1 /* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
4 * We are making the OpenFlow specification and associated documentation
5 * (Software) available for public use and benefit with the expectation
6 * that others will use, modify and enhance the Software and contribute
7 * those enhancements back to the community. However, since we would
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9 * restrictions as possible permission is hereby granted, free of
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11 * the Software under the copyrights without restriction, including
12 * without limitation the rights to use, copy, modify, merge, publish,
13 * distribute, sublicense, and/or sell copies of the Software, and to
14 * permit persons to whom the Software is furnished to do so, subject to
15 * the following conditions:
17 * The above copyright notice and this permission notice shall be
18 * included in all copies or substantial portions of the Software.
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
24 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
25 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
26 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
29 * The name and trademarks of copyright holder(s) may NOT be used in
30 * advertising or publicity pertaining to the Software or any
31 * derivatives without specific, written prior permission.
35 #include "dhcp-client.h"
36 #include <arpa/inet.h>
47 #include "dynamic-string.h"
50 #include "ofp-print.h"
51 #include "poll-loop.h"
53 #define THIS_MODULE VLM_dhcp_client
56 #define DHCLIENT_STATES \
57 DHCLIENT_STATE(INIT, 1 << 0) \
58 DHCLIENT_STATE(INIT_REBOOT, 1 << 1) \
59 DHCLIENT_STATE(REBOOTING, 1 << 2) \
60 DHCLIENT_STATE(SELECTING, 1 << 3) \
61 DHCLIENT_STATE(REQUESTING, 1 << 4) \
62 DHCLIENT_STATE(BOUND, 1 << 5) \
63 DHCLIENT_STATE(RENEWING, 1 << 6) \
64 DHCLIENT_STATE(REBINDING, 1 << 7) \
65 DHCLIENT_STATE(RELEASED, 1 << 8)
67 #define DHCLIENT_STATE(NAME, VALUE) S_##NAME = VALUE,
73 state_name(enum dhclient_state state)
76 #define DHCLIENT_STATE(NAME, VALUE) case S_##NAME: return #NAME;
85 struct netdev *netdev;
87 void (*modify_request)(struct dhcp_msg *, void *aux);
88 bool (*validate_offer)(const struct dhcp_msg *, void *aux);
92 enum dhclient_state state;
93 unsigned int state_entered; /* When we transitioned to this state. */
94 uint32_t xid; /* In host byte order. */
95 uint32_t ipaddr, netmask, router;
97 struct dhcp_msg *binding;
100 unsigned int retransmit, delay; /* Used by send_reliably(). */
102 unsigned int init_delay; /* Used by S_INIT. */
104 time_t lease_expiration;
105 unsigned int bound_timeout;
106 unsigned int renewing_timeout;
107 unsigned int rebinding_timeout;
109 /* Used by dhclient_run() and dhclient_wait() */
110 unsigned int min_timeout;
113 /* Set when we send out a DHCPDISCOVER message. */
119 /* Minimum acceptable lease time, in seconds. */
120 #define MIN_ACCEPTABLE_LEASE 15
122 static void state_transition(struct dhclient *, enum dhclient_state);
123 static unsigned int elapsed_in_this_state(const struct dhclient *cli);
124 static bool timeout(struct dhclient *, unsigned int secs);
126 static void dhclient_msg_init(struct dhclient *, enum dhcp_msg_type,
128 static void send_reliably(struct dhclient *cli,
129 void (*make_packet)(struct dhclient *,
131 static bool do_receive_msg(struct dhclient *, struct dhcp_msg *);
132 static void do_send_msg(struct dhclient *, const struct dhcp_msg *);
133 static bool receive_ack(struct dhclient *);
135 static unsigned int fuzz(unsigned int x, int max_fuzz);
136 static unsigned int calc_t2(unsigned int lease);
137 static unsigned int calc_t1(unsigned int lease, unsigned int t2);
139 static unsigned int clamp(unsigned int x, unsigned int min, unsigned int max);
140 static unsigned int sat_add(unsigned int x, unsigned int y);
141 static unsigned int sat_sub(unsigned int x, unsigned int y);
142 static unsigned int sat_mul(unsigned int x, unsigned int y);
144 /* Creates a new DHCP client to configure the network device 'netdev_name'
147 * If 'modify_request' is non-null, then each DHCP message to discover or
148 * request an address will be passed to it (along with auxiliary data 'aux').
