/*
 * Copyright 2024 Vsevolod Stakhov
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "config.h"
#include "upstream.h"
#include "ottery.h"
#include "ref.h"
#include "cfg_file.h"
#include "rdns.h"
#include "cryptobox.h"
#include "utlist.h"
#include "contrib/libev/ev.h"
#include "logger.h"
#include "contrib/librdns/rdns.h"
#include "contrib/mumhash/mum.h"

#include <math.h>


struct upstream_inet_addr_entry {
	rspamd_inet_addr_t *addr;
	unsigned int priority;
	struct upstream_inet_addr_entry *next;
};

struct upstream_addr_elt {
	rspamd_inet_addr_t *addr;
	unsigned int priority;
	unsigned int errors;
};

struct upstream_list_watcher {
	rspamd_upstream_watch_func func;
	GFreeFunc dtor;
	gpointer ud;
	enum rspamd_upstreams_watch_event events_mask;
	struct upstream_list_watcher *next, *prev;
};

struct upstream {
	unsigned int weight;
	unsigned int cur_weight;
	unsigned int errors;
	unsigned int checked;
	unsigned int dns_requests;
	int active_idx;
	unsigned int ttl;
	char *name;
	ev_timer ev;
	double last_fail;
	double last_resolve;
	gpointer ud;
	enum rspamd_upstream_flag flags;
	struct upstream_list *ls;
	GList *ctx_pos;
	struct upstream_ctx *ctx;

	struct {
		GPtrArray *addr; /* struct upstream_addr_elt */
		unsigned int cur;
	} addrs;

	struct upstream_inet_addr_entry *new_addrs;
	gpointer data;
	char uid[8];
	ref_entry_t ref;
#ifdef UPSTREAMS_THREAD_SAFE
	rspamd_mutex_t *lock;
#endif
};

struct upstream_limits {
	double revive_time;
	double revive_jitter;
	double error_time;
	double dns_timeout;
	double lazy_resolve_time;
	double resolve_min_interval;
	unsigned int max_errors;
	unsigned int dns_retransmits;
};

struct upstream_list {
	char *ups_line;
	struct upstream_ctx *ctx;
	GPtrArray *ups;
	GPtrArray *alive;
	struct upstream_list_watcher *watchers;
	uint64_t hash_seed;
	const struct upstream_limits *limits;
	enum rspamd_upstream_flag flags;
	unsigned int cur_elt;
	enum rspamd_upstream_rotation rot_alg;
#ifdef UPSTREAMS_THREAD_SAFE
	rspamd_mutex_t *lock;
#endif
};

struct upstream_ctx {
	struct rdns_resolver *res;
	struct ev_loop *event_loop;
	struct upstream_limits limits;
	GQueue *upstreams;
	gboolean configured;
	rspamd_mempool_t *pool;
	ref_entry_t ref;
};

#ifndef UPSTREAMS_THREAD_SAFE
#define RSPAMD_UPSTREAM_LOCK(x) \
	do {                        \
	} while (0)
#define RSPAMD_UPSTREAM_UNLOCK(x) \
	do {                          \
	} while (0)
#else
#define RSPAMD_UPSTREAM_LOCK(x) rspamd_mutex_lock(x->lock)
#define RSPAMD_UPSTREAM_UNLOCK(x) rspamd_mutex_unlock(x->lock)
#endif

#define msg_debug_upstream(...) rspamd_conditional_debug_fast(NULL, NULL,                                        \
															  rspamd_upstream_log_id, "upstream", upstream->uid, \
															  G_STRFUNC,                                         \
															  __VA_ARGS__)
#define msg_info_upstream(...) rspamd_default_log_function(G_LOG_LEVEL_INFO,          \
														   "upstream", upstream->uid, \
														   G_STRFUNC,                 \
														   __VA_ARGS__)
#define msg_err_upstream(...) rspamd_default_log_function(G_LOG_LEVEL_INFO,          \
														  "upstream", upstream->uid, \
														  G_STRFUNC,                 \
														  __VA_ARGS__)

INIT_LOG_MODULE(upstream)

/* 4 errors in 10 seconds */
#define DEFAULT_MAX_ERRORS 4
static const unsigned int default_max_errors = DEFAULT_MAX_ERRORS;
#define DEFAULT_REVIVE_TIME 60
static const double default_revive_time = DEFAULT_REVIVE_TIME;
#define DEFAULT_REVIVE_JITTER 0.4
static const double default_revive_jitter = DEFAULT_REVIVE_JITTER;
#define DEFAULT_ERROR_TIME 10
static const double default_error_time = DEFAULT_ERROR_TIME;
#define DEFAULT_DNS_TIMEOUT 1.0
static const double default_dns_timeout = DEFAULT_DNS_TIMEOUT;
#define DEFAULT_DNS_RETRANSMITS 2
static const unsigned int default_dns_retransmits = DEFAULT_DNS_RETRANSMITS;
#define DEFAULT_LAZY_RESOLVE_TIME 3600.0
static const double default_lazy_resolve_time = DEFAULT_LAZY_RESOLVE_TIME;
#define DEFAULT_RESOLVE_MIN_INTERVAL 60.0
static const double default_resolve_min_interval = DEFAULT_RESOLVE_MIN_INTERVAL;

static const struct upstream_limits default_limits = {
	.revive_time = DEFAULT_REVIVE_TIME,
	.revive_jitter = DEFAULT_REVIVE_JITTER,
	.error_time = DEFAULT_ERROR_TIME,
	.dns_timeout = DEFAULT_DNS_TIMEOUT,
	.dns_retransmits = DEFAULT_DNS_RETRANSMITS,
	.max_errors = DEFAULT_MAX_ERRORS,
	.lazy_resolve_time = DEFAULT_LAZY_RESOLVE_TIME,
	.resolve_min_interval = DEFAULT_RESOLVE_MIN_INTERVAL,
};

