1 files changed, 324 insertions, 0 deletions
diff --git a/src/lib/d2srv/dns_client.cc b/src/lib/d2srv/dns_client.cc
new file mode 100644
index 0000000..5798207
--- /dev/null
+++ b/src/lib/d2srv/dns_client.cc
@@ -0,0 +1,324 @@
+// Copyright (C) 2013-2021 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include <config.h>
+
+#include <d2srv/d2_log.h>
+#include <d2srv/dns_client.h>
+#include <dns/messagerenderer.h>
+#include <stats/stats_mgr.h>
+#include <limits>
+
+namespace isc {
+namespace d2 {
+
+namespace {
+
+// OutputBuffer objects are pre-allocated before data is written to them.
+// This is a default number of bytes for the buffers we create within
+// DNSClient class.
+const size_t DEFAULT_BUFFER_SIZE = 128;
+
+}
+
+using namespace isc::util;
+using namespace isc::asiolink;
+using namespace isc::asiodns;
+using namespace isc::dns;
+using namespace isc::stats;
+
+// This class provides the implementation for the DNSClient. This allows for
+// the separation of the DNSClient interface from the implementation details.
+// Currently, implementation uses IOFetch object to handle asynchronous
+// communication with the DNS. This design may be revisited in the future. If
+// implementation is changed, the DNSClient API will remain unchanged thanks
+// to this separation.
+class DNSClientImpl : public asiodns::IOFetch::Callback {
+public:
+    /// @brief A buffer holding response from a DNS.
+    util::OutputBufferPtr in_buf_;
+
+    /// A caller-supplied object which will hold the parsed response from DNS.
+    /// The response object is (or descends from) isc::dns::Message and is
+    /// populated using Message::fromWire().  This method may only be called
+    /// once in the lifetime of a Message instance.  Therefore, response_ is a
+    /// pointer reference thus allowing this class to replace the object
+    /// pointed to with a new Message instance each time a message is
+    /// received. This allows a single DNSClientImpl instance to be used for
+    /// multiple, sequential IOFetch calls. (@todo Trac# 3286 has been opened
+    /// against dns::Message::fromWire.  Should the behavior of fromWire change
+    /// the behavior here with could be reexamined).
+    D2UpdateMessagePtr& response_;
+
+    /// @brief A caller-supplied external callback which is invoked when DNS
+    /// message exchange is complete or interrupted.
+    DNSClient::Callback* callback_;
+
+    /// @brief A Transport Layer protocol used to communicate with a DNS.
+    DNSClient::Protocol proto_;
+
+    /// @brief TSIG context used to sign outbound and verify inbound messages.
+    dns::TSIGContextPtr tsig_context_;
+
+    /// @brief TSIG key name for stats.
+    std::string tsig_key_name_;
+
+    /// @brief Constructor.
+    ///
+    /// @param response_placeholder Message object pointer which will be updated
+    /// with dynamically allocated object holding the DNS server's response.
+    /// @param callback Pointer to an object implementing @c DNSClient::Callback
+    /// class. This object will be called when DNS message exchange completes or
+    /// if an error occurs. NULL value disables callback invocation.
+    /// @param proto caller's preference regarding Transport layer protocol to
+    /// be used by DNS Client to communicate with a server.
+    DNSClientImpl(D2UpdateMessagePtr& response_placeholder,
+                  DNSClient::Callback* callback,
+                  const DNSClient::Protocol proto);
+
+    /// @brief Destructor.
+    virtual ~DNSClientImpl();
+
+    /// @brief This internal callback is called when the DNS update message
+    /// exchange is complete. It further invokes the external callback provided
+    /// by a caller. Before external callback is invoked, an object of the
+    /// D2UpdateMessage type, representing a response from the server is set.
+    virtual void operator()(asiodns::IOFetch::Result result);
+
+    /// @brief Starts asynchronous DNS Update using TSIG.
+    ///
+    /// @param io_service IO service to be used to run the message exchange.
+    /// @param ns_addr DNS server address.
+    /// @param ns_port DNS server port.
+    /// @param update A DNS Update message to be sent to the server.
+    /// @param wait A timeout (in milliseconds) for the response. If a response
+    /// is not received within the timeout, exchange is interrupted. This value
+    /// must not exceed maximal value for 'int' data type.
+    /// @param tsig_key A pointer to an @c D2TsigKeyPtr object that will
+    /// (if not null) be used to sign the DNS Update message and verify the
+    /// response.
