ngx_http_cookie_limit_req_module.c

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 * Copyright (C)  西门吹雪 
 * zhibu1991@gmail.com
 */

#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>
#include <ngx_md5.h>
#include <hiredis/hiredis.h>

static u_char *redis_ip = NULL, *block_second, *cookie_max = NULL;

static redisContext *c;
static redisReply *reply, *reply_cookie_max;

typedef struct {
	u_char color;
	u_char dummy;
	u_short len;
	ngx_queue_t queue;
	ngx_msec_t last;
	/* integer value, 1 corresponds to 0.001 r/s */
	ngx_uint_t excess;
	ngx_uint_t count;
	u_char data[1];
} ngx_http_limit_req_node_t;

typedef struct {
	ngx_rbtree_t rbtree;
	ngx_rbtree_node_t sentinel;
	ngx_queue_t queue;
} ngx_http_limit_req_shctx_t;

typedef struct {
	ngx_http_limit_req_shctx_t *sh;
	ngx_slab_pool_t *shpool;
	/* integer value, 1 corresponds to 0.001 r/s */
	ngx_uint_t rate;
	ngx_http_complex_value_t key;
	ngx_http_limit_req_node_t *node;
} ngx_http_limit_req_ctx_t;

typedef struct {
	ngx_shm_zone_t *shm_zone;
	/* integer value, 1 corresponds to 0.001 r/s */
	ngx_uint_t burst;
	ngx_uint_t nodelay; /* unsigned  nodelay:1 */
} ngx_http_limit_req_limit_t;

typedef struct {
	ngx_array_t limits;
	ngx_uint_t limit_log_level;
	ngx_uint_t delay_log_level;
	ngx_uint_t status_code;
} ngx_http_limit_req_conf_t;

static void ngx_http_limit_req_delay(ngx_http_request_t *r);
static ngx_int_t ngx_http_limit_req_lookup(ngx_http_limit_req_limit_t *limit,
		ngx_uint_t hash, ngx_str_t *key, ngx_uint_t *ep, ngx_uint_t account);
static ngx_msec_t ngx_http_limit_req_account(ngx_http_limit_req_limit_t *limits,
		ngx_uint_t n, ngx_uint_t *ep, ngx_http_limit_req_limit_t **limit);
static void ngx_http_limit_req_expire(ngx_http_limit_req_ctx_t *ctx,
		ngx_uint_t n);
static void *ngx_http_limit_req_create_conf(ngx_conf_t *cf);
static char *ngx_http_limit_req_merge_conf(ngx_conf_t *cf, void *parent,
		void *child);
static char *ngx_http_limit_req_zone(ngx_conf_t *cf, ngx_command_t *cmd,
		void *conf);
static char *ngx_http_limit_req(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static ngx_int_t ngx_http_limit_req_init(ngx_conf_t *cf);

static ngx_conf_enum_t ngx_http_limit_req_log_levels[] = { { ngx_string("info"),
NGX_LOG_INFO }, { ngx_string("notice"), NGX_LOG_NOTICE }, { ngx_string(
		"warn"), NGX_LOG_WARN }, { ngx_string("error"), NGX_LOG_ERR }, {
ngx_null_string, 0 } };

static ngx_conf_num_bounds_t ngx_http_limit_req_status_bounds = {
		ngx_conf_check_num_bounds, 400, 599 };

static ngx_command_t ngx_http_limit_req_commands[] = {

{ ngx_string("cookie_limit_req_zone"), NGX_HTTP_MAIN_CONF | NGX_CONF_TAKE6,
		ngx_http_limit_req_zone, 0, 0, NULL },

{ ngx_string("cookie_limit_req"), NGX_HTTP_MAIN_CONF | NGX_HTTP_SRV_CONF
		| NGX_HTTP_LOC_CONF | NGX_HTTP_LIF_CONF | NGX_CONF_TAKE123,
		ngx_http_limit_req, NGX_HTTP_LOC_CONF_OFFSET, 0, NULL },

{ ngx_string("cookie_limit_req_log_level"), NGX_HTTP_MAIN_CONF
		| NGX_HTTP_SRV_CONF | NGX_HTTP_LOC_CONF | NGX_CONF_TAKE1,
		ngx_conf_set_enum_slot, NGX_HTTP_LOC_CONF_OFFSET, offsetof(
				ngx_http_limit_req_conf_t, limit_log_level),
		&ngx_http_limit_req_log_levels },

