chiark / gitweb /
libsystemd-dhcp: Use be32_t for IP addresses in network order.
[elogind.git] / src / libsystemd-dhcp / dhcp-client.c
index 4d1722f..fe41067 100644 (file)
 
 #define DHCP_CLIENT_MIN_OPTIONS_SIZE            312
 
+struct DHCPLease {
+        uint32_t t1;
+        uint32_t t2;
+        uint32_t lifetime;
+        be32_t address;
+        be32_t server_address;
+        be32_t subnet_mask;
+        be32_t router;
+};
+
+typedef struct DHCPLease DHCPLease;
+
 struct sd_dhcp_client {
         DHCPState state;
+        sd_event *event;
+        sd_event_source *timeout_resend;
         int index;
+        int fd;
+        union sockaddr_union link;
+        sd_event_source *receive_message;
         uint8_t *req_opts;
         size_t req_opts_size;
-        uint32_t last_addr;
+        be32_t last_addr;
         struct ether_addr mac_addr;
         uint32_t xid;
+        usec_t start_time;
+        unsigned int attempt;
+        usec_t request_sent;
+        sd_event_source *timeout_t1;
+        sd_event_source *timeout_t2;
+        sd_event_source *timeout_expire;
+        sd_dhcp_client_cb_t cb;
+        void *userdata;
+        DHCPLease *lease;
 };
 
 static const uint8_t default_req_opts[] = {
@@ -51,6 +77,17 @@ static const uint8_t default_req_opts[] = {
         DHCP_OPTION_NTP_SERVER,
 };
 
+int sd_dhcp_client_set_callback(sd_dhcp_client *client, sd_dhcp_client_cb_t cb,
+                                void *userdata)
+{
+        assert_return(client, -EINVAL);
+
+        client->cb = cb;
+        client->userdata = userdata;
+
+        return 0;
+}
+
 int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option)
 {
         size_t i;
@@ -119,11 +156,158 @@ int sd_dhcp_client_set_mac(sd_dhcp_client *client,
         return 0;
 }
 
+int sd_dhcp_client_get_address(sd_dhcp_client *client, struct in_addr *addr)
+{
+        assert_return(client, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        switch (client->state) {
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_SELECTING:
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_REQUESTING:
+                return -EADDRNOTAVAIL;
+
+        case DHCP_STATE_BOUND:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+                addr->s_addr = client->lease->address;
+
+                break;
+        }
+
+        return 0;
+}
+
+int sd_dhcp_client_get_netmask(sd_dhcp_client *client, struct in_addr *addr)
+{
+        assert_return(client, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        switch (client->state) {
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_SELECTING:
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_REQUESTING:
+                return -EADDRNOTAVAIL;
+
+        case DHCP_STATE_BOUND:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+                addr->s_addr = client->lease->subnet_mask;
+
+                break;
+        }
+
+        return 0;
+}
+
+int sd_dhcp_client_prefixlen(const struct in_addr *addr)
+{
+        int len = 0;
+        uint32_t mask;
+
+        assert_return(addr, -EADDRNOTAVAIL);
+
+        mask = be32toh(addr->s_addr);
+        while (mask) {
+                len++;
+                mask = mask << 1;
+        }
+
+        return len;
+}
+
+int sd_dhcp_client_get_router(sd_dhcp_client *client, struct in_addr *addr)
+{
+        assert_return(client, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        switch (client->state) {
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_SELECTING:
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_REQUESTING:
+                return -EADDRNOTAVAIL;
+
+        case DHCP_STATE_BOUND:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+                addr->s_addr = client->lease->router;
+
+                break;
+        }
+
+        return 0;
+}
+
+static int client_notify(sd_dhcp_client *client, int event)
+{
+        if (client->cb)
+                client->cb(client, event, client->userdata);
+
+        return 0;
+}
+
+static int client_stop(sd_dhcp_client *client, int error)
+{
+        assert_return(client, -EINVAL);
+        assert_return(client->state != DHCP_STATE_INIT &&
+                      client->state != DHCP_STATE_INIT_REBOOT, -EALREADY);
+
+        client->receive_message =
+                sd_event_source_unref(client->receive_message);
+
+        if (client->fd >= 0)
+                close(client->fd);
+        client->fd = -1;
+
+        client->timeout_resend = sd_event_source_unref(client->timeout_resend);
+
+        client->timeout_t1 = sd_event_source_unref(client->timeout_t1);
+        client->timeout_t2 = sd_event_source_unref(client->timeout_t2);
+        client->timeout_expire = sd_event_source_unref(client->timeout_expire);
+
+        client->attempt = 1;
+
+        client_notify(client, error);
+
+        switch (client->state) {
+
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_SELECTING:
+        case DHCP_STATE_REQUESTING:
+        case DHCP_STATE_BOUND:
+
+                client->start_time = 0;
+                client->state = DHCP_STATE_INIT;
+                break;
+
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+
+                break;
+        }
+
+        if (client->lease) {
+                free(client->lease);
+                client->lease = NULL;
+        }
+
+        return 0;
+}
+
 static int client_packet_init(sd_dhcp_client *client, uint8_t type,
-                              DHCPMessage *message, uint8_t **opt,
-                              size_t *optlen)
+                              DHCPMessage *message, uint16_t secs,
+                              uint8_t **opt, size_t *optlen)
 {
         int err;
+        be16_t max_size;
 
