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
8 * like to make the Software available for broadest use, with as few
9 * restrictions as possible permission is hereby granted, free of
10 * charge, to any person obtaining a copy of this Software to deal in
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>
43 #include <sys/types.h>
49 #include "dynamic-string.h"
52 #include "ofp-print.h"
53 #include "poll-loop.h"
55 #define THIS_MODULE VLM_dhcp_client
58 #define DHCLIENT_STATES \
59 DHCLIENT_STATE(INIT, 1 << 0) \
60 DHCLIENT_STATE(INIT_REBOOT, 1 << 1) \
61 DHCLIENT_STATE(REBOOTING, 1 << 2) \
62 DHCLIENT_STATE(SELECTING, 1 << 3) \
63 DHCLIENT_STATE(REQUESTING, 1 << 4) \
64 DHCLIENT_STATE(BOUND, 1 << 5) \
65 DHCLIENT_STATE(RENEWING, 1 << 6) \
66 DHCLIENT_STATE(REBINDING, 1 << 7) \
67 DHCLIENT_STATE(RELEASED, 1 << 8)
69 #define DHCLIENT_STATE(NAME, VALUE) S_##NAME = VALUE,
75 state_name(enum dhclient_state state)
78 #define DHCLIENT_STATE(NAME, VALUE) case S_##NAME: return #NAME;
87 struct netdev *netdev;
89 void (*modify_request)(struct dhcp_msg *, void *aux);
90 bool (*validate_offer)(const struct dhcp_msg *, void *aux);
94 enum dhclient_state state;
95 unsigned int state_entered; /* When we transitioned to this state. */
96 uint32_t xid; /* In host byte order. */
97 uint32_t ipaddr, netmask, router;
99 struct dhcp_msg *binding;
102 unsigned int retransmit, delay; /* Used by send_reliably(). */
104 unsigned int init_delay; /* Used by S_INIT. */
106 time_t lease_expiration;
107 unsigned int bound_timeout;
108 unsigned int renewing_timeout;
109 unsigned int rebinding_timeout;
111 /* Used by dhclient_run() and dhclient_wait() */
112 unsigned int min_timeout;
115 /* Set when we send out a DHCPDISCOVER message. */
121 /* Minimum acceptable lease time, in seconds. */
122 #define MIN_ACCEPTABLE_LEASE 15
124 static void state_transition(struct dhclient *, enum dhclient_state);
125 static unsigned int elapsed_in_this_state(const struct dhclient *cli);
126 static bool timeout(struct dhclient *, unsigned int secs);
128 static void dhclient_msg_init(struct dhclient *, enum dhcp_msg_type,
130 static void send_reliably(struct dhclient *cli,
131 void (*make_packet)(struct dhclient *,
133 static bool do_receive_msg(struct dhclient *, struct dhcp_msg *);
134 static void do_send_msg(struct dhclient *, const struct dhcp_msg *);
135 static bool receive_ack(struct dhclient *);
137 static unsigned int fuzz(unsigned int x, int max_fuzz);
138 static unsigned int calc_t2(unsigned int lease);
139 static unsigned int calc_t1(unsigned int lease, unsigned int t2);
141 static unsigned int clamp(unsigned int x, unsigned int min, unsigned int max);
142 static unsigned int sat_add(unsigned int x, unsigned int y);
143 static unsigned int sat_sub(unsigned int x, unsigned int y);
144 static unsigned int sat_mul(unsigned int x, unsigned int y);
146 /* Creates a new DHCP client to configure the network device 'netdev_name'
149 * If 'modify_request' is non-null, then each DHCP message to discover or
150 * request an address will be passed to it (along with auxiliary data 'aux').
151 * It may then add any desired options to the message for transmission.
153 * If 'validate_offer' is non-null, then each DHCP message that offers an
154 * address will be passed to it (along with auxiliary data 'aux') for
155 * validation: if it returns true, the address will accepted; otherwise, it
158 * The DHCP client will not start advertising for an IP address until
159 * dhclient_init() is called.