{ ngx_string("cookie_limit_req_status"), NGX_HTTP_MAIN_CONF | NGX_HTTP_SRV_CONF
		| NGX_HTTP_LOC_CONF | NGX_HTTP_LIF_CONF | NGX_CONF_TAKE1,
		ngx_conf_set_num_slot, NGX_HTTP_LOC_CONF_OFFSET, offsetof(
				ngx_http_limit_req_conf_t, status_code),
		&ngx_http_limit_req_status_bounds },

ngx_null_command };

static ngx_http_module_t ngx_http_cookie_limit_req_module_ctx = { NULL, /* preconfiguration */
ngx_http_limit_req_init, /* postconfiguration */

NULL, /* create main configuration */
NULL, /* init main configuration */

NULL, /* create server configuration */
NULL, /* merge server configuration */

ngx_http_limit_req_create_conf, /* create location configuration */
ngx_http_limit_req_merge_conf /* merge location configuration */
};

ngx_module_t ngx_http_cookie_limit_req_module = { NGX_MODULE_V1,
		&ngx_http_cookie_limit_req_module_ctx, /* module context */
		ngx_http_limit_req_commands, /* module directives */
		NGX_HTTP_MODULE, /* module type */
		NULL, /* init master */
		NULL, /* init module */
		NULL, /* init process */
		NULL, /* init thread */
		NULL, /* exit thread */
		NULL, /* exit process */
		NULL, /* exit master */
		NGX_MODULE_V1_PADDING };

static ngx_int_t ngx_http_limit_req_handler(ngx_http_request_t *r) {
	uint32_t hash;
	ngx_str_t key;
	ngx_int_t rc;
	ngx_uint_t n, excess;
	ngx_msec_t delay;
	ngx_http_limit_req_ctx_t *ctx;
	ngx_http_limit_req_conf_t *lrcf;
	ngx_http_limit_req_limit_t *limit, *limits;

#if nginx_version >= 1017006
	if (r->main->limit_req_status) {
		return NGX_DECLINED;
	}
#else
	if (r->main->limit_req_set) {
		return NGX_DECLINED;
	}
#endif

	lrcf = ngx_http_get_module_loc_conf(r, ngx_http_cookie_limit_req_module);
	limits = lrcf->limits.elts;

	excess = 0;

	rc = NGX_DECLINED;

#if (NGX_SUPPRESS_WARN)
	limit = NULL;
#endif

	char Host[256];
	struct timeval timeout = { 1, 500000 }; // 1.5 seconds

	if (c == NULL) {
		c = redisConnectWithTimeout((char*) redis_ip, 6379, timeout);
		if (c == NULL || c->err) {
				if (c) {
					if (redis_ip) {
						ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
								"redis connection error: %s %s\n", c->errstr,
								redis_ip ? redis_ip : (u_char * )"[ No configuration of redis]");
					}
					/* Redis if the connection is wrong,
					 *  it does not intercept,
					 *   and returns normally */
					return NGX_DECLINED;
				} else {
					ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
							"redis connection error: can't allocate redis context\n");
				}
			}
	}
   #if (NGX_DEBUG)
	ngx_list_part_t *part;
	ngx_table_elt_t *h;
	ngx_uint_t b;

	part = &r->headers_in.headers.part;
	h = part->elts;

	for (b = 0; /**/; b++) {
		if (b >= part->nelts) {
			if (part->next == NULL) {
				break;
			}

			part = part->next;
			h = part->elts;
			b = 0;
		}
		ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
				"http header_all: \"%s: %V\"", h[b].key.data, &h[b].value);
	}
    #endif

	ngx_md5_t md5;
	ngx_table_elt_t *cookies;
#if nginx_version >= 1023000
	cookies = r->headers_in.cookie;
#else
	cookies = r->headers_in.cookies.elts;
#endif
	char msg[1024];
	const char *fmt_cookies = "%.*s";
	u_char md5_buf[16], md5_buf2[32];
	const char *fmt_base = "%.*s";
	 (void)	snprintf(Host, sizeof(Host), fmt_base,
					r->connection->addr_text.len, r->connection->addr_text.data);

