libsmb/common/smb_domain.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright 2017 Nexenta Systems, Inc.  All rights reserved.
 * Copyright 2022 RackTop Systems, Inc.
 */

/*
 * This file defines the domain environment values and the domain
 * database interface. The database is a single linked list of
 * structures containing domain type, name and SID information.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/list.h>
#include <stdio.h>
#include <strings.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <stdlib.h>
#include <synch.h>
#include <pwd.h>
#include <grp.h>
#include <assert.h>

#include <smbsrv/smbinfo.h>
#include <smbsrv/string.h>
#include <smbsrv/smb_sid.h>
#include <smbsrv/libsmb.h>

#define	SMB_DOMAINS_FILE	"domains"

#define	SMB_DCACHE_UPDATE_WAIT	45	/* seconds */

/*
 * Domain cache states
 */
#define	SMB_DCACHE_STATE_NONE		0
#define	SMB_DCACHE_STATE_READY		1
#define	SMB_DCACHE_STATE_UPDATING	2
#define	SMB_DCACHE_STATE_DESTROYING	3

/*
 * Cache lock modes
 */
#define	SMB_DCACHE_RDLOCK	0
#define	SMB_DCACHE_WRLOCK	1

typedef struct smb_domain_cache {
	list_t		dc_cache;
	rwlock_t	dc_cache_lck;
	uint32_t	dc_state;
	uint32_t	dc_nops;
	mutex_t		dc_mtx;
	cond_t		dc_cv;
	/* domain controller information */
	cond_t		dc_dci_cv;
	boolean_t	dc_dci_valid;
	smb_dcinfo_t	dc_dci;
} smb_domain_cache_t;

static smb_domain_cache_t smb_dcache;

static uint32_t smb_domain_add(smb_domain_type_t, smb_domain_t *);
static uint32_t smb_domain_add_local(void);
static uint32_t smb_domain_add_primary(uint32_t);
static void smb_domain_unlink(void);

static void smb_dcache_create(void);
static void smb_dcache_destroy(void);
static uint32_t smb_dcache_lock(int);
static void smb_dcache_unlock(void);
static void smb_dcache_remove(smb_domain_t *);
static uint32_t smb_dcache_add(smb_domain_t *);
static boolean_t smb_dcache_getdc(smb_dcinfo_t *, boolean_t);
static void smb_dcache_setdc(const smb_dcinfo_t *);
static boolean_t smb_dcache_wait(void);
static uint32_t smb_dcache_updating(void);
static void smb_dcache_ready(void);

/*
 * domain cache one time initialization. This function should
 * only be called during service startup.
 *
 * Returns 0 on success and an error code on failure.
 */
int
smb_domain_init(uint32_t secmode)
{
	smb_domain_t di;
	int rc;

	smb_dcache_create();

	if ((rc = smb_domain_add_local()) != 0)
		return (rc);

	bzero(&di, sizeof (di));
	smb_domain_set_basic_info(NT_BUILTIN_DOMAIN_SIDSTR, "BUILTIN", "", &di);
	(void) smb_domain_add(SMB_DOMAIN_BUILTIN, &di);

	return (smb_domain_add_primary(secmode));
}

/*
 * Destroys the cache upon service termination
 */
void
smb_domain_fini(void)
{
	smb_dcache_destroy();
	smb_domain_unlink();
}

/*
 * Add a domain structure to domain cache. There is no checking
 * for duplicates.
 */
static uint32_t
smb_domain_add(smb_domain_type_t type, smb_domain_t *di)
{
	uint32_t res;

	if (di == NULL || di->di_sid[0] == '\0')
		return (SMB_DOMAIN_INVALID_ARG);

	if ((res = smb_dcache_lock(SMB_DCACHE_WRLOCK)) == SMB_DOMAIN_SUCCESS) {
		di->di_type = type;
		res = smb_dcache_add(di);
		smb_dcache_unlock();
	}

