lib/dns/zt.c

/*	$NetBSD: zt.c,v 1.5 2020/05/24 19:46:23 christos Exp $	*/

/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */

/*! \file */

#include <inttypes.h>
#include <stdbool.h>

#include <isc/atomic.h>
#include <isc/file.h>
#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/string.h>
#include <isc/task.h>
#include <isc/util.h>

#include <dns/log.h>
#include <dns/name.h>
#include <dns/rbt.h>
#include <dns/rdataclass.h>
#include <dns/result.h>
#include <dns/view.h>
#include <dns/zone.h>
#include <dns/zt.h>

struct zt_load_params {
	dns_zt_zoneloaded_t dl;
	bool newonly;
};

struct dns_zt {
	/* Unlocked. */
	unsigned int magic;
	isc_mem_t *mctx;
	dns_rdataclass_t rdclass;
	isc_rwlock_t rwlock;
	dns_zt_allloaded_t loaddone;
	void *loaddone_arg;
	struct zt_load_params *loadparams;

	/* Atomic */
	atomic_bool flush;
	isc_refcount_t references;
	isc_refcount_t loads_pending;

	/* Locked by lock. */
	dns_rbt_t *table;
};

#define ZTMAGIC	     ISC_MAGIC('Z', 'T', 'b', 'l')
#define VALID_ZT(zt) ISC_MAGIC_VALID(zt, ZTMAGIC)

static void
auto_detach(void *, void *);

static isc_result_t
load(dns_zone_t *zone, void *uap);

static isc_result_t
asyncload(dns_zone_t *zone, void *callback);

static isc_result_t
freezezones(dns_zone_t *zone, void *uap);

static isc_result_t
doneloading(dns_zt_t *zt, dns_zone_t *zone, isc_task_t *task);

isc_result_t
dns_zt_create(isc_mem_t *mctx, dns_rdataclass_t rdclass, dns_zt_t **ztp) {
	dns_zt_t *zt;
	isc_result_t result;

	REQUIRE(ztp != NULL && *ztp == NULL);

	zt = isc_mem_get(mctx, sizeof(*zt));

	zt->table = NULL;
	result = dns_rbt_create(mctx, auto_detach, zt, &zt->table);
	if (result != ISC_R_SUCCESS) {
		goto cleanup_zt;
	}

	result = isc_rwlock_init(&zt->rwlock, 0, 0);
	if (result != ISC_R_SUCCESS) {
		goto cleanup_rbt;
	}

	zt->mctx = NULL;
	isc_mem_attach(mctx, &zt->mctx);
	isc_refcount_init(&zt->references, 1);
	atomic_init(&zt->flush, false);
	zt->rdclass = rdclass;
	zt->magic = ZTMAGIC;
	zt->loaddone = NULL;
	zt->loaddone_arg = NULL;
	zt->loadparams = NULL;
	isc_refcount_init(&zt->loads_pending, 0);
	*ztp = zt;

	return (ISC_R_SUCCESS);

cleanup_rbt:
	dns_rbt_destroy(&zt->table);

cleanup_zt:
	isc_mem_put(mctx, zt, sizeof(*zt));

	return (result);
}

isc_result_t
dns_zt_mount(dns_zt_t *zt, dns_zone_t *zone) {
	isc_result_t result;
	dns_zone_t *dummy = NULL;
	dns_name_t *name;

	REQUIRE(VALID_ZT(zt));

	name = dns_zone_getorigin(zone);

	RWLOCK(&zt->rwlock, isc_rwlocktype_write);

	result = dns_rbt_addname(zt->table, name, zone);
	if (result == ISC_R_SUCCESS) {
		dns_zone_attach(zone, &dummy);
	}

	RWUNLOCK(&zt->rwlock, isc_rwlocktype_write);

	return (result);
}

isc_result_t
dns_zt_unmount(dns_zt_t *zt, dns_zone_t *zone) {
	isc_result_t result;
	dns_name_t *name;

	REQUIRE(VALID_ZT(zt));

	name = dns_zone_getorigin(zone);

	RWLOCK(&zt->rwlock, isc_rwlocktype_write);

	result = dns_rbt_deletename(zt->table, name, false);

	RWUNLOCK(&zt->rwlock, isc_rwlocktype_write);

	return (result);
}

isc_result_t
dns_zt_find(dns_zt_t *zt, const dns_name_t *name, unsigned int options,
	    dns_name_t *foundname, dns_zone_t **zonep) {
	isc_result_t result;
	dns_zone_t *dummy = NULL;
	unsigned int rbtoptions = 0;

	REQUIRE(VALID_ZT(zt));

	if ((options & DNS_ZTFIND_NOEXACT) != 0) {
		rbtoptions |= DNS_RBTFIND_NOEXACT;
	}

