proto_dhcpv4_udp.c

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/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: 2743f5a4b80d0ee71c48e3b0d41bdcb422f7d03f $
 * @file proto_dhcpv4_udp.c
 * @brief DHCPv4 handler for UDP.
 *
 * @copyright 2018 The FreeRADIUS server project.
 * @copyright 2018 Alan DeKok (aland@deployingradius.com)
 */
#define LOG_PREFIX "proto_dhcpv4_udp"
 
#include <netdb.h>
#include <freeradius-devel/arp/arp.h>
#include <freeradius-devel/server/protocol.h>
#include <freeradius-devel/util/udp.h>
#include <freeradius-devel/util/trie.h>
#include <freeradius-devel/io/application.h>
#include <freeradius-devel/io/listen.h>
#include <freeradius-devel/io/schedule.h>
#include <freeradius-devel/protocol/dhcpv4/freeradius.internal.h>
#include "proto_dhcpv4.h"
 
extern fr_app_io_t proto_dhcpv4_udp;
 
typedef struct {
        char const                      *name;                  //!< socket name
        int                             sockfd;
 
        fr_io_address_t                 *connection;            //!< for connected sockets.
 
        fr_stats_t                      stats;                  //!< statistics for this socket
}  proto_dhcpv4_udp_thread_t;
 
typedef struct {
        CONF_SECTION                    *cs;                    //!< our configuration
 
        fr_ipaddr_t                     ipaddr;                 //!< IP address to listen on.
 
        fr_ipaddr_t                     src_ipaddr;             //!< IP address to source replies
 
        char const                      *interface;             //!< Interface to bind to.
        char const                      *port_name;             //!< Name of the port for getservent().
 
        uint32_t                        recv_buff;              //!< How big the kernel's receive buffer should be.
 
        uint32_t                        max_packet_size;        //!< for message ring buffer.
        uint32_t                        max_attributes;         //!< Limit maximum decodable attributes.
 
        uint16_t                        port;                   //!< Port to listen on.
        uint16_t                        client_port;            //!< Client port to reply to.
 
        bool                            broadcast;              //!< whether we listen for broadcast packets
 
        bool                            recv_buff_is_set;       //!< Whether we were provided with a receive
                                                                //!< buffer value.
        bool                            dynamic_clients;        //!< whether we have dynamic clients
 
        fr_client_list_t                        *clients;               //!< local clients
        fr_client_t                     *default_client;        //!< default 0/0 client
 
        fr_trie_t                       *trie;                  //!< for parsed networks
        fr_ipaddr_t                     *allow;                 //!< allowed networks for dynamic clients
        fr_ipaddr_t                     *deny;                  //!< denied networks for dynamic clients
} proto_dhcpv4_udp_t;
 
 
static const conf_parser_t networks_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("allow", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_dhcpv4_udp_t, allow) },
        { FR_CONF_OFFSET_TYPE_FLAGS("deny", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_dhcpv4_udp_t, deny) },
 
        CONF_PARSER_TERMINATOR
};
 
 
static const conf_parser_t udp_listen_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("ipaddr", FR_TYPE_IPV4_ADDR, 0, proto_dhcpv4_udp_t, ipaddr) },
        { FR_CONF_OFFSET_TYPE_FLAGS("ipv4addr", FR_TYPE_IPV4_ADDR, 0, proto_dhcpv4_udp_t, ipaddr) },
 
        { FR_CONF_OFFSET_TYPE_FLAGS("src_ipaddr", FR_TYPE_COMBO_IP_ADDR, 0, proto_dhcpv4_udp_t, src_ipaddr) },
 
        { FR_CONF_OFFSET("interface", proto_dhcpv4_udp_t, interface) },
        { FR_CONF_OFFSET("port_name", proto_dhcpv4_udp_t, port_name) },
 
        { FR_CONF_OFFSET("port", proto_dhcpv4_udp_t, port) },
        { FR_CONF_OFFSET("client_port", proto_dhcpv4_udp_t, client_port) },
        { FR_CONF_OFFSET_IS_SET("recv_buff", FR_TYPE_UINT32, 0, proto_dhcpv4_udp_t, recv_buff) },
 
