/* SPDX-License-Identifier: LGPL-2.1+ */
/***
  Copyright © 2014-2015 Intel Corporation. All rights reserved.
***/

#include "nm-sd-adapt-core.h"

#include <errno.h>
#include <sys/ioctl.h>
#include <linux/if_arp.h>
#include <linux/if_infiniband.h>

#include "sd-dhcp6-client.h"

#include "alloc-util.h"
#include "dhcp-identifier.h"
#include "dhcp6-internal.h"
#include "dhcp6-lease-internal.h"
#include "dhcp6-protocol.h"
#include "dns-domain.h"
#include "event-util.h"
#include "fd-util.h"
#include "hostname-util.h"
#include "in-addr-util.h"
#include "network-internal.h"
#include "random-util.h"
#include "socket-util.h"
#include "string-table.h"
#include "util.h"
#include "web-util.h"

#define MAX_MAC_ADDR_LEN INFINIBAND_ALEN

#define IRT_DEFAULT (1 * USEC_PER_DAY)
#define IRT_MINIMUM (600 * USEC_PER_SEC)

/* what to request from the server, addresses (IA_NA) and/or prefixes (IA_PD) */
enum {
        DHCP6_REQUEST_IA_NA                     = 1,
        DHCP6_REQUEST_IA_TA                     = 2, /* currently not used */
        DHCP6_REQUEST_IA_PD                     = 4,
};

struct sd_dhcp6_client {
        unsigned n_ref;

        enum DHCP6State state;
        sd_event *event;
        int event_priority;
        int ifindex;
        DHCP6Address hint_pd_prefix;
        struct in6_addr local_address;
        uint8_t mac_addr[MAX_MAC_ADDR_LEN];
        size_t mac_addr_len;
        uint16_t arp_type;
        DHCP6IA ia_na;
        DHCP6IA ia_pd;
        sd_event_source *timeout_t1;
        sd_event_source *timeout_t2;
        unsigned request;
        be32_t transaction_id;
        usec_t transaction_start;
        struct sd_dhcp6_lease *lease;
        int fd;
        bool information_request;
        bool iaid_set;
        be16_t *req_opts;
        size_t req_opts_allocated;
        size_t req_opts_len;
        char *fqdn;
        char *mudurl;
        sd_event_source *receive_message;
        usec_t retransmit_time;
        uint8_t retransmit_count;
        sd_event_source *timeout_resend;
        sd_event_source *timeout_resend_expire;
        sd_dhcp6_client_callback_t callback;
        void *userdata;
        struct duid duid;
        size_t duid_len;
        usec_t information_request_time_usec;
        usec_t information_refresh_time_usec;
};

static const uint16_t default_req_opts[] = {
        SD_DHCP6_OPTION_DNS_SERVERS,
        SD_DHCP6_OPTION_DOMAIN_LIST,
        SD_DHCP6_OPTION_NTP_SERVER,
        SD_DHCP6_OPTION_SNTP_SERVERS,
};

const char * dhcp6_message_type_table[_DHCP6_MESSAGE_MAX] = {
        [DHCP6_SOLICIT] = "SOLICIT",
        [DHCP6_ADVERTISE] = "ADVERTISE",
        [DHCP6_REQUEST] = "REQUEST",
        [DHCP6_CONFIRM] = "CONFIRM",
        [DHCP6_RENEW] = "RENEW",
        [DHCP6_REBIND] = "REBIND",
        [DHCP6_REPLY] = "REPLY",
        [DHCP6_RELEASE] = "RELEASE",
        [DHCP6_DECLINE] = "DECLINE",
        [DHCP6_RECONFIGURE] = "RECONFIGURE",
        [DHCP6_INFORMATION_REQUEST] = "INFORMATION-REQUEST",
        [DHCP6_RELAY_FORW] = "RELAY-FORW",
        [DHCP6_RELAY_REPL] = "RELAY-REPL",
};

DEFINE_STRING_TABLE_LOOKUP(dhcp6_message_type, int);

const char * dhcp6_message_status_table[_DHCP6_STATUS_MAX] = {
        [DHCP6_STATUS_SUCCESS] = "Success",
        [DHCP6_STATUS_UNSPEC_FAIL] = "Unspecified failure",
        [DHCP6_STATUS_NO_ADDRS_AVAIL] = "No addresses available",
        [DHCP6_STATUS_NO_BINDING] = "Binding unavailable",
        [DHCP6_STATUS_NOT_ON_LINK] = "Not on link",
        [DHCP6_STATUS_USE_MULTICAST] = "Use multicast",
};

DEFINE_STRING_TABLE_LOOKUP(dhcp6_message_status, int);

#define DHCP6_CLIENT_DONT_DESTROY(client) \
        _cleanup_(sd_dhcp6_client_unrefp) _unused_ sd_dhcp6_client *_dont_destroy_##client = sd_dhcp6_client_ref(client)

static int client_start(sd_dhcp6_client *client, enum DHCP6State state);

int sd_dhcp6_client_set_callback(
                sd_dhcp6_client *client,
                sd_dhcp6_client_callback_t cb,
                void *userdata) {

        assert_return(client, -EINVAL);

        client->callback = cb;
        client->userdata = userdata;

        return 0;
}

int sd_dhcp6_client_set_ifindex(sd_dhcp6_client *client, int ifindex) {

        assert_return(client, -EINVAL);
        assert_return(ifindex >= -1, -EINVAL);
        assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);

        client->ifindex = ifindex;
        return 0;
}

int sd_dhcp6_client_set_local_address(
                sd_dhcp6_client *client,
                const struct in6_addr *local_address) {

        assert_return(client, -EINVAL);
        assert_return(local_address, -EINVAL);
        assert_return(in_addr_is_link_local(AF_INET6, (const union in_addr_union *) local_address) > 0, -EINVAL);

        assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);

        client->local_address = *local_address;

        return 0;
}

int sd_dhcp6_client_set_mac(
                sd_dhcp6_client *client,
                const uint8_t *addr, size_t addr_len,
                uint16_t arp_type) {

        assert_return(client, -EINVAL);
        assert_return(addr, -EINVAL);
        assert_return(addr_len > 0 && addr_len <= MAX_MAC_ADDR_LEN, -EINVAL);
        assert_return(arp_type > 0, -EINVAL);

        assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);