149 * It may then add any desired options to the message for transmission.
151 * If 'validate_offer' is non-null, then each DHCP message that offers an
152 * address will be passed to it (along with auxiliary data 'aux') for
153 * validation: if it returns true, the address will accepted; otherwise, it
156 * The DHCP client will not start advertising for an IP address until
157 * dhclient_init() is called.
159 * If successful, returns 0 and sets '*cli' to the new DHCP client. Otherwise,
160 * returns a positive errno value and sets '*cli' to a null pointer. */
162 dhclient_create(const char *netdev_name,
163 void (*modify_request)(struct dhcp_msg *, void *aux),
164 bool (*validate_offer)(const struct dhcp_msg *, void *aux),
165 void *aux, struct dhclient **cli_)
167 struct in_addr any = { INADDR_ANY };
168 struct dhclient *cli;
169 struct netdev *netdev;
174 error = netdev_open(netdev_name, ETH_TYPE_IP, &netdev);
175 /* XXX install socket filter to catch only DHCP packets. */
177 VLOG_ERR("could not open %s network device: %s",
178 netdev_name, strerror(error));
182 error = netdev_set_in4(netdev, any, any);
184 VLOG_ERR("could not remove IPv4 address from %s network device: %s",
185 netdev_name, strerror(error));
186 netdev_close(netdev);
190 cli = xcalloc(1, sizeof *cli);
191 cli->modify_request = modify_request;
192 cli->validate_offer = validate_offer;
194 cli->netdev = netdev;
195 cli->state = S_RELEASED;
196 cli->state_entered = time(0);
197 cli->xid = random_uint32();
200 cli->retransmit = cli->delay = 0;
201 cli->min_timeout = 1;
208 /* Forces 'cli' into a (re)initialization state, in which no address is bound
209 * but the client is advertising to obtain one. If 'requested_ip' is nonzero,
210 * then the client will attempt to re-bind to that IP address; otherwise, it
211 * will not ask for any particular address. */
213 dhclient_init(struct dhclient *cli, uint32_t requested_ip)
215 state_transition(cli, requested_ip ? S_INIT_REBOOT : S_INIT);
216 cli->ipaddr = requested_ip;
217 cli->min_timeout = 0;
221 /* Forces 'cli' to release its bound IP address (if any). The client will not
222 * advertise for a new address until dhclient_init() is called again. */
224 dhclient_release(struct dhclient *cli)
226 if (dhclient_is_bound(cli)) {
228 dhclient_msg_init(cli, DHCPRELEASE, &msg);
229 msg.ciaddr = cli->ipaddr;
230 do_send_msg(cli, &msg);
231 dhcp_msg_uninit(&msg);
234 state_transition(cli, S_RELEASED);
235 cli->min_timeout = UINT_MAX;
239 do_force_renew(struct dhclient *cli, int deadline)
241 time_t now = time(0);
242 unsigned int lease_left = sat_sub(cli->lease_expiration, now);
243 if (lease_left <= deadline) {
244 if (cli->state & (S_RENEWING | S_REBINDING)) {
247 deadline = lease_left;
249 if (cli->state & (S_BOUND | S_RENEWING)) {
250 state_transition(cli, S_RENEWING);
251 cli->renewing_timeout = deadline * 3 / 4;
252 cli->rebinding_timeout = deadline * 1 / 4;
254 state_transition(cli, S_REBINDING);
255 cli->rebinding_timeout = deadline;