        { FR_CONF_OFFSET("broadcast", proto_dhcpv4_udp_t, broadcast) } ,
 
        { FR_CONF_OFFSET("dynamic_clients", proto_dhcpv4_udp_t, dynamic_clients) } ,
        { FR_CONF_POINTER("networks", 0, CONF_FLAG_SUBSECTION, NULL), .subcs = (void const *) networks_config },
 
        { FR_CONF_OFFSET("max_packet_size", proto_dhcpv4_udp_t, max_packet_size), .dflt = "4096" } ,
        { FR_CONF_OFFSET("max_attributes", proto_dhcpv4_udp_t, max_attributes), .dflt = STRINGIFY(DHCPV4_MAX_ATTRIBUTES) } ,
 
        CONF_PARSER_TERMINATOR
};
 
static fr_dict_t const *dict_dhcpv4;
 
extern fr_dict_autoload_t proto_dhcpv4_udp_dict[];
fr_dict_autoload_t proto_dhcpv4_udp_dict[] = {
        { .out = &dict_dhcpv4, .proto = "dhcpv4" },
        { NULL }
};
 
static fr_dict_attr_t const *attr_message_type;
static fr_dict_attr_t const *attr_dhcp_server_identifier;
 
extern fr_dict_attr_autoload_t proto_dhcpv4_udp_dict_attr[];
fr_dict_attr_autoload_t proto_dhcpv4_udp_dict_attr[] = {
        { .out = &attr_message_type, .name = "Message-Type", .type = FR_TYPE_UINT8, .dict = &dict_dhcpv4},
        { .out = &attr_dhcp_server_identifier, .name = "Server-Identifier", .type = FR_TYPE_IPV4_ADDR, .dict = &dict_dhcpv4},
        { NULL }
};
 
static ssize_t mod_read(fr_listen_t *li, void **packet_ctx, fr_time_t *recv_time_p, uint8_t *buffer, size_t buffer_len,
                         size_t *leftover)
{
        proto_dhcpv4_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv4_udp_thread_t);
        fr_io_address_t                 *address, **address_p;
 
        int                             flags;
        ssize_t                         data_size;
        size_t                          packet_len;
        uint8_t                         message_type;
        uint32_t                        xid, ipaddr;
        dhcp_packet_t                   *packet;
 
        *leftover = 0;          /* always for UDP */
 
        /*
         *      Where the addresses should go.  This is a special case
         *      for proto_dhcpv4.
         */
        address_p = (fr_io_address_t **) packet_ctx;
        address = *address_p;
 
        /*
         *      Tell udp_recv if we're connected or not.
         */
        flags = UDP_FLAGS_CONNECTED * (thread->connection != NULL);
 
        data_size = udp_recv(thread->sockfd, flags, &address->socket, buffer, buffer_len, recv_time_p);
        if (data_size < 0) {
                RATE_LIMIT_GLOBAL(PERROR, "Read error (%zd)", data_size);
                return data_size;
        }
 
        if (!data_size) {
                RATE_LIMIT_GLOBAL(WARN, "Got no data - ignoring");
                return 0;
        }
 
        /*
         *      @todo - make this take "&packet_len", as the DHCPv4
         *      packet may be smaller than the parent UDP packet.
         */
        if (!fr_dhcpv4_ok(buffer, data_size, &message_type, &xid)) {
                RATE_LIMIT_GLOBAL(PWARN, "Invalid packet - ignoring");
                return 0;
        }
 
        packet_len = data_size;
 
        /*
         *      We've seen a server reply to this port, but the giaddr
         *      is *not* our address.  Drop it.
         */
        packet = (dhcp_packet_t *) buffer;
        memcpy(&ipaddr, &packet->giaddr, 4);
        if ((packet->opcode == 2) && (ipaddr != address->socket.inet.dst_ipaddr.addr.v4.s_addr)) {
                DEBUG2("Ignoring server reply which was not meant for us (was for %pV).",
                       fr_box_ipaddr(address->socket.inet.dst_ipaddr));
                return 0;
        }
 