        if (arp_type == ARPHRD_ETHER)
                assert_return(addr_len == ETH_ALEN, -EINVAL);
        else if (arp_type == ARPHRD_INFINIBAND)
                assert_return(addr_len == INFINIBAND_ALEN, -EINVAL);
        else
                return -EINVAL;

        if (client->mac_addr_len == addr_len &&
            memcmp(&client->mac_addr, addr, addr_len) == 0)
                return 0;

        memcpy(&client->mac_addr, addr, addr_len);
        client->mac_addr_len = addr_len;
        client->arp_type = arp_type;

        return 0;
}

int sd_dhcp6_client_set_prefix_delegation_hint(
                sd_dhcp6_client *client,
                uint8_t prefixlen,
                const struct in6_addr *pd_address) {

        assert_return(client, -EINVAL);
        assert_return(pd_address, -EINVAL);

        assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);

        client->hint_pd_prefix.iapdprefix.address = *pd_address;
        client->hint_pd_prefix.iapdprefix.prefixlen = prefixlen;

        return 0;
}

static int client_ensure_duid(sd_dhcp6_client *client) {
        if (client->duid_len != 0)
                return 0;

        return dhcp_identifier_set_duid_en(&client->duid, &client->duid_len);
}

/**
 * Sets DUID. If duid is non-null, the DUID is set to duid_type + duid
 * without further modification. Otherwise, if duid_type is supported, DUID
 * is set based on that type. Otherwise, an error is returned.
 */
static int dhcp6_client_set_duid_internal(
                sd_dhcp6_client *client,
                uint16_t duid_type,
                const void *duid,
                size_t duid_len,
                usec_t llt_time) {
        int r;

        assert_return(client, -EINVAL);
        assert_return(duid_len == 0 || duid != NULL, -EINVAL);
        assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);

        if (duid != NULL) {
                r = dhcp_validate_duid_len(duid_type, duid_len, true);
                if (r < 0) {
                        r = dhcp_validate_duid_len(duid_type, duid_len, false);
                        if (r < 0)
                                return log_dhcp6_client_errno(client, r, "Failed to validate length of DUID: %m");
                        log_dhcp6_client(client, "Setting DUID of type %u with unexpected content", duid_type);
                }

                client->duid.type = htobe16(duid_type);
                memcpy(&client->duid.raw.data, duid, duid_len);
                client->duid_len = sizeof(client->duid.type) + duid_len;
        } else
#if 0 /* NM_IGNORED */
                switch (duid_type) {
                case DUID_TYPE_LLT:
                        if (client->mac_addr_len == 0)
                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EOPNOTSUPP), "Failed to set DUID-LLT, MAC address is not set.");

                        r = dhcp_identifier_set_duid_llt(&client->duid, llt_time, client->mac_addr, client->mac_addr_len, client->arp_type, &client->duid_len);
                        if (r < 0)
                                return log_dhcp6_client_errno(client, r, "Failed to set DUID-LLT: %m");
                        break;
                case DUID_TYPE_EN:
                        r = dhcp_identifier_set_duid_en(&client->duid, &client->duid_len);
                        if (r < 0)
                                return log_dhcp6_client_errno(client, r, "Failed to set DUID-EN: %m");
                        break;
                case DUID_TYPE_LL:
                        if (client->mac_addr_len == 0)
                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EOPNOTSUPP), "Failed to set DUID-LL, MAC address is not set.");

                        r = dhcp_identifier_set_duid_ll(&client->duid, client->mac_addr, client->mac_addr_len, client->arp_type, &client->duid_len);
                        if (r < 0)
                                return log_dhcp6_client_errno(client, r, "Failed to set DUID-LL: %m");
                        break;
                case DUID_TYPE_UUID:
                        r = dhcp_identifier_set_duid_uuid(&client->duid, &client->duid_len);
                        if (r < 0)
                                return log_dhcp6_client_errno(client, r, "Failed to set DUID-UUID: %m");
                        break;
                default:
                        return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL), "Invalid DUID type");
                }
#else /* NM_IGNORED */
                g_return_val_if_reached (-EINVAL);
#endif /* NM_IGNORED */

        return 0;
}

int sd_dhcp6_client_set_duid(
                sd_dhcp6_client *client,
                uint16_t duid_type,
                const void *duid,
                size_t duid_len) {
        return dhcp6_client_set_duid_internal(client, duid_type, duid, duid_len, 0);
}

int sd_dhcp6_client_set_duid_llt(
                sd_dhcp6_client *client,
                usec_t llt_time) {
        return dhcp6_client_set_duid_internal(client, DUID_TYPE_LLT, NULL, 0, llt_time);
}

int sd_dhcp6_client_set_iaid(sd_dhcp6_client *client, uint32_t iaid) {
        assert_return(client, -EINVAL);
        assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);

        client->ia_na.ia_na.id = htobe32(iaid);
        client->ia_pd.ia_pd.id = htobe32(iaid);
        client->iaid_set = true;

        return 0;
}

int sd_dhcp6_client_set_fqdn(
                sd_dhcp6_client *client,
                const char *fqdn) {

        assert_return(client, -EINVAL);

        /* Make sure FQDN qualifies as DNS and as Linux hostname */
        if (fqdn &&
            !(hostname_is_valid(fqdn, false) && dns_name_is_valid(fqdn) > 0))
                return -EINVAL;

        return free_and_strdup(&client->fqdn, fqdn);
}

int sd_dhcp6_client_set_information_request(sd_dhcp6_client *client, int enabled) {
        assert_return(client, -EINVAL);
        assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);

        client->information_request = enabled;

        return 0;
}

int sd_dhcp6_client_get_information_request(sd_dhcp6_client *client, int *enabled) {
        assert_return(client, -EINVAL);
        assert_return(enabled, -EINVAL);

