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

Example 56 with Context

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

the class PropertyAdder method allEqual.

static BoolExpr allEqual(Context ctx, List<Expr> exprs) {
    BoolExpr acc = ctx.mkBool(true);
    if (exprs.size() > 1) {
        for (int i = 0; i < exprs.size() - 1; i++) {
            Expr x = exprs.get(i);
            Expr y = exprs.get(i + 1);
            acc = ctx.mkAnd(acc, ctx.mkEq(x, y));
        }
    }
    return acc;
}

Example 57 with Context

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

the class PropertyAdder method instrumentReachability.

/*
   * Add reachability information to the network for a destination edge.
   * Each router will have a boolean variable determining if it can reach
   * the destination. A router is reachable if it has some neighbor that
   * is also reachable.
   */
Map<String, BoolExpr> instrumentReachability(Set<GraphEdge> ges) {
    Context ctx = _encoderSlice.getCtx();
    Solver solver = _encoderSlice.getSolver();
    EncoderSlice slice = _encoderSlice;
    Map<String, BoolExpr> reachableVars = new HashMap<>();
    Map<String, ArithExpr> idVars = new HashMap<>();
    initializeReachabilityVars(slice, ctx, solver, reachableVars, idVars);
    Graph g = _encoderSlice.getGraph();
    for (Entry<String, List<GraphEdge>> entry : g.getEdgeMap().entrySet()) {
        String router = entry.getKey();
        List<GraphEdge> edges = entry.getValue();
        ArithExpr id = idVars.get(router);
        // Add the base case, reachable if we forward to a directly connected interface
        BoolExpr hasDirectRoute = ctx.mkFalse();
        BoolExpr isAbsorbed = ctx.mkFalse();
        SymbolicRoute r = _encoderSlice.getBestNeighborPerProtocol(router, Protocol.CONNECTED);
        for (GraphEdge ge : edges) {
            if (!ge.isAbstract() && ges.contains(ge)) {
                // If a host, consider reachable
                if (g.isHost(router)) {
                    hasDirectRoute = ctx.mkTrue();
                    break;
                }
                // Reachable if we leave the network
                if (ge.getPeer() == null) {
                    BoolExpr fwdIface = _encoderSlice.getForwardsAcross().get(ge.getRouter(), ge);
                    assert (fwdIface != null);
                    hasDirectRoute = ctx.mkOr(hasDirectRoute, fwdIface);
                }
                // Also reachable if connected route and we use it despite not forwarding
                if (r != null) {
                    BitVecExpr dstIp = _encoderSlice.getSymbolicPacket().getDstIp();
                    BitVecExpr ip = ctx.mkBV(ge.getStart().getAddress().getIp().asLong(), 32);
                    BoolExpr reach = ctx.mkAnd(r.getPermitted(), ctx.mkEq(dstIp, ip));
                    isAbsorbed = ctx.mkOr(isAbsorbed, reach);
                }
            }
        }
        // Add the recursive case, where it is reachable through a neighbor
        BoolExpr recursive = recursiveReachability(ctx, slice, edges, idVars, router, id);
        BoolExpr guard = ctx.mkOr(hasDirectRoute, isAbsorbed);
        BoolExpr cond = slice.mkIf(guard, ctx.mkEq(id, ctx.mkInt(1)), recursive);
        solver.add(cond);
    }
    return reachableVars;
}

Example 58 with Context

use of com.microsoft.z3.Context 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 59 with Context

use of com.microsoft.z3.Context 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 60 with Context

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

the class PropertyChecker method addEnvironmentConstraints.

private void addEnvironmentConstraints(Encoder enc, EnvironmentType t) {
    LogicalGraph lg = enc.getMainSlice().getLogicalGraph();
    Context ctx = enc.getCtx();
    switch(t) {
        case ANY:
            break;
        case NONE:
            for (SymbolicRoute vars : lg.getEnvironmentVars().values()) {
                enc.add(ctx.mkNot(vars.getPermitted()));
            }
            break;
        case SANE:
            for (SymbolicRoute vars : lg.getEnvironmentVars().values()) {
                enc.add(ctx.mkLe(vars.getMetric(), ctx.mkInt(50)));
            }
            break;
        default:
            break;
    }
}