257 cli->min_timeout = 0;
260 /* Forces 'cli' to attempt to renew the lease its current IP address (if any)
261 * within 'deadline' seconds. If the deadline is not met, then the client
262 * gives up its IP address binding and re-starts the DHCP process. */
264 dhclient_force_renew(struct dhclient *cli, int deadline)
266 /* Drain the receive queue so that we know that any DHCPACK we process is
267 * freshly received. */
268 netdev_drain(cli->netdev);
270 switch (cli->state) {
281 do_force_renew(cli, deadline);
285 dhclient_init(cli, 0);
290 /* Returns true if 'cli' is bound to an IP address, false otherwise. */
292 dhclient_is_bound(const struct dhclient *cli)
294 return cli->state & (S_BOUND | S_RENEWING | S_REBINDING);
297 /* Returns true if 'cli' has changed from bound to unbound, or vice versa, at
298 * least once since the last time this function was called. */
300 dhclient_changed(struct dhclient *cli)
302 bool changed = cli->changed;
307 /* If 'cli' is bound to an IP address, returns that IP address; otherwise,
310 dhclient_get_ip(const struct dhclient *cli)
312 return dhclient_is_bound(cli) ? cli->ipaddr : 0;
315 /* If 'cli' is bound to an IP address, returns the netmask for that IP address;
316 * otherwise, returns 0. */
318 dhclient_get_netmask(const struct dhclient *cli)
320 return dhclient_is_bound(cli) ? cli->netmask : 0;
323 /* If 'cli' is bound to an IP address, returns the DHCP message that was
324 * received to obtain that IP address (so that the caller can obtain additional
325 * options from it). Otherwise, returns a null pointer. */
326 const struct dhcp_msg *
327 dhclient_get_config(const struct dhclient *cli)
329 return dhclient_is_bound(cli) ? cli->binding : NULL;
335 make_dhcpdiscover(struct dhclient *cli, struct dhcp_msg *msg)
337 cli->secs = elapsed_in_this_state(cli);
338 dhclient_msg_init(cli, DHCPDISCOVER, msg);
340 dhcp_msg_put_ip(msg, DHCP_CODE_REQUESTED_IP, cli->ipaddr);
345 make_dhcprequest(struct dhclient *cli, struct dhcp_msg *msg)
347 dhclient_msg_init(cli, DHCPREQUEST, msg);
348 msg->ciaddr = dhclient_get_ip(cli);
349 if (cli->state == S_REQUESTING) {
350 dhcp_msg_put_ip(msg, DHCP_CODE_SERVER_IDENTIFIER, cli->server_ip);
352 dhcp_msg_put_ip(msg, DHCP_CODE_REQUESTED_IP, cli->ipaddr);
356 do_init(struct dhclient *cli, enum dhclient_state next_state)
358 if (!cli->init_delay) {
359 cli->init_delay = clamp(fuzz(2, 8), 1, 10);
361 if (timeout(cli, cli->init_delay)) {
362 state_transition(cli, next_state);
367 dhclient_run_INIT(struct dhclient *cli)
369 do_init(cli, S_SELECTING);
373 dhclient_run_INIT_REBOOT(struct dhclient *cli)
375 do_init(cli, S_REBOOTING);
379 dhclient_run_REBOOTING(struct dhclient *cli)
381 send_reliably(cli, make_dhcprequest);
382 if (!receive_ack(cli) && timeout(cli, 60)) {
383 state_transition(cli, S_INIT);
388 dhcp_receive(struct dhclient *cli, unsigned int msgs, struct dhcp_msg *msg)
390 while (do_receive_msg(cli, msg)) {
391 if (msg->type < 0 || msg->type > 31 || !((1u << msg->type) & msgs)) {