        *enabled = client->information_request;

        return 0;
}

int sd_dhcp6_client_set_request_option(sd_dhcp6_client *client, uint16_t option) {
        size_t t;

        assert_return(client, -EINVAL);
        assert_return(client->state == DHCP6_STATE_STOPPED, -EBUSY);

        switch(option) {

        case SD_DHCP6_OPTION_DNS_SERVERS:
        case SD_DHCP6_OPTION_DOMAIN_LIST:
        case SD_DHCP6_OPTION_SNTP_SERVERS:
        case SD_DHCP6_OPTION_NTP_SERVER:
        case SD_DHCP6_OPTION_RAPID_COMMIT:
                break;

        default:
                return -EINVAL;
        }

        for (t = 0; t < client->req_opts_len; t++)
                if (client->req_opts[t] == htobe16(option))
                        return -EEXIST;

        if (!GREEDY_REALLOC(client->req_opts, client->req_opts_allocated,
                            client->req_opts_len + 1))
                return -ENOMEM;

        client->req_opts[client->req_opts_len++] = htobe16(option);

        return 0;
}

int sd_dhcp6_client_set_request_mud_url(sd_dhcp6_client *client, char *mudurl) {

        assert_return(client, -EINVAL);
        assert_return(client->state == DHCP6_STATE_STOPPED, -EBUSY);
        assert_return(mudurl, -EINVAL);
        assert_return(strlen(mudurl) <= 255, -EINVAL);
        assert_return(http_url_is_valid(mudurl), -EINVAL);

        return free_and_strdup(&client->mudurl, mudurl);
}

int sd_dhcp6_client_get_prefix_delegation(sd_dhcp6_client *client, int *delegation) {
        assert_return(client, -EINVAL);
        assert_return(delegation, -EINVAL);

        *delegation = FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD);

        return 0;
}

int sd_dhcp6_client_set_prefix_delegation(sd_dhcp6_client *client, int delegation) {
        assert_return(client, -EINVAL);

        SET_FLAG(client->request, DHCP6_REQUEST_IA_PD, delegation);

        return 0;
}

int sd_dhcp6_client_get_address_request(sd_dhcp6_client *client, int *request) {
        assert_return(client, -EINVAL);
        assert_return(request, -EINVAL);

        *request = FLAGS_SET(client->request, DHCP6_REQUEST_IA_NA);

        return 0;
}

int sd_dhcp6_client_set_address_request(sd_dhcp6_client *client, int request) {
        assert_return(client, -EINVAL);

        SET_FLAG(client->request, DHCP6_REQUEST_IA_NA, request);

        return 0;
}

int sd_dhcp6_client_set_transaction_id(sd_dhcp6_client *client, uint32_t transaction_id) {
        assert_return(client, -EINVAL);

        client->transaction_id = transaction_id;

        return 0;
}

int sd_dhcp6_client_get_lease(sd_dhcp6_client *client, sd_dhcp6_lease **ret) {
        assert_return(client, -EINVAL);

        if (!client->lease)
                return -ENOMSG;

        if (ret)
                *ret = client->lease;

        return 0;
}

static void client_notify(sd_dhcp6_client *client, int event) {
        assert(client);

        if (client->callback)
                client->callback(client, event, client->userdata);
}

static int client_reset(sd_dhcp6_client *client) {
        assert(client);

        client->lease = sd_dhcp6_lease_unref(client->lease);

        client->receive_message =
                sd_event_source_unref(client->receive_message);

        client->transaction_id = 0;
        client->transaction_start = 0;

        client->retransmit_time = 0;
        client->retransmit_count = 0;

        (void) event_source_disable(client->timeout_resend);
        (void) event_source_disable(client->timeout_resend_expire);
        (void) event_source_disable(client->timeout_t1);
        (void) event_source_disable(client->timeout_t2);

        client->state = DHCP6_STATE_STOPPED;

        return 0;
}

static void client_stop(sd_dhcp6_client *client, int error) {
        DHCP6_CLIENT_DONT_DESTROY(client);

        assert(client);

        client_notify(client, error);

        client_reset(client);
}

static int client_send_message(sd_dhcp6_client *client, usec_t time_now) {
        _cleanup_free_ DHCP6Message *message = NULL;
        struct in6_addr all_servers =
                IN6ADDR_ALL_DHCP6_RELAY_AGENTS_AND_SERVERS_INIT;
        size_t len, optlen = 512;
        uint8_t *opt;
        int r;
        usec_t elapsed_usec;
        be16_t elapsed_time;

        assert(client);

        len = sizeof(DHCP6Message) + optlen;

        message = malloc0(len);
        if (!message)
                return -ENOMEM;

        opt = (uint8_t *)(message + 1);

        message->transaction_id = client->transaction_id;

        switch(client->state) {
        case DHCP6_STATE_INFORMATION_REQUEST:
                message->type = DHCP6_INFORMATION_REQUEST;

                if (client->mudurl) {
                        r = dhcp6_option_append(&opt, &optlen,
                                                SD_DHCP6_OPTION_MUD_URL, strlen(client->mudurl),
                                                client->mudurl);
                        if (r < 0)
                                return r;
                }

                break;

        case DHCP6_STATE_SOLICITATION:
                message->type = DHCP6_SOLICIT;

                r = dhcp6_option_append(&opt, &optlen,
                                        SD_DHCP6_OPTION_RAPID_COMMIT, 0, NULL);
                if (r < 0)
                        return r;

                if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_NA)) {
                        r = dhcp6_option_append_ia(&opt, &optlen,
                                                   &client->ia_na);
                        if (r < 0)
                                return r;
                }

                if (client->fqdn) {
                        r = dhcp6_option_append_fqdn(&opt, &optlen, client->fqdn);
                        if (r < 0)
                                return r;
                }

                if (client->mudurl) {
                        r = dhcp6_option_append(&opt, &optlen,
                                                SD_DHCP6_OPTION_MUD_URL, strlen(client->mudurl),
                                                client->mudurl);
                        if (r < 0)
                                return r;
                }

                if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD)) {
                        r = dhcp6_option_append_pd(opt, optlen, &client->ia_pd, &client->hint_pd_prefix);
                        if (r < 0)
                                return r;

                        opt += r;
                        optlen -= r;
                }

                break;

        case DHCP6_STATE_REQUEST:
        case DHCP6_STATE_RENEW:

                if (client->state == DHCP6_STATE_REQUEST)
                        message->type = DHCP6_REQUEST;
                else
                        message->type = DHCP6_RENEW;

                r = dhcp6_option_append(&opt, &optlen, SD_DHCP6_OPTION_SERVERID,
                                        client->lease->serverid_len,
                                        client->lease->serverid);
                if (r < 0)
                        return r;

                if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_NA)) {
                        r = dhcp6_option_append_ia(&opt, &optlen,
                                                   &client->lease->ia);
                        if (r < 0)
                                return r;
                }

                if (client->fqdn) {
                        r = dhcp6_option_append_fqdn(&opt, &optlen, client->fqdn);
                        if (r < 0)
                                return r;
                }

                if (client->mudurl) {
                        r = dhcp6_option_append(&opt, &optlen,
                                                SD_DHCP6_OPTION_MUD_URL, strlen(client->mudurl),
                                                client->mudurl);
                        if (r < 0)
                                return r;
                }

                if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD)) {
                        r = dhcp6_option_append_pd(opt, optlen, &client->lease->pd, NULL);
                        if (r < 0)
                                return r;