	if (cookies != NULL && !c->err && c != NULL) {
		(void) snprintf((char *) msg, sizeof(msg), fmt_cookies,
				cookies->value.len, cookies->value.data);

		ngx_md5_init(&md5);
		ngx_md5_update(&md5, msg, cookies->value.len);
		ngx_md5_final(md5_buf, &md5);
		int i;
		for (i = 0; i < 16; i++) {
			sprintf((char *) md5_buf2 + i * 2, "%02X", md5_buf[i]);
		}


		redisCommand(c, "pfadd [%s]Independent_IP %s", Host, (char *)md5_buf2);
		reply_cookie_max = redisCommand(c, "PFCOUNT [%s]Independent_IP", Host);
		if (reply_cookie_max->integer > atoi((char *)cookie_max)) {
			redisCommand(c, "SETEX %s %s %s", Host, block_second, Host);
			redisCommand(c, "DEL [%s]Independent_IP", Host);
		}
		ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
						"cookie: \"%V\" [%s]\n", &cookies->value, (char *)md5_buf2);

	}

	for (n = 0; n < lrcf->limits.nelts; n++) {

		limit = &limits[n];

		ctx = limit->shm_zone->data;

		if (ngx_http_complex_value(r, &ctx->key, &key) != NGX_OK) {
			return NGX_HTTP_INTERNAL_SERVER_ERROR;
		}

		if (key.len == 0) {
			continue;
		}

		if (key.len > 65535) {
			ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
					"the value of the \"%V\" key "
							"is more than 65535 bytes: \"%V\"", &ctx->key.value,
					&key);
			continue;
		}

		hash = ngx_crc32_short(key.data, key.len);

		ngx_shmtx_lock(&ctx->shpool->mutex);

		rc = ngx_http_limit_req_lookup(limit, hash, &key, &excess,
				(n == lrcf->limits.nelts - 1));

		ngx_shmtx_unlock(&ctx->shpool->mutex);


		ngx_log_debug5(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
				"limit_req[%ui]: %i %ui.%03ui %s", n, rc, excess / 1000,
				excess % 1000, r->headers_in.server.data);

		if (rc && strncmp((char *) Host, "127.0.0.1", 9) != 0 && cookies != NULL) {
			if (!c->err) {
				reply = redisCommand(c, "GET white%s", (char *)md5_buf2);
				if (reply->str == NULL) {
					reply = redisCommand(c, "SETEX %s %s %s", (char *)md5_buf2,
							block_second, (char *)md5_buf2);

					/* Increase the history record  */
					reply = redisCommand(c, "SELECT 1");
					reply = redisCommand(c, "SET %s %s", (char *)md5_buf2, (char *)md5_buf2);
					reply = redisCommand(c, "SELECT 0");
					/* Increase the history record */
				}
			}
		}
		if (rc != NGX_AGAIN) {
			break;
		}
	}

	if (rc == NGX_DECLINED) {
		return NGX_DECLINED;
	}

#if nginx_version > 1017005
	r->main->limit_req_status = 1;
#else

	r->main->limit_req_set = 1;
#endif

	if (!c->err) {
		/* return http_status redis*/
		reply = redisCommand(c, "GET %s", (char *) md5_buf2);
		reply_cookie_max = redisCommand(c, "GET %s", Host);
		ngx_log_debug4(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
				"cookie_host [%s] [%s] [%s] [%s]", Host,
				       reply_cookie_max->str ? reply_cookie_max->str : "cookie_max empty",
				(char *)md5_buf2, reply->str ? reply->str : "query md5 empty");
		if (reply->str == NULL && reply_cookie_max->str == NULL) {
			freeReplyObject(reply);
			freeReplyObject(reply_cookie_max);
			return NGX_DECLINED;
		}
		if (reply->str != NULL && reply_cookie_max->str != NULL) {
			if (!ngx_strcmp((char * )Host,
					reply_cookie_max->str) && !ngx_strcmp((char * )Host, reply_cookie_max->str)) {
				ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
						"The number of cookies generated by the host has reached the limit: by zone \"%V\" Host=%s cookie_max=%d",
						&limit->shm_zone->shm.name, Host, atoi((char *)cookie_max));