static void rspamd_upstream_lazy_resolve_cb(struct ev_loop *, ev_timer *, int);

void rspamd_upstreams_library_config(struct rspamd_config *cfg,
									 struct upstream_ctx *ctx,
									 struct ev_loop *event_loop,
									 struct rdns_resolver *resolver)
{
	g_assert(ctx != NULL);
	g_assert(cfg != NULL);

	if (cfg->upstream_error_time) {
		ctx->limits.error_time = cfg->upstream_error_time;
	}
	if (cfg->upstream_max_errors) {
		ctx->limits.max_errors = cfg->upstream_max_errors;
	}
	if (cfg->upstream_revive_time) {
		ctx->limits.revive_time = cfg->upstream_revive_time;
	}
	if (cfg->upstream_lazy_resolve_time) {
		ctx->limits.lazy_resolve_time = cfg->upstream_lazy_resolve_time;
	}
	if (cfg->dns_retransmits) {
		ctx->limits.dns_retransmits = cfg->dns_retransmits;
	}
	if (cfg->dns_timeout) {
		ctx->limits.dns_timeout = cfg->dns_timeout;
	}
	if (cfg->upstream_resolve_min_interval) {
		ctx->limits.resolve_min_interval = cfg->upstream_resolve_min_interval;
	}

	/* Some sanity checks */
	if (ctx->limits.resolve_min_interval > ctx->limits.revive_time) {
		/* We must be able to resolve host during the revive time */
		ctx->limits.resolve_min_interval = ctx->limits.revive_time;
	}

	ctx->event_loop = event_loop;
	ctx->res = resolver;
	ctx->configured = TRUE;

	/* Start lazy resolving */
	if (event_loop && resolver) {
		GList *cur;
		struct upstream *upstream;

		cur = ctx->upstreams->head;

		while (cur) {
			upstream = cur->data;
			if (!ev_can_stop(&upstream->ev) && upstream->ls &&
				!(upstream->flags & RSPAMD_UPSTREAM_FLAG_NORESOLVE)) {
				double when;

				if (upstream->flags & RSPAMD_UPSTREAM_FLAG_SRV_RESOLVE) {
					/* Resolve them immediately ! */
					when = 0.0;
				}
				else {
					when = rspamd_time_jitter(upstream->ls->limits->lazy_resolve_time,
											  upstream->ls->limits->lazy_resolve_time * .1);
				}

				ev_timer_init(&upstream->ev, rspamd_upstream_lazy_resolve_cb,
							  when, 0);
				upstream->ev.data = upstream;
				ev_timer_start(ctx->event_loop, &upstream->ev);
			}

			cur = g_list_next(cur);
		}
	}
}

static void
rspamd_upstream_ctx_dtor(struct upstream_ctx *ctx)
{
	GList *cur;
	struct upstream *u;

	cur = ctx->upstreams->head;

	while (cur) {
		u = cur->data;
		u->ctx = NULL;
		u->ctx_pos = NULL;
		cur = g_list_next(cur);
	}

	g_queue_free(ctx->upstreams);
	rspamd_mempool_delete(ctx->pool);
	g_free(ctx);
}

void rspamd_upstreams_library_unref(struct upstream_ctx *ctx)
{
	REF_RELEASE(ctx);
}

struct upstream_ctx *
rspamd_upstreams_library_init(void)
{
	struct upstream_ctx *ctx;

	ctx = g_malloc0(sizeof(*ctx));
	memcpy(&ctx->limits, &default_limits, sizeof(ctx->limits));
	ctx->pool = rspamd_mempool_new(rspamd_mempool_suggest_size(),
								   "upstreams", 0);

	ctx->upstreams = g_queue_new();
	REF_INIT_RETAIN(ctx, rspamd_upstream_ctx_dtor);

	return ctx;
}

static int
rspamd_upstream_af_to_weight(const rspamd_inet_addr_t *addr)
{
	int ret;

	switch (rspamd_inet_address_get_af(addr)) {
	case AF_UNIX:
		ret = 2;
		break;
	case AF_INET:
		ret = 1;
		break;
	default:
		ret = 0;
		break;
	}

	return ret;
}

/*
 * Select IPv4 addresses before IPv6
 */
static int
rspamd_upstream_addr_sort_func(gconstpointer a, gconstpointer b)
{
	const struct upstream_addr_elt *ip1 = *(const struct upstream_addr_elt **) a,
								   *ip2 = *(const struct upstream_addr_elt **) b;
	int w1, w2;

	if (ip1->priority == 0 && ip2->priority == 0) {
		w1 = rspamd_upstream_af_to_weight(ip1->addr);
		w2 = rspamd_upstream_af_to_weight(ip2->addr);
	}
	else {
		w1 = ip1->priority;
		w2 = ip2->priority;
	}

	/* Inverse order */
	return w2 - w1;
}

static void
rspamd_upstream_set_active(struct upstream_list *ls, struct upstream *upstream)
{
	RSPAMD_UPSTREAM_LOCK(ls);
	g_ptr_array_add(ls->alive, upstream);
	upstream->active_idx = ls->alive->len - 1;

	if (upstream->ctx && upstream->ctx->configured &&
		!(upstream->flags & RSPAMD_UPSTREAM_FLAG_NORESOLVE)) {

		if (ev_can_stop(&upstream->ev)) {
			ev_timer_stop(upstream->ctx->event_loop, &upstream->ev);
		}