	RWLOCK(&zt->rwlock, isc_rwlocktype_read);

	result = dns_rbt_findname(zt->table, name, rbtoptions, foundname,
				  (void **)(void *)&dummy);
	if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
		/*
		 * If DNS_ZTFIND_MIRROR is set and the zone which was
		 * determined to be the deepest match for the supplied name is
		 * a mirror zone which is expired or not yet loaded, treat it
		 * as non-existent.  This will trigger a fallback to recursion
		 * instead of returning a SERVFAIL.
		 *
		 * Note that currently only the deepest match in the zone table
		 * is checked.  Consider a server configured with two mirror
		 * zones: "bar" and its child, "foo.bar".  If zone data is
		 * available for "bar" but not for "foo.bar", a query with
		 * QNAME equal to or below "foo.bar" will cause ISC_R_NOTFOUND
		 * to be returned, not DNS_R_PARTIALMATCH, despite zone data
		 * being available for "bar".  This is considered to be an edge
		 * case, handling which more appropriately is possible, but
		 * arguably not worth the added complexity.
		 */
		if ((options & DNS_ZTFIND_MIRROR) != 0 &&
		    dns_zone_gettype(dummy) == dns_zone_mirror &&
		    !dns_zone_isloaded(dummy))
		{
			result = ISC_R_NOTFOUND;
		} else {
			dns_zone_attach(dummy, zonep);
		}
	}

	RWUNLOCK(&zt->rwlock, isc_rwlocktype_read);

	return (result);
}

void
dns_zt_attach(dns_zt_t *zt, dns_zt_t **ztp) {
	REQUIRE(VALID_ZT(zt));
	REQUIRE(ztp != NULL && *ztp == NULL);

	isc_refcount_increment(&zt->references);

	*ztp = zt;
}

static isc_result_t
flush(dns_zone_t *zone, void *uap) {
	UNUSED(uap);
	return (dns_zone_flush(zone));
}

static void
zt_destroy(dns_zt_t *zt) {
	if (atomic_load_acquire(&zt->flush)) {
		(void)dns_zt_apply(zt, false, NULL, flush, NULL);
	}
	dns_rbt_destroy(&zt->table);
	isc_rwlock_destroy(&zt->rwlock);
	zt->magic = 0;
	isc_mem_putanddetach(&zt->mctx, zt, sizeof(*zt));
}

static void
zt_flushanddetach(dns_zt_t **ztp, bool need_flush) {
	dns_zt_t *zt;

	REQUIRE(ztp != NULL && VALID_ZT(*ztp));

	zt = *ztp;
	*ztp = NULL;

	if (need_flush) {
		atomic_store_release(&zt->flush, true);
	}

	if (isc_refcount_decrement(&zt->references) == 1) {
		zt_destroy(zt);
	}
}

void
dns_zt_flushanddetach(dns_zt_t **ztp) {
	zt_flushanddetach(ztp, true);
}

void
dns_zt_detach(dns_zt_t **ztp) {
	zt_flushanddetach(ztp, false);
}

isc_result_t
dns_zt_load(dns_zt_t *zt, bool stop, bool newonly) {
	isc_result_t result;
	struct zt_load_params params;
	REQUIRE(VALID_ZT(zt));
	params.newonly = newonly;
	RWLOCK(&zt->rwlock, isc_rwlocktype_read);
	result = dns_zt_apply(zt, stop, NULL, load, &params);
	RWUNLOCK(&zt->rwlock, isc_rwlocktype_read);
	return (result);
}

static isc_result_t
load(dns_zone_t *zone, void *paramsv) {
	isc_result_t result;
	struct zt_load_params *params = (struct zt_load_params *)paramsv;
	result = dns_zone_load(zone, params->newonly);
	if (result == DNS_R_CONTINUE || result == DNS_R_UPTODATE ||
	    result == DNS_R_DYNAMIC)
	{
		result = ISC_R_SUCCESS;
	}
	return (result);
}

static void
call_loaddone(dns_zt_t *zt) {
	dns_zt_allloaded_t loaddone = zt->loaddone;
	void *loaddone_arg = zt->loaddone_arg;

	/*
	 * Set zt->loaddone, zt->loaddone_arg and zt->loadparams to NULL
	 * before calling loaddone.
	 */
	zt->loaddone = NULL;
	zt->loaddone_arg = NULL;

	isc_mem_put(zt->mctx, zt->loadparams, sizeof(struct zt_load_params));
	zt->loadparams = NULL;

	/*
	 * Call the callback last.
	 */
	if (loaddone != NULL) {
		loaddone(loaddone_arg);
	}
}

isc_result_t
dns_zt_asyncload(dns_zt_t *zt, bool newonly, dns_zt_allloaded_t alldone,
		 void *arg) {
	isc_result_t result;
	uint_fast32_t loads_pending;