				while (n--) {
					ctx = limits[n].shm_zone->data;

					if (ctx->node == NULL) {
						continue;
					}

					ngx_shmtx_lock(&ctx->shpool->mutex);

					ctx->node->count--;

					ngx_shmtx_unlock(&ctx->shpool->mutex);

					ctx->node = NULL;
				}
				freeReplyObject(reply);
				freeReplyObject(reply_cookie_max);
				return lrcf->status_code;
			}
		}
		if (reply->str == NULL) {
			if (!ngx_strcmp((char * )Host, reply_cookie_max->str)) {
				ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
									"The number of cookies generated by the host has reached the limit: by zone \"%V\" Host=%s cookie_max=%d",
									&limit->shm_zone->shm.name, Host, atoi((char *)cookie_max));

				while (n--) {
					ctx = limits[n].shm_zone->data;

					if (ctx->node == NULL) {
						continue;
					}

					ngx_shmtx_lock(&ctx->shpool->mutex);

					ctx->node->count--;

					ngx_shmtx_unlock(&ctx->shpool->mutex);

					ctx->node = NULL;
				}
				freeReplyObject(reply_cookie_max);
				return lrcf->status_code;
			}
			freeReplyObject(reply);
			return NGX_DECLINED;
		} else {
			if (!ngx_strcmp((char * )md5_buf2, reply->str)) {
				ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
						"limiting cookie requests, excess: %ui.%03ui by zone \"%V\" lock=%s",
						excess / 1000, excess % 1000,
						&limit->shm_zone->shm.name, (char * )md5_buf2);

				while (n--) {
					ctx = limits[n].shm_zone->data;

					if (ctx->node == NULL) {
						continue;
					}

					ngx_shmtx_lock(&ctx->shpool->mutex);

					ctx->node->count--;

					ngx_shmtx_unlock(&ctx->shpool->mutex);

					ctx->node = NULL;
				}
				freeReplyObject(reply);
				return lrcf->status_code;
			}
		}
		if (reply_cookie_max->str == NULL) {
			if (!ngx_strcmp((char * )md5_buf2, reply->str)) {
				ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
						"limiting cookie requests, excess: %ui.%03ui by zone \"%V\" lock=%s",
						excess / 1000, excess % 1000,
						&limit->shm_zone->shm.name, (char * )md5_buf2);

				while (n--) {
					ctx = limits[n].shm_zone->data;

					if (ctx->node == NULL) {
						continue;
					}

					ngx_shmtx_lock(&ctx->shpool->mutex);

					ctx->node->count--;

					ngx_shmtx_unlock(&ctx->shpool->mutex);

					ctx->node = NULL;
				}
				freeReplyObject(reply);
				return lrcf->status_code;
			}
			freeReplyObject(reply_cookie_max);
			return NGX_DECLINED;
		}
	}

	/* rc == NGX_AGAIN || rc == NGX_OK */

	if (rc == NGX_AGAIN) {
		excess = 0;
	}

	delay = ngx_http_limit_req_account(limits, n, &excess, &limit);

	if (!delay) {
		return NGX_DECLINED;
	}

	ngx_log_error(lrcf->delay_log_level, r->connection->log, 0,
			"delaying request, excess: %ui.%03ui, by zone \"%V\"",
			excess / 1000, excess % 1000, &limit->shm_zone->shm.name);

	if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
		return NGX_HTTP_INTERNAL_SERVER_ERROR;
	}

	r->read_event_handler = ngx_http_test_reading;
	r->write_event_handler = ngx_http_limit_req_delay;
	ngx_add_timer(r->connection->write, delay);

	if (!c->err) {
		redisFree(c);
	}
	return NGX_AGAIN;
}

static void ngx_http_limit_req_delay(ngx_http_request_t *r) {
	ngx_event_t *wev;

	ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
			"limit_req delay");

	wev = r->connection->write;

	if (wev->delayed) {

		if (ngx_handle_write_event(wev, 0) != NGX_OK) {
			ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
		}

		return;
	}

	if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
		ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
		return;
	}

	r->read_event_handler = ngx_http_block_reading;
	r->write_event_handler = ngx_http_core_run_phases;

	ngx_http_core_run_phases(r);

