batfish by batfish.

the class PropertyAdder method instrumentLoop.

/*
   * Instruments the network to check if a router will be part
   * of a routing loop.
   */
BoolExpr instrumentLoop(String router) {
    Context ctx = _encoderSlice.getCtx();
    Solver solver = _encoderSlice.getSolver();
    String sliceName = _encoderSlice.getSliceName();
    // Add on-loop variables to track a loop
    Map<String, BoolExpr> onLoop = new HashMap<>();
    Graph graph = _encoderSlice.getGraph();
    for (String r : graph.getRouters()) {
        String name = _encoderSlice.getEncoder().getId() + "_" + sliceName + "_on-loop_" + router + "_" + r;
        BoolExpr var = ctx.mkBoolConst(name);
        onLoop.put(r, var);
        _encoderSlice.getAllVariables().put(var.toString(), var);
    }
    for (Entry<String, List<GraphEdge>> entry : graph.getEdgeMap().entrySet()) {
        String r = entry.getKey();
        List<GraphEdge> edges = entry.getValue();
        BoolExpr var = onLoop.get(r);
        BoolExpr acc = ctx.mkBool(false);
        for (GraphEdge edge : edges) {
            if (!edge.isAbstract()) {
                BoolExpr fwd = _encoderSlice.getForwardsAcross().get(r, edge);
                String peer = edge.getPeer();
                if (peer != null) {
                    if (peer.equals(router)) {
                        // If next hop is static route router, then on loop
                        acc = ctx.mkOr(acc, fwd);
                    } else {
                        // Otherwise check if next hop also is on the loop
                        BoolExpr peerOnLoop = onLoop.get(peer);
                        acc = ctx.mkOr(acc, ctx.mkAnd(fwd, peerOnLoop));
                    }
                }
            }
        }
        solver.add(ctx.mkEq(var, acc));
    }
    return onLoop.get(router);
}

Example 62 with BoolExpr

use of com.microsoft.z3.BoolExpr in project batfish by batfish.

the class PropertyChecker method checkRoutingLoop.

/*
   * Checks for routing loops in the network. For efficiency reasons,
   * we only check for loops with routers that use static routes since
   * these can override the usual loop-prevention mechanisms.
   */
public AnswerElement checkRoutingLoop(HeaderQuestion q) {
    Graph graph = new Graph(_batfish);
    // Collect all relevant destinations
    List<Prefix> prefixes = new ArrayList<>();
    graph.getStaticRoutes().forEach((router, ifaceName, srs) -> {
        for (StaticRoute sr : srs) {
            prefixes.add(sr.getNetwork());
        }
    });
    SortedSet<IpWildcard> pfxs = new TreeSet<>();
    for (Prefix prefix : prefixes) {
        pfxs.add(new IpWildcard(prefix));
    }
    q.getHeaderSpace().setDstIps(pfxs);
    // Collect all routers that use static routes as a
    // potential node along a loop
    List<String> routers = new ArrayList<>();
    for (Entry<String, Configuration> entry : graph.getConfigurations().entrySet()) {
        String router = entry.getKey();
        Configuration conf = entry.getValue();
        if (conf.getDefaultVrf().getStaticRoutes().size() > 0) {
            routers.add(router);
        }
    }
    Encoder enc = new Encoder(_settings, graph, q);
    enc.computeEncoding();
    Context ctx = enc.getCtx();
    EncoderSlice slice = enc.getMainSlice();
    PropertyAdder pa = new PropertyAdder(slice);
    BoolExpr someLoop = ctx.mkBool(false);
    for (String router : routers) {
        BoolExpr hasLoop = pa.instrumentLoop(router);
        someLoop = ctx.mkOr(someLoop, hasLoop);
    }
    enc.add(someLoop);
    VerificationResult result = enc.verify().getFirst();
    return new SmtOneAnswerElement(result);
}

Example 63 with BoolExpr

use of com.microsoft.z3.BoolExpr in project batfish by batfish.