+    void doUpdate(asiolink::IOService& io_service,
+                  const asiolink::IOAddress& ns_addr,
+                  const uint16_t ns_port,
+                  D2UpdateMessage& update,
+                  const unsigned int wait,
+                  const D2TsigKeyPtr& tsig_key);
+
+    /// @brief This function maps the IO error to the DNSClient error.
+    ///
+    /// @param result The IOFetch result to be converted to DNSClient status.
+    /// @return The DNSClient status corresponding to the IOFetch result.
+    DNSClient::Status getStatus(const asiodns::IOFetch::Result result);
+
+    /// @brief This function updates statistics.
+    ///
+    /// @param stat The statistic name to be incremented.
+    /// @param update_key The flag indicating if the key statistics should also
+    /// be updated.
+    void incrStats(const std::string& stat, bool update_key = true);
+};
+
+DNSClientImpl::DNSClientImpl(D2UpdateMessagePtr& response_placeholder,
+                             DNSClient::Callback* callback,
+                             const DNSClient::Protocol proto)
+    : in_buf_(new OutputBuffer(DEFAULT_BUFFER_SIZE)),
+      response_(response_placeholder), callback_(callback), proto_(proto) {
+
+    // Response should be an empty pointer. It gets populated by the
+    // operator() method.
+    if (response_) {
+        isc_throw(isc::BadValue, "Response buffer pointer should be null");
+    }
+
+    // @todo Currently we only support UDP. The support for TCP is planned for
+    // the future release.
+    if (proto_ == DNSClient::TCP) {
+        isc_throw(isc::NotImplemented, "TCP is currently not supported as a"
+                  << " Transport protocol for DNS Updates; please use UDP");
+    }
+
+    // Given that we already eliminated the possibility that TCP is used, it
+    // would be sufficient  to check that (proto != DNSClient::UDP). But, once
+    // support TCP is added the check above will disappear and the extra check
+    // will be needed here anyway.
+    // Note that cascaded check is used here instead of:
+    //   if (proto_ != DNSClient::TCP && proto_ != DNSClient::UDP)..
+    // because some versions of GCC compiler complain that check above would
+    // be always 'false' due to limited range of enumeration. In fact, it is
+    // possible to pass out of range integral value through enum and it should
+    // be caught here.
+    if (proto_ != DNSClient::TCP) {
+        if (proto_ != DNSClient::UDP) {
+            isc_throw(isc::NotImplemented, "invalid transport protocol type '"
+                      << proto_ << "' specified for DNS Updates");
+        }
+    }
+}
+
+DNSClientImpl::~DNSClientImpl() {
+}
+
+void
+DNSClientImpl::operator()(asiodns::IOFetch::Result result) {
+    // Get the status from IO. If no success, we just call user's callback
+    // and pass the status code.
+    DNSClient::Status status = getStatus(result);
+    if (status == DNSClient::SUCCESS) {
+        // Allocate a new response message. (Note that Message::fromWire
+        // may only be run once per message, so we need to start fresh
+        // each time.)
+        response_.reset(new D2UpdateMessage(D2UpdateMessage::INBOUND));
+
+        // Server's response may be corrupted. In such case, fromWire will
+        // throw an exception. We want to catch this exception to return
+        // appropriate status code to the caller and log this event.
+        try {
+            response_->fromWire(in_buf_->getData(), in_buf_->getLength(),
+                                tsig_context_.get());
+            incrStats("update-success");
+        } catch (const isc::Exception& ex) {
+            status = DNSClient::INVALID_RESPONSE;
+            LOG_DEBUG(d2_to_dns_logger, isc::log::DBGLVL_TRACE_DETAIL,
+                      DHCP_DDNS_INVALID_RESPONSE).arg(ex.what());
+            incrStats("update-error");
+        }
+
+        if (tsig_context_) {
+            // Context is a one-shot deal, get rid of it.
+            tsig_context_.reset();
+        }
+    } else if (status == DNSClient::TIMEOUT) {
+        incrStats("update-timeout");
+    } else {
+        incrStats("update-error");
+    }
+
+    // Once we are done with internal business, let's call a callback supplied
+    // by a caller.