		/* Start lazy (or not so lazy) names resolution */
		double when;

		if (upstream->flags & RSPAMD_UPSTREAM_FLAG_SRV_RESOLVE) {
			/* Resolve them immediately ! */
			when = 0.0;
		}
		else {
			when = rspamd_time_jitter(upstream->ls->limits->lazy_resolve_time,
									  upstream->ls->limits->lazy_resolve_time * .1);
		}
		ev_timer_init(&upstream->ev, rspamd_upstream_lazy_resolve_cb,
					  when, 0);
		upstream->ev.data = upstream;
		msg_debug_upstream("start lazy resolving for %s in %.0f seconds",
						   upstream->name, when);
		ev_timer_start(upstream->ctx->event_loop, &upstream->ev);
	}

	RSPAMD_UPSTREAM_UNLOCK(ls);
}

static void
rspamd_upstream_addr_elt_dtor(gpointer a)
{
	struct upstream_addr_elt *elt = a;

	if (elt) {
		rspamd_inet_address_free(elt->addr);
		g_free(elt);
	}
}

static void
rspamd_upstream_update_addrs(struct upstream *upstream)
{
	unsigned int addr_cnt, i, port;
	gboolean seen_addr, reset_errors = FALSE;
	struct upstream_inet_addr_entry *cur, *tmp;
	GPtrArray *new_addrs;
	struct upstream_addr_elt *addr_elt, *naddr;

	/*
	 * We need first of all get the saved port, since DNS gives us no
	 * idea about what port has been used previously
	 */
	RSPAMD_UPSTREAM_LOCK(upstream);

	if (upstream->addrs.addr->len > 0 && upstream->new_addrs) {
		addr_elt = g_ptr_array_index(upstream->addrs.addr, 0);
		port = rspamd_inet_address_get_port(addr_elt->addr);

		/* Now calculate new addrs count */
		addr_cnt = 0;
		LL_FOREACH(upstream->new_addrs, cur)
		{
			addr_cnt++;
		}

		/* At 10% probability reset errors on addr elements */
		if (rspamd_random_double_fast() > 0.9) {
			reset_errors = TRUE;
			msg_debug_upstream("reset errors on upstream %s",
							   upstream->name);
		}

		new_addrs = g_ptr_array_new_full(addr_cnt, rspamd_upstream_addr_elt_dtor);

		/* Copy addrs back */
		LL_FOREACH(upstream->new_addrs, cur)
		{
			seen_addr = FALSE;
			naddr = NULL;
			/* Ports are problematic, set to compare in the next block */
			rspamd_inet_address_set_port(cur->addr, port);

			PTR_ARRAY_FOREACH(upstream->addrs.addr, i, addr_elt)
			{
				if (rspamd_inet_address_compare(addr_elt->addr, cur->addr, FALSE) == 0) {
					naddr = g_malloc0(sizeof(*naddr));
					naddr->addr = cur->addr;
					naddr->errors = reset_errors ? 0 : addr_elt->errors;
					seen_addr = TRUE;

					break;
				}
			}

			if (!seen_addr) {
				naddr = g_malloc0(sizeof(*naddr));
				naddr->addr = cur->addr;
				naddr->errors = 0;
				msg_debug_upstream("new address for %s: %s",
								   upstream->name,
								   rspamd_inet_address_to_string_pretty(naddr->addr));
			}
			else {
				msg_debug_upstream("existing address for %s: %s",
								   upstream->name,
								   rspamd_inet_address_to_string_pretty(cur->addr));
			}

			g_ptr_array_add(new_addrs, naddr);
		}

		/* Free old addresses */
		g_ptr_array_free(upstream->addrs.addr, TRUE);

		upstream->addrs.cur = 0;
		upstream->addrs.addr = new_addrs;
		g_ptr_array_sort(upstream->addrs.addr, rspamd_upstream_addr_sort_func);
	}

	LL_FOREACH_SAFE(upstream->new_addrs, cur, tmp)
	{
		/* Do not free inet address pointer since it has been transferred to up */
		g_free(cur);
	}

	upstream->new_addrs = NULL;
	RSPAMD_UPSTREAM_UNLOCK(upstream);
}

static void
rspamd_upstream_dns_cb(struct rdns_reply *reply, void *arg)
{
	struct upstream *up = (struct upstream *) arg;
	struct rdns_reply_entry *entry;
	struct upstream_inet_addr_entry *up_ent;

	if (reply->code == RDNS_RC_NOERROR) {
		entry = reply->entries;

		RSPAMD_UPSTREAM_LOCK(up);
		while (entry) {

			if (entry->type == RDNS_REQUEST_A) {
				up_ent = g_malloc0(sizeof(*up_ent));
				up_ent->addr = rspamd_inet_address_new(AF_INET,
													   &entry->content.a.addr);
				LL_PREPEND(up->new_addrs, up_ent);
			}
			else if (entry->type == RDNS_REQUEST_AAAA) {
				up_ent = g_malloc0(sizeof(*up_ent));
				up_ent->addr = rspamd_inet_address_new(AF_INET6,
													   &entry->content.aaa.addr);
				LL_PREPEND(up->new_addrs, up_ent);
			}
			entry = entry->next;
		}

		RSPAMD_UPSTREAM_UNLOCK(up);
	}

	up->dns_requests--;

	if (up->dns_requests == 0) {
		rspamd_upstream_update_addrs(up);
	}

	REF_RELEASE(up);
}

struct rspamd_upstream_srv_dns_cb {
	struct upstream *up;
	unsigned int priority;
	unsigned int port;
	unsigned int requests_inflight;
};

/* Used when we have resolved SRV record and resolved addrs */
static void
rspamd_upstream_dns_srv_phase2_cb(struct rdns_reply *reply, void *arg)
{
	struct rspamd_upstream_srv_dns_cb *cbdata =
		(struct rspamd_upstream_srv_dns_cb *) arg;
	struct upstream *up;
	struct rdns_reply_entry *entry;
	struct upstream_inet_addr_entry *up_ent;

	up = cbdata->up;

	if (reply->code == RDNS_RC_NOERROR) {
		entry = reply->entries;