}

static void ngx_http_limit_req_rbtree_insert_value(ngx_rbtree_node_t *temp,
		ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel) {
	ngx_rbtree_node_t **p;
	ngx_http_limit_req_node_t *lrn, *lrnt;

	for (;;) {

		if (node->key < temp->key) {

			p = &temp->left;

		} else if (node->key > temp->key) {

			p = &temp->right;

		} else { /* node->key == temp->key */

			lrn = (ngx_http_limit_req_node_t *) &node->color;
			lrnt = (ngx_http_limit_req_node_t *) &temp->color;

			p = (ngx_memn2cmp(lrn->data, lrnt->data, lrn->len, lrnt->len) < 0) ?
					&temp->left : &temp->right;
		}

		if (*p == sentinel) {
			break;
		}

		temp = *p;
	}

	*p = node;
	node->parent = temp;
	node->left = sentinel;
	node->right = sentinel;
	ngx_rbt_red(node);
}

static ngx_int_t ngx_http_limit_req_lookup(ngx_http_limit_req_limit_t *limit,
		ngx_uint_t hash, ngx_str_t *key, ngx_uint_t *ep, ngx_uint_t account) {
	size_t size;
	ngx_int_t rc, excess;
	ngx_msec_t now;
	ngx_msec_int_t ms;
	ngx_rbtree_node_t *node, *sentinel;
	ngx_http_limit_req_ctx_t *ctx;
	ngx_http_limit_req_node_t *lr;

	now = ngx_current_msec;

	ctx = limit->shm_zone->data;

	node = ctx->sh->rbtree.root;
	sentinel = ctx->sh->rbtree.sentinel;

	while (node != sentinel) {

		if (hash < node->key) {
			node = node->left;
			continue;
		}

		if (hash > node->key) {
			node = node->right;
			continue;
		}

		/* hash == node->key */

		lr = (ngx_http_limit_req_node_t *) &node->color;

		rc = ngx_memn2cmp(key->data, lr->data, key->len, (size_t) lr->len);

		if (rc == 0) {
			ngx_queue_remove(&lr->queue);
			ngx_queue_insert_head(&ctx->sh->queue, &lr->queue);

			ms = (ngx_msec_int_t) (now - lr->last);

			excess = lr->excess - ctx->rate * ngx_abs(ms) / 1000 + 1000;

			if (excess < 0) {
				excess = 0;
			}

			*ep = excess;

			if ((ngx_uint_t) excess > limit->burst) {
				return NGX_BUSY;
			}

			if (account) {
				lr->excess = excess;
				lr->last = now;
				return NGX_OK;
			}

			lr->count++;

			ctx->node = lr;

			return NGX_AGAIN;
		}

		node = (rc < 0) ? node->left : node->right;
	}

	*ep = 0;

	size = offsetof(ngx_rbtree_node_t, color)
			+ offsetof(ngx_http_limit_req_node_t, data) + key->len;

	ngx_http_limit_req_expire(ctx, 1);

	node = ngx_slab_alloc_locked(ctx->shpool, size);

	if (node == NULL) {
		ngx_http_limit_req_expire(ctx, 0);

		node = ngx_slab_alloc_locked(ctx->shpool, size);
		if (node == NULL) {
			ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
					"could not allocate node%s", ctx->shpool->log_ctx);
			return NGX_ERROR;
		}
	}

	node->key = hash;

	lr = (ngx_http_limit_req_node_t *) &node->color;

	lr->len = (u_short) key->len;
	lr->excess = 0;

	ngx_memcpy(lr->data, key->data, key->len);

	ngx_rbtree_insert(&ctx->sh->rbtree, node);

	ngx_queue_insert_head(&ctx->sh->queue, &lr->queue);

	if (account) {
		lr->last = now;
		lr->count = 0;
		return NGX_OK;
	}

	lr->last = 0;
	lr->count = 1;

	ctx->node = lr;

	return NGX_AGAIN;
}

static ngx_msec_t ngx_http_limit_req_account(ngx_http_limit_req_limit_t *limits,
		ngx_uint_t n, ngx_uint_t *ep, ngx_http_limit_req_limit_t **limit) {
	ngx_int_t excess;
	ngx_msec_t now, delay, max_delay;
	ngx_msec_int_t ms;
	ngx_http_limit_req_ctx_t *ctx;
	ngx_http_limit_req_node_t *lr;

	excess = *ep;

	if (excess == 0 || (*limit)->nodelay) {
		max_delay = 0;