+    if (callback_ != NULL) {
+        (*callback_)(status);
+    }
+}
+
+DNSClient::Status
+DNSClientImpl::getStatus(const asiodns::IOFetch::Result result) {
+    switch (result) {
+    case IOFetch::SUCCESS:
+        return (DNSClient::SUCCESS);
+
+    case IOFetch::TIME_OUT:
+        return (DNSClient::TIMEOUT);
+
+    case IOFetch::STOPPED:
+        return (DNSClient::IO_STOPPED);
+
+    default:
+        ;
+    }
+    return (DNSClient::OTHER);
+}
+
+void
+DNSClientImpl::doUpdate(asiolink::IOService& io_service,
+                        const IOAddress& ns_addr,
+                        const uint16_t ns_port,
+                        D2UpdateMessage& update,
+                        const unsigned int wait,
+                        const D2TsigKeyPtr& tsig_key) {
+    // The underlying implementation which we use to send DNS Updates uses
+    // signed integers for timeout. If we want to avoid overflows we need to
+    // respect this limitation here.
+    if (wait > DNSClient::getMaxTimeout()) {
+        isc_throw(isc::BadValue, "A timeout value for DNS Update request must"
+                  " not exceed " << DNSClient::getMaxTimeout()
+                  << ". Provided timeout value is '" << wait << "'");
+    }
+
+    // Create a TSIG context if we have a key, otherwise clear the context
+    // pointer.  Message marshalling uses non-null context is the indicator
+    // that TSIG should be used.
+    if (tsig_key) {
+        tsig_context_ = tsig_key->createContext();
+        tsig_key_name_ = tsig_key->getKeyName().toText();
+    } else {
+        tsig_context_.reset();
+        tsig_key_name_.clear();
+    }
+
+    // A renderer is used by the toWire function which creates the on-wire data
+    // from the DNS Update message. A renderer has its internal buffer where it
+    // renders data by default. However, this buffer can't be directly accessed.
+    // Fortunately, the renderer's API accepts user-supplied buffers. So, let's
+    // create our own buffer and pass it to the renderer so as the message is
+    // rendered to this buffer. Finally, we pass this buffer to IOFetch.
+    dns::MessageRenderer renderer;
+    OutputBufferPtr msg_buf(new OutputBuffer(DEFAULT_BUFFER_SIZE));
+    renderer.setBuffer(msg_buf.get());
+
+    // Render DNS Update message. This may throw a bunch of exceptions if
+    // invalid message object is given.
+    update.toWire(renderer, tsig_context_.get());
+
+    // IOFetch has all the mechanisms that we need to perform asynchronous
+    // communication with the DNS server. The last but one argument points to
+    // this object as a completion callback for the message exchange. As a
+    // result operator()(Status) will be called.
+
+    // Timeout value is explicitly cast to the int type to avoid warnings about
+    // overflows when doing implicit cast. It should have been checked by the
+    // caller that the unsigned timeout value will fit into int.
+    IOFetch io_fetch(IOFetch::UDP, io_service, msg_buf, ns_addr, ns_port,
+                     in_buf_, this, static_cast<int>(wait));
+
+    // Post the task to the task queue in the IO service. Caller will actually
+    // run these tasks by executing IOService::run.
+    io_service.post(io_fetch);
+
+    // Update sent statistics.
+    incrStats("update-sent");
+    if (tsig_key) {
+        incrStats("update-signed", false);
+    } else {
+        incrStats("update-unsigned", false);
+    }
+}
+
+void
+DNSClientImpl::incrStats(const std::string& stat, bool update_key) {
+    StatsMgr& mgr = StatsMgr::instance();
+    mgr.addValue(stat, static_cast<int64_t>(1));
+    if (update_key && !tsig_key_name_.empty()) {
+        mgr.addValue(StatsMgr::generateName("key", tsig_key_name_, stat),
+                     static_cast<int64_t>(1));
+    }
+}
+
+DNSClient::DNSClient(D2UpdateMessagePtr& response_placeholder,
+                     Callback* callback, const DNSClient::Protocol proto)
+    : impl_(new DNSClientImpl(response_placeholder, callback, proto)) {
+}
+
+DNSClient::~DNSClient() {
+}
+
+unsigned int
+DNSClient::getMaxTimeout() {
+    static const unsigned int max_timeout = std::numeric_limits<int>::max();
+    return (max_timeout);
+}
+
+void
+DNSClient::doUpdate(asiolink::IOService& io_service,
+                    const IOAddress& ns_addr,
+                    const uint16_t ns_port,
+                    D2UpdateMessage& update,
+                    const unsigned int wait,
+                    const D2TsigKeyPtr& tsig_key) {
+    impl_->doUpdate(io_service, ns_addr, ns_port, update, wait, tsig_key);
+}
+
+} // namespace d2
+} // namespace isc