                        opt += r;
                        optlen -= r;
                }

                break;

        case DHCP6_STATE_REBIND:
                message->type = DHCP6_REBIND;

                if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_NA)) {
                        r = dhcp6_option_append_ia(&opt, &optlen, &client->lease->ia);
                        if (r < 0)
                                return r;
                }

                if (client->fqdn) {
                        r = dhcp6_option_append_fqdn(&opt, &optlen, client->fqdn);
                        if (r < 0)
                                return r;
                }

                if (client->mudurl) {
                        r = dhcp6_option_append(&opt, &optlen,
                                                SD_DHCP6_OPTION_MUD_URL, strlen(client->mudurl),
                                                client->mudurl);
                        if (r < 0)
                                return r;
                }

                if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD)) {
                        r = dhcp6_option_append_pd(opt, optlen, &client->lease->pd, NULL);
                        if (r < 0)
                                return r;

                        opt += r;
                        optlen -= r;
                }

                break;

        case DHCP6_STATE_STOPPED:
        case DHCP6_STATE_BOUND:
                return -EINVAL;
        }

        r = dhcp6_option_append(&opt, &optlen, SD_DHCP6_OPTION_ORO,
                                client->req_opts_len * sizeof(be16_t),
                                client->req_opts);
        if (r < 0)
                return r;

        assert(client->duid_len);
        r = dhcp6_option_append(&opt, &optlen, SD_DHCP6_OPTION_CLIENTID,
                                client->duid_len, &client->duid);
        if (r < 0)
                return r;

        elapsed_usec = time_now - client->transaction_start;
        if (elapsed_usec < 0xffff * USEC_PER_MSEC * 10)
                elapsed_time = htobe16(elapsed_usec / USEC_PER_MSEC / 10);
        else
                elapsed_time = 0xffff;

        r = dhcp6_option_append(&opt, &optlen, SD_DHCP6_OPTION_ELAPSED_TIME,
                                sizeof(elapsed_time), &elapsed_time);
        if (r < 0)
                return r;

        r = dhcp6_network_send_udp_socket(client->fd, &all_servers, message,
                                          len - optlen);
        if (r < 0)
                return r;

        log_dhcp6_client(client, "Sent %s",
                         dhcp6_message_type_to_string(message->type));

        return 0;
}

static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata) {
        sd_dhcp6_client *client = userdata;

        assert(s);
        assert(client);
        assert(client->lease);

        (void) event_source_disable(client->timeout_t2);

        log_dhcp6_client(client, "Timeout T2");

        client_start(client, DHCP6_STATE_REBIND);

        return 0;
}

static int client_timeout_t1(sd_event_source *s, uint64_t usec, void *userdata) {
        sd_dhcp6_client *client = userdata;

        assert(s);
        assert(client);
        assert(client->lease);

        (void) event_source_disable(client->timeout_t1);

        log_dhcp6_client(client, "Timeout T1");

        client_start(client, DHCP6_STATE_RENEW);

        return 0;
}

static int client_timeout_resend_expire(sd_event_source *s, uint64_t usec, void *userdata) {
        sd_dhcp6_client *client = userdata;
        DHCP6_CLIENT_DONT_DESTROY(client);
        enum DHCP6State state;

        assert(s);
        assert(client);
        assert(client->event);

        state = client->state;

        client_stop(client, SD_DHCP6_CLIENT_EVENT_RESEND_EXPIRE);

        /* RFC 3315, section 18.1.4., says that "...the client may choose to
           use a Solicit message to locate a new DHCP server..." */
        if (state == DHCP6_STATE_REBIND)
                client_start(client, DHCP6_STATE_SOLICITATION);

        return 0;
}

static usec_t client_timeout_compute_random(usec_t val) {
        return val - (random_u32() % USEC_PER_SEC) * val / 10 / USEC_PER_SEC;
}

static int client_timeout_resend(sd_event_source *s, uint64_t usec, void *userdata) {
        int r = 0;
        sd_dhcp6_client *client = userdata;
        usec_t time_now, init_retransmit_time = 0, max_retransmit_time = 0;
        usec_t max_retransmit_duration = 0;
        uint8_t max_retransmit_count = 0;
        char time_string[FORMAT_TIMESPAN_MAX];

        assert(s);
        assert(client);
        assert(client->event);

        (void) event_source_disable(client->timeout_resend);

        switch (client->state) {
        case DHCP6_STATE_INFORMATION_REQUEST:
                init_retransmit_time = DHCP6_INF_TIMEOUT;
                max_retransmit_time = DHCP6_INF_MAX_RT;

                break;

        case DHCP6_STATE_SOLICITATION:

                if (client->retransmit_count && client->lease) {
                        client_start(client, DHCP6_STATE_REQUEST);
                        return 0;
                }

                init_retransmit_time = DHCP6_SOL_TIMEOUT;
                max_retransmit_time = DHCP6_SOL_MAX_RT;

                break;

        case DHCP6_STATE_REQUEST:
                init_retransmit_time = DHCP6_REQ_TIMEOUT;
                max_retransmit_time = DHCP6_REQ_MAX_RT;
                max_retransmit_count = DHCP6_REQ_MAX_RC;

                break;

        case DHCP6_STATE_RENEW:
                init_retransmit_time = DHCP6_REN_TIMEOUT;
                max_retransmit_time = DHCP6_REN_MAX_RT;

                /* RFC 3315, section 18.1.3. says max retransmit duration will
                   be the remaining time until T2. Instead of setting MRD,
                   wait for T2 to trigger with the same end result */

                break;

        case DHCP6_STATE_REBIND:
                init_retransmit_time = DHCP6_REB_TIMEOUT;
                max_retransmit_time = DHCP6_REB_MAX_RT;

                if (event_source_is_enabled(client->timeout_resend_expire) <= 0) {
                        uint32_t expire = 0;