         *opt = (uint8_t *)(message + 1);
 
@@ -136,6 +320,10 @@ static int client_packet_init(sd_dhcp_client *client, uint8_t type,
         message->hlen = ETHER_ADDR_LEN;
         message->xid = htobe32(client->xid);
 
+        /* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
+           refuse to issue an DHCP lease if 'secs' is set to zero */
+        message->secs = htobe16(secs);
+
         memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
         (*opt)[0] = 0x63;
         (*opt)[1] = 0x82;
@@ -163,6 +351,17 @@ static int client_packet_init(sd_dhcp_client *client, uint8_t type,
                                          client->req_opts);
                 if (err < 0)
                         return err;
+
+                /* Some DHCP servers will send bigger DHCP packets than the
+                   defined default size unless the Maximum Messge Size option
+                   is explicitely set */
+                max_size = htobe16(DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE +
+                                   DHCP_CLIENT_MIN_OPTIONS_SIZE);
+                err = dhcp_option_append(opt, optlen,
+                                         DHCP_OPTION_MAXIMUM_MESSAGE_SIZE,
+                                         2, &max_size);
+                if (err < 0)
+                        return err;
         }
 
         return 0;
@@ -189,7 +388,29 @@ static uint16_t client_checksum(void *buf, int len)
         return ~((sum & 0xffff) + (sum >> 16));
 }
 
-static int client_send_discover(sd_dhcp_client *client)
+static void client_append_ip_headers(DHCPPacket *packet, uint16_t len)
+{
+        packet->ip.version = IPVERSION;
+        packet->ip.ihl = DHCP_IP_SIZE / 4;
+        packet->ip.tot_len = htobe16(len);
+
+        packet->ip.protocol = IPPROTO_UDP;
+        packet->ip.saddr = INADDR_ANY;
+        packet->ip.daddr = INADDR_BROADCAST;
+
+        packet->udp.source = htobe16(DHCP_PORT_CLIENT);
+        packet->udp.dest = htobe16(DHCP_PORT_SERVER);
+        packet->udp.len = htobe16(len - DHCP_IP_SIZE);
+
+        packet->ip.check = packet->udp.len;
+        packet->udp.check = client_checksum(&packet->ip.ttl, len - 8);
+
+        packet->ip.ttl = IPDEFTTL;
+        packet->ip.check = 0;
+        packet->ip.check = client_checksum(&packet->ip, DHCP_IP_SIZE);
+}
+
+static int client_send_discover(sd_dhcp_client *client, uint16_t secs)
 {
         int err = 0;
         _cleanup_free_ DHCPPacket *discover;
@@ -205,7 +426,7 @@ static int client_send_discover(sd_dhcp_client *client)
                 return -ENOMEM;
 
         err = client_packet_init(client, DHCP_DISCOVER, &discover->dhcp,
-                                 &opt, &optlen);
+                                 secs, &opt, &optlen);
         if (err < 0)
                 return err;
 