	} else {
		ctx = (*limit)->shm_zone->data;
		max_delay = excess * 1000 / ctx->rate;
	}

	while (n--) {
		ctx = limits[n].shm_zone->data;
		lr = ctx->node;

		if (lr == NULL) {
			continue;
		}

		ngx_shmtx_lock(&ctx->shpool->mutex);

		now = ngx_current_msec;
		ms = (ngx_msec_int_t) (now - lr->last);

		excess = lr->excess - ctx->rate * ngx_abs(ms) / 1000 + 1000;

		if (excess < 0) {
			excess = 0;
		}

		lr->last = now;
		lr->excess = excess;
		lr->count--;

		ngx_shmtx_unlock(&ctx->shpool->mutex);

		ctx->node = NULL;

		if (limits[n].nodelay) {
			continue;
		}

		delay = excess * 1000 / ctx->rate;

		if (delay > max_delay) {
			max_delay = delay;
			*ep = excess;
			*limit = &limits[n];
		}
	}

	return max_delay;
}

static void ngx_http_limit_req_expire(ngx_http_limit_req_ctx_t *ctx,
		ngx_uint_t n) {
	ngx_int_t excess;
	ngx_msec_t now;
	ngx_queue_t *q;
	ngx_msec_int_t ms;
	ngx_rbtree_node_t *node;
	ngx_http_limit_req_node_t *lr;

	now = ngx_current_msec;

	/*
	 * n == 1 deletes one or two zero rate entries
	 * n == 0 deletes oldest entry by force
	 *        and one or two zero rate entries
	 */

	while (n < 3) {

		if (ngx_queue_empty(&ctx->sh->queue)) {
			return;
		}

		q = ngx_queue_last(&ctx->sh->queue);

		lr = ngx_queue_data(q, ngx_http_limit_req_node_t, queue);

		if (lr->count) {

			/*
			 * There is not much sense in looking further,
			 * because we bump nodes on the lookup stage.
			 */

			return;
		}

		if (n++ != 0) {

			ms = (ngx_msec_int_t) (now - lr->last);
			ms = ngx_abs(ms);

			if (ms < 60000) {
				return;
			}

			excess = lr->excess - ctx->rate * ms / 1000;

			if (excess > 0) {
				return;
			}
		}

		ngx_queue_remove(q);

		node = (ngx_rbtree_node_t *) ((u_char *) lr
				- offsetof(ngx_rbtree_node_t, color));

		ngx_rbtree_delete(&ctx->sh->rbtree, node);

		ngx_slab_free_locked(ctx->shpool, node);
	}
}

static ngx_int_t ngx_http_limit_req_init_zone(ngx_shm_zone_t *shm_zone,
		void *data) {
	ngx_http_limit_req_ctx_t *octx = data;

	size_t len;
	ngx_http_limit_req_ctx_t *ctx;

	ctx = shm_zone->data;

	if (octx) {
		if (ctx->key.value.len != octx->key.value.len
				|| ngx_strncmp(ctx->key.value.data, octx->key.value.data,
						ctx->key.value.len) != 0) {
			ngx_log_error(NGX_LOG_EMERG, shm_zone->shm.log, 0,
					"limit_req \"%V\" uses the \"%V\" key "
							"while previously it used the \"%V\" key",
					&shm_zone->shm.name, &ctx->key.value, &octx->key.value);
			return NGX_ERROR;
		}

		ctx->sh = octx->sh;
		ctx->shpool = octx->shpool;

		return NGX_OK;
	}

	ctx->shpool = (ngx_slab_pool_t *) shm_zone->shm.addr;

	if (shm_zone->shm.exists) {
		ctx->sh = ctx->shpool->data;

		return NGX_OK;
	}

	ctx->sh = ngx_slab_alloc(ctx->shpool, sizeof(ngx_http_limit_req_shctx_t));
	if (ctx->sh == NULL) {
		return NGX_ERROR;
	}

	ctx->shpool->data = ctx->sh;

	ngx_rbtree_init(&ctx->sh->rbtree, &ctx->sh->sentinel,
			ngx_http_limit_req_rbtree_insert_value);