161 * If successful, returns 0 and sets '*cli' to the new DHCP client. Otherwise,
162 * returns a positive errno value and sets '*cli' to a null pointer. */
164 dhclient_create(const char *netdev_name,
165 void (*modify_request)(struct dhcp_msg *, void *aux),
166 bool (*validate_offer)(const struct dhcp_msg *, void *aux),
167 void *aux, struct dhclient **cli_)
169 struct dhclient *cli;
170 struct netdev *netdev;
175 error = netdev_open(netdev_name, ETH_TYPE_IP, &netdev);
176 /* XXX install socket filter to catch only DHCP packets. */
178 VLOG_ERR("could not open %s network device: %s",
179 netdev_name, strerror(error));
183 error = netdev_turn_flags_on(netdev, NETDEV_UP, false);
185 VLOG_ERR("could not bring %s device up: %s",
186 netdev_name, strerror(error));
187 netdev_close(netdev);
191 cli = xcalloc(1, sizeof *cli);
192 cli->modify_request = modify_request;
193 cli->validate_offer = validate_offer;
195 cli->netdev = netdev;
196 cli->state = S_RELEASED;
197 cli->state_entered = time(0);
198 cli->xid = random_uint32();
201 cli->retransmit = cli->delay = 0;
202 cli->min_timeout = 1;
209 /* Forces 'cli' into a (re)initialization state, in which no address is bound
210 * but the client is advertising to obtain one. If 'requested_ip' is nonzero,
211 * then the client will attempt to re-bind to that IP address; otherwise, it
212 * will not ask for any particular address. */
214 dhclient_init(struct dhclient *cli, uint32_t requested_ip)
216 state_transition(cli, requested_ip ? S_INIT_REBOOT : S_INIT);
217 cli->ipaddr = requested_ip;
218 cli->min_timeout = 0;
222 /* Forces 'cli' to release its bound IP address (if any). The client will not
223 * advertise for a new address until dhclient_init() is called again. */
225 dhclient_release(struct dhclient *cli)
227 if (dhclient_is_bound(cli)) {
229 dhclient_msg_init(cli, DHCPRELEASE, &msg);
230 msg.ciaddr = cli->ipaddr;
231 do_send_msg(cli, &msg);
232 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 and 'cli' has a default gateway, returns
324 * that default gateway; otherwise, returns 0. */
326 dhclient_get_router(const struct dhclient *cli)
328 return dhclient_is_bound(cli) ? cli->router : 0;
331 /* If 'cli' is bound to an IP address, returns the DHCP message that was
332 * received to obtain that IP address (so that the caller can obtain additional
333 * options from it). Otherwise, returns a null pointer. */
334 const struct dhcp_msg *
335 dhclient_get_config(const struct dhclient *cli)
337 return dhclient_is_bound(cli) ? cli->binding : NULL;
340 /* Configures the network device backing 'cli' to the network address and other
341 * parameters obtained via DHCP. If no address is bound on 'cli', removes any
342 * configured address from 'cli'.