392 VLOG_DBG("received unexpected %s in %s state: %s",
393 dhcp_type_name(msg->type), state_name(cli->state),
394 dhcp_msg_to_string(msg, &cli->s));
395 } else if (msg->xid != cli->xid) {
396 VLOG_DBG("ignoring %s with xid != %08"PRIx32" in %s state: %s",
397 dhcp_type_name(msg->type), msg->xid,
398 state_name(cli->state), dhcp_msg_to_string(msg, &cli->s));
402 dhcp_msg_uninit(msg);
408 validate_offered_options(struct dhclient *cli, const struct dhcp_msg *msg)
410 uint32_t lease, netmask;
411 if (!dhcp_msg_get_secs(msg, DHCP_CODE_LEASE_TIME, 0, &lease)) {
412 VLOG_WARN("%s lacks lease time: %s",
413 dhcp_type_name(msg->type), dhcp_msg_to_string(msg, &cli->s));
414 } else if (!dhcp_msg_get_ip(msg, DHCP_CODE_SUBNET_MASK, 0, &netmask)) {
415 VLOG_WARN("%s lacks netmask: %s",
416 dhcp_type_name(msg->type), dhcp_msg_to_string(msg, &cli->s));
417 } else if (lease < MIN_ACCEPTABLE_LEASE) {
418 VLOG_WARN("Ignoring %s with %"PRIu32"-second lease time: %s",
419 dhcp_type_name(msg->type), lease,
420 dhcp_msg_to_string(msg, &cli->s));
421 } else if (cli->validate_offer && !cli->validate_offer(msg, cli->aux)) {
422 VLOG_DBG("client validation hook refused offer: %s",
423 dhcp_msg_to_string(msg, &cli->s));
431 dhclient_run_SELECTING(struct dhclient *cli)
435 send_reliably(cli, make_dhcpdiscover);
436 if (cli->server_ip && timeout(cli, 60)) {
438 state_transition(cli, S_INIT);
440 for (; dhcp_receive(cli, 1u << DHCPOFFER, &msg); dhcp_msg_uninit(&msg)) {
441 if (!validate_offered_options(cli, &msg)) {
444 if (!dhcp_msg_get_ip(&msg, DHCP_CODE_SERVER_IDENTIFIER,
445 0, &cli->server_ip)) {
446 VLOG_WARN("DHCPOFFER lacks server identifier: %s",
447 dhcp_msg_to_string(&msg, &cli->s));
451 VLOG_DBG("accepting DHCPOFFER: %s", dhcp_msg_to_string(&msg, &cli->s));
452 cli->ipaddr = msg.yiaddr;
453 state_transition(cli, S_REQUESTING);
459 receive_ack(struct dhclient *cli)
463 if (!dhcp_receive(cli, (1u << DHCPACK) | (1u << DHCPNAK), &msg)) {
465 } else if (msg.type == DHCPNAK) {
466 dhcp_msg_uninit(&msg);
467 state_transition(cli, S_INIT);
469 } else if (!validate_offered_options(cli, &msg)) {
470 dhcp_msg_uninit(&msg);
473 uint32_t lease = 0, t1 = 0, t2 = 0;
476 dhcp_msg_uninit(cli->binding);
478 cli->binding = xmalloc(sizeof *cli->binding);
480 dhcp_msg_copy(cli->binding, &msg);
482 dhcp_msg_get_secs(&msg, DHCP_CODE_LEASE_TIME, 0, &lease);
483 dhcp_msg_get_secs(&msg, DHCP_CODE_T1, 0, &t1);
484 dhcp_msg_get_secs(&msg, DHCP_CODE_T2, 0, &t2);
485 assert(lease >= MIN_ACCEPTABLE_LEASE);
487 if (!t2 || t2 >= lease) {
490 if (!t1 || t1 >= t2) {
491 t1 = calc_t1(lease, t2);
494 cli->lease_expiration = sat_add(time(0), lease);
495 cli->bound_timeout = t1;
496 cli->renewing_timeout = t2 - t1;
497 cli->rebinding_timeout = lease - t2;
499 cli->ipaddr = msg.yiaddr;
500 dhcp_msg_get_ip(&msg, DHCP_CODE_SUBNET_MASK, 0, &cli->netmask);
501 if (!dhcp_msg_get_ip(&msg, DHCP_CODE_ROUTER, 0, &cli->router)) {
502 cli->router = INADDR_ANY;
504 state_transition(cli, S_BOUND);
505 VLOG_DBG("Bound: %s", dhcp_msg_to_string(&msg, &cli->s));
