1 files changed, 72 insertions, 0 deletions
diff --git a/src/lib/dhcp/pkt_filter.cc b/src/lib/dhcp/pkt_filter.cc
new file mode 100644
index 0000000..770d71d
--- /dev/null
+++ b/src/lib/dhcp/pkt_filter.cc
@@ -0,0 +1,72 @@
+// Copyright (C) 2013-2019 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 <dhcp/iface_mgr.h>
+#include <dhcp/pkt_filter.h>
+
+#include <sys/socket.h>
+#include <fcntl.h>
+
+namespace isc {
+namespace dhcp {
+
+int
+PktFilter::openFallbackSocket(const isc::asiolink::IOAddress& addr,
+                              const uint16_t port) {
+    // Create socket.
+    int sock = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sock < 0) {
+        isc_throw(SocketConfigError, "failed to create fallback socket for"
+                  " address " << addr << ", port " << port
+                  << ", reason: " << strerror(errno));
+    }
+    // Set the close-on-exec flag.
+    if (fcntl(sock, F_SETFD, FD_CLOEXEC) < 0) {
+        close(sock);
+        isc_throw(SocketConfigError, "Failed to set close-on-exec flag"
+                  << " on fallback socket for address " << addr
+                  << ", port " << port
+                  << ", reason: " << strerror(errno));
+    }
+    // Bind the socket to a specified address and port.
+    struct sockaddr_in addr4;
+    memset(&addr4, 0, sizeof(addr4));
+    addr4.sin_family = AF_INET;
+    addr4.sin_addr.s_addr = htonl(addr.toUint32());
+    addr4.sin_port = htons(port);
+
+    if (bind(sock, reinterpret_cast<struct sockaddr*>(&addr4),
+             sizeof(addr4)) < 0) {
+        // Get the error message immediately after the bind because the
+        // invocation to close() below would override the errno.
+        char* errmsg = strerror(errno);
+        // Remember to close the socket if we failed to bind it.
+        close(sock);
+        isc_throw(SocketConfigError, "failed to bind fallback socket to"
+                  " address " << addr << ", port " << port
+                  << ", reason: " << errmsg
+                  << " - is another DHCP server running?");
+    }
+
+    // Set socket to non-blocking mode. This is to prevent the read from the
+    // fallback socket to block message processing on the primary socket.
+    if (fcntl(sock, F_SETFL, O_NONBLOCK) != 0) {
+        // Get the error message immediately after the bind because the
+        // invocation to close() below would override the errno.
+        char* errmsg = strerror(errno);
+        close(sock);
+        isc_throw(SocketConfigError, "failed to set SO_NONBLOCK option on the"
+                  " fallback socket, bound to " << addr << ", port "
+                  << port << ", reason: " << errmsg);
+    }
+    // Successfully created and bound a fallback socket. Return a descriptor.
+    return (sock);
+}
+
+
+} // end of isc::dhcp namespace
+} // end of isc namespace