        /*
         *      proto_dhcpv4 sets the priority
         */
 
        /*
         *      Print out what we received.
         */
        DEBUG2("Received %s XID %08x length %d %s", dhcp_message_types[message_type], xid,
               (int) packet_len, thread->name);
 
        return packet_len;
}
 
 
static ssize_t mod_write(fr_listen_t *li, void *packet_ctx, UNUSED fr_time_t request_time,
                         uint8_t *buffer, size_t buffer_len, UNUSED size_t written)
{
        proto_dhcpv4_udp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv4_udp_t);
        proto_dhcpv4_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv4_udp_thread_t);
 
        fr_io_track_t                   *track = talloc_get_type_abort(packet_ctx, fr_io_track_t);
        proto_dhcpv4_track_t            *request = talloc_get_type_abort(track->packet, proto_dhcpv4_track_t);
        fr_socket_t                     socket;
 
        int                             flags;
        ssize_t                         data_size;
 
        /*
         *      @todo - share a stats interface with the parent?  or
         *      put the stats in the listener, so that proto_dhcpv4
         *      can update them, too.. <sigh>
         */
        thread->stats.total_responses++;
 
        flags = UDP_FLAGS_CONNECTED * (thread->connection != NULL);
 
        /*
         *      Swap src/dst IP/port
         */
        fr_socket_addr_swap(&socket, &track->address->socket);
 
        /*
         *      Figure out which kind of packet we're sending.
         */
        if (!thread->connection) {
                uint8_t const *code, *sid;
                dhcp_packet_t *packet = (dhcp_packet_t *) buffer;
#ifdef WITH_IFINDEX_IPADDR_RESOLUTION
                fr_ipaddr_t primary;
#endif
 
                /*
                 *      This isn't available in the packet header.
                 */
                code = fr_dhcpv4_packet_get_option(packet, buffer_len, attr_message_type);
                if (!code || (code[1] < 1) || (code[2] == 0) || (code[2] > FR_DHCP_LEASE_ACTIVE)) {
                        WARN("Silently discarding reply due to invalid or missing message type");
                        return 0;
                }
 
                /*
                 *      Set the source IP we'll use for sending the packets.
                 *
                 *      - if src_ipaddr is unicast, use that
                 *      - else if socket wasn't bound to *, then use that
                 *      - else if we have ifindex, get main IP from that interface and use that.
                 *      - else for offer/ack, look at option 54, for Server Identification and use that
                 *      - else leave source IP as whatever is already in "socket.inet.src_ipaddr".
                 */
                if (!fr_ipaddr_is_inaddr_any(&inst->src_ipaddr)) {
                        socket.inet.src_ipaddr = inst->src_ipaddr;
                } else if (!fr_ipaddr_is_inaddr_any(&inst->ipaddr)) {
                        socket.inet.src_ipaddr = inst->ipaddr;
#ifdef WITH_IFINDEX_IPADDR_RESOLUTION
                } else if ((address->socket.inet.ifindex > 0) &&
                           (fr_ipaddr_from_ifindex(&primary, thread->sockfd, &socket.inet.dst_ipaddr.af,
                                                   &socket.inet.ifindex) == 0)) {
                        socket.inet.src_ipaddr = primary;
#endif
                } else if (((code[2] == FR_DHCP_OFFER) || (code[2] == FR_DHCP_ACK)) &&
                           ((sid = fr_dhcpv4_packet_get_option(packet, buffer_len, attr_dhcp_server_identifier)) != NULL) &&
                           (sid[1] == 4)) {
                        memcpy(&socket.inet.src_ipaddr.addr.v4.s_addr, sid + 2, 4);
                }
 
                /*
                 *      If we're forwarding the Discover or Request,
                 *      then we need to figure out where to forward it
                 *      to?
                 */
                if ((code[2] == FR_DHCP_DISCOVER) || (code[2] == FR_DHCP_REQUEST)) {
                        WARN("Silently discarding client request, as we do not know where to send it");
                        return 0;
                }
 
