proto_dhcpv6_udp.c

Go to the documentation of this file.

/*
 *   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: 3781706c2ea85223718671f9ea139f3d8afbdce2 $
 * @file proto_dhcpv6_udp.c
 * @brief DHCPv6 handler for UDP.
 *
 * @copyright 2020 Network RADIUS SAS (legal@networkradius.com)
 */
#define LOG_PREFIX "proto_dhcpv6_udp"
 
#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/dhcpv6/freeradius.internal.h>
#include "proto_dhcpv6.h"
 
extern fr_app_io_t proto_dhcpv6_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_dhcpv6_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().
        fr_ethernet_t                   ethernet;               //!< ethernet address associated with the interface
 
        uint32_t                        recv_buff;              //!< How big the kernel's receive buffer should be.
 
        uint32_t                        hop_limit;              //!< for multicast addresses
        uint32_t                        max_packet_size;        //!< for message ring buffer.
        uint32_t                        max_attributes;         //!< Limit maximum decodable attributes.
 
        uint16_t                        port;                   //!< Port to listen on.
 
        bool                            multicast;              //!< whether or not we listen for multicast 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_dhcpv6_udp_t;
 
 
static const conf_parser_t networks_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("allow", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_dhcpv6_udp_t, allow) },
        { FR_CONF_OFFSET_TYPE_FLAGS("deny", FR_TYPE_COMBO_IP_PREFIX , CONF_FLAG_MULTI, proto_dhcpv6_udp_t, deny) },
 
        CONF_PARSER_TERMINATOR
};
 
 
static const conf_parser_t udp_listen_config[] = {
        { FR_CONF_OFFSET_TYPE_FLAGS("ipaddr", FR_TYPE_IPV6_ADDR, 0, proto_dhcpv6_udp_t, ipaddr) },
        { FR_CONF_OFFSET_TYPE_FLAGS("ipv6addr", FR_TYPE_IPV6_ADDR, 0, proto_dhcpv6_udp_t, ipaddr) },
 
        { FR_CONF_OFFSET_TYPE_FLAGS("src_ipaddr", FR_TYPE_COMBO_IP_ADDR, 0, proto_dhcpv6_udp_t, src_ipaddr) },
 
        { FR_CONF_OFFSET("interface", proto_dhcpv6_udp_t, interface) },
        { FR_CONF_OFFSET("port_name", proto_dhcpv6_udp_t, port_name) },
 
        { FR_CONF_OFFSET("port", proto_dhcpv6_udp_t, port), .dflt = "547"  },
        { FR_CONF_OFFSET_IS_SET("recv_buff", FR_TYPE_UINT32, 0, proto_dhcpv6_udp_t, recv_buff) },
 
        { FR_CONF_OFFSET("hop_limit", proto_dhcpv6_udp_t, hop_limit) },
 
        { FR_CONF_OFFSET("dynamic_clients", proto_dhcpv6_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_dhcpv6_udp_t, max_packet_size), .dflt = "8192" } ,
        { FR_CONF_OFFSET("max_attributes", proto_dhcpv6_udp_t, max_attributes), .dflt = STRINGIFY(DHCPV6_MAX_ATTRIBUTES) } ,
 
        CONF_PARSER_TERMINATOR
};
 
static fr_dict_t const *dict_dhcpv6;
 
extern fr_dict_autoload_t proto_dhcpv6_udp_dict[];
fr_dict_autoload_t proto_dhcpv6_udp_dict[] = {
        { .out = &dict_dhcpv6, .proto = "dhcpv6" },
        DICT_AUTOLOAD_TERMINATOR
};
 
static fr_dict_attr_t const *attr_packet_type;
static fr_dict_attr_t const *attr_client_id;
static fr_dict_attr_t const *attr_relay_message;
 
extern fr_dict_attr_autoload_t proto_dhcpv6_udp_dict_attr[];
fr_dict_attr_autoload_t proto_dhcpv6_udp_dict_attr[] = {
        { .out = &attr_packet_type, .name = "Packet-Type", .type = FR_TYPE_UINT32, .dict = &dict_dhcpv6},
        { .out = &attr_client_id, .name = "Client-ID", .type = FR_TYPE_STRUCT, .dict = &dict_dhcpv6},
        { .out = &attr_relay_message, .name = "Relay-Message", .type = FR_TYPE_GROUP, .dict = &dict_dhcpv6 },
        DICT_AUTOLOAD_TERMINATOR
};
 