                        r = dhcp6_lease_ia_rebind_expire(&client->lease->ia, &expire);
                        if (r < 0) {
                                client_stop(client, r);
                                return 0;
                        }
                        max_retransmit_duration = expire * USEC_PER_SEC;
                }

                break;

        case DHCP6_STATE_STOPPED:
        case DHCP6_STATE_BOUND:
                return 0;
        }

        if (max_retransmit_count > 0 &&
            client->retransmit_count >= max_retransmit_count) {
                client_stop(client, SD_DHCP6_CLIENT_EVENT_RETRANS_MAX);
                return 0;
        }

        r = sd_event_now(client->event, clock_boottime_or_monotonic(), &time_now);
        if (r < 0)
                goto error;

        r = client_send_message(client, time_now);
        if (r >= 0)
                client->retransmit_count++;

        if (client->retransmit_time == 0) {
                client->retransmit_time =
                        client_timeout_compute_random(init_retransmit_time);

                if (client->state == DHCP6_STATE_SOLICITATION)
                        client->retransmit_time += init_retransmit_time / 10;

        } else {
                if (max_retransmit_time > 0 &&
                    client->retransmit_time > max_retransmit_time / 2)
                        client->retransmit_time = client_timeout_compute_random(max_retransmit_time);
                else
                        client->retransmit_time += client_timeout_compute_random(client->retransmit_time);
        }

        log_dhcp6_client(client, "Next retransmission in %s",
                         format_timespan(time_string, FORMAT_TIMESPAN_MAX, client->retransmit_time, USEC_PER_SEC));

        r = event_reset_time(client->event, &client->timeout_resend,
                             clock_boottime_or_monotonic(),
                             time_now + client->retransmit_time, 10 * USEC_PER_MSEC,
                             client_timeout_resend, client,
                             client->event_priority, "dhcp6-resend-timer", true);
        if (r < 0)
                goto error;

        if (max_retransmit_duration > 0 && event_source_is_enabled(client->timeout_resend_expire) <= 0) {

                log_dhcp6_client(client, "Max retransmission duration %"PRIu64" secs",
                                 max_retransmit_duration / USEC_PER_SEC);

                r = event_reset_time(client->event, &client->timeout_resend_expire,
                                     clock_boottime_or_monotonic(),
                                     time_now + max_retransmit_duration, USEC_PER_SEC,
                                     client_timeout_resend_expire, client,
                                     client->event_priority, "dhcp6-resend-expire-timer", true);
                if (r < 0)
                        goto error;
        }

error:
        if (r < 0)
                client_stop(client, r);

        return 0;
}

static int client_ensure_iaid(sd_dhcp6_client *client) {
        int r;
        uint32_t iaid;

        assert(client);

        if (client->iaid_set)
                return 0;

        r = dhcp_identifier_set_iaid(client->ifindex, client->mac_addr, client->mac_addr_len, true, &iaid);
        if (r < 0)
                return r;

        client->ia_na.ia_na.id = iaid;
        client->ia_pd.ia_pd.id = iaid;
        client->iaid_set = true;

        return 0;
}

static int client_parse_message(
                sd_dhcp6_client *client,
                DHCP6Message *message,
                size_t len,
                sd_dhcp6_lease *lease) {

        uint32_t lt_t1 = ~0, lt_t2 = ~0;
        bool clientid = false;
        size_t pos = 0;
        usec_t irt = IRT_DEFAULT;
        int r;

        assert(client);
        assert(message);
        assert(len >= sizeof(DHCP6Message));
        assert(lease);

        len -= sizeof(DHCP6Message);

        while (pos < len) {
                DHCP6Option *option = (DHCP6Option *) &message->options[pos];
                uint16_t optcode, optlen;
                be32_t iaid_lease;
                uint8_t *optval;
                int status;

                if (len < pos + offsetof(DHCP6Option, data))
                        return -ENOBUFS;

                optcode = be16toh(option->code);
                optlen = be16toh(option->len);
                optval = option->data;

                if (len < pos + offsetof(DHCP6Option, data) + optlen)
                        return -ENOBUFS;

                switch (optcode) {
                case SD_DHCP6_OPTION_CLIENTID:
                        if (clientid) {
                                log_dhcp6_client(client, "%s contains multiple clientids",
                                                 dhcp6_message_type_to_string(message->type));
                                return -EINVAL;
                        }

                        if (optlen != client->duid_len ||
                            memcmp(&client->duid, optval, optlen) != 0) {
                                log_dhcp6_client(client, "%s DUID does not match",
                                                 dhcp6_message_type_to_string(message->type));

                                return -EINVAL;
                        }
                        clientid = true;

                        break;

                case SD_DHCP6_OPTION_SERVERID:
                        r = dhcp6_lease_get_serverid(lease, NULL, NULL);
                        if (r >= 0) {
                                log_dhcp6_client(client, "%s contains multiple serverids",
                                                 dhcp6_message_type_to_string(message->type));
                                return -EINVAL;
                        }

                        r = dhcp6_lease_set_serverid(lease, optval, optlen);
                        if (r < 0)
                                return r;

                        break;

                case SD_DHCP6_OPTION_PREFERENCE:
                        if (optlen != 1)
                                return -EINVAL;

                        r = dhcp6_lease_set_preference(lease, optval[0]);
                        if (r < 0)
                                return r;

                        break;

                case SD_DHCP6_OPTION_STATUS_CODE:
                        status = dhcp6_option_parse_status(option, optlen + sizeof(DHCP6Option));
                        if (status < 0)
                                return status;

                        if (status > 0) {
                                log_dhcp6_client(client, "%s Status %s",
                                                 dhcp6_message_type_to_string(message->type),
                                                 dhcp6_message_status_to_string(status));

                                return -EINVAL;
                        }

                        break;

                case SD_DHCP6_OPTION_IA_NA:
                        if (client->state == DHCP6_STATE_INFORMATION_REQUEST) {
                                log_dhcp6_client(client, "Information request ignoring IA NA option");

                                break;
                        }

                        r = dhcp6_option_parse_ia(option, &lease->ia);
                        if (r < 0 && r != -ENOMSG)
                                return r;

                        r = dhcp6_lease_get_iaid(lease, &iaid_lease);
                        if (r < 0)
                                return r;