344 * To use a dhclient as a regular DHCP client that binds and unbinds from IP
345 * addresses in the usual fashion, call this function after dhclient_run() if
346 * anything has changed, like so:
349 * if (dhclient_changed(cli)) {
350 * dhclient_configure_netdev(cli);
355 dhclient_configure_netdev(struct dhclient *cli)
357 struct in_addr addr = { dhclient_get_ip(cli) };
358 struct in_addr mask = { dhclient_get_netmask(cli) };
359 struct in_addr router = { dhclient_get_router(cli) };
362 error = netdev_set_in4(cli->netdev, addr, mask);
364 VLOG_ERR("could not set %s address "IP_FMT"/"IP_FMT": %s",
365 netdev_get_name(cli->netdev),
366 IP_ARGS(&addr.s_addr), IP_ARGS(&mask.s_addr),
370 if (!error && router.s_addr) {
371 error = netdev_add_router(cli->netdev, router);
373 VLOG_ERR("failed to add default route to "IP_FMT" on %s: %s",
374 IP_ARGS(&router), netdev_get_name(cli->netdev),
382 /* If 'cli' is bound and the binding includes DNS domain parameters, updates
383 * /etc/resolv.conf will be updated to match the received parameters. Returns
384 * 0 if successful, otherwise a positive errno value. */
386 dhclient_update_resolv_conf(struct dhclient *cli)
390 bool has_domain_name;
395 if (!dhclient_is_bound(cli)) {
398 if (!dhcp_msg_get_ip(cli->binding, DHCP_CODE_DNS_SERVER, 0, &dns_server)) {
399 VLOG_DBG("binding does not include any DNS servers");
403 sprintf(new_name, "/etc/resolv.conf.tmp%ld", (long int) getpid());
404 new = fopen(new_name, "w");
406 VLOG_WARN("%s: create: %s", new_name, strerror(errno));
410 domain_name = dhcp_msg_get_string(cli->binding, DHCP_CODE_DOMAIN_NAME);
411 has_domain_name = domain_name != NULL;
413 if (strspn(domain_name, "-_.0123456789abcdefghijklmnopqrstuvwxyz"
414 "ABCDEFGHIJKLMNOPQRSTUVWXYZ") == strlen(domain_name)) {
415 fprintf(new, "domain %s\n", domain_name);
417 VLOG_WARN("ignoring invalid domain name %s", domain_name);
418 has_domain_name = false;
421 VLOG_DBG("binding does not include domain name");
425 for (i = 0; dhcp_msg_get_ip(cli->binding, DHCP_CODE_DNS_SERVER,
426 i, &dns_server); i++) {
427 fprintf(new, "nameserver "IP_FMT"\n", IP_ARGS(&dns_server));
430 old = fopen("/etc/resolv.conf", "r");
434 while (fgets(line, sizeof line, old)) {
435 char *kw = xmemdup0(line, strcspn(line, " \t\r\n"));
436 if (strcmp(kw, "nameserver")
438 || (strcmp(kw, "domain") && strcmp(kw, "search")))) {
445 VLOG_DBG("/etc/resolv.conf: open: %s", strerror(errno));
448 if (fclose(new) < 0) {
449 VLOG_WARN("%s: close: %s", new_name, strerror(errno));
453 if (rename(new_name, "/etc/resolv.conf") < 0) {
454 VLOG_WARN("failed to rename %s to /etc/resolv.conf: %s",
455 new_name, strerror(errno));
465 make_dhcpdiscover(struct dhclient *cli, struct dhcp_msg *msg)
467 cli->secs = elapsed_in_this_state(cli);
468 dhclient_msg_init(cli, DHCPDISCOVER, msg);
470 dhcp_msg_put_ip(msg, DHCP_CODE_REQUESTED_IP, cli->ipaddr);
475 make_dhcprequest(struct dhclient *cli, struct dhcp_msg *msg)
477 dhclient_msg_init(cli, DHCPREQUEST, msg);
478 msg->ciaddr = dhclient_get_ip(cli);
479 if (cli->state == S_REQUESTING) {
480 dhcp_msg_put_ip(msg, DHCP_CODE_SERVER_IDENTIFIER, cli->server_ip);
