src/lease.c

/* dnsmasq is Copyright (c) 2000-2009 Simon Kelley

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 dated June, 1991, or
   (at your option) version 3 dated 29 June, 2007.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "dnsmasq.h"

#ifdef HAVE_DHCP

static struct dhcp_lease *leases = NULL, *old_leases = NULL;
static int dns_dirty, file_dirty, leases_left;

void lease_init(time_t now) {
    unsigned long ei;
    struct in_addr addr;
    struct dhcp_lease* lease;
    int clid_len, hw_len, hw_type;
    FILE* leasestream;

    /* These two each hold a DHCP option max size 255
       and get a terminating zero added */
    daemon->dhcp_buff = safe_malloc(256);
    daemon->dhcp_buff2 = safe_malloc(256);

    leases_left = daemon->dhcp_max;

    if (daemon->options & OPT_LEASE_RO) {
        /* run "<lease_change_script> init" once to get the
       initial state of the database. If leasefile-ro is
       set without a script, we just do without any
       lease database. */
#ifdef HAVE_SCRIPT
        if (daemon->lease_change_command) {
            strcpy(daemon->dhcp_buff, daemon->lease_change_command);
            strcat(daemon->dhcp_buff, " init");
            leasestream = popen(daemon->dhcp_buff, "r");
        } else
#endif
        {
            file_dirty = dns_dirty = 0;
            return;
        }

    } else {
        /* NOTE: need a+ mode to create file if it doesn't exist */
        leasestream = daemon->lease_stream = fopen(daemon->lease_file, "a+");

        if (!leasestream)
            die(_("cannot open or create lease file %s: %s"), daemon->lease_file, EC_FILE);

        /* a+ mode leaves pointer at end. */
        rewind(leasestream);
    }

    /* client-id max length is 255 which is 255*2 digits + 254 colons
       borrow DNS packet buffer which is always larger than 1000 bytes */
    if (leasestream)
        while (fscanf(leasestream, "%lu %255s %16s %255s %764s", &ei, daemon->dhcp_buff2,
                      daemon->namebuff, daemon->dhcp_buff, daemon->packet) == 5) {
            hw_len = parse_hex(daemon->dhcp_buff2, (unsigned char*) daemon->dhcp_buff2,
                               DHCP_CHADDR_MAX, NULL, &hw_type);
            /* For backwards compatibility, no explict MAC address type means ether. */
            if (hw_type == 0 && hw_len != 0) hw_type = ARPHRD_ETHER;

            addr.s_addr = inet_addr(daemon->namebuff);

            /* decode hex in place */
            clid_len = 0;
            if (strcmp(daemon->packet, "*") != 0)
                clid_len =
                    parse_hex(daemon->packet, (unsigned char*) daemon->packet, 255, NULL, NULL);

            if (!(lease = lease_allocate(addr))) die(_("too many stored leases"), NULL, EC_MISC);

#ifdef HAVE_BROKEN_RTC
            if (ei != 0)
                lease->expires = (time_t) ei + now;
            else
                lease->expires = (time_t) 0;
            lease->length = ei;
#else
            /* strictly time_t is opaque, but this hack should work on all sane systems,
               even when sizeof(time_t) == 8 */
            lease->expires = (time_t) ei;
#endif

            lease_set_hwaddr(lease, (unsigned char*) daemon->dhcp_buff2,
                             (unsigned char*) daemon->packet, hw_len, hw_type, clid_len);

            if (strcmp(daemon->dhcp_buff, "*") != 0)
                lease_set_hostname(lease, daemon->dhcp_buff, 0);

            /* set these correctly: the "old" events are generated later from
               the startup synthesised SIGHUP. */
            lease->new = lease->changed = 0;
        }

#ifdef HAVE_SCRIPT
    if (!daemon->lease_stream) {
        int rc = 0;

        /* shell returns 127 for "command not found", 126 for bad permissions. */
        if (!leasestream || (rc = pclose(leasestream)) == -1 || WEXITSTATUS(rc) == 127 ||
            WEXITSTATUS(rc) == 126) {
            if (WEXITSTATUS(rc) == 127)
                errno = ENOENT;
            else if (WEXITSTATUS(rc) == 126)
                errno = EACCES;
            die(_("cannot run lease-init script %s: %s"), daemon->lease_change_command, EC_FILE);
        }

        if (WEXITSTATUS(rc) != 0) {
            sprintf(daemon->dhcp_buff, "%d", WEXITSTATUS(rc));
            die(_("lease-init script returned exit code %s"), daemon->dhcp_buff,
                WEXITSTATUS(rc) + EC_INIT_OFFSET);
        }
    }
#endif

