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
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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
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29 * The name and trademarks of copyright holder(s) may NOT be used in
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31 * derivatives without specific, written prior permission.
34 #include "dhcp-client.h"
35 #include <arpa/inet.h>
46 #include "dynamic-string.h"
49 #include "ofp-print.h"
50 #include "poll-loop.h"
52 #define THIS_MODULE VLM_dhcp_client
55 #define DHCLIENT_STATES \
56 DHCLIENT_STATE(INIT, 1 << 0) \
57 DHCLIENT_STATE(INIT_REBOOT, 1 << 1) \
58 DHCLIENT_STATE(REBOOTING, 1 << 2) \
59 DHCLIENT_STATE(SELECTING, 1 << 3) \
60 DHCLIENT_STATE(REQUESTING, 1 << 4) \
61 DHCLIENT_STATE(BOUND, 1 << 5) \
62 DHCLIENT_STATE(RENEWING, 1 << 6) \
63 DHCLIENT_STATE(REBINDING, 1 << 7) \
64 DHCLIENT_STATE(RELEASED, 1 << 8)
66 #define DHCLIENT_STATE(NAME, VALUE) S_##NAME = VALUE,
72 state_name(enum dhclient_state state)
75 #define DHCLIENT_STATE(NAME, VALUE) case S_##NAME: return #NAME;
84 struct netdev *netdev;
86 void (*modify_request)(struct dhcp_msg *, void *aux);
87 bool (*validate_offer)(const struct dhcp_msg *, void *aux);
91 enum dhclient_state state;
92 unsigned int state_entered; /* When we transitioned to this state. */
93 uint32_t xid; /* In host byte order. */
94 uint32_t ipaddr, netmask, router;
96 struct dhcp_msg *binding;
99 unsigned int retransmit, delay; /* Used by send_reliably(). */
101 unsigned int init_delay; /* Used by S_INIT. */
103 time_t lease_expiration;
104 unsigned int bound_timeout;
105 unsigned int renewing_timeout;
106 unsigned int rebinding_timeout;
108 /* Used by dhclient_run() and dhclient_wait() */
109 unsigned int min_timeout;
112 /* Set when we send out a DHCPDISCOVER message. */
118 /* Minimum acceptable lease time, in seconds. */
119 #define MIN_ACCEPTABLE_LEASE 15
121 static void state_transition(struct dhclient *, enum dhclient_state);
122 static unsigned int elapsed_in_this_state(const struct dhclient *cli);
123 static bool timeout(struct dhclient *, unsigned int secs);
125 static void dhclient_msg_init(struct dhclient *, enum dhcp_msg_type,
127 static void send_reliably(struct dhclient *cli,
128 void (*make_packet)(struct dhclient *,
130 static bool do_receive_msg(struct dhclient *, struct dhcp_msg *);
131 static void do_send_msg(struct dhclient *, const struct dhcp_msg *);
132 static bool receive_ack(struct dhclient *);
134 static unsigned int fuzz(unsigned int x, int max_fuzz);
135 static unsigned int calc_t2(unsigned int lease);
136 static unsigned int calc_t1(unsigned int lease, unsigned int t2);
138 static unsigned int clamp(unsigned int x, unsigned int min, unsigned int max);
139 static unsigned int sat_add(unsigned int x, unsigned int y);
140 static unsigned int sat_sub(unsigned int x, unsigned int y);
141 static unsigned int sat_mul(unsigned int x, unsigned int y);
143 /* Creates a new DHCP client to configure the network device 'netdev_name'
146 * If 'modify_request' is non-null, then each DHCP message to discover or
147 * request an address will be passed to it (along with auxiliary data 'aux').
148 * It may then add any desired options to the message for transmission.
150 * If 'validate_offer' is non-null, then each DHCP message that offers an
151 * address will be passed to it (along with auxiliary data 'aux') for
152 * validation: if it returns true, the address will accepted; otherwise, it
155 * The DHCP client will not start advertising for an IP address until
156 * dhclient_init() is called.