		RSPAMD_UPSTREAM_LOCK(up);
		while (entry) {

			if (entry->type == RDNS_REQUEST_A) {
				up_ent = g_malloc0(sizeof(*up_ent));
				up_ent->addr = rspamd_inet_address_new(AF_INET,
													   &entry->content.a.addr);
				up_ent->priority = cbdata->priority;
				rspamd_inet_address_set_port(up_ent->addr, cbdata->port);
				LL_PREPEND(up->new_addrs, up_ent);
			}
			else if (entry->type == RDNS_REQUEST_AAAA) {
				up_ent = g_malloc0(sizeof(*up_ent));
				up_ent->addr = rspamd_inet_address_new(AF_INET6,
													   &entry->content.aaa.addr);
				up_ent->priority = cbdata->priority;
				rspamd_inet_address_set_port(up_ent->addr, cbdata->port);
				LL_PREPEND(up->new_addrs, up_ent);
			}
			entry = entry->next;
		}

		RSPAMD_UPSTREAM_UNLOCK(up);
	}

	up->dns_requests--;
	cbdata->requests_inflight--;

	if (cbdata->requests_inflight == 0) {
		g_free(cbdata);
	}

	if (up->dns_requests == 0) {
		rspamd_upstream_update_addrs(up);
	}

	REF_RELEASE(up);
}

static void
rspamd_upstream_dns_srv_cb(struct rdns_reply *reply, void *arg)
{
	struct upstream *upstream = (struct upstream *) arg;
	struct rdns_reply_entry *entry;
	struct rspamd_upstream_srv_dns_cb *ncbdata;

	if (reply->code == RDNS_RC_NOERROR) {
		entry = reply->entries;

		RSPAMD_UPSTREAM_LOCK(upstream);
		while (entry) {
			/* XXX: we ignore weight as it contradicts with upstreams logic */
			if (entry->type == RDNS_REQUEST_SRV) {
				msg_debug_upstream("got srv reply for %s: %s "
								   "(weight=%d, priority=%d, port=%d)",
								   upstream->name, entry->content.srv.target,
								   entry->content.srv.weight, entry->content.srv.priority,
								   entry->content.srv.port);
				ncbdata = g_malloc0(sizeof(*ncbdata));
				ncbdata->priority = entry->content.srv.weight;
				ncbdata->port = entry->content.srv.port;
				/* XXX: for all entries? */
				upstream->ttl = entry->ttl;

				if (rdns_make_request_full(upstream->ctx->res,
										   rspamd_upstream_dns_srv_phase2_cb, ncbdata,
										   upstream->ls->limits->dns_timeout,
										   upstream->ls->limits->dns_retransmits,
										   1, entry->content.srv.target, RDNS_REQUEST_A) != NULL) {
					upstream->dns_requests++;
					REF_RETAIN(upstream);
					ncbdata->requests_inflight++;
				}

				if (rdns_make_request_full(upstream->ctx->res,
										   rspamd_upstream_dns_srv_phase2_cb, ncbdata,
										   upstream->ls->limits->dns_timeout,
										   upstream->ls->limits->dns_retransmits,
										   1, entry->content.srv.target, RDNS_REQUEST_AAAA) != NULL) {
					upstream->dns_requests++;
					REF_RETAIN(upstream);
					ncbdata->requests_inflight++;
				}

				if (ncbdata->requests_inflight == 0) {
					g_free(ncbdata);
				}
			}
			entry = entry->next;
		}

		RSPAMD_UPSTREAM_UNLOCK(upstream);
	}

	upstream->dns_requests--;
	REF_RELEASE(upstream);
}

static void
rspamd_upstream_revive_cb(struct ev_loop *loop, ev_timer *w, int revents)
{
	struct upstream *upstream = (struct upstream *) w->data;

	RSPAMD_UPSTREAM_LOCK(upstream);
	ev_timer_stop(loop, w);

	msg_debug_upstream("revive upstream %s", upstream->name);

	if (upstream->ls) {
		rspamd_upstream_set_active(upstream->ls, upstream);
	}

	RSPAMD_UPSTREAM_UNLOCK(upstream);
	g_assert(upstream->ref.refcount > 1);
	REF_RELEASE(upstream);
}

static void
rspamd_upstream_resolve_addrs(const struct upstream_list *ls,
							  struct upstream *upstream)
{

	if (upstream->ctx->res != NULL &&
		upstream->ctx->configured &&
		upstream->dns_requests == 0 &&
		!(upstream->flags & RSPAMD_UPSTREAM_FLAG_NORESOLVE)) {

		double now = ev_now(upstream->ctx->event_loop);

		if (now - upstream->last_resolve < upstream->ctx->limits.resolve_min_interval) {
			msg_info_upstream("do not resolve upstream %s as it was checked %.0f "
							  "seconds ago (%.0f is minimum)",
							  upstream->name, now - upstream->last_resolve,
							  upstream->ctx->limits.resolve_min_interval);

			return;
		}

		/* Resolve name of the upstream one more time */
		if (upstream->name[0] != '/') {
			upstream->last_resolve = now;

