示例#1
0
文件: Cache.java 项目: lemmy/dnsjava
 public boolean clean() {
   Iterator it = names();
   while (it.hasNext()) {
     Name name;
     try {
       name = (Name) it.next();
     } catch (ConcurrentModificationException e) {
       return false;
     }
     Object[] elements = findExactSets(name);
     for (int i = 0; i < elements.length; i++) {
       Element element = (Element) elements[i];
       if (element.expired()) removeSet(name, element.getType(), element);
     }
   }
   return true;
 }
示例#2
0
文件: Cache.java 项目: lemmy/dnsjava
  /**
   * Looks up Records in the Cache. This follows CNAMEs and handles negatively cached data.
   *
   * @param name The name to look up
   * @param type The type to look up
   * @param minCred The minimum acceptable credibility
   * @return A SetResponse object
   * @see SetResponse
   * @see Credibility
   */
  public SetResponse lookupRecords(Name name, short type, byte minCred) {
    SetResponse cr = null;
    boolean verbose = Options.check("verbosecache");
    Object o = lookup(name, type);

    if (verbose) logLookup(name, type, "Starting");

    if (o == null || o == NXRRSET) {
      /*
       * The name exists, but the type was not found.  Or, the
       * name does not exist and no parent does either.  Punt.
       */
      if (verbose) logLookup(name, type, "no information found");
      return SetResponse.ofType(SetResponse.UNKNOWN);
    }

    Object[] objects;
    if (o instanceof Element) objects = new Object[] {o};
    else objects = (Object[]) o;

    int nelements = 0;
    for (int i = 0; i < objects.length; i++) {
      Element element = (Element) objects[i];
      if (element.expired()) {
        if (verbose) {
          logLookup(name, type, element.toString());
          logLookup(name, type, "expired: ignoring");
        }
        removeSet(name, type, element);
        objects[i] = null;
      } else if (element.credibility < minCred) {
        if (verbose) {
          logLookup(name, type, element.toString());
          logLookup(name, type, "not credible: ignoring");
        }
        objects[i] = null;
      } else {
        nelements++;
      }
    }
    if (nelements == 0) {
      /* We have data, but can't use it.  Punt. */
      if (verbose) logLookup(name, type, "no useful data found");
      return SetResponse.ofType(SetResponse.UNKNOWN);
    }

    /*
     * We have something at the name.  It could be the answer,
     * a CNAME, DNAME, or NS, or a negative cache entry.
     *
     * Ignore wildcards, since it's pretty unlikely that any will be
     * cached.  The occasional extra query is easily balanced by the
     * reduced number of lookups.
     */

    for (int i = 0; i < objects.length; i++) {
      if (objects[i] == null) continue;
      Element element = (Element) objects[i];
      if (verbose) logLookup(name, type, element.toString());
      RRset rrset = null;
      if (element instanceof PositiveElement) rrset = ((PositiveElement) element).rrset;

      /* Is this a negatively cached entry? */
      if (rrset == null) {
        /*
         * If this is an NXDOMAIN entry, return NXDOMAIN.
         */
        if (element.getType() == 0) {
          if (verbose) logLookup(name, type, "NXDOMAIN");
          return SetResponse.ofType(SetResponse.NXDOMAIN);
        }

        /*
         * If we're not looking for type ANY, return NXRRSET.
         * Otherwise ignore this.
         */
        if (type != Type.ANY) {
          if (verbose) logLookup(name, type, "NXRRSET");
          return SetResponse.ofType(SetResponse.NXRRSET);
        } else {
          if (verbose) logLookup(name, type, "ANY query; " + "ignoring NXRRSET");
          continue;
        }
      }

      short rtype = rrset.getType();
      Name rname = rrset.getName();
      if (name.equals(rname)) {
        if (type != Type.CNAME && type != Type.ANY && rtype == Type.CNAME) {
          if (verbose) logLookup(name, type, "cname");
          return new SetResponse(SetResponse.CNAME, rrset);
        } else if (type != Type.NS && type != Type.ANY && rtype == Type.NS) {
          if (verbose) logLookup(name, type, "exact delegation");
          return new SetResponse(SetResponse.DELEGATION, rrset);
        } else {
          if (verbose) logLookup(name, type, "exact match");
          if (cr == null) cr = new SetResponse(SetResponse.SUCCESSFUL);
          cr.addRRset(rrset);
        }
      } else if (name.subdomain(rname)) {
        if (rtype == Type.DNAME) {
          if (verbose) logLookup(name, type, "dname");
          return new SetResponse(SetResponse.DNAME, rrset);
        } else if (rtype == Type.NS) {
          if (verbose) logLookup(name, type, "parent delegation");
          return new SetResponse(SetResponse.DELEGATION, rrset);
        } else {
          if (verbose)
            logLookup(name, type, "ignoring rrset (" + rname + " " + Type.string(rtype) + ")");
        }
      } else {
        if (verbose)
          logLookup(name, type, "ignoring rrset (" + rname + " " + Type.string(rtype) + ")");
      }
    }

    /*
     * As far as I can tell, the only legitimate time cr will be null is
     * if we queried for ANY and only saw negative responses, but not an
     * NXDOMAIN.  Return UNKNOWN.
     */
    if (cr == null && type == Type.ANY) return SetResponse.ofType(SetResponse.UNKNOWN);
    else if (cr == null)
      throw new IllegalStateException(
          "looking up (" + name + " " + Type.string(type) + "): " + "cr == null.");
    return cr;
  }