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_dhcpv6_udp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv6_udp_t);
        proto_dhcpv6_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv6_udp_thread_t);
        fr_io_address_t                 *address, **address_p;
 
        int                             flags;
        ssize_t                         data_size;
        size_t                          packet_len;
        uint32_t                        xid;
        fr_dhcpv6_packet_t              *packet;
 
        *leftover = 0;          /* always for UDP */
 
        /*
         *      Where the addresses should go.  This is a special case
         *      for proto_dhcpv6.
         */
        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 ((size_t) data_size < sizeof(fr_dhcpv6_packet_t)) {
                RATE_LIMIT_GLOBAL(WARN, "Insufficient data - 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 = (fr_dhcpv6_packet_t *) buffer;
        if (!packet->code || (packet->code >= FR_DHCPV6_CODE_MAX)) {
                RATE_LIMIT_GLOBAL(WARN, "Unsupported packet code %d - ignoring", packet->code);
                return 0;
        }
 
        /*
         *      RFC 8415 Section 18.4 forbids certain types of packets
         *      from being received on a unicast address.
         */
        if (!inst->multicast) {
                if ((packet->code == FR_DHCPV6_SOLICIT) ||
                    (packet->code == FR_DHCPV6_REBIND) ||
                    (packet->code == FR_DHCPV6_CONFIRM)) {
                        RATE_LIMIT_GLOBAL(WARN, "Unicast packet %s - ignoring", fr_dhcpv6_packet_names[packet->code]);
                        return 0;
                }
        } /* else it was multicast... remember that */
 
        /*
         *      @todo - make this take "&packet_len", as the DHCPv4
         *      packet may be smaller than the parent UDP packet.
         */
        if (fr_dhcpv6_ok(buffer, data_size, inst->max_attributes) <= 0) {
                RATE_LIMIT_GLOBAL(PWARN, "Invalid packet - ignoring");
                return 0;
        }
 
        /*
         *      proto_dhcpv6 sets the priority
         */
 
        xid = fr_nbo_to_uint24(packet->transaction_id);
 
        /*
         *      Print out what we received.
         */
        DEBUG2("Received %s XID %08x length %d %s", fr_dhcpv6_packet_names[packet->code], 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_dhcpv6_udp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv6_udp_t);
        proto_dhcpv6_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv6_udp_thread_t);
 
        fr_io_track_t                   *track = talloc_get_type_abort(packet_ctx, fr_io_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_dhcpv6
         *      can update them, too.. <sigh>
         */
        thread->stats.total_responses++;
 
        flags = UDP_FLAGS_CONNECTED * (thread->connection != NULL);
 
        /*
         *      Send packets to the originator, EXCEPT that we always
         *      originate packets from our src_ipaddr.
         */
        fr_socket_addr_swap(&socket, &track->address->socket);
        if (!fr_ipaddr_is_inaddr_any(&inst->src_ipaddr)) socket.inet.src_ipaddr = inst->src_ipaddr;
 
        /*
         *      Figure out which kind of packet we're sending.
         */
        if (!thread->connection) {
                // @todo - figure out where to send the packet
        }
 
        /*
         *      proto_dhcpv6 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_dhcpv6_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv6_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_dhcpv6_udp_t              *inst = talloc_get_type_abort(instance, proto_dhcpv6_udp_t);
 
        *ipproto = IPPROTO_UDP;
        *dynamic_clients = inst->dynamic_clients;
        *trie = inst->trie;
}
 