	return (res);
}

/*
 * Lookup a domain by its name. The passed name is the NETBIOS or fully
 * qualified DNS name or non-qualified DNS name.
 *
 * If the requested domain is found and given 'di' pointer is not NULL
 * it'll be filled with the domain information and B_TRUE is returned.
 * If the caller only needs to check a domain existence it can pass
 * NULL for 'di' and just check the return value.
 *
 * If the domain is not in the cache B_FALSE is returned.
 */
boolean_t
smb_domain_lookup_name(char *name, smb_domain_t *di)
{
	boolean_t found = B_FALSE;
	smb_domain_t *dcnode;
	char *p;

	bzero(di, sizeof (smb_domain_t));

	if (name == NULL || *name == '\0')
		return (B_FALSE);

	if (smb_dcache_lock(SMB_DCACHE_RDLOCK) != SMB_DOMAIN_SUCCESS)
		return (B_FALSE);

	dcnode = list_head(&smb_dcache.dc_cache);
	while (dcnode) {
		found = (smb_strcasecmp(dcnode->di_nbname, name, 0) == 0) ||
		    (smb_strcasecmp(dcnode->di_fqname, name, 0) == 0);

		if (found) {
			if (di)
				*di = *dcnode;
			break;
		}

		if ((p = strchr(dcnode->di_fqname, '.')) != NULL) {
			*p = '\0';
			found = (smb_strcasecmp(dcnode->di_fqname, name,
			    0) == 0);
			*p = '.';
			if (found) {
				if (di)
					*di = *dcnode;
				break;
			}
		}

		dcnode = list_next(&smb_dcache.dc_cache, dcnode);
	}

	smb_dcache_unlock();
	return (found);
}

/*
 * Lookup a domain by its SID.
 *
 * If the requested domain is found and given 'di' pointer is not NULL
 * it'll be filled with the domain information and B_TRUE is returned.
 * If the caller only needs to check a domain existence it can pass
 * NULL for 'di' and just check the return value.
 *
 * If the domain is not in the cache B_FALSE is returned.
 */
boolean_t
smb_domain_lookup_sid(smb_sid_t *sid, smb_domain_t *di)
{
	boolean_t found = B_FALSE;
	smb_domain_t *dcnode;
	char sidstr[SMB_SID_STRSZ];

	bzero(di, sizeof (smb_domain_t));

	if (sid == NULL)
		return (B_FALSE);

	smb_sid_tostr(sid, sidstr);

	if (smb_dcache_lock(SMB_DCACHE_RDLOCK) != SMB_DOMAIN_SUCCESS)
		return (B_FALSE);

	dcnode = list_head(&smb_dcache.dc_cache);
	while (dcnode) {
		found = (strcmp(dcnode->di_sid, sidstr) == 0);
		if (found) {
			if (di)
				*di = *dcnode;
			break;
		}

		dcnode = list_next(&smb_dcache.dc_cache, dcnode);
	}

	smb_dcache_unlock();
	return (found);
}

/*
 * Lookup a domain by its type.
 *
 * If the requested domain is found and given 'di' pointer is not NULL
 * it'll be filled with the domain information and B_TRUE is returned.
 * If the caller only needs to check a domain existence it can pass
 * NULL for 'di' and just check the return value.
 *
 * If the domain is not in the cache B_FALSE is returned.
 */
boolean_t
smb_domain_lookup_type(smb_domain_type_t type, smb_domain_t *di)
{
	boolean_t found = B_FALSE;
	smb_domain_t *dcnode;

	bzero(di, sizeof (smb_domain_t));

	if (smb_dcache_lock(SMB_DCACHE_RDLOCK) != SMB_DOMAIN_SUCCESS)
		return (B_FALSE);

	dcnode = list_head(&smb_dcache.dc_cache);
	while (dcnode) {
		if (dcnode->di_type == type) {
			found = B_TRUE;
			if (di)
				*di = *dcnode;
			break;
		}

		dcnode = list_next(&smb_dcache.dc_cache, dcnode);
	}

	smb_dcache_unlock();
	return (found);
}

/*
 * Returns primary domain information plus the name of
 * the selected domain controller.
 *
 * Returns TRUE on success.
 */
boolean_t
smb_domain_getinfo(smb_domainex_t *dxi)
{
	boolean_t rv;