@@ -221,34 +442,487 @@ static int client_send_discover(sd_dhcp_client *client)
         if (err < 0)
                 return err;
 
-        discover->ip.version = IPVERSION;
-        discover->ip.ihl = sizeof(discover->ip) >> 2;
-        discover->ip.tot_len = htobe16(len);
+        client_append_ip_headers(discover, len);
+
+        err = dhcp_network_send_raw_socket(client->fd, &client->link,
+                                           discover, len);
+
+        return err;
+}
+
+static int client_send_request(sd_dhcp_client *client, uint16_t secs)
+{
+        _cleanup_free_ DHCPPacket *request;
+        size_t optlen, len;
+        int err;
+        uint8_t *opt;
+
+        optlen = DHCP_CLIENT_MIN_OPTIONS_SIZE;
+        len = DHCP_MESSAGE_SIZE + optlen;
+
+        request = malloc0(len);
+        if (!request)
+                return -ENOMEM;
+
+        err = client_packet_init(client, DHCP_REQUEST, &request->dhcp, secs,
+                                 &opt, &optlen);
+        if (err < 0)
+                return err;
+
+        if (client->state == DHCP_STATE_REQUESTING) {
+                err = dhcp_option_append(&opt, &optlen,
+                                         DHCP_OPTION_REQUESTED_IP_ADDRESS,
+                                         4, &client->lease->address);
+                if (err < 0)
+                        return err;
+
+                err = dhcp_option_append(&opt, &optlen,
+                                         DHCP_OPTION_SERVER_IDENTIFIER,
+                                         4, &client->lease->server_address);
+                if (err < 0)
+                        return err;
+        }
+
+        err = dhcp_option_append(&opt, &optlen, DHCP_OPTION_END, 0, NULL);
+        if (err < 0)
+                return err;
+
+        client_append_ip_headers(request, len);
+
+        err = dhcp_network_send_raw_socket(client->fd, &client->link,
+                                           request, len);
+
+        return err;
+}
+
+static int client_timeout_resend(sd_event_source *s, uint64_t usec,
+                                 void *userdata)
+{
+        sd_dhcp_client *client = userdata;
+        usec_t next_timeout;
+        uint16_t secs;
+        int err = 0;
+
+        secs = (usec - client->start_time) / USEC_PER_SEC;
+
+        if (client->attempt < 64)
+                client->attempt *= 2;
+
+        next_timeout = usec + (client->attempt - 1) * USEC_PER_SEC +
+                (random_u() & 0x1fffff);
+
+        err = sd_event_add_monotonic(client->event, next_timeout,
+                                     10 * USEC_PER_MSEC,
+                                     client_timeout_resend, client,
+                                     &client->timeout_resend);
+        if (err < 0)
+                goto error;
+
+        switch (client->state) {
+        case DHCP_STATE_INIT:
+                err = client_send_discover(client, secs);
+                if (err >= 0) {
+                        client->state = DHCP_STATE_SELECTING;
+                        client->attempt = 1;
+                } else {
+                        if (client->attempt >= 64)
+                                goto error;
+                }
+
+                break;
+
+        case DHCP_STATE_SELECTING:
+                err = client_send_discover(client, secs);
+                if (err < 0 && client->attempt >= 64)
+                        goto error;
+
+                break;
+
+        case DHCP_STATE_REQUESTING:
+                err = client_send_request(client, secs);
+                if (err < 0 && client->attempt >= 64)
+                         goto error;
+
+                client->request_sent = usec;
+
+                break;
+
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_BOUND:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+
+                break;
+        }
+
+        return 0;
+
+error:
+        client_stop(client, err);
+
+        /* Errors were dealt with when stopping the client, don't spill