                        if (client->ia_na.ia_na.id != iaid_lease) {
                                log_dhcp6_client(client, "%s has wrong IAID for IA NA",
                                                 dhcp6_message_type_to_string(message->type));
                                return -EINVAL;
                        }

                        if (lease->ia.addresses) {
                                lt_t1 = MIN(lt_t1, be32toh(lease->ia.ia_na.lifetime_t1));
                                lt_t2 = MIN(lt_t2, be32toh(lease->ia.ia_na.lifetime_t1));
                        }

                        break;

                case SD_DHCP6_OPTION_IA_PD:
                        if (client->state == DHCP6_STATE_INFORMATION_REQUEST) {
                                log_dhcp6_client(client, "Information request ignoring IA PD option");

                                break;
                        }

                        r = dhcp6_option_parse_ia(option, &lease->pd);
                        if (r < 0 && r != -ENOMSG)
                                return r;

                        r = dhcp6_lease_get_pd_iaid(lease, &iaid_lease);
                        if (r < 0)
                                return r;

                        if (client->ia_pd.ia_pd.id != iaid_lease) {
                                log_dhcp6_client(client, "%s has wrong IAID for IA PD",
                                                 dhcp6_message_type_to_string(message->type));
                                return -EINVAL;
                        }

                        if (lease->pd.addresses) {
                                lt_t1 = MIN(lt_t1, be32toh(lease->pd.ia_pd.lifetime_t1));
                                lt_t2 = MIN(lt_t2, be32toh(lease->pd.ia_pd.lifetime_t2));
                        }

                        break;

                case SD_DHCP6_OPTION_RAPID_COMMIT:
                        r = dhcp6_lease_set_rapid_commit(lease);
                        if (r < 0)
                                return r;

                        break;

                case SD_DHCP6_OPTION_DNS_SERVERS:
                        r = dhcp6_lease_set_dns(lease, optval, optlen);
                        if (r < 0)
                                return r;

                        break;

                case SD_DHCP6_OPTION_DOMAIN_LIST:
                        r = dhcp6_lease_set_domains(lease, optval, optlen);
                        if (r < 0)
                                return r;

                        break;

                case SD_DHCP6_OPTION_NTP_SERVER:
                        r = dhcp6_lease_set_ntp(lease, optval, optlen);
                        if (r < 0)
                                return r;

                        break;

                case SD_DHCP6_OPTION_SNTP_SERVERS:
                        r = dhcp6_lease_set_sntp(lease, optval, optlen);
                        if (r < 0)
                                return r;

                        break;

                case SD_DHCP6_OPTION_INFORMATION_REFRESH_TIME:
                        if (optlen != 4)
                                return -EINVAL;

                        irt = unaligned_read_be32((be32_t *) optval) * USEC_PER_SEC;
                        break;
                }

                pos += offsetof(DHCP6Option, data) + optlen;
        }

        if (!clientid) {
                log_dhcp6_client(client, "%s has incomplete options",
                                 dhcp6_message_type_to_string(message->type));
                return -EINVAL;
        }

        if (client->state != DHCP6_STATE_INFORMATION_REQUEST) {
                r = dhcp6_lease_get_serverid(lease, NULL, NULL);
                if (r < 0) {
                        log_dhcp6_client(client, "%s has no server id",
                                         dhcp6_message_type_to_string(message->type));
                        return -EINVAL;
                }

        } else {
                if (lease->ia.addresses) {
                        lease->ia.ia_na.lifetime_t1 = htobe32(lt_t1);
                        lease->ia.ia_na.lifetime_t2 = htobe32(lt_t2);
                }

                if (lease->pd.addresses) {
                        lease->pd.ia_pd.lifetime_t1 = htobe32(lt_t1);
                        lease->pd.ia_pd.lifetime_t2 = htobe32(lt_t2);
                }
        }

        client->information_refresh_time_usec = MAX(irt, IRT_MINIMUM);

        return 0;
}

static int client_receive_reply(sd_dhcp6_client *client, DHCP6Message *reply, size_t len) {
        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
        bool rapid_commit;
        int r;

        assert(client);
        assert(reply);

        if (reply->type != DHCP6_REPLY)
                return 0;

        r = dhcp6_lease_new(&lease);
        if (r < 0)
                return -ENOMEM;

        r = client_parse_message(client, reply, len, lease);
        if (r < 0)
                return r;

        if (client->state == DHCP6_STATE_SOLICITATION) {
                r = dhcp6_lease_get_rapid_commit(lease, &rapid_commit);
                if (r < 0)
                        return r;

                if (!rapid_commit)
                        return 0;
        }

        sd_dhcp6_lease_unref(client->lease);
        client->lease = TAKE_PTR(lease);

        return DHCP6_STATE_BOUND;
}

static int client_receive_advertise(sd_dhcp6_client *client, DHCP6Message *advertise, size_t len) {
        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
        uint8_t pref_advertise = 0, pref_lease = 0;
        int r;

        if (advertise->type != DHCP6_ADVERTISE)
                return 0;

        r = dhcp6_lease_new(&lease);
        if (r < 0)
                return r;

        r = client_parse_message(client, advertise, len, lease);
        if (r < 0)
                return r;

        r = dhcp6_lease_get_preference(lease, &pref_advertise);
        if (r < 0)
                return r;

        r = dhcp6_lease_get_preference(client->lease, &pref_lease);

        if (r < 0 || pref_advertise > pref_lease) {
                sd_dhcp6_lease_unref(client->lease);
                client->lease = TAKE_PTR(lease);
                r = 0;
        }

        if (pref_advertise == 255 || client->retransmit_count > 1)
                r = DHCP6_STATE_REQUEST;

        return r;
}

static int client_receive_message(
                sd_event_source *s,
                int fd, uint32_t
                revents,
                void *userdata) {

        sd_dhcp6_client *client = userdata;
        DHCP6_CLIENT_DONT_DESTROY(client);
        _cleanup_free_ DHCP6Message *message = NULL;
        ssize_t buflen, len;
        int r = 0;

        assert(s);
        assert(client);
        assert(client->event);

        buflen = next_datagram_size_fd(fd);
        if (buflen == -ENETDOWN) {
                /* the link is down. Don't return an error or the I/O event
                   source will be disconnected and we won't be able to receive
                   packets again when the link comes back. */
                return 0;
        }
        if (buflen < 0)
                return buflen;

        message = malloc(buflen);
        if (!message)
                return -ENOMEM;

        len = recv(fd, message, buflen, 0);
        if (len < 0) {
                /* see comment above for why we shouldn't error out on ENETDOWN. */
                if (IN_SET(errno, EAGAIN, EINTR, ENETDOWN))
                        return 0;

                return log_dhcp6_client_errno(client, errno, "Could not receive message from UDP socket: %m");

