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diff --git a/src/lib/dhcp/socket_info.h b/src/lib/dhcp/socket_info.h
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+++ b/src/lib/dhcp/socket_info.h
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+// Copyright (C) 2018 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/.
+
+#ifndef DHCP_SOCKET_INFO_H
+#define DHCP_SOCKET_INFO_H
+
+#include <asiolink/io_address.h>
+#include <cstdint>
+
+
+namespace isc {
+
+namespace dhcp {
+
+/// Holds information about socket.
+struct SocketInfo {
+
+    isc::asiolink::IOAddress addr_; /// bound address
+    uint16_t port_;   /// socket port
+    uint16_t family_; /// IPv4 or IPv6
+
+    /// @brief Socket descriptor (a.k.a. primary socket).
+    int sockfd_;
+
+    /// @brief Fallback socket descriptor.
+    ///
+    /// This socket descriptor holds the handle to the fallback socket.
+    /// The fallback socket is created when there is a need for the regular
+    /// datagram socket to be bound to an IP address and port, besides
+    /// primary socket (sockfd_) which is actually used to receive and process
+    /// the DHCP messages. The fallback socket (if exists) is always associated
+    /// with the primary socket. In particular, the need for the fallback socket
+    /// arises when raw socket is a primary one. When primary socket is open,
+    /// it is bound to an interface not the address and port. The implications
+    /// include the possibility that the other process (e.g. the other instance
+    /// of DHCP server) will bind to the same address and port through which the
+    /// raw socket receives the DHCP messages. Another implication is that the
+    /// kernel, being unaware of the DHCP server operating through the raw
+    /// socket, will respond with the ICMP "Destination port unreachable"
+    /// messages when DHCP messages are only received through the raw socket.
+    /// In order to workaround the issues mentioned here, the fallback socket
+    /// should be opened so as/ the kernel is aware that the certain address
+    /// and port is in use.
+    ///
+    /// The fallback description is supposed to be set to a negative value if
+    /// the fallback socket is closed (not open).
+    int fallbackfd_;
+
+    /// @brief SocketInfo constructor.
+    ///
+    /// @param addr An address the socket is bound to.
+    /// @param port A port the socket is bound to.
+    /// @param sockfd Socket descriptor.
+    /// @param fallbackfd A descriptor of the fallback socket.
+    SocketInfo(const isc::asiolink::IOAddress& addr, const uint16_t port,
+               const int sockfd, const int fallbackfd = -1)
+        : addr_(addr), port_(port), family_(addr.getFamily()),
+          sockfd_(sockfd), fallbackfd_(fallbackfd) { }
+
+};
+
+}; // namespace isc::dhcp
+}; // namespace isc
+
+#endif // DHCP_SOCKET_INFO_H