	REQUIRE(VALID_ZT(zt));

	/*
	 * Obtain a reference to zt->loads_pending so that asyncload can
	 * safely decrement both zt->references and zt->loads_pending
	 * without going to zero.
	 */
	loads_pending = isc_refcount_increment0(&zt->loads_pending);
	INSIST(loads_pending == 0);

	/*
	 * Only one dns_zt_asyncload call at a time should be active so
	 * these pointers should be NULL.  They are set back to NULL
	 * before the zt->loaddone (alldone) is called in call_loaddone.
	 */
	INSIST(zt->loadparams == NULL);
	INSIST(zt->loaddone == NULL);
	INSIST(zt->loaddone_arg == NULL);

	zt->loadparams = isc_mem_get(zt->mctx, sizeof(struct zt_load_params));
	zt->loadparams->dl = doneloading;
	zt->loadparams->newonly = newonly;
	zt->loaddone = alldone;
	zt->loaddone_arg = arg;

	RWLOCK(&zt->rwlock, isc_rwlocktype_read);
	result = dns_zt_apply(zt, false, NULL, asyncload, zt);
	RWUNLOCK(&zt->rwlock, isc_rwlocktype_read);

	/*
	 * Have all the loads completed?
	 */
	if (isc_refcount_decrement(&zt->loads_pending) == 1) {
		call_loaddone(zt);
	}

	return (result);
}

/*
 * Initiates asynchronous loading of zone 'zone'.  'callback' is a
 * pointer to a function which will be used to inform the caller when
 * the zone loading is complete.
 */
static isc_result_t
asyncload(dns_zone_t *zone, void *zt_) {
	isc_result_t result;
	struct dns_zt *zt = (dns_zt_t *)zt_;
	REQUIRE(zone != NULL);

	isc_refcount_increment(&zt->references);
	isc_refcount_increment(&zt->loads_pending);

	result = dns_zone_asyncload(zone, zt->loadparams->newonly,
				    *zt->loadparams->dl, zt);
	if (result != ISC_R_SUCCESS) {
		/*
		 * Caller is holding a reference to zt->loads_pending
		 * and zt->references so these can't decrement to zero.
		 */
		INSIST(isc_refcount_decrement(&zt->loads_pending) > 1);
		INSIST(isc_refcount_decrement(&zt->references) > 1);
	}
	return (ISC_R_SUCCESS);
}

isc_result_t
dns_zt_freezezones(dns_zt_t *zt, bool freeze) {
	isc_result_t result, tresult;

	REQUIRE(VALID_ZT(zt));

	RWLOCK(&zt->rwlock, isc_rwlocktype_read);
	result = dns_zt_apply(zt, false, &tresult, freezezones, &freeze);
	RWUNLOCK(&zt->rwlock, isc_rwlocktype_read);
	if (tresult == ISC_R_NOTFOUND) {
		tresult = ISC_R_SUCCESS;
	}
	return ((result == ISC_R_SUCCESS) ? tresult : result);
}

static isc_result_t
freezezones(dns_zone_t *zone, void *uap) {
	bool freeze = *(bool *)uap;
	bool frozen;
	isc_result_t result = ISC_R_SUCCESS;
	char classstr[DNS_RDATACLASS_FORMATSIZE];
	char zonename[DNS_NAME_FORMATSIZE];
	dns_zone_t *raw = NULL;
	dns_view_t *view;
	const char *vname;
	const char *sep;
	int level;

	dns_zone_getraw(zone, &raw);
	if (raw != NULL) {
		zone = raw;
	}
	if (dns_zone_gettype(zone) != dns_zone_master) {
		if (raw != NULL) {
			dns_zone_detach(&raw);
		}
		return (ISC_R_SUCCESS);
	}
	if (!dns_zone_isdynamic(zone, true)) {
		if (raw != NULL) {
			dns_zone_detach(&raw);
		}
		return (ISC_R_SUCCESS);
	}

	frozen = dns_zone_getupdatedisabled(zone);
	if (freeze) {
		if (frozen) {
			result = DNS_R_FROZEN;
		}
		if (result == ISC_R_SUCCESS) {
			result = dns_zone_flush(zone);
		}
		if (result == ISC_R_SUCCESS) {
			dns_zone_setupdatedisabled(zone, freeze);
		}
	} else {
		if (frozen) {
			result = dns_zone_loadandthaw(zone);
			if (result == DNS_R_CONTINUE ||
			    result == DNS_R_UPTODATE) {
				result = ISC_R_SUCCESS;
			}
		}
	}
	view = dns_zone_getview(zone);
	if (strcmp(view->name, "_bind") == 0 || strcmp(view->name, "_defaul"
								   "t") == 0)
	{
		vname = "";
		sep = "";
	} else {
		vname = view->name;
		sep = " ";
	}
	dns_rdataclass_format(dns_zone_getclass(zone), classstr,
			      sizeof(classstr));
	dns_name_format(dns_zone_getorigin(zone), zonename, sizeof(zonename));
	level = (result != ISC_R_SUCCESS) ? ISC_LOG_ERROR : ISC_LOG_DEBUG(1);
	isc_log_write(dns_lctx, DNS_LOGCATEGORY_GENERAL, DNS_LOGMODULE_ZONE,
		      level, "%s zone '%s/%s'%s%s: %s",
		      freeze ? "freezing" : "thawing", zonename, classstr, sep,
		      vname, isc_result_totext(result));
	if (raw != NULL) {
		dns_zone_detach(&raw);
	}
	return (result);
}