158 * If successful, returns 0 and sets '*cli' to the new DHCP client. Otherwise,
159 * returns a positive errno value and sets '*cli' to a null pointer. */
161 dhclient_create(const char *netdev_name,
162 void (*modify_request)(struct dhcp_msg *, void *aux),
163 bool (*validate_offer)(const struct dhcp_msg *, void *aux),
164 void *aux, struct dhclient **cli_)
166 struct in_addr any = { INADDR_ANY };
167 struct dhclient *cli;
168 struct netdev *netdev;
173 error = netdev_open(netdev_name, ETH_TYPE_IP, &netdev);
174 /* XXX install socket filter to catch only DHCP packets. */
176 VLOG_ERR("could not open %s network device: %s",
177 netdev_name, strerror(error));
181 error = netdev_set_in4(netdev, any, any);
183 VLOG_ERR("could not remove IPv4 address from %s network device: %s",
184 netdev_name, strerror(error));
185 netdev_close(netdev);
189 cli = xcalloc(1, sizeof *cli);
190 cli->modify_request = modify_request;
191 cli->validate_offer = validate_offer;
193 cli->netdev = netdev;
194 cli->state = S_RELEASED;
195 cli->state_entered = time(0);
196 cli->xid = random_uint32();
199 cli->retransmit = cli->delay = 0;
200 cli->min_timeout = 1;
207 /* Forces 'cli' into a (re)initialization state, in which no address is bound
208 * but the client is advertising to obtain one. If 'requested_ip' is nonzero,
209 * then the client will attempt to re-bind to that IP address; otherwise, it
210 * will not ask for any particular address. */
212 dhclient_init(struct dhclient *cli, uint32_t requested_ip)
214 state_transition(cli, requested_ip ? S_INIT_REBOOT : S_INIT);
215 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);
233 state_transition(cli, S_RELEASED);
234 cli->min_timeout = UINT_MAX;
238 do_force_renew(struct dhclient *cli, int deadline)
240 time_t now = time(0);
241 unsigned int lease_left = sat_sub(cli->lease_expiration, now);
242 if (lease_left <= deadline) {
243 if (cli->state & (S_RENEWING | S_REBINDING)) {
246 deadline = lease_left;
248 if (cli->state & (S_BOUND | S_RENEWING)) {
249 state_transition(cli, S_RENEWING);
250 cli->renewing_timeout = deadline * 3 / 4;
251 cli->rebinding_timeout = deadline * 1 / 4;
253 state_transition(cli, S_REBINDING);
254 cli->rebinding_timeout = deadline;
256 cli->min_timeout = 0;
259 /* Forces 'cli' to attempt to renew the lease its current IP address (if any)
260 * within 'deadline' seconds. If the deadline is not met, then the client
261 * gives up its IP address binding and re-starts the DHCP process. */
263 dhclient_force_renew(struct dhclient *cli, int deadline)
265 /* Drain the receive queue so that we know that any DHCPACK we process is
266 * freshly received. */
267 netdev_drain(cli->netdev);
269 switch (cli->state) {
280 do_force_renew(cli, deadline);
284 dhclient_init(cli, 0);
289 /* Returns true if 'cli' is bound to an IP address, false otherwise. */
291 dhclient_is_bound(const struct dhclient *cli)
293 return cli->state & (S_BOUND | S_RENEWING | S_REBINDING);
296 /* Returns true if 'cli' has changed from bound to unbound, or vice versa, at
297 * least once since the last time this function was called. */
299 dhclient_changed(struct dhclient *cli)
301 bool changed = cli->changed;
306 /* If 'cli' is bound to an IP address, returns that IP address; otherwise,
309 dhclient_get_ip(const struct dhclient *cli)