+           errors into the event loop handler */
+        return 0;
+}
+
+static int client_timeout_expire(sd_event_source *s, uint64_t usec,
+                                 void *userdata)
+{
+        sd_dhcp_client *client = userdata;
+
+        client_stop(client, DHCP_EVENT_EXPIRED);
+
+        return 0;
+}
+
+static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata)
+{
+        return 0;
+}
+
+static int client_timeout_t1(sd_event_source *s, uint64_t usec, void *userdata)
+{
+        return 0;
+}
+
+static int client_parse_offer(uint8_t code, uint8_t len, const uint8_t *option,
+                              void *user_data)
+{
+        DHCPLease *lease = user_data;
+        be32_t val;
+
+        switch(code) {
+
+        case DHCP_OPTION_IP_ADDRESS_LEASE_TIME:
+                if (len == 4) {
+                        memcpy(&val, option, 4);
+                        lease->lifetime = be32toh(val);
+                }
+
+                break;
+
+        case DHCP_OPTION_SERVER_IDENTIFIER:
+                if (len >= 4)
+                        memcpy(&lease->server_address, option, 4);
+
+                break;
+
+        case DHCP_OPTION_SUBNET_MASK:
+                if (len >= 4)
+                        memcpy(&lease->subnet_mask, option, 4);
+
+                break;
+
+        case DHCP_OPTION_ROUTER:
+                if (len >= 4)
+                        memcpy(&lease->router, option, 4);
+
+                break;
+
+        case DHCP_OPTION_RENEWAL_T1_TIME:
+                if (len == 4) {
+                        memcpy(&val, option, 4);
+                        lease->t1 = be32toh(val);
+                }
+
+                break;
+
+        case DHCP_OPTION_REBINDING_T2_TIME:
+                if (len == 4) {
+                        memcpy(&val, option, 4);
+                        lease->t2 = be32toh(val);
+                }
+
+                break;
+        }
+
+        return 0;
+}
+
+static int client_verify_headers(sd_dhcp_client *client, DHCPPacket *message,
+                                 size_t len)
+{
+        size_t hdrlen;
+
+        if (len < (DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE))
+                return -EINVAL;
+
+        hdrlen = message->ip.ihl * 4;
+        if (hdrlen < 20 || hdrlen > len || client_checksum(&message->ip,
+                                                           hdrlen))
+                return -EINVAL;
+
+        message->ip.check = message->udp.len;
+        message->ip.ttl = 0;
+
+        if (hdrlen + be16toh(message->udp.len) > len ||
+            client_checksum(&message->ip.ttl, be16toh(message->udp.len) + 12))
+                return -EINVAL;
+
+        if (be16toh(message->udp.source) != DHCP_PORT_SERVER ||
+            be16toh(message->udp.dest) != DHCP_PORT_CLIENT)
+                return -EINVAL;
+
+        if (message->dhcp.op != BOOTREPLY)
+                return -EINVAL;
+
+        if (be32toh(message->dhcp.xid) != client->xid)
+                return -EINVAL;
+
+        if (memcmp(&message->dhcp.chaddr[0], &client->mac_addr.ether_addr_octet,
+                    ETHER_ADDR_LEN))
+                return -EINVAL;
+
+        return 0;
+}
+
+static int client_receive_offer(sd_dhcp_client *client, DHCPPacket *offer,
+                                size_t len)
+{
+        int err;
+        DHCPLease *lease;
+
+        err = client_verify_headers(client, offer, len);
+        if (err < 0)
+                return err;
+
+        lease = new0(DHCPLease, 1);
+        if (!lease)
+                return -ENOMEM;
+
+        len = len - DHCP_IP_UDP_SIZE;
+        if (dhcp_option_parse(&offer->dhcp, len, client_parse_offer,
+                              lease) != DHCP_OFFER)
+                goto error;
+
+        lease->address = offer->dhcp.yiaddr;
+
+        if (lease->address == INADDR_ANY ||
+            lease->server_address == INADDR_ANY ||
+            lease->subnet_mask == INADDR_ANY ||
+            lease->lifetime == 0)
+                goto error;
+
+        client->lease = lease;
 