482 dhcp_msg_put_ip(msg, DHCP_CODE_REQUESTED_IP, cli->ipaddr);
486 do_init(struct dhclient *cli, enum dhclient_state next_state)
488 if (!cli->init_delay) {
489 cli->init_delay = clamp(fuzz(2, 8), 1, 10);
491 if (timeout(cli, cli->init_delay)) {
492 state_transition(cli, next_state);
497 dhclient_run_INIT(struct dhclient *cli)
499 do_init(cli, S_SELECTING);
503 dhclient_run_INIT_REBOOT(struct dhclient *cli)
505 do_init(cli, S_REBOOTING);
509 dhclient_run_REBOOTING(struct dhclient *cli)
511 send_reliably(cli, make_dhcprequest);
512 if (!receive_ack(cli) && timeout(cli, 60)) {
513 state_transition(cli, S_INIT);
518 dhcp_receive(struct dhclient *cli, unsigned int msgs, struct dhcp_msg *msg)
520 while (do_receive_msg(cli, msg)) {
521 if (msg->type < 0 || msg->type > 31 || !((1u << msg->type) & msgs)) {
522 VLOG_DBG("received unexpected %s in %s state: %s",
523 dhcp_type_name(msg->type), state_name(cli->state),
524 dhcp_msg_to_string(msg, false, &cli->s));
525 } else if (msg->xid != cli->xid) {
526 VLOG_DBG("ignoring %s with xid != %08"PRIx32" in %s state: %s",
527 dhcp_type_name(msg->type), msg->xid,
528 state_name(cli->state),
529 dhcp_msg_to_string(msg, false, &cli->s));
533 dhcp_msg_uninit(msg);
539 validate_offered_options(struct dhclient *cli, const struct dhcp_msg *msg)
541 uint32_t lease, netmask;
542 if (!dhcp_msg_get_secs(msg, DHCP_CODE_LEASE_TIME, 0, &lease)) {
543 VLOG_WARN("%s lacks lease time: %s", dhcp_type_name(msg->type),
544 dhcp_msg_to_string(msg, false, &cli->s));
545 } else if (!dhcp_msg_get_ip(msg, DHCP_CODE_SUBNET_MASK, 0, &netmask)) {
546 VLOG_WARN("%s lacks netmask: %s", dhcp_type_name(msg->type),
547 dhcp_msg_to_string(msg, false, &cli->s));
548 } else if (lease < MIN_ACCEPTABLE_LEASE) {
549 VLOG_WARN("Ignoring %s with %"PRIu32"-second lease time: %s",
550 dhcp_type_name(msg->type), lease,
551 dhcp_msg_to_string(msg, false, &cli->s));
552 } else if (cli->validate_offer && !cli->validate_offer(msg, cli->aux)) {
553 VLOG_DBG("client validation hook refused offer: %s",
554 dhcp_msg_to_string(msg, false, &cli->s));
562 dhclient_run_SELECTING(struct dhclient *cli)
566 send_reliably(cli, make_dhcpdiscover);
567 if (cli->server_ip && timeout(cli, 60)) {
569 state_transition(cli, S_INIT);
571 for (; dhcp_receive(cli, 1u << DHCPOFFER, &msg); dhcp_msg_uninit(&msg)) {
572 if (!validate_offered_options(cli, &msg)) {
575 if (!dhcp_msg_get_ip(&msg, DHCP_CODE_SERVER_IDENTIFIER,
576 0, &cli->server_ip)) {
577 VLOG_WARN("DHCPOFFER lacks server identifier: %s",
578 dhcp_msg_to_string(&msg, false, &cli->s));
582 VLOG_DBG("accepting DHCPOFFER: %s",
583 dhcp_msg_to_string(&msg, false, &cli->s));
584 cli->ipaddr = msg.yiaddr;
585 state_transition(cli, S_REQUESTING);
591 receive_ack(struct dhclient *cli)
595 if (!dhcp_receive(cli, (1u << DHCPACK) | (1u << DHCPNAK), &msg)) {
597 } else if (msg.type == DHCPNAK) {
598 dhcp_msg_uninit(&msg);
599 state_transition(cli, S_INIT);
601 } else if (!validate_offered_options(cli, &msg)) {
602 dhcp_msg_uninit(&msg);
605 uint32_t lease = 0, t1 = 0, t2 = 0;
608 dhcp_msg_uninit(cli->binding);
610 cli->binding = xmalloc(sizeof *cli->binding);