	/* Note: this waits for the dcache lock. */
	rv = smb_domain_lookup_type(SMB_DOMAIN_PRIMARY, &dxi->d_primary);
	if (!rv) {
		syslog(LOG_ERR, "smb_domain_getinfo: no primary domain");
		return (B_FALSE);
	}

	/*
	 * The 2nd arg TRUE means this will wait for DC info.
	 *
	 * Note that we do NOT hold the dcache rwlock here
	 * (not even as reader) because we already have what we
	 * need from the dcache (our primary domain) and we don't
	 * want to interfere with the DC locator which will take
	 * the dcache lock as writer to update the domain info.
	 */
	rv = smb_dcache_getdc(&dxi->d_dci, B_TRUE);
	if (!rv) {
		syslog(LOG_ERR, "smb_domain_getinfo: no DC info");
		return (B_FALSE);
	}

	return (B_TRUE);
}

/*
 * Get the name of the current DC (if any)
 * Does NOT block.
 */
void
smb_domain_current_dc(smb_dcinfo_t *dci)
{
	(void) smb_dcache_getdc(dci, B_FALSE);
}

/*
 * Transfer the cache to updating state.
 * In this state any request for reading the cache would
 * be blocked until the update is finished.
 */
uint32_t
smb_domain_start_update(void)
{
	return (smb_dcache_updating());
}

/*
 * Transfer the cache from updating to ready state.
 */
void
smb_domain_end_update(void)
{
	smb_dcache_ready();
}

/*
 * Mark the current domain controller (DC) info invalid
 * until the DC locator calls smb_domain_update().
 */
void
smb_domain_bad_dc(void)
{
	(void) mutex_lock(&smb_dcache.dc_mtx);
	smb_dcache.dc_dci_valid = B_FALSE;
	(void) mutex_unlock(&smb_dcache.dc_mtx);
}

/*
 * Updates the cache with given information for the primary
 * domain, possible trusted domains and the selected domain
 * controller.
 *
 * Before adding the new entries existing entries of type
 * primary and trusted will be removed from cache.
 */
void
smb_domain_update(smb_domainex_t *dxi)
{
	smb_domain_t *dcnode;
	int i;

	if (smb_dcache_lock(SMB_DCACHE_WRLOCK) != SMB_DOMAIN_SUCCESS)
		return;

	dcnode = list_head(&smb_dcache.dc_cache);
	while (dcnode) {
		if ((dcnode->di_type == SMB_DOMAIN_PRIMARY) ||
		    (dcnode->di_type == SMB_DOMAIN_TRUSTED)) {
			smb_dcache_remove(dcnode);
			dcnode = list_head(&smb_dcache.dc_cache);
		} else {
			dcnode = list_next(&smb_dcache.dc_cache, dcnode);
		}
	}

	dxi->d_primary.di_type = SMB_DOMAIN_PRIMARY;
	if (smb_dcache_add(&dxi->d_primary) == SMB_DOMAIN_SUCCESS) {
		for (i = 0, dcnode = dxi->d_trusted.td_domains;
		    i < dxi->d_trusted.td_num;
		    i++, dcnode++) {
			dcnode->di_type = SMB_DOMAIN_TRUSTED;
			(void) smb_dcache_add(dcnode);
		}
		smb_dcache_setdc(&dxi->d_dci);
	}

	smb_dcache_unlock();
}

/*
 * Write the list of domains to /var/run/smb/domains.
 */
void
smb_domain_save(void)
{
	char		fname[MAXPATHLEN];
	char		tag;
	smb_domain_t	*domain;
	FILE		*fp;
	struct passwd	*pwd;
	struct group	*grp;
	uid_t		uid;
	gid_t		gid;

	(void) snprintf(fname, MAXPATHLEN, "%s/%s",
	    SMB_VARRUN_DIR, SMB_DOMAINS_FILE);

	if ((fp = fopen(fname, "w")) == NULL)
		return;

	pwd = getpwnam("root");
	grp = getgrnam("sys");
	uid = (pwd == NULL) ? 0 : pwd->pw_uid;
	gid = (grp == NULL) ? 3 : grp->gr_gid;