			/*
			 * If upstream name has a port, then we definitely need to resolve
			 * merely host part!
			 */
			char dns_name[253 + 1]; /* 253 == max dns name + \0 */
			const char *semicolon_pos = strchr(upstream->name, ':');

			if (semicolon_pos != NULL && semicolon_pos > upstream->name) {
				if (sizeof(dns_name) > semicolon_pos - upstream->name) {
					rspamd_strlcpy(dns_name, upstream->name,
								   semicolon_pos - upstream->name + 1);
				}
				else {
					/* XXX: truncated */
					msg_err_upstream("internal error: upstream name is larger than"
									 "max DNS name: %s",
									 upstream->name);
					rspamd_strlcpy(dns_name, upstream->name, sizeof(dns_name));
				}
			}
			else {
				rspamd_strlcpy(dns_name, upstream->name, sizeof(dns_name));
			}

			if (upstream->flags & RSPAMD_UPSTREAM_FLAG_SRV_RESOLVE) {
				if (rdns_make_request_full(upstream->ctx->res,
										   rspamd_upstream_dns_srv_cb, upstream,
										   ls->limits->dns_timeout, ls->limits->dns_retransmits,
										   1, dns_name, RDNS_REQUEST_SRV) != NULL) {
					upstream->dns_requests++;
					REF_RETAIN(upstream);
				}
			}
			else {
				if (rdns_make_request_full(upstream->ctx->res,
										   rspamd_upstream_dns_cb, upstream,
										   ls->limits->dns_timeout, ls->limits->dns_retransmits,
										   1, dns_name, RDNS_REQUEST_A) != NULL) {
					upstream->dns_requests++;
					REF_RETAIN(upstream);
				}

				if (rdns_make_request_full(upstream->ctx->res,
										   rspamd_upstream_dns_cb, upstream,
										   ls->limits->dns_timeout, ls->limits->dns_retransmits,
										   1, dns_name, RDNS_REQUEST_AAAA) != NULL) {
					upstream->dns_requests++;
					REF_RETAIN(upstream);
				}
			}
		}
	}
	else if (upstream->dns_requests != 0) {
		msg_info_upstream("do not resolve upstream %s as another request for "
						  "resolving has been already issued",
						  upstream->name);
	}
}

static void
rspamd_upstream_lazy_resolve_cb(struct ev_loop *loop, ev_timer *w, int revents)
{
	struct upstream *up = (struct upstream *) w->data;

	RSPAMD_UPSTREAM_LOCK(up);
	ev_timer_stop(loop, w);

	if (up->ls) {
		rspamd_upstream_resolve_addrs(up->ls, up);

		if (up->ttl == 0 || up->ttl > up->ls->limits->lazy_resolve_time) {
			w->repeat = rspamd_time_jitter(up->ls->limits->lazy_resolve_time,
										   up->ls->limits->lazy_resolve_time * .1);
		}
		else {
			w->repeat = up->ttl;
		}

		ev_timer_again(loop, w);
	}

	RSPAMD_UPSTREAM_UNLOCK(up);
}

static void
rspamd_upstream_set_inactive(struct upstream_list *ls, struct upstream *upstream)
{
	double ntim;
	unsigned int i;
	struct upstream *cur;
	struct upstream_list_watcher *w;

	g_assert(upstream != NULL);
	RSPAMD_UPSTREAM_LOCK(ls);
	g_ptr_array_remove_index(ls->alive, upstream->active_idx);
	upstream->active_idx = -1;

	/* We need to update all indices */
	for (i = 0; i < ls->alive->len; i++) {
		cur = g_ptr_array_index(ls->alive, i);
		cur->active_idx = i;
	}

	if (upstream->ctx) {
		rspamd_upstream_resolve_addrs(ls, upstream);

		REF_RETAIN(upstream);
		ntim = rspamd_time_jitter(ls->limits->revive_time,
								  ls->limits->revive_time * ls->limits->revive_jitter);

		if (ev_can_stop(&upstream->ev)) {
			ev_timer_stop(upstream->ctx->event_loop, &upstream->ev);
		}

		msg_debug_upstream("mark upstream %s inactive; revive in %.0f seconds",
						   upstream->name, ntim);
		ev_timer_init(&upstream->ev, rspamd_upstream_revive_cb, ntim, 0);
		upstream->ev.data = upstream;

		if (upstream->ctx->event_loop != NULL && upstream->ctx->configured) {
			ev_timer_start(upstream->ctx->event_loop, &upstream->ev);
		}
	}

	DL_FOREACH(upstream->ls->watchers, w)
	{
		if (w->events_mask & RSPAMD_UPSTREAM_WATCH_OFFLINE) {
			w->func(upstream, RSPAMD_UPSTREAM_WATCH_OFFLINE, upstream->errors, w->ud);
		}
	}

	RSPAMD_UPSTREAM_UNLOCK(ls);
}

void rspamd_upstream_fail(struct upstream *upstream,
						  gboolean addr_failure,
						  const char *reason)
{
	double error_rate = 0, max_error_rate = 0;
	double sec_last, sec_cur;
	struct upstream_addr_elt *addr_elt;
	struct upstream_list_watcher *w;

	g_assert(upstream != NULL);
	msg_debug_upstream("upstream %s failed; reason: %s",
					   upstream->name,
					   reason);

	if (upstream->ctx && upstream->active_idx != -1 && upstream->ls) {
		sec_cur = rspamd_get_ticks(FALSE);

		RSPAMD_UPSTREAM_LOCK(upstream);
		if (upstream->errors == 0) {
			/* We have the first error */
			upstream->last_fail = sec_cur;
			upstream->errors = 1;

			if (upstream->ls && upstream->dns_requests == 0) {
				/* Try to re-resolve address immediately */
				rspamd_upstream_resolve_addrs(upstream->ls, upstream);
			}

			DL_FOREACH(upstream->ls->watchers, w)
			{
				if (w->events_mask & RSPAMD_UPSTREAM_WATCH_FAILURE) {
					w->func(upstream, RSPAMD_UPSTREAM_WATCH_FAILURE, 1, w->ud);
				}
			}
		}
		else {
			sec_last = upstream->last_fail;

			if (sec_cur >= sec_last) {
				upstream->errors++;