                /*
                 *      We have GIADDR in the packet, so send it
                 *      there.  The packet is FROM our IP address and
                 *      port, TO the destination IP address, at the
                 *      same (i.e. server) port.
                 *
                 *      RFC 2131 page 23
                 *
                 *      "If the 'giaddr' field in a DHCP message from
                 *      a client is non-zero, the server sends any
                 *      return messages to the 'DHCP server' port on
                 *      the BOOTP relay agent whose address appears in
                 *      'giaddr'.
                 */
                if (packet->giaddr != INADDR_ANY) {
                        DEBUG("Reply will be sent to giaddr.");
                        socket.inet.dst_ipaddr.addr.v4.s_addr = packet->giaddr;
                        socket.inet.dst_port = inst->port;
                        socket.inet.src_port = inst->port;
 
                        /*
                         *      Increase the hop count for client
                         *      packets sent to the next gateway.
                         */
                        if ((code[2] == FR_DHCP_DISCOVER) ||
                            (code[2] == FR_DHCP_REQUEST)) {
                                packet->opcode = 1; /* client message */
                                packet->hops = request->hops + 1;
                        } else {
                                packet->opcode = 2; /* server message */
                        }
 
                        goto send_reply;
                }
 
                packet->opcode = 2; /* server message */
 
                /*
                 *      If the client port is specified, use it.
                 *
                 *      RFC 2131 page 23.
                 *
                 *      "DHCP messages from a server to a client are sent
                 *      to the 'DHCP client' port (68)"
                 */
                if (inst->client_port) socket.inet.dst_port = inst->client_port;
 
                /*
                 *      NAKs are broadcast when there's no giaddr.
                 *
                 *      RFC 2131 page 23.
                 *
                 *      "In all cases, when 'giaddr' is zero, the server
                 *      broadcasts any DHCPNAK messages to 0xffffffff."
                 */
                if (code[2] == FR_DHCP_NAK) {
                        DEBUG("Reply will be broadcast due to NAK.");
                        socket.inet.dst_ipaddr.addr.v4.s_addr = INADDR_BROADCAST;
                        goto send_reply;
                }
 
                /*
                 *      The original packet has CIADDR, so we unicast
                 *      the reply there.
                 *
                 *      RFC 2131 page 23.
                 *
                 *      "If the 'giaddr' field is zero and the
                 *      'ciaddr' field is nonzero, then the server
                 *      unicasts DHCPOFFER and DHCPACK messages to the
                 *      address in 'ciaddr'."
                 */
                if (request->ciaddr != INADDR_ANY) {
                        DEBUG("Reply will be unicast to CIADDR from original packet.");
                        memcpy(&socket.inet.dst_ipaddr.addr.v4.s_addr, &request->ciaddr, 4);
                        goto send_reply;
                }
 
                /*
                 *      The original packet requested a broadcast
                 *      reply, so we broadcast the reply.
                 *
                 *      RFC 2131 page 23.
                 *
                 *      "If 'giaddr' is zero and 'ciaddr' is zero, and
                 *      the broadcast bit is set, then the server
                 *      broadcasts DHCPOFFER and DHCPACK messages to
                 *      0xffffffff."
                 */
                if (request->broadcast) {
                        DEBUG("Reply will be broadcast due to client request.");
                        socket.inet.dst_ipaddr.addr.v4.s_addr = INADDR_BROADCAST;
                        goto send_reply;
                }
 
                /*
                 *      The original packet was unicast to us, such as
                 *      via a relay.  We have a unicast destination
                 *      address, so we just use that.
                 *
                 *      This extension isn't in the RFC, but we find it useful.
                 */
                if ((packet->yiaddr == htonl(INADDR_ANY)) &&
                    (socket.inet.dst_ipaddr.addr.v4.s_addr != htonl(INADDR_BROADCAST))) {
                        DEBUG("Reply will be unicast to source IP from original packet.");
                        goto send_reply;
                }
 