511 dhclient_run_REQUESTING(struct dhclient *cli)
513 send_reliably(cli, make_dhcprequest);
514 if (!receive_ack(cli) && timeout(cli, 60)) {
515 state_transition(cli, S_INIT);
520 dhclient_run_BOUND(struct dhclient *cli)
522 if (timeout(cli, cli->bound_timeout)) {
523 state_transition(cli, S_RENEWING);
528 dhclient_run_RENEWING(struct dhclient *cli)
530 send_reliably(cli, make_dhcprequest);
531 if (!receive_ack(cli) && timeout(cli, cli->renewing_timeout)) {
532 state_transition(cli, S_REBINDING);
537 dhclient_run_REBINDING(struct dhclient *cli)
539 send_reliably(cli, make_dhcprequest);
540 if (!receive_ack(cli) && timeout(cli, cli->rebinding_timeout)) {
541 state_transition(cli, S_INIT);
546 dhclient_run_RELEASED(struct dhclient *cli UNUSED)
551 /* Processes the DHCP protocol for 'cli'. */
553 dhclient_run(struct dhclient *cli)
557 old_state = cli->state;
558 cli->min_timeout = UINT_MAX;
560 switch (cli->state) {
561 #define DHCLIENT_STATE(NAME, VALUE) \
562 case S_##NAME: dhclient_run_##NAME(cli); break;
564 #undef DHCLIENT_STATE
568 } while (cli->state != old_state);
571 /* Sets up poll timeouts to wake up the poll loop when 'cli' needs to do some
574 dhclient_wait(struct dhclient *cli)
576 if (cli->min_timeout != UINT_MAX) {
577 poll_timer_wait(sat_mul(cli->min_timeout, 1000));
579 /* Reset timeout to 1 second. This will have no effect ordinarily, because
580 * dhclient_run() will typically set it back to a higher value. If,
581 * however, the caller fails to call dhclient_run() before its next call to
582 * dhclient_wait() we won't potentially block forever. */
583 cli->min_timeout = 1;
585 if (cli->state & (S_SELECTING | S_REQUESTING | S_RENEWING | S_REBINDING)) {
586 netdev_recv_wait(cli->netdev);
591 state_transition(struct dhclient *cli, enum dhclient_state state)
593 bool was_bound = dhclient_is_bound(cli);
595 VLOG_DBG("entering %s", state_name(state));
597 cli->state_entered = time(0);
598 cli->retransmit = cli->delay = 0;
599 am_bound = dhclient_is_bound(cli);
600 if (was_bound != am_bound) {
601 struct in_addr addr, mask;
606 VLOG_WARN("%s: binding to "IP_FMT"/"IP_FMT,
607 netdev_get_name(cli->netdev),
608 IP_ARGS(&cli->ipaddr), IP_ARGS(&cli->netmask));
609 addr.s_addr = cli->ipaddr;
610 mask.s_addr = cli->netmask;
612 VLOG_WARN("%s: unbinding IPv4 network address",
613 netdev_get_name(cli->netdev));
614 addr.s_addr = mask.s_addr = INADDR_ANY;
616 error = netdev_set_in4(cli->netdev, addr, mask);
618 VLOG_ERR("could not set %s address "IP_FMT"/"IP_FMT": %s",
619 netdev_get_name(cli->netdev),
620 IP_ARGS(&addr.s_addr), IP_ARGS(&mask.s_addr),
623 if (am_bound && !error && cli->router) {
624 struct in_addr router = { cli->router };
625 error = netdev_add_router(cli->netdev, router);
626 VLOG_WARN("%s: configuring router "IP_FMT,
627 netdev_get_name(cli->netdev), IP_ARGS(cli->router));
629 VLOG_ERR("failed to add default route to "IP_FMT" on %s: %s",
630 IP_ARGS(&router), netdev_get_name(cli->netdev),
635 assert(cli->binding != NULL);