311 return dhclient_is_bound(cli) ? cli->ipaddr : 0;
314 /* If 'cli' is bound to an IP address, returns the netmask for that IP address;
315 * otherwise, returns 0. */
317 dhclient_get_netmask(const struct dhclient *cli)
319 return dhclient_is_bound(cli) ? cli->netmask : 0;
322 /* If 'cli' is bound to an IP address, returns the DHCP message that was
323 * received to obtain that IP address (so that the caller can obtain additional
324 * options from it). Otherwise, returns a null pointer. */
325 const struct dhcp_msg *
326 dhclient_get_config(const struct dhclient *cli)
328 return dhclient_is_bound(cli) ? cli->binding : NULL;
334 make_dhcpdiscover(struct dhclient *cli, struct dhcp_msg *msg)
336 cli->secs = elapsed_in_this_state(cli);
337 dhclient_msg_init(cli, DHCPDISCOVER, msg);
339 dhcp_msg_put_ip(msg, DHCP_CODE_REQUESTED_IP, cli->ipaddr);
344 make_dhcprequest(struct dhclient *cli, struct dhcp_msg *msg)
346 dhclient_msg_init(cli, DHCPREQUEST, msg);
347 msg->ciaddr = dhclient_get_ip(cli);
348 if (cli->state == S_REQUESTING) {
349 dhcp_msg_put_ip(msg, DHCP_CODE_SERVER_IDENTIFIER, cli->server_ip);
351 dhcp_msg_put_ip(msg, DHCP_CODE_REQUESTED_IP, cli->ipaddr);
355 do_init(struct dhclient *cli, enum dhclient_state next_state)
357 if (!cli->init_delay) {
358 cli->init_delay = clamp(fuzz(2, 8), 1, 10);
360 if (timeout(cli, cli->init_delay)) {
361 state_transition(cli, next_state);
366 dhclient_run_INIT(struct dhclient *cli)
368 do_init(cli, S_SELECTING);
372 dhclient_run_INIT_REBOOT(struct dhclient *cli)
374 do_init(cli, S_REBOOTING);
378 dhclient_run_REBOOTING(struct dhclient *cli)
380 send_reliably(cli, make_dhcprequest);
381 if (!receive_ack(cli) && timeout(cli, 60)) {
382 state_transition(cli, S_INIT);
387 dhcp_receive(struct dhclient *cli, unsigned int msgs, struct dhcp_msg *msg)
389 while (do_receive_msg(cli, msg)) {
390 if (msg->type < 0 || msg->type > 31 || !((1u << msg->type) & msgs)) {
391 VLOG_DBG("received unexpected %s in %s state: %s",
392 dhcp_type_name(msg->type), state_name(cli->state),
393 dhcp_msg_to_string(msg, &cli->s));
394 } else if (msg->xid != cli->xid) {
395 VLOG_DBG("ignoring %s with xid != %08"PRIx32" in %s state: %s",
396 dhcp_type_name(msg->type), msg->xid,
397 state_name(cli->state), dhcp_msg_to_string(msg, &cli->s));
401 dhcp_msg_uninit(msg);
407 validate_offered_options(struct dhclient *cli, const struct dhcp_msg *msg)
409 uint32_t lease, netmask;
410 if (!dhcp_msg_get_secs(msg, DHCP_CODE_LEASE_TIME, 0, &lease)) {
411 VLOG_WARN("%s lacks lease time: %s",
412 dhcp_type_name(msg->type), dhcp_msg_to_string(msg, &cli->s));
413 } else if (!dhcp_msg_get_ip(msg, DHCP_CODE_SUBNET_MASK, 0, &netmask)) {
414 VLOG_WARN("%s lacks netmask: %s",
415 dhcp_type_name(msg->type), dhcp_msg_to_string(msg, &cli->s));
416 } else if (lease < MIN_ACCEPTABLE_LEASE) {
417 VLOG_WARN("Ignoring %s with %"PRIu32"-second lease time: %s",
418 dhcp_type_name(msg->type), lease,
419 dhcp_msg_to_string(msg, &cli->s));
420 } else if (cli->validate_offer && !cli->validate_offer(msg, cli->aux)) {
421 VLOG_DBG("client validation hook refused offer: %s",
422 dhcp_msg_to_string(msg, &cli->s));
430 dhclient_run_SELECTING(struct dhclient *cli)
434 send_reliably(cli, make_dhcpdiscover);
435 if (cli->server_ip && timeout(cli, 60)) {
437 state_transition(cli, S_INIT);