                /*
                 *      RFC 2131 page 23.
                 *
                 *      "If the broadcast bit is not set and 'giaddr'
                 *      is zero and 'ciaddr' is zero, then the server
                 *      unicasts DHCPOFFER and DHCPACK messages to the
                 *      client's hardware address and 'yiaddr'
                 *      address."
                 */
                switch (code[2]) {
                        /*
                         *      OFFERs are sent to YIADDR if we
                         *      received a unicast packet from YIADDR.
                         *      Otherwise, they are unicast to YIADDR
                         *      (if we can update ARP), otherwise they
                         *      are broadcast.
                         */
                case FR_DHCP_OFFER:
                        /*
                         *      If the packet was unicast from the
                         *      client, unicast it back without
                         *      updating the ARP table.  We presume
                         *      that the ARP table has been updated by
                         *      the OS, since we received a unicast
                         *      packet.
                         *
                         *      This check simply makes sure that we
                         *      don't needlessly update the ARP table.
                         */
                        if (memcmp(&socket.inet.dst_ipaddr.addr.v4.s_addr, &packet->yiaddr, 4) == 0) {
                                DEBUG("Reply will be unicast to YIADDR.");
 
#ifdef SIOCSARP
                        } else if (inst->broadcast && inst->interface) {
                                uint8_t macaddr[6];
                                uint8_t ipaddr[4];
 
                                memcpy(&ipaddr, &packet->yiaddr, 4);
                                memcpy(&macaddr, &packet->chaddr, 6);
 
                                /*
                                 *      Else the OFFER was broadcast.
                                 *      This socket is listening for
                                 *      broadcast packets on a
                                 *      particular interface.  We're
                                 *      too lazy to write raw UDP
                                 *      packets, so we update our
                                 *      local ARP table and then
                                 *      unicast the reply.
                                 */
                                if (fr_arp_entry_add(thread->sockfd, inst->interface, ipaddr, macaddr) == 0) {
                                        DEBUG("Reply will be unicast to YIADDR, done ARP table updates.");
                                        memcpy(&socket.inet.dst_ipaddr.addr.v4.s_addr, &packet->yiaddr, 4);
                                } else {
                                        DEBUG("Failed adding ARP entry.  Reply will be broadcast.");
                                        socket.inet.dst_ipaddr.addr.v4.s_addr = INADDR_BROADCAST;
                                }
 
#endif
                        } else {
                                DEBUG("Reply will be broadcast as we do not create raw UDP sockets.");
                                socket.inet.dst_ipaddr.addr.v4.s_addr = INADDR_BROADCAST;
                        }
                        break;
 
                        /*
                         *      ACKs are unicast to YIADDR
                         */
                case FR_DHCP_ACK:
                        DEBUG("Reply will be unicast to YIADDR.");
                        memcpy(&socket.inet.dst_ipaddr.addr.v4.s_addr, &packet->yiaddr, 4);
                        break;
 
                default:
                        WARN("Silently discarding reply due to unimplemented message type %d", code[2]);
                        return 0;
                }
 
        send_reply:
                DEBUG("Sending %s XID %08x from %pV:%d to %pV:%d", dhcp_message_types[code[2]], packet->xid,
                      fr_box_ipaddr(socket.inet.src_ipaddr), socket.inet.src_port,
                      fr_box_ipaddr(socket.inet.dst_ipaddr), socket.inet.dst_port);
        }
 
        /*
         *      proto_dhcpv4 takes care of suppressing do-not-respond, etc.
         */
        data_size = udp_send(&socket, flags, buffer, buffer_len);
 
        /*
         *      This socket is dead.  That's an error...
         */
        if (data_size <= 0) return data_size;
 
        return data_size;
}
 
 
static int mod_connection_set(fr_listen_t *li, fr_io_address_t *connection)
{
        proto_dhcpv4_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv4_udp_thread_t);
 
        thread->connection = connection;
        return 0;
}
 
 
static void mod_network_get(int *ipproto, bool *dynamic_clients, fr_trie_t const **trie, void *instance)
{
        proto_dhcpv4_udp_t              *inst = talloc_get_type_abort(instance, proto_dhcpv4_udp_t);
 