 
/** Open a UDP listener for DHCPv6
 *
 */
static int mod_open(fr_listen_t *li)
{
        proto_dhcpv6_udp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv6_udp_t);
        proto_dhcpv6_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv6_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) {
                cf_log_err(li->cs, "Failed opening UDP socket - %s", fr_strerror());
        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.
         */
        if (1) {
                int on = 1;
 
                if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEPORT, &on, sizeof(on)) < 0) {
                        cf_log_err(li->cs, "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) {
                        cf_log_warn(li->cs, "Failed setting 'recv_buf' - %s", fr_syserror(errno));
                }
        }
#endif
 
        /*
         *      SUID up is really only needed if interface is set, OR port <1024.
         */
        rad_suid_up();
        rcode = fr_socket_bind(sockfd, inst->interface, &ipaddr, &port);
        rad_suid_down();
        if (rcode < 0) {
                cf_log_err(li->cs, "Failed binding to socket - %s", fr_strerror());
                cf_log_err(li->cs, DOC_ROOT_REF(troubleshooting/network/bind));
        close_error:
                close(sockfd);
                goto error;
        }
 
        /*
         *      If the user specified a multicast address, then join
         *      that group.
         */
        if (inst->multicast) {
                struct ipv6_mreq mreq;
 
                mreq.ipv6mr_multiaddr = inst->ipaddr.addr.v6;
                mreq.ipv6mr_interface = if_nametoindex(inst->interface);
                if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq, sizeof(mreq)) < 0) {
                        PERROR("Failed joining multicast group %pV ", fr_box_ipaddr(inst->ipaddr));
                        goto close_error;
                }
 
                if (inst->hop_limit) {
                        int hop_limit = inst->hop_limit;
 
                        if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS,
                                       (char *) &hop_limit, sizeof(hop_limit)) < 0) {
                                ERROR("Failed to set multicast hop_limit: %s", fr_syserror(errno));
                                goto close_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_dhcpv6_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_dhcpv6_udp_t const        *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv6_udp_t);
        proto_dhcpv6_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv6_udp_thread_t);
 
        thread->sockfd = fd;
 
        thread->name = fr_app_io_socket_name(thread, &proto_dhcpv6_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_dhcpv6_track_t *t;
        uint8_t const *option;
        size_t t_size = sizeof(*t);
        size_t option_len;
 
        /*
         *      Relay packets can be nested to almost any depth.
         */
        while (packet[0] ==  FR_DHCPV6_RELAY_FORWARD) {
                if (packet_len < (2 + 32)) return NULL;
 
                /*
                 *      fr_dhcpv6_option_find() ensures that the
                 *      option header and data are contained within
                 *      the given packet.
                 */
                option = fr_dhcpv6_option_find(packet + 2 + 32, packet + packet_len, attr_relay_message->attr);
                if (!option) return NULL;
 
                option_len = fr_nbo_to_uint16(option + 2);
 
                packet = option + 4; /* skip option header */
                packet_len = option_len;
        }
 
        if (packet_len <= 4) return NULL;
 
        /*
         *      Search the packet options.
         */
        option = fr_dhcpv6_option_find(packet + 4, packet + packet_len, attr_client_id->attr);
        if (!option) return NULL;
 
        option_len = fr_nbo_to_uint16(option + 2);
 
        if (option_len > ((packet - option) + packet_len)) return NULL;
 
        t = (proto_dhcpv6_track_t *) talloc_zero_array(track, uint8_t, t_size + option_len);
        if (!t) return NULL;
 
        talloc_set_name_const(t, "proto_dhcpv6_track_t");
 
        memcpy(&t->header, packet, 4); /* packet code + 24-bit transaction ID */
 
        memcpy(&t->client_id[0], option + 4, option_len);
        t->client_id_len = option_len;
 