439 for (; dhcp_receive(cli, 1u << DHCPOFFER, &msg); dhcp_msg_uninit(&msg)) {
440 if (!validate_offered_options(cli, &msg)) {
443 if (!dhcp_msg_get_ip(&msg, DHCP_CODE_SERVER_IDENTIFIER,
444 0, &cli->server_ip)) {
445 VLOG_WARN("DHCPOFFER lacks server identifier: %s",
446 dhcp_msg_to_string(&msg, &cli->s));
450 VLOG_DBG("accepting DHCPOFFER: %s", dhcp_msg_to_string(&msg, &cli->s));
451 cli->ipaddr = msg.yiaddr;
452 state_transition(cli, S_REQUESTING);
458 receive_ack(struct dhclient *cli)
462 if (!dhcp_receive(cli, (1u << DHCPACK) | (1u << DHCPNAK), &msg)) {
464 } else if (msg.type == DHCPNAK) {
465 dhcp_msg_uninit(&msg);
466 state_transition(cli, S_INIT);
468 } else if (!validate_offered_options(cli, &msg)) {
469 dhcp_msg_uninit(&msg);
472 uint32_t lease = 0, t1 = 0, t2 = 0;
475 dhcp_msg_uninit(cli->binding);
477 cli->binding = xmalloc(sizeof *cli->binding);
479 dhcp_msg_copy(cli->binding, &msg);
481 dhcp_msg_get_secs(&msg, DHCP_CODE_LEASE_TIME, 0, &lease);
482 dhcp_msg_get_secs(&msg, DHCP_CODE_T1, 0, &t1);
483 dhcp_msg_get_secs(&msg, DHCP_CODE_T2, 0, &t2);
484 assert(lease >= MIN_ACCEPTABLE_LEASE);
486 if (!t2 || t2 >= lease) {
489 if (!t1 || t1 >= t2) {
490 t1 = calc_t1(lease, t2);
493 cli->lease_expiration = sat_add(time(0), lease);
494 cli->bound_timeout = t1;
495 cli->renewing_timeout = t2 - t1;
496 cli->rebinding_timeout = lease - t2;
498 cli->ipaddr = msg.yiaddr;
499 dhcp_msg_get_ip(&msg, DHCP_CODE_SUBNET_MASK, 0, &cli->netmask);
500 if (!dhcp_msg_get_ip(&msg, DHCP_CODE_ROUTER, 0, &cli->router)) {
501 cli->router = INADDR_ANY;
503 state_transition(cli, S_BOUND);
504 VLOG_DBG("Bound: %s", dhcp_msg_to_string(&msg, &cli->s));
510 dhclient_run_REQUESTING(struct dhclient *cli)
512 send_reliably(cli, make_dhcprequest);
513 if (!receive_ack(cli) && timeout(cli, 60)) {
514 state_transition(cli, S_INIT);
519 dhclient_run_BOUND(struct dhclient *cli)
521 if (timeout(cli, cli->bound_timeout)) {
522 state_transition(cli, S_RENEWING);
527 dhclient_run_RENEWING(struct dhclient *cli)
529 send_reliably(cli, make_dhcprequest);
530 if (!receive_ack(cli) && timeout(cli, cli->renewing_timeout)) {
531 state_transition(cli, S_REBINDING);
536 dhclient_run_REBINDING(struct dhclient *cli)
538 send_reliably(cli, make_dhcprequest);
539 if (!receive_ack(cli) && timeout(cli, cli->rebinding_timeout)) {
540 state_transition(cli, S_INIT);
545 dhclient_run_RELEASED(struct dhclient *cli UNUSED)
550 /* Processes the DHCP protocol for 'cli'. */
552 dhclient_run(struct dhclient *cli)
556 old_state = cli->state;
557 cli->min_timeout = UINT_MAX;
559 switch (cli->state) {
560 #define DHCLIENT_STATE(NAME, VALUE) \
561 case S_##NAME: dhclient_run_##NAME(cli); break;
563 #undef DHCLIENT_STATE
567 } while (cli->state != old_state);
570 /* Sets up poll timeouts to wake up the poll loop when 'cli' needs to do some
573 dhclient_wait(struct dhclient *cli)
575 if (cli->min_timeout != UINT_MAX) {
576 poll_timer_wait(sat_mul(cli->min_timeout, 1000));
578 /* Reset timeout to 1 second. This will have no effect ordinarily, because
579 * dhclient_run() will typically set it back to a higher value. If,
580 * however, the caller fails to call dhclient_run() before its next call to
581 * dhclient_wait() we won't potentially block forever. */
582 cli->min_timeout = 1;