	ngx_queue_init(&ctx->sh->queue);

	len = sizeof(" in limit_req zone \"\"") + shm_zone->shm.name.len;

	ctx->shpool->log_ctx = ngx_slab_alloc(ctx->shpool, len);
	if (ctx->shpool->log_ctx == NULL) {
		return NGX_ERROR;
	}

	ngx_sprintf(ctx->shpool->log_ctx, " in limit_req zone \"%V\"%Z",
			&shm_zone->shm.name);

	ctx->shpool->log_nomem = 0;

	return NGX_OK;
}

static void *
ngx_http_limit_req_create_conf(ngx_conf_t *cf) {
	ngx_http_limit_req_conf_t *conf;

	conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_limit_req_conf_t));
	if (conf == NULL) {
		return NULL;
	}

	/*
	 * set by ngx_pcalloc():
	 *
	 *     conf->limits.elts = NULL;
	 */

	conf->limit_log_level = NGX_CONF_UNSET_UINT;
	conf->status_code = NGX_CONF_UNSET_UINT;

	return conf;
}

static char *
ngx_http_limit_req_merge_conf(ngx_conf_t *cf, void *parent, void *child) {
	ngx_http_limit_req_conf_t *prev = parent;
	ngx_http_limit_req_conf_t *conf = child;

	if (conf->limits.elts == NULL) {
		conf->limits = prev->limits;
	}

	ngx_conf_merge_uint_value(conf->limit_log_level, prev->limit_log_level,
			NGX_LOG_ERR);

	conf->delay_log_level =
			(conf->limit_log_level == NGX_LOG_INFO) ?
					NGX_LOG_INFO : conf->limit_log_level + 1;

	ngx_conf_merge_uint_value(conf->status_code, prev->status_code,
			NGX_HTTP_SERVICE_UNAVAILABLE);

	return NGX_CONF_OK;
}

static char *
ngx_http_limit_req_zone(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) {
	u_char *p;
	size_t len;
	ssize_t size;
	ngx_str_t *value, name, s;
	ngx_int_t rate, scale;
	ngx_uint_t i;
	ngx_shm_zone_t *shm_zone;
	ngx_http_limit_req_ctx_t *ctx;
	ngx_http_compile_complex_value_t ccv;

	value = cf->args->elts;

	ctx = ngx_pcalloc(cf->pool, sizeof(ngx_http_limit_req_ctx_t));
	if (ctx == NULL) {
		return NGX_CONF_ERROR ;
	}

	ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));

	ccv.cf = cf;
	ccv.value = &value[1];
	ccv.complex_value = &ctx->key;

	if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
		return NGX_CONF_ERROR ;
	}

	size = 0;
	rate = 1;
	scale = 1;
	name.len = 0;

	for (i = 2; i < cf->args->nelts; i++) {

		if (ngx_strncmp(value[i].data, "zone=", 5) == 0) {

			name.data = value[i].data + 5;

			p = (u_char *) ngx_strchr(name.data, ':');

			if (p == NULL) {
				ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
						"invalid zone size \"%V\"", &value[i]);
				return NGX_CONF_ERROR ;
			}

			name.len = p - name.data;

			s.data = p + 1;
			s.len = value[i].data + value[i].len - s.data;

			size = ngx_parse_size(&s);

			if (size == NGX_ERROR) {
				ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
						"invalid zone size \"%V\"", &value[i]);
				return NGX_CONF_ERROR ;
			}

			if (size < (ssize_t) (8 * ngx_pagesize)) {
				ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
						"zone \"%V\" is too small", &value[i]);
				return NGX_CONF_ERROR ;
			}

			continue;
		}

		if (ngx_strncmp(value[i].data, "rate=", 5) == 0) {

			len = value[i].len;
			p = value[i].data + len - 3;

			if (ngx_strncmp(p, "r/s", 3) == 0) {
				scale = 1;
				len -= 3;