    /* Some leases may have expired */
    file_dirty = 0;
    lease_prune(NULL, now);
    dns_dirty = 1;
}

void lease_update_from_configs(void) {
    /* changes to the config may change current leases. */

    struct dhcp_lease* lease;
    struct dhcp_config* config;
    char* name;

    for (lease = leases; lease; lease = lease->next)
        if ((config = find_config(daemon->dhcp_conf, NULL, lease->clid, lease->clid_len,
                                  lease->hwaddr, lease->hwaddr_len, lease->hwaddr_type, NULL)) &&
            (config->flags & CONFIG_NAME) &&
            (!(config->flags & CONFIG_ADDR) || config->addr.s_addr == lease->addr.s_addr))
            lease_set_hostname(lease, config->hostname, 1);
        else if ((name = host_from_dns(lease->addr)))
            lease_set_hostname(lease, name, 1); /* updates auth flag only */
}

static void ourprintf(int* errp, char* format, ...) {
    va_list ap;

    va_start(ap, format);
    if (!(*errp) && vfprintf(daemon->lease_stream, format, ap) < 0) *errp = errno;
    va_end(ap);
}

void lease_update_file(time_t now) {
    struct dhcp_lease* lease;
    time_t next_event;
    int i, err = 0;

    if (file_dirty != 0 && daemon->lease_stream) {
        errno = 0;
        rewind(daemon->lease_stream);
        if (errno != 0 || ftruncate(fileno(daemon->lease_stream), 0) != 0) err = errno;

        for (lease = leases; lease; lease = lease->next) {
#ifdef HAVE_BROKEN_RTC
            ourprintf(&err, "%u ", lease->length);
#else
            ourprintf(&err, "%lu ", (unsigned long) lease->expires);
#endif
            if (lease->hwaddr_type != ARPHRD_ETHER || lease->hwaddr_len == 0)
                ourprintf(&err, "%.2x-", lease->hwaddr_type);
            for (i = 0; i < lease->hwaddr_len; i++) {
                ourprintf(&err, "%.2x", lease->hwaddr[i]);
                if (i != lease->hwaddr_len - 1) ourprintf(&err, ":");
            }

            ourprintf(&err, " %s ", inet_ntoa(lease->addr));
            ourprintf(&err, "%s ", lease->hostname ? lease->hostname : "*");

            if (lease->clid && lease->clid_len != 0) {
                for (i = 0; i < lease->clid_len - 1; i++) ourprintf(&err, "%.2x:", lease->clid[i]);
                ourprintf(&err, "%.2x\n", lease->clid[i]);
            } else
                ourprintf(&err, "*\n");
        }

        if (fflush(daemon->lease_stream) != 0 || fsync(fileno(daemon->lease_stream)) < 0)
            err = errno;

        if (!err) file_dirty = 0;
    }

    /* Set alarm for when the first lease expires + slop. */
    for (next_event = 0, lease = leases; lease; lease = lease->next)
        if (lease->expires != 0 &&
            (next_event == 0 || difftime(next_event, lease->expires + 10) > 0.0))
            next_event = lease->expires + 10;

    if (err) {
        if (next_event == 0 || difftime(next_event, LEASE_RETRY + now) > 0.0)
            next_event = LEASE_RETRY + now;

        my_syslog(MS_DHCP | LOG_ERR, _("failed to write %s: %s (retry in %us)"), daemon->lease_file,
                  strerror(err), (unsigned int) difftime(next_event, now));
    }

    if (next_event != 0) alarm((unsigned) difftime(next_event, now));
}

void lease_update_dns(void) {
    struct dhcp_lease* lease;

    if (daemon->port != 0 && dns_dirty) {
        cache_unhash_dhcp();

        for (lease = leases; lease; lease = lease->next) {
            if (lease->fqdn) cache_add_dhcp_entry(lease->fqdn, &lease->addr, lease->expires);

            if (!(daemon->options & OPT_DHCP_FQDN) && lease->hostname)
                cache_add_dhcp_entry(lease->hostname, &lease->addr, lease->expires);
        }

        dns_dirty = 0;
    }
}

void lease_prune(struct dhcp_lease* target, time_t now) {
    struct dhcp_lease *lease, *tmp, **up;

    for (lease = leases, up = &leases; lease; lease = tmp) {
        tmp = lease->next;
        if ((lease->expires != 0 && difftime(now, lease->expires) > 0) || lease == target) {
            file_dirty = 1;
            if (lease->hostname) dns_dirty = 1;