584 if (cli->state & (S_SELECTING | S_REQUESTING | S_RENEWING | S_REBINDING)) {
585 netdev_recv_wait(cli->netdev);
590 state_transition(struct dhclient *cli, enum dhclient_state state)
592 bool was_bound = dhclient_is_bound(cli);
594 VLOG_DBG("entering %s", state_name(state));
596 cli->state_entered = time(0);
597 cli->retransmit = cli->delay = 0;
598 am_bound = dhclient_is_bound(cli);
599 if (was_bound != am_bound) {
600 struct in_addr addr, mask;
605 VLOG_WARN("%s: binding to "IP_FMT"/"IP_FMT,
606 netdev_get_name(cli->netdev),
607 IP_ARGS(&cli->ipaddr), IP_ARGS(&cli->netmask));
608 addr.s_addr = cli->ipaddr;
609 mask.s_addr = cli->netmask;
611 VLOG_WARN("%s: unbinding IPv4 network address",
612 netdev_get_name(cli->netdev));
613 addr.s_addr = mask.s_addr = INADDR_ANY;
615 error = netdev_set_in4(cli->netdev, addr, mask);
617 VLOG_ERR("could not set %s address "IP_FMT"/"IP_FMT": %s",
618 netdev_get_name(cli->netdev),
619 IP_ARGS(&addr.s_addr), IP_ARGS(&mask.s_addr),
622 if (am_bound && !error && cli->router) {
623 struct in_addr router = { cli->router };
624 error = netdev_add_router(cli->netdev, router);
625 VLOG_WARN("%s: configuring router "IP_FMT,
626 netdev_get_name(cli->netdev), IP_ARGS(cli->router));
628 VLOG_ERR("failed to add default route to "IP_FMT" on %s: %s",
629 IP_ARGS(&router), netdev_get_name(cli->netdev),
634 assert(cli->binding != NULL);
636 dhcp_msg_uninit(cli->binding);
641 if (cli->state & (S_SELECTING | S_REQUESTING | S_REBOOTING)) {
642 netdev_drain(cli->netdev);
647 send_reliably(struct dhclient *cli,
648 void (*make_packet)(struct dhclient *, struct dhcp_msg *))
650 if (timeout(cli, cli->retransmit)) {
652 make_packet(cli, &msg);
653 if (cli->modify_request) {
654 cli->modify_request(&msg, cli->aux);
656 do_send_msg(cli, &msg);
657 cli->delay = MIN(64, MAX(4, cli->delay * 2));
658 cli->retransmit += fuzz(cli->delay, 1);
659 timeout(cli, cli->retransmit);
660 dhcp_msg_uninit(&msg);
665 dhclient_msg_init(struct dhclient *cli, enum dhcp_msg_type type,
666 struct dhcp_msg *msg)
669 msg->op = DHCP_BOOTREQUEST;
671 msg->secs = cli->secs;
673 memcpy(msg->chaddr, netdev_get_etheraddr(cli->netdev), ETH_ADDR_LEN);
678 elapsed_in_this_state(const struct dhclient *cli)
680 return time(0) - cli->state_entered;
684 timeout(struct dhclient *cli, unsigned int secs)
686 cli->min_timeout = MIN(cli->min_timeout, secs);
687 return time(0) >= sat_add(cli->state_entered, secs);
691 do_receive_msg(struct dhclient *cli, struct dhcp_msg *msg)
695 buffer_init(&b, netdev_get_mtu(cli->netdev) + VLAN_ETH_HEADER_LEN);
696 for (; cli->received < 50; cli->received++) {
697 const struct ip_header *ip;
698 const struct dhcp_header *dhcp;
703 error = netdev_recv(cli->netdev, &b);
708 flow_extract(&b, 0, &flow);
709 if (flow.dl_type != htons(ETH_TYPE_IP)
710 || flow.nw_proto != IP_TYPE_UDP
711 || flow.tp_dst != htons(68)
712 || !(eth_addr_is_broadcast(flow.dl_dst)
713 || eth_addr_equals(flow.dl_dst,
714 netdev_get_etheraddr(cli->netdev)))) {
719 if (IP_IS_FRAGMENT(ip->ip_frag_off)) {
720 /* We don't do reassembly. */
721 VLOG_WARN("ignoring fragmented DHCP datagram");
727 VLOG_WARN("ignoring DHCP datagram with missing payload");
731 buffer_pull(&b, b.l7 - b.data);
732 error = dhcp_parse(msg, &b);
734 VLOG_DBG("received %s", dhcp_msg_to_string(msg, &cli->s));