	(void) lockf(fileno(fp), F_LOCK, 0);
	(void) fchmod(fileno(fp), 0600);
	(void) fchown(fileno(fp), uid, gid);

	if (smb_dcache_lock(SMB_DCACHE_RDLOCK) != SMB_DOMAIN_SUCCESS)
		return;

	domain = list_head(&smb_dcache.dc_cache);
	while (domain) {
		switch (domain->di_type) {
		case SMB_DOMAIN_PRIMARY:
			tag = '*';
			break;

		case SMB_DOMAIN_TRUSTED:
		case SMB_DOMAIN_UNTRUSTED:
			tag = '-';
			break;

		case SMB_DOMAIN_LOCAL:
			tag = '.';
			break;
		default:
			domain = list_next(&smb_dcache.dc_cache, domain);
			continue;
		}

		(void) fprintf(fp, "[%c] [%s] [%s]\n",
		    tag, domain->di_nbname, domain->di_sid);

		domain = list_next(&smb_dcache.dc_cache, domain);
	}

	smb_dcache_unlock();
	(void) lockf(fileno(fp), F_ULOCK, 0);
	(void) fclose(fp);
}

/*
 * List the domains in /var/run/smb/domains.
 */
void
smb_domain_show(void)
{
	char buf[MAXPATHLEN];
	char *p;
	FILE *fp;

	(void) snprintf(buf, MAXPATHLEN, "%s/%s",
	    SMB_VARRUN_DIR, SMB_DOMAINS_FILE);

	if ((fp = fopen(buf, "r")) != NULL) {
		(void) lockf(fileno(fp), F_LOCK, 0);

		while (fgets(buf, MAXPATHLEN, fp) != NULL) {
			if ((p = strchr(buf, '\n')) != NULL)
				*p = '\0';
			(void) printf("%s\n", buf);
		}

		(void) lockf(fileno(fp), F_ULOCK, 0);
		(void) fclose(fp);
	}
}

void
smb_domain_set_basic_info(char *sid, char *nb_domain, char *fq_domain,
    smb_domain_t *di)
{
	if (sid == NULL || nb_domain == NULL || fq_domain == NULL ||
	    di == NULL)
		return;

	(void) strlcpy(di->di_sid, sid, SMB_SID_STRSZ);
	(void) strlcpy(di->di_nbname, nb_domain, NETBIOS_NAME_SZ);
	(void) smb_strupr(di->di_nbname);
	(void) strlcpy(di->di_fqname, fq_domain, MAXHOSTNAMELEN);
	di->di_binsid = NULL;
}

void
smb_domain_set_dns_info(char *sid, char *nb_domain, char *fq_domain,
    char *forest, char *guid, smb_domain_t *di)
{
	if (di == NULL || forest == NULL || guid == NULL)
		return;

	/* Caller zeros out *di before this. */
	smb_domain_set_basic_info(sid, nb_domain, fq_domain, di);
	(void) strlcpy(di->di_u.di_dns.ddi_forest, forest, MAXHOSTNAMELEN);
	(void) strlcpy(di->di_u.di_dns.ddi_guid, guid,
	    UUID_PRINTABLE_STRING_LENGTH);
}

void
smb_domain_set_trust_info(char *sid, char *nb_domain, char *fq_domain,
    uint32_t trust_dir, uint32_t trust_type, uint32_t trust_attrs,
    smb_domain_t *di)
{
	smb_domain_trust_t *ti;

	if (di == NULL)
		return;

	/* Caller zeros out *di before this. */
	di->di_type = SMB_DOMAIN_TRUSTED;
	ti = &di->di_u.di_trust;
	smb_domain_set_basic_info(sid, nb_domain, fq_domain, di);
	ti->dti_trust_direction = trust_dir;
	ti->dti_trust_type = trust_type;
	ti->dti_trust_attrs = trust_attrs;
}

/*
 * Remove the /var/run/smb/domains file.
 */
static void
smb_domain_unlink(void)
{
	char fname[MAXPATHLEN];

	(void) snprintf(fname, MAXPATHLEN, "%s/%s",
	    SMB_VARRUN_DIR, SMB_DOMAINS_FILE);
	(void) unlink(fname);
}