-        discover->ip.protocol = IPPROTO_UDP;
-        discover->ip.saddr = INADDR_ANY;
-        discover->ip.daddr = INADDR_BROADCAST;
+        return 0;
+
+error:
+        free(lease);
+
+        return -ENOMSG;
+}
+
+static int client_receive_ack(sd_dhcp_client *client, DHCPPacket *offer,
+                              size_t len)
+{
+        int r;
+        DHCPLease *lease;
+
+        r = client_verify_headers(client, offer, len);
+        if (r < 0)
+                return r;
+
+        lease = new0(DHCPLease, 1);
+        if (!lease)
+                return -ENOBUFS;
+
+        len = len - DHCP_IP_UDP_SIZE;
+        r = dhcp_option_parse(&offer->dhcp, len, client_parse_offer, lease);
 
-        discover->udp.source = htobe16(DHCP_PORT_CLIENT);
-        discover->udp.dest = htobe16(DHCP_PORT_SERVER);
-        discover->udp.len = htobe16(len - sizeof(discover->ip));
+        if (r != DHCP_ACK)
+                goto error;
 
-        discover->ip.check = discover->udp.len;
-        discover->udp.check = client_checksum(&discover->ip.ttl,
-                                              len - 8);
+        lease->address = offer->dhcp.yiaddr;
 
-        discover->ip.ttl = IPDEFTTL;
-        discover->ip.check = 0;
-        discover->ip.check = client_checksum(&discover->ip,
-                                             sizeof(discover->ip));
+        if (lease->address == INADDR_ANY ||
+            lease->server_address == INADDR_ANY ||
+            lease->subnet_mask == INADDR_ANY || lease->lifetime == 0) {
+                r = -ENOMSG;
+                goto error;
+        }
+
+        r = DHCP_EVENT_IP_ACQUIRE;
+        if (client->lease) {
+                if (client->lease->address != lease->address ||
+                    client->lease->subnet_mask != lease->subnet_mask ||
+                    client->lease->router != lease->router) {
+                        r = DHCP_EVENT_IP_CHANGE;
+                }
+
+                free(client->lease);
+        }
+
+        client->lease = lease;
 
-        err = dhcp_network_send_raw_packet(client->index, discover, len);
+        return r;
+
+error:
+        free(lease);
+
+        return r;
+}
+
+static uint64_t client_compute_timeout(uint64_t request_sent,
+                                       uint32_t lifetime)
+{
+        return request_sent + (lifetime - 3) * USEC_PER_SEC +
+                + (random_u() & 0x1fffff);
+}
+
+static int client_set_lease_timeouts(sd_dhcp_client *client, uint64_t usec)
+{
+        int err;
+        uint64_t next_timeout;
+
+        if (client->lease->lifetime < 10)
+                return -EINVAL;
+
+        if (!client->lease->t1)
+                client->lease->t1 = client->lease->lifetime / 2;
+
+        next_timeout = client_compute_timeout(client->request_sent,
+                                              client->lease->t1);
+        if (next_timeout < usec)
+                return -EINVAL;
+
+        err = sd_event_add_monotonic(client->event, next_timeout,
+                                     10 * USEC_PER_MSEC,
+                                     client_timeout_t1, client,
+                                     &client->timeout_t1);
+        if (err < 0)
+                return err;
+
+        if (!client->lease->t2)
+                client->lease->t2 = client->lease->lifetime * 7 / 8;
+
+        if (client->lease->t2 < client->lease->t1)
+                return -EINVAL;
+
+        if (client->lease->lifetime < client->lease->t2)
+                return -EINVAL;
+
+        next_timeout = client_compute_timeout(client->request_sent,
+                                              client->lease->t2);
+        if (next_timeout < usec)
+                return -EINVAL;
+
+        err = sd_event_add_monotonic(client->event, next_timeout,
+                                     10 * USEC_PER_MSEC,
+                                     client_timeout_t2, client,
+                                     &client->timeout_t2);
+        if (err < 0)
+                return err;
+
+        next_timeout = client_compute_timeout(client->request_sent,
+                                              client->lease->lifetime);
+        if (next_timeout < usec)
+                return -EINVAL;
+
+        err = sd_event_add_monotonic(client->event, next_timeout,
+                                     10 * USEC_PER_MSEC,
+                                     client_timeout_expire, client,
+                                     &client->timeout_expire);
+        if (err < 0)
+                return err;
+
+        return 0;
+}
+
+static int client_receive_raw_message(sd_event_source *s, int fd,
+                                      uint32_t revents, void *userdata)
+{
+        sd_dhcp_client *client = userdata;
+        uint8_t buf[sizeof(DHCPPacket) + DHCP_CLIENT_MIN_OPTIONS_SIZE];
+        int buflen = sizeof(buf);
+        int len, r = 0;
+        DHCPPacket *message;
+        usec_t time_now;
+
+        len = read(fd, &buf, buflen);
+        if (len < 0)
+                return 0;
+
+        r = sd_event_get_now_monotonic(client->event, &time_now);
+        if (r < 0)
+                goto error;
+
+        message = (DHCPPacket *)&buf;
+
+        switch (client->state) {
+        case DHCP_STATE_SELECTING:
+
+                if (client_receive_offer(client, message, len) >= 0) {
+
+                        client->timeout_resend =
+                                sd_event_source_unref(client->timeout_resend);
+
+                        client->state = DHCP_STATE_REQUESTING;
+                        client->attempt = 1;
+
+                        r = sd_event_add_monotonic(client->event, time_now, 0,
+                                                   client_timeout_resend,
+                                                   client,
+                                                   &client->timeout_resend);
+                        if (r < 0)
+                                goto error;
+                }
+
+                break;
+
+        case DHCP_STATE_REQUESTING:
+
+                r = client_receive_ack(client, message, len);
+                if (r == DHCP_EVENT_NO_LEASE)
+                        goto error;
+
+                if (r >= 0) {
+                        client->timeout_resend =
+                                sd_event_source_unref(client->timeout_resend);
+
+                        client->state = DHCP_STATE_BOUND;
+                        client->attempt = 1;
+
+                        client->last_addr = client->lease->address;
+
+                        r = client_set_lease_timeouts(client, time_now);
+                        if (r < 0 )
+                                goto error;
+
+                        client_notify(client, DHCP_EVENT_IP_ACQUIRE);
+
+                        close(client->fd);
+                        client->fd = -1;
+                        client->receive_message =
+                                sd_event_source_unref(client->receive_message);
+                }
+
+                r = 0;
+
+                break;
+
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_BOUND:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+
+                break;
+        }
+
+error:
+        if (r < 0 || r == DHCP_EVENT_NO_LEASE)
+                return client_stop(client, r);
 