739 netdev_drain(cli->netdev);
745 do_send_msg(struct dhclient *cli, const struct dhcp_msg *msg)
748 struct eth_header eh;
750 struct udp_header th;
754 buffer_init(&b, ETH_TOTAL_MAX);
755 buffer_reserve(&b, ETH_HEADER_LEN + IP_HEADER_LEN + UDP_HEADER_LEN);
757 dhcp_assemble(msg, &b);
759 memcpy(eh.eth_src, netdev_get_etheraddr(cli->netdev), ETH_ADDR_LEN);
760 memcpy(eh.eth_dst, eth_addr_broadcast, ETH_ADDR_LEN);
761 eh.eth_type = htons(ETH_TYPE_IP);
763 nh.ip_ihl_ver = IP_IHL_VER(5, IP_VERSION);
765 nh.ip_tot_len = htons(IP_HEADER_LEN + UDP_HEADER_LEN + b.size);
766 /* We can't guarantee uniqueness of ip_id versus the host's, screwing up
767 * fragment reassembly, so prevent fragmentation and use an all-zeros
768 * ip_id. RFC 791 doesn't say we can do this, but Linux does the same
769 * thing for DF packets, so it must not screw anything up. */
771 nh.ip_frag_off = htons(IP_DONT_FRAGMENT);
773 nh.ip_proto = IP_TYPE_UDP;
775 nh.ip_src = dhclient_get_ip(cli);
776 /* XXX need to use UDP socket for nonzero server IPs so that we can get
777 * routing table support.
779 * if (...have server IP and in appropriate state...) {
780 * nh.ip_dst = cli->server_ip;
782 * nh.ip_dst = INADDR_BROADCAST;
785 nh.ip_dst = INADDR_BROADCAST;
786 nh.ip_csum = csum(&nh, sizeof nh);
788 th.udp_src = htons(66);
789 th.udp_dst = htons(67);
790 th.udp_len = htons(UDP_HEADER_LEN + b.size);
792 udp_csum = csum_add32(0, nh.ip_src);
793 udp_csum = csum_add32(udp_csum, nh.ip_dst);
794 udp_csum = csum_add16(udp_csum, IP_TYPE_UDP << 8);
795 udp_csum = csum_add16(udp_csum, th.udp_len);
796 udp_csum = csum_continue(udp_csum, &th, sizeof th);
797 th.udp_csum = csum_finish(csum_continue(udp_csum, b.data, b.size));
799 buffer_push(&b, &th, sizeof th);
800 buffer_push(&b, &nh, sizeof nh);
801 buffer_push(&b, &eh, sizeof eh);
803 /* Don't try to send the frame if it's too long for an Ethernet frame. We
804 * disregard the network device's actual MTU because we don't want the
805 * frame to have to be discarded or fragmented if it travels over a regular
806 * Ethernet at some point. 1500 bytes should be enough for anyone. */
807 if (b.size <= ETH_TOTAL_MAX) {
808 VLOG_DBG("sending %s", dhcp_msg_to_string(msg, &cli->s));
809 error = netdev_send(cli->netdev, &b);
811 VLOG_ERR("send failed on %s: %s",
812 netdev_get_name(cli->netdev), strerror(error));
815 VLOG_ERR("cannot send %zu-byte Ethernet frame", b.size);
822 fuzz(unsigned int x, int max_fuzz)
824 /* Generate number in range [-max_fuzz, +max_fuzz]. */
825 int fuzz = random_range(max_fuzz * 2 + 1) - max_fuzz;
826 unsigned int y = x + fuzz;
827 return fuzz >= 0 ? (y >= x ? y : UINT_MAX) : (y <= x ? y : 0);
831 sat_add(unsigned int x, unsigned int y)
833 return x + y >= x ? x + y : UINT_MAX;
837 sat_sub(unsigned int x, unsigned int y)
839 return x >= y ? x - y : 0;
843 sat_mul(unsigned int x, unsigned int y)
846 return x <= UINT_MAX / y ? x * y : UINT_MAX;
850 clamp(unsigned int x, unsigned int min, unsigned int max)
852 return x < min ? min : x > max ? max : x;
856 calc_t2(unsigned int lease)
858 unsigned int base = lease * 0.875;
859 return lease >= 60 ? clamp(fuzz(base, 10), 0, lease - 1) : base;
863 calc_t1(unsigned int lease, unsigned int t2)
865 unsigned int base = lease / 2;
866 return lease >= 60 ? clamp(fuzz(base, 10), 0, t2 - 1) : base;