        *ipproto = IPPROTO_UDP;
        *dynamic_clients = inst->dynamic_clients;
        *trie = inst->trie;
}
 
 
/** Open a UDP listener for DHCPV4
 *
 */
static int mod_open(fr_listen_t *li)
{
        proto_dhcpv4_udp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv4_udp_t);
        proto_dhcpv4_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv4_udp_thread_t);
 
        int                             sockfd, rcode;
        fr_ipaddr_t                     ipaddr = inst->ipaddr;
        uint16_t                        port = inst->port;
 
        li->fd = sockfd = fr_socket_server_udp(&inst->ipaddr, &port, inst->port_name, true);
        if (sockfd < 0) {
                PERROR("Failed opening UDP socket");
        error:
                return -1;
        }
 
        li->app_io_addr = fr_socket_addr_alloc_inet_src(li, IPPROTO_UDP, 0, &inst->ipaddr, port);
 
        /*
         *      Set SO_REUSEPORT before bind, so that all packets can
         *      listen on the same destination IP address.
         */
        {
                int on = 1;
 
                if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEPORT, &on, sizeof(on)) < 0) {
                        ERROR("Failed to set socket 'reuseport': %s", fr_syserror(errno));
                        close(sockfd);
                        return -1;
                }
        }
 
#ifdef SO_RCVBUF
        if (inst->recv_buff_is_set) {
                int opt;
 
                opt = inst->recv_buff;
                if (setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &opt, sizeof(int)) < 0) {
                        WARN("Failed setting 'recv_buf': %s", fr_syserror(errno));
                }
        }
#endif
 
        if (inst->broadcast) {
                int on = 1;
 
                if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on)) < 0) {
                        ERROR("Failed to set broadcast option: %s", fr_syserror(errno));
                        close(sockfd);
                        return -1;
                }
        }
 
        rcode = fr_socket_bind(sockfd, inst->interface, &ipaddr, &port);
        if (rcode < 0) {
                close(sockfd);
                PERROR("Failed binding socket");
                goto error;
        }
 
        thread->sockfd = sockfd;
 
        fr_assert((cf_parent(inst->cs) != NULL) && (cf_parent(cf_parent(inst->cs)) != NULL));   /* listen { ... } */
 
        thread->name = fr_app_io_socket_name(thread, &proto_dhcpv4_udp,
                                             NULL, 0,
                                             &inst->ipaddr, inst->port,
                                             inst->interface);
 
        return 0;
}
 
 
/** Set the file descriptor for this socket.
 *
 */
static int mod_fd_set(fr_listen_t *li, int fd)
{
        proto_dhcpv4_udp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv4_udp_t);
        proto_dhcpv4_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv4_udp_thread_t);
 
        thread->sockfd = fd;
 
        thread->name = fr_app_io_socket_name(thread, &proto_dhcpv4_udp,
                                             &thread->connection->socket.inet.src_ipaddr,
                                             thread->connection->socket.inet.src_port,
                                             &inst->ipaddr, inst->port,
                                             inst->interface);
 
        return 0;
}
 
 
static void *mod_track_create(UNUSED void const *instance, UNUSED void *thread_instance, UNUSED fr_client_t *client,
                              fr_io_track_t *track, uint8_t const *packet, size_t packet_len)
{
        proto_dhcpv4_track_t *t;
        dhcp_packet_t const *dhcp = (dhcp_packet_t const *) packet;
        uint8_t const  *option;
 
        option = fr_dhcpv4_packet_get_option(dhcp, packet_len, attr_message_type);
        if (!option || (option[1] == 0)) {
                DEBUG("No %s in the packet - ignoring", attr_message_type->name);
                return NULL;
        }
 
        t = talloc_zero(track, proto_dhcpv4_track_t);
        if (!t) return NULL;
 
        memcpy(&t->xid, &dhcp->xid, sizeof(t->xid));
 
        t->message_type = option[2];
 