/*
 * Add an entry for the local domain to the domain cache
 */
static uint32_t
smb_domain_add_local(void)
{
	char *lsidstr;
	char hostname[NETBIOS_NAME_SZ];
	char fq_name[MAXHOSTNAMELEN];
	smb_domain_t di;

	if ((lsidstr = smb_config_get_localsid()) == NULL)
		return (SMB_DOMAIN_NOMACHINE_SID);

	if (smb_getnetbiosname(hostname, NETBIOS_NAME_SZ) != 0) {
		free(lsidstr);
		return (SMB_DOMAIN_NOMACHINE_SID);
	}

	bzero(&di, sizeof (di));
	*fq_name = '\0';
	(void) smb_getfqhostname(fq_name, MAXHOSTNAMELEN);
	smb_domain_set_basic_info(lsidstr, hostname, fq_name, &di);
	(void) smb_domain_add(SMB_DOMAIN_LOCAL, &di);

	free(lsidstr);
	return (SMB_DOMAIN_SUCCESS);
}

/*
 * Add an entry for the primary domain to the domain cache
 */
static uint32_t
smb_domain_add_primary(uint32_t secmode)
{
	char sidstr[SMB_SID_STRSZ];
	char fq_name[MAXHOSTNAMELEN];
	char nb_name[NETBIOS_NAME_SZ];
	smb_domain_t di;
	int rc;

	if (secmode != SMB_SECMODE_DOMAIN)
		return (SMB_DOMAIN_SUCCESS);

	rc = smb_config_getstr(SMB_CI_DOMAIN_SID, sidstr, sizeof (sidstr));
	if (rc != SMBD_SMF_OK)
		return (SMB_DOMAIN_NODOMAIN_SID);

	rc = smb_config_getstr(SMB_CI_DOMAIN_NAME, nb_name, NETBIOS_NAME_SZ);
	if ((rc != SMBD_SMF_OK) || (*nb_name == '\0'))
		return (SMB_DOMAIN_NODOMAIN_NAME);

	bzero(&di, sizeof (di));
	(void) smb_getfqdomainname(fq_name, MAXHOSTNAMELEN);
	smb_domain_set_basic_info(sidstr, nb_name, fq_name, &di);
	(void) smb_domain_add(SMB_DOMAIN_PRIMARY, &di);
	return (SMB_DOMAIN_SUCCESS);
}

/*
 * Initialize the domain cache.
 * This function does not populate the cache.
 */
static void
smb_dcache_create(void)
{
	(void) mutex_lock(&smb_dcache.dc_mtx);
	if (smb_dcache.dc_state != SMB_DCACHE_STATE_NONE) {
		(void) mutex_unlock(&smb_dcache.dc_mtx);
		return;
	}

	list_create(&smb_dcache.dc_cache, sizeof (smb_domain_t),
	    offsetof(smb_domain_t, di_lnd));

	smb_dcache.dc_nops = 0;
	bzero(&smb_dcache.dc_dci, sizeof (smb_dcache.dc_dci));
	smb_dcache.dc_dci_valid = B_FALSE;
	smb_dcache.dc_state = SMB_DCACHE_STATE_READY;
	(void) mutex_unlock(&smb_dcache.dc_mtx);
}

/*
 * Removes and frees all the cache entries
 */
static void
smb_dcache_flush(void)
{
	smb_domain_t *di;

	(void) rw_wrlock(&smb_dcache.dc_cache_lck);
	while ((di = list_head(&smb_dcache.dc_cache)) != NULL)
		smb_dcache_remove(di);
	(void) rw_unlock(&smb_dcache.dc_cache_lck);
}

/*
 * Destroys the cache.
 */
static void
smb_dcache_destroy(void)
{
	(void) mutex_lock(&smb_dcache.dc_mtx);
	if ((smb_dcache.dc_state == SMB_DCACHE_STATE_READY) ||
	    (smb_dcache.dc_state == SMB_DCACHE_STATE_UPDATING)) {
		smb_dcache.dc_state = SMB_DCACHE_STATE_DESTROYING;
		while (smb_dcache.dc_nops > 0)
			(void) cond_wait(&smb_dcache.dc_cv,
			    &smb_dcache.dc_mtx);

		smb_dcache_flush();
		list_destroy(&smb_dcache.dc_cache);

		smb_dcache.dc_state = SMB_DCACHE_STATE_NONE;
	}
	(void) mutex_unlock(&smb_dcache.dc_mtx);
}