            *up = lease->next; /* unlink */

            /* Put on old_leases list 'till we
               can run the script */
            lease->next = old_leases;
            old_leases = lease;

            leases_left++;
        } else
            up = &lease->next;
    }
}

struct dhcp_lease* lease_find_by_client(unsigned char* hwaddr, int hw_len, int hw_type,
                                        unsigned char* clid, int clid_len) {
    struct dhcp_lease* lease;

    if (clid)
        for (lease = leases; lease; lease = lease->next)
            if (lease->clid && clid_len == lease->clid_len &&
                memcmp(clid, lease->clid, clid_len) == 0)
                return lease;

    for (lease = leases; lease; lease = lease->next)
        if ((!lease->clid || !clid) && hw_len != 0 && lease->hwaddr_len == hw_len &&
            lease->hwaddr_type == hw_type && memcmp(hwaddr, lease->hwaddr, hw_len) == 0)
            return lease;

    return NULL;
}

struct dhcp_lease* lease_find_by_addr(struct in_addr addr) {
    struct dhcp_lease* lease;

    for (lease = leases; lease; lease = lease->next)
        if (lease->addr.s_addr == addr.s_addr) return lease;

    return NULL;
}

struct dhcp_lease* lease_allocate(struct in_addr addr) {
    struct dhcp_lease* lease;
    if (!leases_left || !(lease = whine_malloc(sizeof(struct dhcp_lease)))) return NULL;

    memset(lease, 0, sizeof(struct dhcp_lease));
    lease->new = 1;
    lease->addr = addr;
    lease->hwaddr_len = 256; /* illegal value */
    lease->expires = 1;
#ifdef HAVE_BROKEN_RTC
    lease->length = 0xffffffff; /* illegal value */
#endif
    lease->next = leases;
    leases = lease;

    file_dirty = 1;
    leases_left--;

    return lease;
}

void lease_set_expires(struct dhcp_lease* lease, unsigned int len, time_t now) {
    time_t exp = now + (time_t) len;

    if (len == 0xffffffff) {
        exp = 0;
        len = 0;
    }

    if (exp != lease->expires) {
        dns_dirty = 1;
        lease->expires = exp;
#ifndef HAVE_BROKEN_RTC
        lease->aux_changed = file_dirty = 1;
#endif
    }

#ifdef HAVE_BROKEN_RTC
    if (len != lease->length) {
        lease->length = len;
        lease->aux_changed = file_dirty = 1;
    }
#endif
}

void lease_set_hwaddr(struct dhcp_lease* lease, unsigned char* hwaddr, unsigned char* clid,
                      int hw_len, int hw_type, int clid_len) {
    if (hw_len != lease->hwaddr_len || hw_type != lease->hwaddr_type ||
        (hw_len != 0 && memcmp(lease->hwaddr, hwaddr, hw_len) != 0)) {
        memcpy(lease->hwaddr, hwaddr, hw_len);
        lease->hwaddr_len = hw_len;
        lease->hwaddr_type = hw_type;
        lease->changed = file_dirty = 1; /* run script on change */
    }

    /* only update clid when one is available, stops packets
       without a clid removing the record. Lease init uses
       clid_len == 0 for no clid. */
    if (clid_len != 0 && clid) {
        if (!lease->clid) lease->clid_len = 0;

        if (lease->clid_len != clid_len) {
            lease->aux_changed = file_dirty = 1;
            free(lease->clid);
            if (!(lease->clid = whine_malloc(clid_len))) return;
        } else if (memcmp(lease->clid, clid, clid_len) != 0)
            lease->aux_changed = file_dirty = 1;

        lease->clid_len = clid_len;
        memcpy(lease->clid, clid, clid_len);
    }
}

static void kill_name(struct dhcp_lease* lease) {
    /* run script to say we lost our old name */

    /* this shouldn't happen unless updates are very quick and the
       script very slow, we just avoid a memory leak if it does. */
    free(lease->old_hostname);

    /* If we know the fqdn, pass that. The helper will derive the
       unqualified name from it, free the unqulaified name here. */

    if (lease->fqdn) {
        lease->old_hostname = lease->fqdn;
        free(lease->hostname);
    } else
        lease->old_hostname = lease->hostname;

    lease->hostname = lease->fqdn = NULL;
}

void lease_set_hostname(struct dhcp_lease* lease, char* name, int auth) {
    struct dhcp_lease* lease_tmp;
    char *new_name = NULL, *new_fqdn = NULL;

    if (lease->hostname && name && hostname_isequal(lease->hostname, name)) {
        lease->auth_name = auth;
        return;
    }

    if (!name && !lease->hostname) return;

