1 files changed, 165 insertions, 0 deletions
diff --git a/src/lib/util/watch_socket.cc b/src/lib/util/watch_socket.cc
new file mode 100644
index 0000000..6ffb396
--- /dev/null
+++ b/src/lib/util/watch_socket.cc
@@ -0,0 +1,165 @@
+// Copyright (C) 2014-2020 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/.
+
+/// @file watch_socket.cc
+
+#include <config.h>
+
+//#include <dhcp_ddns/dhcp_ddns_log.h>
+#include <util/watch_socket.h>
+
+#include <fcntl.h>
+#include <errno.h>
+#include <sstream>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+namespace isc {
+namespace util {
+
+
+const int WatchSocket::SOCKET_NOT_VALID;
+const uint32_t WatchSocket::MARKER;
+
+WatchSocket::WatchSocket()
+    : source_(SOCKET_NOT_VALID), sink_(SOCKET_NOT_VALID) {
+    // Open the pipe.
+    int fds[2];
+    if (pipe(fds)) {
+        const char* errstr = strerror(errno);
+        isc_throw(WatchSocketError, "Cannot construct pipe: " << errstr);
+    }
+
+    source_ = fds[1];
+    sink_ = fds[0];
+
+    if (fcntl(source_, F_SETFD, FD_CLOEXEC)) {
+        const char* errstr = strerror(errno);
+        isc_throw(WatchSocketError, "Cannot set source to close-on-exec: "
+                                     << errstr);
+    }
+
+    if (fcntl(sink_, F_SETFD, FD_CLOEXEC)) {
+        const char* errstr = strerror(errno);
+        isc_throw(WatchSocketError, "Cannot set sink to close-on-exec: "
+                                     << errstr);
+    }
+
+    if (fcntl(sink_, F_SETFL, O_NONBLOCK)) {
+        const char* errstr = strerror(errno);
+        isc_throw(WatchSocketError, "Cannot set sink to non-blocking: "
+                                     << errstr);
+    }
+}
+
+WatchSocket::~WatchSocket() {
+    closeSocket();
+}
+
+void
+WatchSocket::markReady() {
+    // Make sure it hasn't been orphaned!  Otherwise we may get SIGPIPE.  We
+    // use fcntl to check as select() on some systems may show it as ready to
+    // read.
+    if (fcntl(sink_, F_GETFL) < 0) {
+        closeSocket();
+        isc_throw(WatchSocketError, "WatchSocket markReady failed:"
+                  " select_fd was closed!");
+    }
+
+    if (!isReady()) {
+        int nbytes = write (source_, &MARKER, sizeof(MARKER));
+        if (nbytes != sizeof(MARKER)) {
+            // If there's an error get the error message than close
+            // the pipe.  This should ensure any further use of the socket
+            // or testing the fd with select_fd will fail.
+            const char* errstr = strerror(errno);
+            closeSocket();
+            isc_throw(WatchSocketError, "WatchSocket markReady failed:"
+                      << " bytes written: " << nbytes << " : " << errstr);
+        }
+    }
+}
+
+bool
+WatchSocket::isReady() {
+    // Report it as not ready rather than error here.
+    if (sink_ == SOCKET_NOT_VALID) {
+        return (false);
+    }
+
+    // Use ioctl FIONREAD vs polling select as it is faster.
+    int len;
+    int result = ioctl(sink_, FIONREAD, &len);
+    // Return true only if read ready, treat error same as not ready.
+    return ((result == 0) && (len > 0));
+}
+
+void
+WatchSocket::clearReady() {
+    if (isReady()) {
+        uint32_t buf = 0;
+        int nbytes = read (sink_, &buf, sizeof(buf));
+        if ((nbytes != sizeof(MARKER) || (buf != MARKER))) {
+            // If there's an error get the error message than close
+            // the pipe.  This should ensure any further use of the socket
+            // or testing the fd with select_fd will fail.
+            const char* errstr = strerror(errno);
+            closeSocket();
+            isc_throw(WatchSocketError, "WatchSocket clearReady failed: "
+                      "bytes read: " << nbytes << " : "
+                      "value read: " << buf << " error :" << errstr);
+        }
+    }
+}
+
+bool
+WatchSocket::closeSocket(std::string& error_string) {
+    std::ostringstream s;
+    // Close the pipe fds.  Technically a close can fail (hugely unlikely)
+    // but there's no recovery for it either.  If one does fail we log it
+    // and go on. Plus this is called by the destructor and no one likes
+    // destructors that throw.
+    if (source_ != SOCKET_NOT_VALID) {
+        if (close(source_)) {
+            // An error occurred.
+            s << "Could not close source: " << strerror(errno);
+        }
+
+        source_ = SOCKET_NOT_VALID;
+    }
+
+    if (sink_ != SOCKET_NOT_VALID) {
+        if (close(sink_)) {
+            // An error occurred.
+            if (error_string.empty()) {
+                s << "could not close sink: " << strerror(errno);
+            }
+        }
+
+        sink_ = SOCKET_NOT_VALID;
+    }
+
+    error_string = s.str();
+
+    // If any errors have been reported, return false.
+    return (error_string.empty() ? true : false);
+}
+
+void
+WatchSocket::closeSocket() {
+    std::string error_string;
+    closeSocket(error_string);
+}
+
+int
+WatchSocket::getSelectFd() {
+    return (sink_);
+}
+
+} // namespace isc::util
+} // namespace isc