612 dhcp_msg_copy(cli->binding, &msg);
614 dhcp_msg_get_secs(&msg, DHCP_CODE_LEASE_TIME, 0, &lease);
615 dhcp_msg_get_secs(&msg, DHCP_CODE_T1, 0, &t1);
616 dhcp_msg_get_secs(&msg, DHCP_CODE_T2, 0, &t2);
617 assert(lease >= MIN_ACCEPTABLE_LEASE);
619 if (!t2 || t2 >= lease) {
622 if (!t1 || t1 >= t2) {
623 t1 = calc_t1(lease, t2);
626 cli->lease_expiration = sat_add(time(0), lease);
627 cli->bound_timeout = t1;
628 cli->renewing_timeout = t2 - t1;
629 cli->rebinding_timeout = lease - t2;
631 cli->ipaddr = msg.yiaddr;
632 dhcp_msg_get_ip(&msg, DHCP_CODE_SUBNET_MASK, 0, &cli->netmask);
633 if (!dhcp_msg_get_ip(&msg, DHCP_CODE_ROUTER, 0, &cli->router)) {
634 cli->router = INADDR_ANY;
636 state_transition(cli, S_BOUND);
637 VLOG_DBG("Bound: %s", dhcp_msg_to_string(&msg, false, &cli->s));
643 dhclient_run_REQUESTING(struct dhclient *cli)
645 send_reliably(cli, make_dhcprequest);
646 if (!receive_ack(cli) && timeout(cli, 60)) {
647 state_transition(cli, S_INIT);
652 dhclient_run_BOUND(struct dhclient *cli)
654 if (timeout(cli, cli->bound_timeout)) {
655 state_transition(cli, S_RENEWING);
660 dhclient_run_RENEWING(struct dhclient *cli)
662 send_reliably(cli, make_dhcprequest);
663 if (!receive_ack(cli) && timeout(cli, cli->renewing_timeout)) {
664 state_transition(cli, S_REBINDING);
669 dhclient_run_REBINDING(struct dhclient *cli)
671 send_reliably(cli, make_dhcprequest);
672 if (!receive_ack(cli) && timeout(cli, cli->rebinding_timeout)) {
673 state_transition(cli, S_INIT);
678 dhclient_run_RELEASED(struct dhclient *cli UNUSED)
683 /* Processes the DHCP protocol for 'cli'. */
685 dhclient_run(struct dhclient *cli)
689 old_state = cli->state;
690 cli->min_timeout = UINT_MAX;
692 switch (cli->state) {
693 #define DHCLIENT_STATE(NAME, VALUE) \
694 case S_##NAME: dhclient_run_##NAME(cli); break;
696 #undef DHCLIENT_STATE
700 } while (cli->state != old_state);
703 /* Sets up poll timeouts to wake up the poll loop when 'cli' needs to do some
706 dhclient_wait(struct dhclient *cli)
708 if (cli->min_timeout != UINT_MAX) {
709 poll_timer_wait(sat_mul(cli->min_timeout, 1000));
711 /* Reset timeout to 1 second. This will have no effect ordinarily, because
712 * dhclient_run() will typically set it back to a higher value. If,
713 * however, the caller fails to call dhclient_run() before its next call to
714 * dhclient_wait() we won't potentially block forever. */
715 cli->min_timeout = 1;
717 if (cli->state & (S_SELECTING | S_REQUESTING | S_RENEWING | S_REBINDING)) {
718 netdev_recv_wait(cli->netdev);
723 state_transition(struct dhclient *cli, enum dhclient_state state)
725 bool was_bound = dhclient_is_bound(cli);
727 if (cli->state != state) {
728 VLOG_DBG("entering %s", state_name(state));
731 cli->state_entered = time(0);
732 cli->retransmit = cli->delay = 0;
733 am_bound = dhclient_is_bound(cli);
734 if (was_bound != am_bound) {
737 assert(cli->binding != NULL);
738 VLOG_WARN("%s: obtained address "IP_FMT", netmask "IP_FMT,
739 netdev_get_name(cli->netdev),
740 IP_ARGS(&cli->ipaddr), IP_ARGS(&cli->netmask));
742 VLOG_WARN("%s: obtained default gateway "IP_FMT,