				DL_FOREACH(upstream->ls->watchers, w)
				{
					if (w->events_mask & RSPAMD_UPSTREAM_WATCH_FAILURE) {
						w->func(upstream, RSPAMD_UPSTREAM_WATCH_FAILURE,
								upstream->errors, w->ud);
					}
				}

				if (sec_cur - sec_last >= upstream->ls->limits->error_time) {
					error_rate = ((double) upstream->errors) / (sec_cur - sec_last);
					max_error_rate = ((double) upstream->ls->limits->max_errors) /
									 upstream->ls->limits->error_time;
				}

				if (error_rate > max_error_rate) {
					/* Remove upstream from the active list */
					if (upstream->ls->ups->len > 1) {
						msg_debug_upstream("mark upstream %s inactive; "
										   "reason: %s; %.2f "
										   "error rate (%d errors), "
										   "%.2f max error rate, "
										   "%.1f first error time, "
										   "%.1f current ts, "
										   "%d upstreams left",
										   upstream->name,
										   reason,
										   error_rate,
										   upstream->errors,
										   max_error_rate,
										   sec_last,
										   sec_cur,
										   upstream->ls->alive->len - 1);
						rspamd_upstream_set_inactive(upstream->ls, upstream);
						upstream->errors = 0;
					}
					else {
						msg_debug_upstream("cannot mark last alive upstream %s "
										   "inactive; reason: %s; %.2f "
										   "error rate (%d errors), "
										   "%.2f max error rate, "
										   "%.1f first error time, "
										   "%.1f current ts",
										   upstream->name,
										   reason,
										   error_rate,
										   upstream->errors,
										   max_error_rate,
										   sec_last,
										   sec_cur);
						/* Just re-resolve addresses */
						if (sec_cur - sec_last > upstream->ls->limits->revive_time) {
							upstream->errors = 0;
							rspamd_upstream_resolve_addrs(upstream->ls, upstream);
						}
					}
				}
				else if (sec_cur - sec_last >= upstream->ls->limits->error_time) {
					/* Forget the whole interval */
					upstream->last_fail = sec_cur;
					upstream->errors = 1;
				}
			}
		}

		if (addr_failure) {
			/* Also increase count of errors for this specific address */
			if (upstream->addrs.addr) {
				addr_elt = g_ptr_array_index(upstream->addrs.addr,
											 upstream->addrs.cur);
				addr_elt->errors++;
			}
		}

		RSPAMD_UPSTREAM_UNLOCK(upstream);
	}
}

void rspamd_upstream_ok(struct upstream *upstream)
{
	struct upstream_addr_elt *addr_elt;
	struct upstream_list_watcher *w;

	RSPAMD_UPSTREAM_LOCK(upstream);
	if (upstream->errors > 0 && upstream->active_idx != -1 && upstream->ls) {
		/* We touch upstream if and only if it is active */
		msg_debug_upstream("reset errors on upstream %s (was %ud)", upstream->name, upstream->errors);
		upstream->errors = 0;

		if (upstream->addrs.addr) {
			addr_elt = g_ptr_array_index(upstream->addrs.addr, upstream->addrs.cur);
			addr_elt->errors = 0;
		}

		DL_FOREACH(upstream->ls->watchers, w)
		{
			if (w->events_mask & RSPAMD_UPSTREAM_WATCH_SUCCESS) {
				w->func(upstream, RSPAMD_UPSTREAM_WATCH_SUCCESS, 0, w->ud);
			}
		}
	}

	RSPAMD_UPSTREAM_UNLOCK(upstream);
}

void rspamd_upstream_set_weight(struct upstream *up, unsigned int weight)
{
	RSPAMD_UPSTREAM_LOCK(up);
	up->weight = weight;
	RSPAMD_UPSTREAM_UNLOCK(up);
}

#define SEED_CONSTANT 0xa574de7df64e9b9dULL

struct upstream_list *
rspamd_upstreams_create(struct upstream_ctx *ctx)
{
	struct upstream_list *ls;

	ls = g_malloc0(sizeof(*ls));
	ls->hash_seed = SEED_CONSTANT;
	ls->ups = g_ptr_array_new();
	ls->alive = g_ptr_array_new();

#ifdef UPSTREAMS_THREAD_SAFE
	ls->lock = rspamd_mutex_new();
#endif
	ls->cur_elt = 0;
	ls->ctx = ctx;
	ls->rot_alg = RSPAMD_UPSTREAM_UNDEF;

	if (ctx) {
		ls->limits = &ctx->limits;
	}
	else {
		ls->limits = &default_limits;
	}

	return ls;
}

gsize rspamd_upstreams_count(struct upstream_list *ups)
{
	return ups != NULL ? ups->ups->len : 0;
}

gsize rspamd_upstreams_alive(struct upstream_list *ups)
{
	return ups != NULL ? ups->alive->len : 0;
}

static void
rspamd_upstream_dtor(struct upstream *up)
{
	struct upstream_inet_addr_entry *cur, *tmp;

	if (up->new_addrs) {
		LL_FOREACH_SAFE(up->new_addrs, cur, tmp)
		{
			/* Here we need to free pointer as well */
			rspamd_inet_address_free(cur->addr);
			g_free(cur);
		}
	}

	if (up->addrs.addr) {
		g_ptr_array_free(up->addrs.addr, TRUE);
	}

#ifdef UPSTREAMS_THREAD_SAFE
	rspamd_mutex_free(up->lock);
#endif

	if (up->ctx) {

		if (ev_can_stop(&up->ev)) {
			ev_timer_stop(up->ctx->event_loop, &up->ev);
		}

		g_queue_delete_link(up->ctx->upstreams, up->ctx_pos);
		REF_RELEASE(up->ctx);
	}

	g_free(up);
}

rspamd_inet_addr_t *
rspamd_upstream_addr_next(struct upstream *up)
{
	unsigned int idx = up->addrs.cur, next_idx = up->addrs.cur, cur_af,
				 min_errors, min_errors_idx;
	struct upstream_addr_elt *e1, *e2;