        /*
         *      Track most packets by chaddr.  For lease queries, that
         *      field can be the client address being queried, not the
         *      address of the system which sent the packet.  So
         *      instead for lease queries, we use giaddr, which MUST
         *      exist according to RFC 4388 Section 6.3
         */
        if (option[2] != FR_DHCP_LEASE_QUERY) {
                if (dhcp->hlen == 6) memcpy(&t->chaddr, &dhcp->chaddr, 6);
        }
 
        t->broadcast = ((dhcp->flags & FR_FLAGS_VALUE_BROADCAST) != 0);
        t->hops = dhcp->hops;
        memcpy(&t->ciaddr, &dhcp->ciaddr, sizeof(t->ciaddr));
        memcpy(&t->giaddr, &dhcp->giaddr, sizeof(t->giaddr));
 
        return t;
}
 
static int mod_track_compare(UNUSED void const *instance, UNUSED void *thread_instance, UNUSED fr_client_t *client,
                             void const *one, void const *two)
{
        int ret;
        proto_dhcpv4_track_t const *a = one;
        proto_dhcpv4_track_t const *b = two;
 
        /*
         *      The tree is ordered by XIDs, which are (hopefully)
         *      pseudo-randomly distributed.
         */
        ret = memcmp(&a->xid, &b->xid, sizeof(a->xid));
        if (ret != 0) return ret;
 
        /*
         *      Hardware addresses should also be randomly distributed.
         */
        ret = memcmp(&a->chaddr, &b->chaddr, sizeof(a->chaddr));
        if (ret != 0) return ret;
 
        /*
         *      Compare giaddr, but not ciaddr
         */
        ret = memcmp(&a->giaddr, &b->giaddr, sizeof(a->giaddr));
        if (ret != 0) return ret;
 
        return (a->message_type < b->message_type) - (a->message_type > b->message_type);
}
 
static char const *mod_name(fr_listen_t *li)
{
        proto_dhcpv4_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv4_udp_thread_t);
 
        return thread->name;
}
 
 
static int mod_instantiate(module_inst_ctx_t const *mctx)
{
        proto_dhcpv4_udp_t      *inst = talloc_get_type_abort(mctx->mi->data, proto_dhcpv4_udp_t);
        CONF_SECTION            *conf = mctx->mi->conf;
        size_t                  num;
        CONF_ITEM               *ci;
        CONF_SECTION            *server_cs;
        fr_client_t             *client;
 
        inst->cs = conf;
 
        /*
         *      Complain if no "ipaddr" is set.
         */
        if (inst->ipaddr.af == AF_UNSPEC) {
                cf_log_err(conf, "No 'ipaddr' was specified in the 'udp' section");
                return -1;
        }
 
        if (inst->ipaddr.af != AF_INET) {
                cf_log_err(conf, "DHCPv4 transport cannot use IPv6 for 'ipaddr'");
                return -1;
        }
 
        /*
         *      If src_ipaddr is defined, it must be of the same address family as "ipaddr"
         */
        if ((inst->src_ipaddr.af != AF_UNSPEC) &&
            (inst->src_ipaddr.af != inst->ipaddr.af)) {
                cf_log_err(conf, "Both 'ipaddr' and 'src_ipaddr' must be from the same address family");
                return -1;
        }
 
        /*
         *      Set src_ipaddr to INADDR_NONE if not otherwise specified
         */
        if (inst->src_ipaddr.af == AF_UNSPEC) {
                memset(&inst->src_ipaddr, 0, sizeof(inst->src_ipaddr));
                inst->src_ipaddr.af = AF_INET;
        }
 
        if (inst->recv_buff_is_set) {
                FR_INTEGER_BOUND_CHECK("recv_buff", inst->recv_buff, >=, 32);
                FR_INTEGER_BOUND_CHECK("recv_buff", inst->recv_buff, <=, INT_MAX);
        }
 