743 netdev_get_name(cli->netdev), IP_ARGS(&cli->router));
746 dhcp_msg_uninit(cli->binding);
750 VLOG_WARN("%s: network address unbound",
751 netdev_get_name(cli->netdev));
754 if (cli->state & (S_SELECTING | S_REQUESTING | S_REBOOTING)) {
755 netdev_drain(cli->netdev);
760 send_reliably(struct dhclient *cli,
761 void (*make_packet)(struct dhclient *, struct dhcp_msg *))
763 if (timeout(cli, cli->retransmit)) {
765 make_packet(cli, &msg);
766 if (cli->modify_request) {
767 cli->modify_request(&msg, cli->aux);
769 do_send_msg(cli, &msg);
770 cli->delay = MIN(64, MAX(4, cli->delay * 2));
771 cli->retransmit += fuzz(cli->delay, 1);
772 timeout(cli, cli->retransmit);
773 dhcp_msg_uninit(&msg);
778 dhclient_msg_init(struct dhclient *cli, enum dhcp_msg_type type,
779 struct dhcp_msg *msg)
782 msg->op = DHCP_BOOTREQUEST;
784 msg->secs = cli->secs;
786 memcpy(msg->chaddr, netdev_get_etheraddr(cli->netdev), ETH_ADDR_LEN);
790 elapsed_in_this_state(const struct dhclient *cli)
792 return time(0) - cli->state_entered;
796 timeout(struct dhclient *cli, unsigned int secs)
798 cli->min_timeout = MIN(cli->min_timeout, secs);
799 return time(0) >= sat_add(cli->state_entered, secs);
803 do_receive_msg(struct dhclient *cli, struct dhcp_msg *msg)
807 buffer_init(&b, netdev_get_mtu(cli->netdev) + VLAN_ETH_HEADER_LEN);
808 for (; cli->received < 50; cli->received++) {
809 const struct ip_header *ip;
810 const struct dhcp_header *dhcp;
815 error = netdev_recv(cli->netdev, &b);
820 flow_extract(&b, 0, &flow);
821 if (flow.dl_type != htons(ETH_TYPE_IP)
822 || flow.nw_proto != IP_TYPE_UDP
823 || flow.tp_dst != htons(68)
824 || !(eth_addr_is_broadcast(flow.dl_dst)
825 || eth_addr_equals(flow.dl_dst,
826 netdev_get_etheraddr(cli->netdev)))) {
831 if (IP_IS_FRAGMENT(ip->ip_frag_off)) {
832 /* We don't do reassembly. */
833 VLOG_WARN("ignoring fragmented DHCP datagram");
839 VLOG_WARN("ignoring DHCP datagram with missing payload");
843 buffer_pull(&b, b.l7 - b.data);
844 error = dhcp_parse(msg, &b);
846 VLOG_DBG("received %s", dhcp_msg_to_string(msg, false, &cli->s));
851 netdev_drain(cli->netdev);
858 do_send_msg(struct dhclient *cli, const struct dhcp_msg *msg)
861 struct eth_header eh;
863 struct udp_header th;
867 buffer_init(&b, ETH_TOTAL_MAX);
868 buffer_reserve(&b, ETH_HEADER_LEN + IP_HEADER_LEN + UDP_HEADER_LEN);
870 dhcp_assemble(msg, &b);
872 memcpy(eh.eth_src, netdev_get_etheraddr(cli->netdev), ETH_ADDR_LEN);
873 memcpy(eh.eth_dst, eth_addr_broadcast, ETH_ADDR_LEN);
874 eh.eth_type = htons(ETH_TYPE_IP);
876 nh.ip_ihl_ver = IP_IHL_VER(5, IP_VERSION);
878 nh.ip_tot_len = htons(IP_HEADER_LEN + UDP_HEADER_LEN + b.size);
879 /* We can't guarantee uniqueness of ip_id versus the host's, screwing up
880 * fragment reassembly, so prevent fragmentation and use an all-zeros
881 * ip_id. RFC 791 doesn't say we can do this, but Linux does the same
882 * thing for DF packets, so it must not screw anything up. */
884 nh.ip_frag_off = htons(IP_DONT_FRAGMENT);
886 nh.ip_proto = IP_TYPE_UDP;
888 nh.ip_src = dhclient_get_ip(cli);
889 /* XXX need to use UDP socket for nonzero server IPs so that we can get
890 * routing table support.