	/*
	 * We apply the following algorithm:
	 * 1) Get the current element and it's AF
	 * 2) If the next element has the same AF, then we just move to the next element
	 * 3) If the next element has different AF, then we should find the next element with the same AF
	 * 4) If we cannot find such element, then we return the next element (switching AF)
	 */

	e1 = g_ptr_array_index(up->addrs.addr, up->addrs.cur);
	cur_af = rspamd_inet_address_get_af(e1->addr);
	min_errors = e1->errors;
	min_errors_idx = idx;

	for (;;) {
		unsigned int new_af;
		next_idx = (next_idx + 1) % up->addrs.addr->len;
		e2 = g_ptr_array_index(up->addrs.addr, next_idx);

		if (e2->errors < min_errors) {
			min_errors = e2->errors;
			min_errors_idx = next_idx;
		}

		if (next_idx == idx) {
			/* We did a full circle, so we have to select something else */
			if (e2->errors == 0) {
				/* No errors on the current address, so we can use it */
			}
			else {
				/* We have some errors, so we had to select the address with the lowest err count */
				next_idx = min_errors_idx;
			}

			/* Always stop on full circle */
			break;
		}

		new_af = rspamd_inet_address_get_af(e2->addr);

		if (cur_af == new_af && e2->errors <= e1->errors) {
			/* Same AF */
			up->addrs.cur = next_idx;
			return e2->addr;
		}
	}

	e2 = g_ptr_array_index(up->addrs.addr, next_idx);
	up->addrs.cur = next_idx;

	return e2->addr;
}

rspamd_inet_addr_t *
rspamd_upstream_addr_cur(const struct upstream *up)
{
	struct upstream_addr_elt *elt;

	elt = g_ptr_array_index(up->addrs.addr, up->addrs.cur);

	return elt->addr;
}

const char *
rspamd_upstream_name(struct upstream *up)
{
	return up->name;
}

int rspamd_upstream_port(struct upstream *up)
{
	struct upstream_addr_elt *elt;

	elt = g_ptr_array_index(up->addrs.addr, up->addrs.cur);
	return rspamd_inet_address_get_port(elt->addr);
}

gboolean
rspamd_upstreams_add_upstream(struct upstream_list *ups, const char *str,
							  uint16_t def_port, enum rspamd_upstream_parse_type parse_type,
							  void *data)
{
	struct upstream *upstream;
	GPtrArray *addrs = NULL;
	unsigned int i, slen;
	rspamd_inet_addr_t *addr;
	enum rspamd_parse_host_port_result ret = RSPAMD_PARSE_ADDR_FAIL;

	upstream = g_malloc0(sizeof(*upstream));
	slen = strlen(str);

	switch (parse_type) {
	case RSPAMD_UPSTREAM_PARSE_DEFAULT:
		if (slen > sizeof("service=") &&
			RSPAMD_LEN_CHECK_STARTS_WITH(str, slen, "service=")) {
			const char *plus_pos, *service_pos, *semicolon_pos;

			/* Accept service=srv_name+hostname[:priority] */
			service_pos = str + sizeof("service=") - 1;
			plus_pos = strchr(service_pos, '+');

			if (plus_pos != NULL) {
				semicolon_pos = strchr(plus_pos + 1, ':');

				if (semicolon_pos) {
					upstream->weight = strtoul(semicolon_pos + 1, NULL, 10);
				}
				else {
					semicolon_pos = plus_pos + strlen(plus_pos);
				}

				/*
				 * Now our name is _service._tcp.<domain>
				 * where <domain> is string between semicolon_pos and plus_pos +1
				 * while service is a string between service_pos and plus_pos
				 */
				unsigned int namelen = (semicolon_pos - (plus_pos + 1)) +
									   (plus_pos - service_pos) +
									   (sizeof("tcp") - 1) +
									   4;
				addrs = g_ptr_array_sized_new(1);
				upstream->name = ups->ctx ? rspamd_mempool_alloc(ups->ctx->pool, namelen + 1) : g_malloc(namelen + 1);

				rspamd_snprintf(upstream->name, namelen + 1,
								"_%*s._tcp.%*s",
								(int) (plus_pos - service_pos), service_pos,
								(int) (semicolon_pos - (plus_pos + 1)), plus_pos + 1);
				upstream->flags |= RSPAMD_UPSTREAM_FLAG_SRV_RESOLVE;
				ret = RSPAMD_PARSE_ADDR_RESOLVED;
			}
		}
		else {
			ret = rspamd_parse_host_port_priority(str, &addrs,
												  &upstream->weight,
												  &upstream->name, def_port,
												  FALSE,
												  ups->ctx ? ups->ctx->pool : NULL);
		}
		break;
	case RSPAMD_UPSTREAM_PARSE_NAMESERVER:
		addrs = g_ptr_array_sized_new(1);
		if (rspamd_parse_inet_address(&addr, str, strlen(str),
									  RSPAMD_INET_ADDRESS_PARSE_DEFAULT)) {
			if (ups->ctx) {
				upstream->name = rspamd_mempool_strdup(ups->ctx->pool, str);
			}
			else {
				upstream->name = g_strdup(str);
			}
			if (rspamd_inet_address_get_port(addr) == 0) {
				rspamd_inet_address_set_port(addr, def_port);
			}

			g_ptr_array_add(addrs, addr);
			ret = RSPAMD_PARSE_ADDR_NUMERIC;