        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_dhcpv6_track_t const *a = one;
        proto_dhcpv6_track_t const *b = two;
 
        ret = memcmp(&a->header, &b->header, sizeof(a->header));
        if (ret != 0) return ret;
 
        ret = (a->client_id_len < b->client_id_len) - (a->client_id_len > b->client_id_len);
        if (ret != 0) return ret;
 
        return memcmp(a->client_id, b->client_id, a->client_id_len);
}
 
 
static char const *mod_name(fr_listen_t *li)
{
        proto_dhcpv6_udp_thread_t       *thread = talloc_get_type_abort(li->thread_instance, proto_dhcpv6_udp_thread_t);
 
        return thread->name;
}
 
 
static int mod_instantiate(module_inst_ctx_t const *mctx)
{
        proto_dhcpv6_udp_t      *inst = talloc_get_type_abort(mctx->mi->data, proto_dhcpv6_udp_t);
        size_t                  num;
        CONF_ITEM               *ci;
        CONF_SECTION            *server_cs;
        fr_client_t             *client;
        CONF_SECTION            *conf = mctx->mi->conf;
 
        inst->cs = conf;
 
        /*
         *      Complain if no "ipaddr" is set.
         */
        if (inst->ipaddr.af == AF_UNSPEC) {
                if (!inst->interface) {
                        cf_log_err(conf, "No 'ipaddr' was specified in the 'udp' section");
                        return -1;
                }
 
                /*
                 *      If there's a named interface, maybe we can
                 *      find a link-local address for it.  If so, just
                 *      use that.
                 */
                if (inst->interface &&
                    (fr_interface_to_ipaddr(inst->interface, &inst->ipaddr, AF_INET6, true) < 0)) {
                        cf_log_err(conf, "No 'ipaddr' specified, and we cannot determine one for interface '%s'",
                                   inst->interface);
                                return -1;
                }
        }
 
        if (inst->ipaddr.af != AF_INET6) {
                cf_log_err(conf, "DHCPv6 cannot use IPv4 for 'ipaddr'");
                return -1;
        }
 
        /*
         *      Remember if we're a multicast socket.
         */
        inst->multicast = (fr_ipaddr_is_multicast(&inst->ipaddr) == 1);
 
        /*
         *      Set src_ipaddr to ipaddr if not otherwise specified
         */
        if (inst->src_ipaddr.af == AF_UNSPEC) {
                if (!inst->multicast) {
                        inst->src_ipaddr = inst->ipaddr;
 
                        /*
                         *      If the admin didn't specify an
                         *      interface, then try to find one
                         *      automatically.  We only do this for
                         *      link-local addresses.
                         */
                        if (!inst->interface) {
                                inst->interface = fr_ipaddr_to_interface(inst, &inst->ipaddr);
                                if (!inst->interface) {
                                interface_fail:
                                        cf_log_err(conf, "No 'interface' specified, and we cannot "
                                                   "determine one for 'ipaddr = %pV'",
                                                   fr_box_ipaddr(inst->ipaddr));
                                        return -1;
                                }
                        }
 
                } else {
                        /*
                         *      Multicast addresses MUST specify an interface.
                         */
                        if (!inst->interface) goto interface_fail;
 
                        if (fr_interface_to_ipaddr(inst->interface, &inst->src_ipaddr, AF_INET6, true) < 0) {
                                cf_log_err(conf, "No 'src_ipaddr' specified, and we cannot determine "
                                           "one for 'ipaddr = %pV' and interface '%s'",
                                           fr_box_ipaddr(inst->ipaddr), inst->interface);
                                return -1;
                        }
                }
        }
 
        /*
         *      src_ipaddr must be of the same address family as "ipaddr"
         */
        if (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;
        }
 
        /*
         *      Get the MAC address associated with this interface.
         *      It can be used to create a server ID.
         */
        if (inst->interface) fr_interface_to_ethernet(inst->interface, &inst->ethernet);
 
        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, >=, 4);
        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 = ntohs(s->s_port);
        }
 
        /*
         *      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 = (fr_ipaddr_t ) {
                .af = AF_INET6,
        };
 
        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_dhcpv6_udp_t const *inst = talloc_get_type_abort_const(li->app_io_instance, proto_dhcpv6_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_dhcpv6_udp = {
        .common = {
                .magic                  = MODULE_MAGIC_INIT,
                .name                   = "dhcpv6_udp",
                .config                 = udp_listen_config,
                .inst_size              = sizeof(proto_dhcpv6_udp_t),
                .thread_inst_size       = sizeof(proto_dhcpv6_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,
};