892 * if (...have server IP and in appropriate state...) {
893 * nh.ip_dst = cli->server_ip;
895 * nh.ip_dst = INADDR_BROADCAST;
898 nh.ip_dst = INADDR_BROADCAST;
899 nh.ip_csum = csum(&nh, sizeof nh);
901 th.udp_src = htons(66);
902 th.udp_dst = htons(67);
903 th.udp_len = htons(UDP_HEADER_LEN + b.size);
905 udp_csum = csum_add32(0, nh.ip_src);
906 udp_csum = csum_add32(udp_csum, nh.ip_dst);
907 udp_csum = csum_add16(udp_csum, IP_TYPE_UDP << 8);
908 udp_csum = csum_add16(udp_csum, th.udp_len);
909 udp_csum = csum_continue(udp_csum, &th, sizeof th);
910 th.udp_csum = csum_finish(csum_continue(udp_csum, b.data, b.size));
912 buffer_push(&b, &th, sizeof th);
913 buffer_push(&b, &nh, sizeof nh);
914 buffer_push(&b, &eh, sizeof eh);
916 /* Don't try to send the frame if it's too long for an Ethernet frame. We
917 * disregard the network device's actual MTU because we don't want the
918 * frame to have to be discarded or fragmented if it travels over a regular
919 * Ethernet at some point. 1500 bytes should be enough for anyone. */
920 if (b.size <= ETH_TOTAL_MAX) {
921 VLOG_DBG("sending %s", dhcp_msg_to_string(msg, false, &cli->s));
922 error = netdev_send(cli->netdev, &b);
924 VLOG_ERR("send failed on %s: %s",
925 netdev_get_name(cli->netdev), strerror(error));
928 VLOG_ERR("cannot send %zu-byte Ethernet frame", b.size);
935 fuzz(unsigned int x, int max_fuzz)
937 /* Generate number in range [-max_fuzz, +max_fuzz]. */
938 int fuzz = random_range(max_fuzz * 2 + 1) - max_fuzz;
939 unsigned int y = x + fuzz;
940 return fuzz >= 0 ? (y >= x ? y : UINT_MAX) : (y <= x ? y : 0);
944 sat_add(unsigned int x, unsigned int y)
946 return x + y >= x ? x + y : UINT_MAX;
950 sat_sub(unsigned int x, unsigned int y)
952 return x >= y ? x - y : 0;
956 sat_mul(unsigned int x, unsigned int y)
959 return x <= UINT_MAX / y ? x * y : UINT_MAX;
963 clamp(unsigned int x, unsigned int min, unsigned int max)
965 return x < min ? min : x > max ? max : x;
969 calc_t2(unsigned int lease)
971 unsigned int base = lease * 0.875;
972 return lease >= 60 ? clamp(fuzz(base, 10), 0, lease - 1) : base;
976 calc_t1(unsigned int lease, unsigned int t2)
978 unsigned int base = lease / 2;
979 return lease >= 60 ? clamp(fuzz(base, 10), 0, t2 - 1) : base;