			} else if (ngx_strncmp(p, "r/m", 3) == 0) {
				scale = 60;
				len -= 3;
			}

			rate = ngx_atoi(value[i].data + 5, len - 5);
			if (rate <= 0) {
				ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid rate \"%V\"",
						&value[i]);
				return NGX_CONF_ERROR ;
			}

			continue;
		}

		if (ngx_strncmp(value[i].data, "redis=", 6) == 0) {

			len = value[i].len;
			redis_ip = value[i].data + 6;

			continue;
		}

		if (ngx_strncmp(value[i].data, "block_second=", 13) == 0) {

			len = value[i].len;
			block_second = value[i].data + 13;

			continue;
		}

		if (ngx_strncmp(value[i].data, "cookie_max=", 11) == 0) {

				len = value[i].len;
				cookie_max = value[i].data + 11;

				continue;
			}

		ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid parameter \"%V\"",
				&value[i]);
		return NGX_CONF_ERROR ;
	}

	if (name.len == 0) {
		ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
				"\"%V\" must have \"zone\" parameter", &cmd->name);
		return NGX_CONF_ERROR ;
	}

	ctx->rate = rate * 1000 / scale;

	shm_zone = ngx_shared_memory_add(cf, &name, size,
			&ngx_http_cookie_limit_req_module);
	if (shm_zone == NULL) {
		return NGX_CONF_ERROR ;
	}

	if (shm_zone->data) {
		ctx = shm_zone->data;

		ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
				"%V \"%V\" is already bound to key \"%V\"", &cmd->name, &name,
				&ctx->key.value);
		return NGX_CONF_ERROR ;
	}

	shm_zone->init = ngx_http_limit_req_init_zone;
	shm_zone->data = ctx;

	return NGX_CONF_OK;
}

static char *
ngx_http_limit_req(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) {
	ngx_http_limit_req_conf_t *lrcf = conf;

	ngx_int_t burst;
	ngx_str_t *value, s;
	ngx_uint_t i, nodelay;
	ngx_shm_zone_t *shm_zone;
	ngx_http_limit_req_limit_t *limit, *limits;

	value = cf->args->elts;

	shm_zone = NULL;
	burst = 0;
	nodelay = 0;

	for (i = 1; i < cf->args->nelts; i++) {

		if (ngx_strncmp(value[i].data, "zone=", 5) == 0) {

			s.len = value[i].len - 5;
			s.data = value[i].data + 5;

			shm_zone = ngx_shared_memory_add(cf, &s, 0,
					&ngx_http_cookie_limit_req_module);
			if (shm_zone == NULL) {
				return NGX_CONF_ERROR ;
			}

			continue;
		}

		if (ngx_strncmp(value[i].data, "burst=", 6) == 0) {

			burst = ngx_atoi(value[i].data + 6, value[i].len - 6);
			if (burst <= 0) {
				ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
						"invalid burst rate \"%V\"", &value[i]);
				return NGX_CONF_ERROR ;
			}

			continue;
		}

		if (ngx_strcmp(value[i].data, "nodelay") == 0) {
			nodelay = 1;
			continue;
		}

		ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid parameter \"%V\"",
				&value[i]);
		return NGX_CONF_ERROR ;
	}

	if (shm_zone == NULL) {
		ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
				"\"%V\" must have \"zone\" parameter", &cmd->name);
		return NGX_CONF_ERROR ;
	}

	limits = lrcf->limits.elts;

	if (limits == NULL) {
		if (ngx_array_init(&lrcf->limits, cf->pool, 1,
				sizeof(ngx_http_limit_req_limit_t)) != NGX_OK) {
			return NGX_CONF_ERROR ;
		}
	}

	for (i = 0; i < lrcf->limits.nelts; i++) {
		if (shm_zone == limits[i].shm_zone) {
			return "is duplicate";
		}
	}

	limit = ngx_array_push(&lrcf->limits);
	if (limit == NULL) {
		return NGX_CONF_ERROR ;
	}

	limit->shm_zone = shm_zone;
	limit->burst = burst * 1000;
	limit->nodelay = nodelay;

	return NGX_CONF_OK;
}

static ngx_int_t ngx_http_limit_req_init(ngx_conf_t *cf) {
	ngx_http_handler_pt *h;
	ngx_http_core_main_conf_t *cmcf;

	cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);

	h = ngx_array_push(&cmcf->phases[NGX_HTTP_PREACCESS_PHASE].handlers);
	if (h == NULL) {
		return NGX_ERROR;
	}

	*h = ngx_http_limit_req_handler;

	return NGX_OK;
}