637 dhcp_msg_uninit(cli->binding);
642 if (cli->state & (S_SELECTING | S_REQUESTING | S_REBOOTING)) {
643 netdev_drain(cli->netdev);
648 send_reliably(struct dhclient *cli,
649 void (*make_packet)(struct dhclient *, struct dhcp_msg *))
651 if (timeout(cli, cli->retransmit)) {
653 make_packet(cli, &msg);
654 if (cli->modify_request) {
655 cli->modify_request(&msg, cli->aux);
657 do_send_msg(cli, &msg);
658 cli->delay = MIN(64, MAX(4, cli->delay * 2));
659 cli->retransmit += fuzz(cli->delay, 1);
660 timeout(cli, cli->retransmit);
661 dhcp_msg_uninit(&msg);
666 dhclient_msg_init(struct dhclient *cli, enum dhcp_msg_type type,
667 struct dhcp_msg *msg)
670 msg->op = DHCP_BOOTREQUEST;
672 msg->secs = cli->secs;
674 memcpy(msg->chaddr, netdev_get_etheraddr(cli->netdev), ETH_ADDR_LEN);
679 elapsed_in_this_state(const struct dhclient *cli)
681 return time(0) - cli->state_entered;
685 timeout(struct dhclient *cli, unsigned int secs)
687 cli->min_timeout = MIN(cli->min_timeout, secs);
688 return time(0) >= sat_add(cli->state_entered, secs);
692 do_receive_msg(struct dhclient *cli, struct dhcp_msg *msg)
696 buffer_init(&b, netdev_get_mtu(cli->netdev) + VLAN_ETH_HEADER_LEN);
697 for (; cli->received < 50; cli->received++) {
698 const struct ip_header *ip;
699 const struct dhcp_header *dhcp;
704 error = netdev_recv(cli->netdev, &b);
709 flow_extract(&b, 0, &flow);
710 if (flow.dl_type != htons(ETH_TYPE_IP)
711 || flow.nw_proto != IP_TYPE_UDP
712 || flow.tp_dst != htons(68)
713 || !(eth_addr_is_broadcast(flow.dl_dst)
714 || eth_addr_equals(flow.dl_dst,
715 netdev_get_etheraddr(cli->netdev)))) {
720 if (IP_IS_FRAGMENT(ip->ip_frag_off)) {
721 /* We don't do reassembly. */
722 VLOG_WARN("ignoring fragmented DHCP datagram");
728 VLOG_WARN("ignoring DHCP datagram with missing payload");
732 buffer_pull(&b, b.l7 - b.data);
733 error = dhcp_parse(msg, &b);
735 VLOG_DBG("received %s", dhcp_msg_to_string(msg, &cli->s));
740 netdev_drain(cli->netdev);
746 do_send_msg(struct dhclient *cli, const struct dhcp_msg *msg)
749 struct eth_header eh;
751 struct udp_header th;
755 buffer_init(&b, ETH_TOTAL_MAX);
756 buffer_reserve(&b, ETH_HEADER_LEN + IP_HEADER_LEN + UDP_HEADER_LEN);
758 dhcp_assemble(msg, &b);
760 memcpy(eh.eth_src, netdev_get_etheraddr(cli->netdev), ETH_ADDR_LEN);
761 memcpy(eh.eth_dst, eth_addr_broadcast, ETH_ADDR_LEN);
762 eh.eth_type = htons(ETH_TYPE_IP);
764 nh.ip_ihl_ver = IP_IHL_VER(5, IP_VERSION);
766 nh.ip_tot_len = htons(IP_HEADER_LEN + UDP_HEADER_LEN + b.size);
767 /* We can't guarantee uniqueness of ip_id versus the host's, screwing up
768 * fragment reassembly, so prevent fragmentation and use an all-zeros
769 * ip_id. RFC 791 doesn't say we can do this, but Linux does the same
770 * thing for DF packets, so it must not screw anything up. */
772 nh.ip_frag_off = htons(IP_DONT_FRAGMENT);
774 nh.ip_proto = IP_TYPE_UDP;
776 nh.ip_src = dhclient_get_ip(cli);
777 /* XXX need to use UDP socket for nonzero server IPs so that we can get
778 * routing table support.