the class PropertyChecker method relateFailures.

private BoolExpr relateFailures(Encoder enc1, Encoder enc2) {
    BoolExpr related = enc1.mkTrue();
    for (GraphEdge ge : enc1.getMainSlice().getGraph().getAllRealEdges()) {
        ArithExpr a1 = enc1.getSymbolicFailures().getFailedVariable(ge);
        ArithExpr a2 = enc2.getSymbolicFailures().getFailedVariable(ge);
        assert a1 != null;
        assert a2 != null;
        related = enc1.mkEq(a1, a2);
    }
    return related;
}

Example 64 with BoolExpr

use of com.microsoft.z3.BoolExpr in project batfish by batfish.

the class PropertyChecker method checkBlackHole.

/*
   * Compute if there can ever be a black hole for routers that are
   * not at the edge of the network. This is almost certainly a bug.
   */
public AnswerElement checkBlackHole(HeaderQuestion q) {
    Graph graph = new Graph(_batfish);
    Encoder enc = new Encoder(_settings, graph, q);
    enc.computeEncoding();
    Context ctx = enc.getCtx();
    EncoderSlice slice = enc.getMainSlice();
    // Collect routers that have no host/environment edge
    List<String> toCheck = new ArrayList<>();
    for (Entry<String, List<GraphEdge>> entry : graph.getEdgeMap().entrySet()) {
        String router = entry.getKey();
        List<GraphEdge> edges = entry.getValue();
        boolean check = true;
        for (GraphEdge edge : edges) {
            if (edge.getEnd() == null) {
                check = false;
                break;
            }
        }
        if (check) {
            toCheck.add(router);
        }
    }
    // Ensure the router never receives traffic and then drops the traffic
    BoolExpr someBlackHole = ctx.mkBool(false);
    for (String router : toCheck) {
        Map<GraphEdge, BoolExpr> edges = slice.getSymbolicDecisions().getDataForwarding().get(router);
        BoolExpr doesNotFwd = ctx.mkBool(true);
        for (Map.Entry<GraphEdge, BoolExpr> entry : edges.entrySet()) {
            BoolExpr dataFwd = entry.getValue();
            doesNotFwd = ctx.mkAnd(doesNotFwd, ctx.mkNot(dataFwd));
        }
        BoolExpr isFwdTo = ctx.mkBool(false);
        Set<String> neighbors = graph.getNeighbors().get(router);
        for (String n : neighbors) {
            for (Map.Entry<GraphEdge, BoolExpr> entry : slice.getSymbolicDecisions().getDataForwarding().get(n).entrySet()) {
                GraphEdge ge = entry.getKey();
                BoolExpr fwd = entry.getValue();
                if (router.equals(ge.getPeer())) {
                    isFwdTo = ctx.mkOr(isFwdTo, fwd);
                }
            }
        }
        someBlackHole = ctx.mkOr(someBlackHole, ctx.mkAnd(isFwdTo, doesNotFwd));
    }
    enc.add(someBlackHole);
    VerificationResult result = enc.verify().getFirst();
    return new SmtOneAnswerElement(result);
}

Example 65 with BoolExpr

use of com.microsoft.z3.BoolExpr in project batfish by batfish.

the class PropertyChecker method ignoredDestinations.

/*
   * Creates a boolean variable representing destinations we don't want
   * to consider due to local differences.
   */
private BoolExpr ignoredDestinations(Context ctx, EncoderSlice e1, String r1, Configuration conf1) {
    BoolExpr validDest = ctx.mkBool(true);
    for (Protocol proto1 : e1.getProtocols().get(r1)) {
        Set<Prefix> prefixes = Graph.getOriginatedNetworks(conf1, proto1);
        BoolExpr dest = e1.relevantOrigination(prefixes);
        validDest = ctx.mkAnd(validDest, ctx.mkNot(dest));
    }
    return validDest;
}