/*
 * Lock the cache with the specified mode.
 * If the cache is in updating state and a read lock is
 * requested, the lock won't be granted until either the
 * update is finished or SMB_DCACHE_UPDATE_WAIT has passed.
 *
 * Whenever a lock is granted, the number of inflight cache
 * operations is incremented.
 */
static uint32_t
smb_dcache_lock(int mode)
{
	(void) mutex_lock(&smb_dcache.dc_mtx);
	switch (smb_dcache.dc_state) {
	case SMB_DCACHE_STATE_NONE:
	case SMB_DCACHE_STATE_DESTROYING:
	default:
		(void) mutex_unlock(&smb_dcache.dc_mtx);
		return (SMB_DOMAIN_INTERNAL_ERR);

	case SMB_DCACHE_STATE_UPDATING:
		if (mode == SMB_DCACHE_RDLOCK) {
			/*
			 * Read operations should wait until the update
			 * is completed.
			 */
			if (!smb_dcache_wait()) {
				(void) mutex_unlock(&smb_dcache.dc_mtx);
				return (SMB_DOMAIN_INTERNAL_ERR);
			}
		}
		/* FALLTHROUGH */

	case SMB_DCACHE_STATE_READY:
		smb_dcache.dc_nops++;
		break;
	}
	(void) mutex_unlock(&smb_dcache.dc_mtx);

	/*
	 * Lock has to be taken outside the mutex otherwise
	 * there could be a deadlock
	 */
	if (mode == SMB_DCACHE_RDLOCK)
		(void) rw_rdlock(&smb_dcache.dc_cache_lck);
	else
		(void) rw_wrlock(&smb_dcache.dc_cache_lck);

	return (SMB_DOMAIN_SUCCESS);
}

/*
 * Decrement the number of inflight operations and then unlock.
 */
static void
smb_dcache_unlock(void)
{
	(void) mutex_lock(&smb_dcache.dc_mtx);
	assert(smb_dcache.dc_nops > 0);
	smb_dcache.dc_nops--;
	(void) cond_broadcast(&smb_dcache.dc_cv);
	(void) mutex_unlock(&smb_dcache.dc_mtx);

	(void) rw_unlock(&smb_dcache.dc_cache_lck);
}

static uint32_t
smb_dcache_add(smb_domain_t *di)
{
	smb_domain_t *dcnode;

	assert(di->di_type != 0);

	if ((dcnode = malloc(sizeof (smb_domain_t))) == NULL)
		return (SMB_DOMAIN_NO_MEMORY);

	*dcnode = *di;
	dcnode->di_binsid = smb_sid_fromstr(dcnode->di_sid);
	if (dcnode->di_binsid == NULL) {
		free(dcnode);
		return (SMB_DOMAIN_NO_MEMORY);
	}

	list_insert_tail(&smb_dcache.dc_cache, dcnode);
	return (SMB_DOMAIN_SUCCESS);
}

static void
smb_dcache_remove(smb_domain_t *di)
{
	list_remove(&smb_dcache.dc_cache, di);
	smb_sid_free(di->di_binsid);
	free(di);
}

static void
smb_dcache_setdc(const smb_dcinfo_t *dci)
{
	(void) mutex_lock(&smb_dcache.dc_mtx);
	smb_dcache.dc_dci = *dci; /* struct assignment! */
	smb_dcache.dc_dci_valid = B_TRUE;
	(void) cond_broadcast(&smb_dcache.dc_dci_cv);
	(void) mutex_unlock(&smb_dcache.dc_mtx);
}