780 * if (...have server IP and in appropriate state...) {
781 * nh.ip_dst = cli->server_ip;
783 * nh.ip_dst = INADDR_BROADCAST;
786 nh.ip_dst = INADDR_BROADCAST;
787 nh.ip_csum = csum(&nh, sizeof nh);
789 th.udp_src = htons(66);
790 th.udp_dst = htons(67);
791 th.udp_len = htons(UDP_HEADER_LEN + b.size);
793 udp_csum = csum_add32(0, nh.ip_src);
794 udp_csum = csum_add32(udp_csum, nh.ip_dst);
795 udp_csum = csum_add16(udp_csum, IP_TYPE_UDP << 8);
796 udp_csum = csum_add16(udp_csum, th.udp_len);
797 udp_csum = csum_continue(udp_csum, &th, sizeof th);
798 th.udp_csum = csum_finish(csum_continue(udp_csum, b.data, b.size));
800 buffer_push(&b, &th, sizeof th);
801 buffer_push(&b, &nh, sizeof nh);
802 buffer_push(&b, &eh, sizeof eh);
804 /* Don't try to send the frame if it's too long for an Ethernet frame. We
805 * disregard the network device's actual MTU because we don't want the
806 * frame to have to be discarded or fragmented if it travels over a regular
807 * Ethernet at some point. 1500 bytes should be enough for anyone. */
808 if (b.size <= ETH_TOTAL_MAX) {
809 VLOG_DBG("sending %s", dhcp_msg_to_string(msg, &cli->s));
810 error = netdev_send(cli->netdev, &b);
812 VLOG_ERR("send failed on %s: %s",
813 netdev_get_name(cli->netdev), strerror(error));
816 VLOG_ERR("cannot send %zu-byte Ethernet frame", b.size);
823 fuzz(unsigned int x, int max_fuzz)
825 /* Generate number in range [-max_fuzz, +max_fuzz]. */
826 int fuzz = random_range(max_fuzz * 2 + 1) - max_fuzz;
827 unsigned int y = x + fuzz;
828 return fuzz >= 0 ? (y >= x ? y : UINT_MAX) : (y <= x ? y : 0);
832 sat_add(unsigned int x, unsigned int y)
834 return x + y >= x ? x + y : UINT_MAX;
838 sat_sub(unsigned int x, unsigned int y)
840 return x >= y ? x - y : 0;
844 sat_mul(unsigned int x, unsigned int y)
847 return x <= UINT_MAX / y ? x * y : UINT_MAX;
851 clamp(unsigned int x, unsigned int min, unsigned int max)
853 return x < min ? min : x > max ? max : x;
857 calc_t2(unsigned int lease)
859 unsigned int base = lease * 0.875;
860 return lease >= 60 ? clamp(fuzz(base, 10), 0, lease - 1) : base;
864 calc_t1(unsigned int lease, unsigned int t2)
866 unsigned int base = lease / 2;
867 return lease >= 60 ? clamp(fuzz(base, 10), 0, t2 - 1) : base;