        FR_INTEGER_BOUND_CHECK("max_packet_size", inst->max_packet_size, >=, MIN_PACKET_SIZE);
        FR_INTEGER_BOUND_CHECK("max_packet_size", inst->max_packet_size, <=, 65536);
 
        if (!inst->port) {
                struct servent *s;
 
                if (!inst->port_name) {
                        cf_log_err(conf, "No 'port' was specified in the 'udp' section");
                        return -1;
                }
 
                s = getservbyname(inst->port_name, "udp");
                if (!s) {
                        cf_log_err(conf, "Unknown value for 'port_name = %s", inst->port_name);
                        return -1;
                }
 
                inst->port = ntohl(s->s_port);
        }
 
#ifdef SIOCSARP
        /*
         *      If we're listening for broadcast requests, we MUST
         */
        if (inst->broadcast && !inst->interface) {
                cf_log_warn(conf, "You SHOULD set 'interface' if you have set 'broadcast = yes'.");
                cf_log_warn(conf, "All replies will be broadcast, as ARP updates require 'interface' to be set.");
        }
#endif
 
        /*
         *      Parse and create the trie for dynamic clients, even if
         *      there's no dynamic clients.
         */
        num = talloc_array_length(inst->allow);
        if (!num) {
                if (inst->dynamic_clients) {
                        cf_log_err(conf, "The 'allow' subsection MUST contain at least one 'network' entry when 'dynamic_clients = true'.");
                        return -1;
                }
        } else {
                inst->trie = fr_master_io_network(inst, inst->ipaddr.af, inst->allow, inst->deny);
                if (!inst->trie) {
                        cf_log_perr(conf, "Failed creating list of networks");
                        return -1;
                }
        }
 
        ci = cf_section_to_item(mctx->mi->parent->conf); /* listen { ... } */
        fr_assert(ci != NULL);
        ci = cf_parent(ci);
        fr_assert(ci != NULL);
 
        server_cs = cf_item_to_section(ci);
 
        /*
         *      Look up local clients, if they exist.
         *
         *      @todo - ensure that we only parse clients which are
         *      for IPPROTO_UDP, and don't require a "secret".
         */
        if (cf_section_find_next(server_cs, NULL, "client", CF_IDENT_ANY)) {
                inst->clients = client_list_parse_section(server_cs, IPPROTO_UDP, false);
                if (!inst->clients) {
                        cf_log_err(conf, "Failed creating local clients");
                        return -1;
                }
        }
 
        /*
         *      Create a fake client.
         */
        client = inst->default_client = talloc_zero(inst, fr_client_t);
        if (!inst->default_client) return 0;
 
        client->ipaddr.af = AF_INET;
        client->ipaddr.addr.v4.s_addr = htonl(INADDR_NONE);
        client->src_ipaddr = client->ipaddr;
 
        client->longname = client->shortname = client->secret = talloc_strdup(client, "default");
        client->nas_type = talloc_strdup(client, "other");
 
        return 0;
}
 
static fr_client_t *mod_client_find(fr_listen_t *li, fr_ipaddr_t const *ipaddr, int ipproto)
{
        proto_dhcpv4_udp_t const *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv4_udp_t);
 
        /*
         *      Prefer local clients.
         */
        if (inst->clients) {
                fr_client_t *client;
 
                client = client_find(inst->clients, ipaddr, ipproto);
                if (client) return client;
        }
 
        return inst->default_client;
}
 
fr_app_io_t proto_dhcpv4_udp = {
        .common = {
                .magic                  = MODULE_MAGIC_INIT,
                .name                   = "dhcpv4_udp",
                .config                 = udp_listen_config,
                .inst_size              = sizeof(proto_dhcpv4_udp_t),
                .thread_inst_size       = sizeof(proto_dhcpv4_udp_thread_t),
                .instantiate            = mod_instantiate,
        },
        .default_message_size   = 4096,
        .track_duplicates       = true,
 
        .open                   = mod_open,
        .read                   = mod_read,
        .write                  = mod_write,
        .fd_set                 = mod_fd_set,
        .track_create           = mod_track_create,
        .track_compare          = mod_track_compare,
        .connection_set         = mod_connection_set,
        .network_get            = mod_network_get,
        .client_find            = mod_client_find,
        .get_name               = mod_name,
};