void
dns_zt_setviewcommit(dns_zt_t *zt) {
	dns_rbtnode_t *node;
	dns_rbtnodechain_t chain;
	isc_result_t result;

	REQUIRE(VALID_ZT(zt));

	dns_rbtnodechain_init(&chain);

	result = dns_rbtnodechain_first(&chain, zt->table, NULL, NULL);
	while (result == DNS_R_NEWORIGIN || result == ISC_R_SUCCESS) {
		result = dns_rbtnodechain_current(&chain, NULL, NULL, &node);
		if (result == ISC_R_SUCCESS && node->data != NULL) {
			dns_zone_setviewcommit(node->data);
		}

		result = dns_rbtnodechain_next(&chain, NULL, NULL);
	}

	dns_rbtnodechain_invalidate(&chain);
}

void
dns_zt_setviewrevert(dns_zt_t *zt) {
	dns_rbtnode_t *node;
	dns_rbtnodechain_t chain;
	isc_result_t result;

	REQUIRE(VALID_ZT(zt));

	dns_rbtnodechain_init(&chain);

	result = dns_rbtnodechain_first(&chain, zt->table, NULL, NULL);
	while (result == DNS_R_NEWORIGIN || result == ISC_R_SUCCESS) {
		result = dns_rbtnodechain_current(&chain, NULL, NULL, &node);
		if (result == ISC_R_SUCCESS && node->data != NULL) {
			dns_zone_setviewrevert(node->data);
		}

		result = dns_rbtnodechain_next(&chain, NULL, NULL);
	}

	dns_rbtnodechain_invalidate(&chain);
}

isc_result_t
dns_zt_apply(dns_zt_t *zt, bool stop, isc_result_t *sub,
	     isc_result_t (*action)(dns_zone_t *, void *), void *uap) {
	dns_rbtnode_t *node;
	dns_rbtnodechain_t chain;
	isc_result_t result, tresult = ISC_R_SUCCESS;
	dns_zone_t *zone;

	REQUIRE(VALID_ZT(zt));
	REQUIRE(action != NULL);

	dns_rbtnodechain_init(&chain);
	result = dns_rbtnodechain_first(&chain, zt->table, NULL, NULL);
	if (result == ISC_R_NOTFOUND) {
		/*
		 * The tree is empty.
		 */
		tresult = result;
		result = ISC_R_NOMORE;
	}
	while (result == DNS_R_NEWORIGIN || result == ISC_R_SUCCESS) {
		result = dns_rbtnodechain_current(&chain, NULL, NULL, &node);
		if (result == ISC_R_SUCCESS) {
			zone = node->data;
			if (zone != NULL) {
				result = (action)(zone, uap);
			}
			if (result != ISC_R_SUCCESS && stop) {
				tresult = result;
				goto cleanup; /* don't break */
			} else if (result != ISC_R_SUCCESS &&
				   tresult == ISC_R_SUCCESS) {
				tresult = result;
			}
		}
		result = dns_rbtnodechain_next(&chain, NULL, NULL);
	}
	if (result == ISC_R_NOMORE) {
		result = ISC_R_SUCCESS;
	}

cleanup:
	dns_rbtnodechain_invalidate(&chain);
	if (sub != NULL) {
		*sub = tresult;
	}

	return (result);
}

/*
 * Decrement the loads_pending counter; when counter reaches
 * zero, call the loaddone callback that was initially set by
 * dns_zt_asyncload().
 */
static isc_result_t
doneloading(dns_zt_t *zt, dns_zone_t *zone, isc_task_t *task) {
	UNUSED(zone);
	UNUSED(task);

	REQUIRE(VALID_ZT(zt));

	if (isc_refcount_decrement(&zt->loads_pending) == 1) {
		call_loaddone(zt);
	}

	if (isc_refcount_decrement(&zt->references) == 1) {
		zt_destroy(zt);
	}

	return (ISC_R_SUCCESS);
}

/***
 *** Private
 ***/

static void
auto_detach(void *data, void *arg) {
	dns_zone_t *zone = data;

	UNUSED(arg);
	dns_zone_detach(&zone);
}