/*
 * Get information about our domain controller.  If the wait arg
 * is true, wait for the DC locator to finish before copying.
 * Returns TRUE on success (have DC info).
 */
static boolean_t
smb_dcache_getdc(smb_dcinfo_t *dci, boolean_t wait)
{
	timestruc_t to;
	boolean_t rv;
	int err;

	to.tv_sec = time(NULL) + SMB_DCACHE_UPDATE_WAIT;
	to.tv_nsec = 0;

	(void) mutex_lock(&smb_dcache.dc_mtx);

	while (wait && !smb_dcache.dc_dci_valid) {
		err = cond_timedwait(&smb_dcache.dc_dci_cv,
		    &smb_dcache.dc_mtx, &to);
		if (err == ETIME)
			break;
	}
	*dci = smb_dcache.dc_dci; /* struct assignment! */
	rv = smb_dcache.dc_dci_valid;

	(void) mutex_unlock(&smb_dcache.dc_mtx);

	return (rv);
}

/*
 * Waits for SMB_DCACHE_UPDATE_WAIT seconds if cache is in
 * UPDATING state. Upon wake up returns true if cache is
 * ready to be used, otherwise it returns false.
 */
static boolean_t
smb_dcache_wait(void)
{
	timestruc_t to;
	int err;

	assert(MUTEX_HELD(&smb_dcache.dc_mtx));

	to.tv_sec = time(NULL) + SMB_DCACHE_UPDATE_WAIT;
	to.tv_nsec = 0;
	while (smb_dcache.dc_state == SMB_DCACHE_STATE_UPDATING) {
		err = cond_timedwait(&smb_dcache.dc_cv,
		    &smb_dcache.dc_mtx, &to);
		if (err == ETIME)
			break;
	}

	return (smb_dcache.dc_state == SMB_DCACHE_STATE_READY);
}

/*
 * Transfers the cache into UPDATING state, this will ensure
 * any read access to the cache will be stalled until the
 * update is finished. This is to avoid providing incomplete,
 * inconsistent or stale information.
 *
 * If another thread is already updating the cache, other
 * callers will wait until cache is no longer in UPDATING
 * state. The return code is decided based on the new
 * state of the cache.
 */
static uint32_t
smb_dcache_updating(void)
{
	uint32_t rc;

	(void) mutex_lock(&smb_dcache.dc_mtx);
	switch (smb_dcache.dc_state) {
	case SMB_DCACHE_STATE_READY:
		smb_dcache.dc_state = SMB_DCACHE_STATE_UPDATING;
		rc = SMB_DOMAIN_SUCCESS;
		break;

	case SMB_DCACHE_STATE_UPDATING:
		while (smb_dcache.dc_state == SMB_DCACHE_STATE_UPDATING)
			(void) cond_wait(&smb_dcache.dc_cv,
			    &smb_dcache.dc_mtx);

		if (smb_dcache.dc_state == SMB_DCACHE_STATE_READY) {
			smb_dcache.dc_state = SMB_DCACHE_STATE_UPDATING;
			rc = SMB_DOMAIN_SUCCESS;
		} else {
			rc = SMB_DOMAIN_NO_CACHE;
		}
		break;

	case SMB_DCACHE_STATE_NONE:
	case SMB_DCACHE_STATE_DESTROYING:
		rc = SMB_DOMAIN_NO_CACHE;
		break;

	default:
		rc = SMB_DOMAIN_SUCCESS;
		break;
	}

	(void) mutex_unlock(&smb_dcache.dc_mtx);
	return (rc);
}

/*
 * Transfers the cache from UPDATING to READY state.
 *
 * Nothing will happen if the cache is no longer available
 * or it is being destroyed.
 */
static void
smb_dcache_ready(void)
{
	(void) mutex_lock(&smb_dcache.dc_mtx);
	switch (smb_dcache.dc_state) {
	case SMB_DCACHE_STATE_UPDATING:
		smb_dcache.dc_state = SMB_DCACHE_STATE_READY;
		(void) cond_broadcast(&smb_dcache.dc_cv);
		break;

	case SMB_DCACHE_STATE_NONE:
	case SMB_DCACHE_STATE_DESTROYING:
		break;

	default:
		assert(0);
	}
	(void) mutex_unlock(&smb_dcache.dc_mtx);
}