         return 0;
 }
 
 int sd_dhcp_client_start(sd_dhcp_client *client)
 {
+        int err;
+
         assert_return(client, -EINVAL);
         assert_return(client->index >= 0, -EINVAL);
         assert_return(client->state == DHCP_STATE_INIT ||
@@ -256,19 +930,68 @@ int sd_dhcp_client_start(sd_dhcp_client *client)
 
         client->xid = random_u();
 
-        return client_send_discover(client);
+        client->fd = dhcp_network_bind_raw_socket(client->index,
+                                                  &client->link);
+
+        if (client->fd < 0) {
+                err = client->fd;
+                goto error;
+        }
+
+        err = sd_event_add_io(client->event, client->fd, EPOLLIN,
+                              client_receive_raw_message, client,
+                              &client->receive_message);
+        if (err < 0)
+                goto error;
+
+        client->start_time = now(CLOCK_MONOTONIC);
+        err = sd_event_add_monotonic(client->event, client->start_time, 0,
+                                     client_timeout_resend, client,
+                                     &client->timeout_resend);
+        if (err < 0)
+                goto error;
+
+        return 0;
+
+error:
+        client_stop(client, err);
+
+        return err;
 }
 
-sd_dhcp_client *sd_dhcp_client_new(void)
+int sd_dhcp_client_stop(sd_dhcp_client *client)
+{
+        return client_stop(client, DHCP_EVENT_STOP);
+}
+
+sd_dhcp_client *sd_dhcp_client_free(sd_dhcp_client *client)
+{
+        assert_return(client, NULL);
+
+        sd_dhcp_client_stop(client);
+
+        sd_event_unref(client->event);
+        free(client->req_opts);
+        free(client);
+
+        return NULL;
+}
+
+sd_dhcp_client *sd_dhcp_client_new(sd_event *event)
 {
         sd_dhcp_client *client;
 
+        assert_return(event, NULL);
+
         client = new0(sd_dhcp_client, 1);
         if (!client)
                 return NULL;
 
+        client->event = sd_event_ref(event);
         client->state = DHCP_STATE_INIT;
         client->index = -1;
+        client->fd = -1;
+        client->attempt = 1;
 
         client->req_opts_size = ELEMENTSOF(default_req_opts);