        }
        if ((size_t) len < sizeof(DHCP6Message)) {
                log_dhcp6_client(client, "Too small to be DHCP6 message: ignoring");
                return 0;
        }

        switch(message->type) {
        case DHCP6_SOLICIT:
        case DHCP6_REQUEST:
        case DHCP6_CONFIRM:
        case DHCP6_RENEW:
        case DHCP6_REBIND:
        case DHCP6_RELEASE:
        case DHCP6_DECLINE:
        case DHCP6_INFORMATION_REQUEST:
        case DHCP6_RELAY_FORW:
        case DHCP6_RELAY_REPL:
                return 0;

        case DHCP6_ADVERTISE:
        case DHCP6_REPLY:
        case DHCP6_RECONFIGURE:
                break;

        default:
                log_dhcp6_client(client, "Unknown message type %d", message->type);
                return 0;
        }

        if (client->transaction_id != (message->transaction_id &
                                       htobe32(0x00ffffff)))
                return 0;

        switch (client->state) {
        case DHCP6_STATE_INFORMATION_REQUEST:
                r = client_receive_reply(client, message, len);
                if (r < 0)
                        return 0;

                client_notify(client, SD_DHCP6_CLIENT_EVENT_INFORMATION_REQUEST);

                client_start(client, DHCP6_STATE_STOPPED);

                break;

        case DHCP6_STATE_SOLICITATION:
                r = client_receive_advertise(client, message, len);

                if (r == DHCP6_STATE_REQUEST) {
                        client_start(client, r);

                        break;
                }

                _fallthrough_; /* for Soliciation Rapid Commit option check */
        case DHCP6_STATE_REQUEST:
        case DHCP6_STATE_RENEW:
        case DHCP6_STATE_REBIND:

                r = client_receive_reply(client, message, len);
                if (r < 0)
                        return 0;

                if (r == DHCP6_STATE_BOUND) {

                        r = client_start(client, DHCP6_STATE_BOUND);
                        if (r < 0) {
                                client_stop(client, r);
                                return 0;
                        }

                        client_notify(client, SD_DHCP6_CLIENT_EVENT_IP_ACQUIRE);
                }

                break;

        case DHCP6_STATE_BOUND:

                break;

        case DHCP6_STATE_STOPPED:
                return 0;
        }

        log_dhcp6_client(client, "Recv %s",
                         dhcp6_message_type_to_string(message->type));

        return 0;
}

static int client_get_lifetime(sd_dhcp6_client *client, uint32_t *lifetime_t1,
                               uint32_t *lifetime_t2) {
        assert_return(client, -EINVAL);
        assert_return(client->lease, -EINVAL);

        if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_NA) && client->lease->ia.addresses) {
                *lifetime_t1 = be32toh(client->lease->ia.ia_na.lifetime_t1);
                *lifetime_t2 = be32toh(client->lease->ia.ia_na.lifetime_t2);

                return 0;
        }

        if (FLAGS_SET(client->request, DHCP6_REQUEST_IA_PD) && client->lease->pd.addresses) {
                *lifetime_t1 = be32toh(client->lease->pd.ia_pd.lifetime_t1);
                *lifetime_t2 = be32toh(client->lease->pd.ia_pd.lifetime_t2);

                return 0;
        }

        return -ENOMSG;
}

static int client_start(sd_dhcp6_client *client, enum DHCP6State state) {
        int r;
        usec_t timeout, time_now;
        char time_string[FORMAT_TIMESPAN_MAX];
        uint32_t lifetime_t1, lifetime_t2;

        assert_return(client, -EINVAL);
        assert_return(client->event, -EINVAL);
        assert_return(client->ifindex > 0, -EINVAL);
        assert_return(client->state != state, -EINVAL);

        (void) event_source_disable(client->timeout_resend_expire);
        (void) event_source_disable(client->timeout_resend);
        client->retransmit_time = 0;
        client->retransmit_count = 0;

        r = sd_event_now(client->event, clock_boottime_or_monotonic(), &time_now);
        if (r < 0)
                return r;

        if (!client->receive_message) {
                r = sd_event_add_io(client->event, &client->receive_message,
                                    client->fd, EPOLLIN, client_receive_message,
                                    client);
                if (r < 0)
                        goto error;

                r = sd_event_source_set_priority(client->receive_message,
                                                 client->event_priority);
                if (r < 0)
                        goto error;

                r = sd_event_source_set_description(client->receive_message,
                                                    "dhcp6-receive-message");
                if (r < 0)
                        goto error;
        }

        switch (state) {
        case DHCP6_STATE_STOPPED:
                if (client->state == DHCP6_STATE_INFORMATION_REQUEST) {
                        client->state = DHCP6_STATE_STOPPED;

                        return 0;
                }

                _fallthrough_;
        case DHCP6_STATE_SOLICITATION:
                client->state = DHCP6_STATE_SOLICITATION;

                break;

        case DHCP6_STATE_INFORMATION_REQUEST:
        case DHCP6_STATE_REQUEST:
        case DHCP6_STATE_RENEW:
        case DHCP6_STATE_REBIND:

                client->state = state;

                break;

        case DHCP6_STATE_BOUND:

                r = client_get_lifetime(client, &lifetime_t1, &lifetime_t2);
                if (r < 0)
                        goto error;

                if (lifetime_t1 == 0xffffffff || lifetime_t2 == 0xffffffff) {
                        log_dhcp6_client(client, "Infinite T1 0x%08x or T2 0x%08x",
                                         lifetime_t1, lifetime_t2);