    /* If a machine turns up on a new net without dropping the old lease,
       or two machines claim the same name, then we end up with two interfaces with
       the same name. Check for that here and remove the name from the old lease.
       Don't allow a name from the client to override a name from dnsmasq config. */

    if (name) {
        if ((new_name = whine_malloc(strlen(name) + 1))) {
            char* suffix = get_domain(lease->addr);
            strcpy(new_name, name);
            if (suffix && (new_fqdn = whine_malloc(strlen(new_name) + strlen(suffix) + 2))) {
                strcpy(new_fqdn, name);
                strcat(new_fqdn, ".");
                strcat(new_fqdn, suffix);
            }
        }

        /* Depending on mode, we check either unqualified name or FQDN. */
        for (lease_tmp = leases; lease_tmp; lease_tmp = lease_tmp->next) {
            if (daemon->options & OPT_DHCP_FQDN) {
                if (!new_fqdn || !lease_tmp->fqdn || !hostname_isequal(lease_tmp->fqdn, new_fqdn))
                    continue;
            } else {
                if (!new_name || !lease_tmp->hostname ||
                    !hostname_isequal(lease_tmp->hostname, new_name))
                    continue;
            }

            if (lease_tmp->auth_name && !auth) {
                free(new_name);
                free(new_fqdn);
                return;
            }

            kill_name(lease_tmp);
            break;
        }
    }

    if (lease->hostname) kill_name(lease);

    lease->hostname = new_name;
    lease->fqdn = new_fqdn;
    lease->auth_name = auth;

    file_dirty = 1;
    dns_dirty = 1;
    lease->changed = 1; /* run script on change */
}

void lease_set_interface(struct dhcp_lease* lease, int interface) {
    if (lease->last_interface == interface) return;

    lease->last_interface = interface;
    lease->changed = 1;
}

void rerun_scripts(void) {
    struct dhcp_lease* lease;

    for (lease = leases; lease; lease = lease->next) lease->changed = 1;
}

/* deleted leases get transferred to the old_leases list.
   remove them here, after calling the lease change
   script. Also run the lease change script on new/modified leases.

   Return zero if nothing to do. */
int do_script_run(time_t now) {
    struct dhcp_lease* lease;

    if (old_leases) {
        lease = old_leases;

        /* If the lease still has an old_hostname, do the "old" action on that first */
        if (lease->old_hostname) {
#ifdef HAVE_SCRIPT
            queue_script(ACTION_OLD_HOSTNAME, lease, lease->old_hostname, now);
#endif
            free(lease->old_hostname);
            lease->old_hostname = NULL;
            return 1;
        } else {
            kill_name(lease);
#ifdef HAVE_SCRIPT
            queue_script(ACTION_DEL, lease, lease->old_hostname, now);
#endif
            old_leases = lease->next;

            free(lease->old_hostname);
            free(lease->clid);
            free(lease->vendorclass);
            free(lease->userclass);
            free(lease->supplied_hostname);
            free(lease);

            return 1;
        }
    }

    /* make sure we announce the loss of a hostname before its new location. */
    for (lease = leases; lease; lease = lease->next)
        if (lease->old_hostname) {
#ifdef HAVE_SCRIPT
            queue_script(ACTION_OLD_HOSTNAME, lease, lease->old_hostname, now);
#endif
            free(lease->old_hostname);
            lease->old_hostname = NULL;
            return 1;
        }

    for (lease = leases; lease; lease = lease->next)
        if (lease->new || lease->changed ||
            (lease->aux_changed && (daemon->options & OPT_LEASE_RO))) {
#ifdef HAVE_SCRIPT
            queue_script(lease->new ? ACTION_ADD : ACTION_OLD, lease,
                         lease->fqdn ? lease->fqdn : lease->hostname, now);
#endif
            lease->new = lease->changed = lease->aux_changed = 0;

            /* these are used for the "add" call, then junked, since they're not in the database */
            free(lease->vendorclass);
            lease->vendorclass = NULL;

            free(lease->userclass);
            lease->userclass = NULL;

            free(lease->supplied_hostname);
            lease->supplied_hostname = NULL;

            return 1;
        }

    return 0; /* nothing to do */
}

#endif