                        return 0;
                }

                timeout = client_timeout_compute_random(lifetime_t1 * USEC_PER_SEC);

                log_dhcp6_client(client, "T1 expires in %s",
                                 format_timespan(time_string, FORMAT_TIMESPAN_MAX, timeout, USEC_PER_SEC));

                r = event_reset_time(client->event, &client->timeout_t1,
                                     clock_boottime_or_monotonic(),
                                     time_now + timeout, 10 * USEC_PER_SEC,
                                     client_timeout_t1, client,
                                     client->event_priority, "dhcp6-t1-timeout", true);
                if (r < 0)
                        goto error;

                timeout = client_timeout_compute_random(lifetime_t2 * USEC_PER_SEC);

                log_dhcp6_client(client, "T2 expires in %s",
                                 format_timespan(time_string, FORMAT_TIMESPAN_MAX, timeout, USEC_PER_SEC));

                r = event_reset_time(client->event, &client->timeout_t2,
                                     clock_boottime_or_monotonic(),
                                     time_now + timeout, 10 * USEC_PER_SEC,
                                     client_timeout_t2, client,
                                     client->event_priority, "dhcp6-t2-timeout", true);
                if (r < 0)
                        goto error;

                client->state = state;

                return 0;
        }

        client->transaction_id = random_u32() & htobe32(0x00ffffff);
        client->transaction_start = time_now;

        r = event_reset_time(client->event, &client->timeout_resend,
                             clock_boottime_or_monotonic(),
                             0, 0,
                             client_timeout_resend, client,
                             client->event_priority, "dhcp6-resend-timeout", true);
        if (r < 0)
                goto error;

        return 0;

 error:
        client_reset(client);
        return r;
}

int sd_dhcp6_client_stop(sd_dhcp6_client *client) {
        assert_return(client, -EINVAL);

        client_stop(client, SD_DHCP6_CLIENT_EVENT_STOP);

        client->fd = safe_close(client->fd);

        return 0;
}

int sd_dhcp6_client_is_running(sd_dhcp6_client *client) {
        assert_return(client, -EINVAL);

        return client->state != DHCP6_STATE_STOPPED;
}

int sd_dhcp6_client_start(sd_dhcp6_client *client) {
        enum DHCP6State state = DHCP6_STATE_SOLICITATION;
        int r = 0;

        assert_return(client, -EINVAL);
        assert_return(client->event, -EINVAL);
        assert_return(client->ifindex > 0, -EINVAL);
        assert_return(in_addr_is_link_local(AF_INET6, (const union in_addr_union *) &client->local_address) > 0, -EINVAL);

        if (!IN_SET(client->state, DHCP6_STATE_STOPPED))
                return -EBUSY;

        if (!client->information_request && !client->request)
                return -EINVAL;

        r = client_reset(client);
        if (r < 0)
                return r;

        r = client_ensure_iaid(client);
        if (r < 0)
                return r;

        r = client_ensure_duid(client);
        if (r < 0)
                return r;

        if (client->fd < 0) {
                r = dhcp6_network_bind_udp_socket(client->ifindex, &client->local_address);
                if (r < 0) {
                        _cleanup_free_ char *p = NULL;

                        (void) in_addr_to_string(AF_INET6, (const union in_addr_union*) &client->local_address, &p);
                        return log_dhcp6_client_errno(client, r,
                                                      "Failed to bind to UDP socket at address %s: %m", strna(p));
                }

                client->fd = r;
        }

        if (client->information_request) {
                usec_t t = now(CLOCK_MONOTONIC);

                if (t < usec_add(client->information_request_time_usec, client->information_refresh_time_usec))
                        return 0;

                client->information_request_time_usec = t;
                state = DHCP6_STATE_INFORMATION_REQUEST;
        }

        log_dhcp6_client(client, "Started in %s mode",
                         client->information_request? "Information request":
                         "Managed");

        return client_start(client, state);
}

int sd_dhcp6_client_attach_event(sd_dhcp6_client *client, sd_event *event, int64_t priority) {
        int r;

        assert_return(client, -EINVAL);
        assert_return(!client->event, -EBUSY);

        if (event)
                client->event = sd_event_ref(event);
        else {
                r = sd_event_default(&client->event);
                if (r < 0)
                        return 0;
        }

        client->event_priority = priority;

        return 0;
}

int sd_dhcp6_client_detach_event(sd_dhcp6_client *client) {
        assert_return(client, -EINVAL);

        client->event = sd_event_unref(client->event);

        return 0;
}

sd_event *sd_dhcp6_client_get_event(sd_dhcp6_client *client) {
        assert_return(client, NULL);

        return client->event;
}

static sd_dhcp6_client *dhcp6_client_free(sd_dhcp6_client *client) {
        assert(client);

        client->timeout_resend = sd_event_source_unref(client->timeout_resend);
        client->timeout_resend_expire = sd_event_source_unref(client->timeout_resend_expire);
        client->timeout_t1 = sd_event_source_unref(client->timeout_t1);
        client->timeout_t2 = sd_event_source_unref(client->timeout_t2);

        client_reset(client);

        client->fd = safe_close(client->fd);

        sd_dhcp6_client_detach_event(client);

        free(client->req_opts);
        free(client->fqdn);
        free(client->mudurl);
        return mfree(client);
}

DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp6_client, sd_dhcp6_client, dhcp6_client_free);

int sd_dhcp6_client_new(sd_dhcp6_client **ret) {
        _cleanup_(sd_dhcp6_client_unrefp) sd_dhcp6_client *client = NULL;
        _cleanup_free_ be16_t *req_opts = NULL;
        size_t t;

        assert_return(ret, -EINVAL);

        req_opts = new(be16_t, ELEMENTSOF(default_req_opts));
        if (!req_opts)
                return -ENOMEM;

        for (t = 0; t < ELEMENTSOF(default_req_opts); t++)
                req_opts[t] = htobe16(default_req_opts[t]);

        client = new(sd_dhcp6_client, 1);
        if (!client)
                return -ENOMEM;

        *client = (sd_dhcp6_client) {
                .n_ref = 1,
                .ia_na.type = SD_DHCP6_OPTION_IA_NA,
                .ia_pd.type = SD_DHCP6_OPTION_IA_PD,
                .ifindex = -1,
                .request = DHCP6_REQUEST_IA_NA,
                .fd = -1,
                .req_opts_len = ELEMENTSOF(default_req_opts),
                .hint_pd_prefix.iapdprefix.lifetime_preferred = (be32_t) -1,
                .hint_pd_prefix.iapdprefix.lifetime_valid = (be32_t) -1,
                .req_opts = TAKE_PTR(req_opts),
        };

        *ret = TAKE_PTR(client);

        return 0;
}