			if (ups->ctx) {
				rspamd_mempool_add_destructor(ups->ctx->pool,
											  (rspamd_mempool_destruct_t) rspamd_inet_address_free,
											  addr);
				rspamd_mempool_add_destructor(ups->ctx->pool,
											  (rspamd_mempool_destruct_t) rspamd_ptr_array_free_hard,
											  addrs);
			}
		}
		else {
			g_ptr_array_free(addrs, TRUE);
		}

		break;
	}

	if (ret == RSPAMD_PARSE_ADDR_FAIL) {
		g_free(upstream);
		return FALSE;
	}
	else {
		upstream->flags |= ups->flags;

		if (ret == RSPAMD_PARSE_ADDR_NUMERIC) {
			/* Add noresolve flag */
			upstream->flags |= RSPAMD_UPSTREAM_FLAG_NORESOLVE;
		}
		for (i = 0; i < addrs->len; i++) {
			addr = g_ptr_array_index(addrs, i);
			rspamd_upstream_add_addr(upstream, rspamd_inet_address_copy(addr, NULL));
		}
	}

	if (upstream->weight == 0 && ups->rot_alg == RSPAMD_UPSTREAM_MASTER_SLAVE) {
		/* Special heuristic for master-slave rotation */
		if (ups->ups->len == 0) {
			/* Prioritize the first */
			upstream->weight = 1;
		}
	}

	g_ptr_array_add(ups->ups, upstream);
	upstream->ud = data;
	upstream->cur_weight = upstream->weight;
	upstream->ls = ups;
	REF_INIT_RETAIN(upstream, rspamd_upstream_dtor);
#ifdef UPSTREAMS_THREAD_SAFE
	upstream->lock = rspamd_mutex_new();
#endif
	upstream->ctx = ups->ctx;

	if (upstream->ctx) {
		REF_RETAIN(ups->ctx);
		g_queue_push_tail(ups->ctx->upstreams, upstream);
		upstream->ctx_pos = g_queue_peek_tail_link(ups->ctx->upstreams);
	}

	unsigned int h = rspamd_cryptobox_fast_hash(upstream->name,
												strlen(upstream->name), 0);
	memset(upstream->uid, 0, sizeof(upstream->uid));
	rspamd_encode_base32_buf((const unsigned char *) &h, sizeof(h),
							 upstream->uid, sizeof(upstream->uid) - 1, RSPAMD_BASE32_DEFAULT);

	msg_debug_upstream("added upstream %s (%s)", upstream->name,
					   upstream->flags & RSPAMD_UPSTREAM_FLAG_NORESOLVE ? "numeric ip" : "DNS name");
	g_ptr_array_sort(upstream->addrs.addr, rspamd_upstream_addr_sort_func);
	rspamd_upstream_set_active(ups, upstream);

	return TRUE;
}

void rspamd_upstreams_set_flags(struct upstream_list *ups,
								enum rspamd_upstream_flag flags)
{
	ups->flags = flags;
}

void rspamd_upstreams_set_rotation(struct upstream_list *ups,
								   enum rspamd_upstream_rotation rot)
{
	ups->rot_alg = rot;
}

gboolean
rspamd_upstream_add_addr(struct upstream *up, rspamd_inet_addr_t *addr)
{
	struct upstream_addr_elt *elt;
	/*
	 * XXX: slow and inefficient
	 */
	if (up->addrs.addr == NULL) {
		up->addrs.addr = g_ptr_array_new_full(8, rspamd_upstream_addr_elt_dtor);
	}

	elt = g_malloc0(sizeof(*elt));
	elt->addr = addr;
	g_ptr_array_add(up->addrs.addr, elt);
	g_ptr_array_sort(up->addrs.addr, rspamd_upstream_addr_sort_func);

	return TRUE;
}

gboolean
rspamd_upstreams_parse_line_len(struct upstream_list *ups,
								const char *str, gsize len, uint16_t def_port, void *data)
{
	const char *end = str + len, *p = str;
	const char *separators = ";, \n\r\t";
	char *tmp;
	unsigned int span_len;
	gboolean ret = FALSE;

	if (RSPAMD_LEN_CHECK_STARTS_WITH(p, len, "random:")) {
		ups->rot_alg = RSPAMD_UPSTREAM_RANDOM;
		p += sizeof("random:") - 1;
	}
	else if (RSPAMD_LEN_CHECK_STARTS_WITH(p, len, "master-slave:")) {
		ups->rot_alg = RSPAMD_UPSTREAM_MASTER_SLAVE;
		p += sizeof("master-slave:") - 1;
	}
	else if (RSPAMD_LEN_CHECK_STARTS_WITH(p, len, "round-robin:")) {
		ups->rot_alg = RSPAMD_UPSTREAM_ROUND_ROBIN;
		p += sizeof("round-robin:") - 1;
	}
	else if (RSPAMD_LEN_CHECK_STARTS_WITH(p, len, "hash:")) {
		ups->rot_alg = RSPAMD_UPSTREAM_HASHED;
		p += sizeof("hash:") - 1;
	}

	while (p < end) {
		span_len = rspamd_memcspn(p, separators, end - p);

		if (span_len > 0) {
			tmp = g_malloc(span_len + 1);
			rspamd_strlcpy(tmp, p, span_len + 1);

			if (rspamd_upstreams_add_upstream(ups, tmp, def_port,
											  RSPAMD_UPSTREAM_PARSE_DEFAULT,
											  data)) {
				ret = TRUE;
			}

			g_free(tmp);
		}

		p += span_len;
		/* Skip separators */
		if (p < end) {
			p += rspamd_memspn(p, separators, end - p);
		}
	}

	if (!ups->ups_line) {
		ups->ups_line = g_malloc(len + 1);
		rspamd_strlcpy(ups->ups_line, str, len + 1);
	}

	return ret;
}


gboolean
rspamd_upstreams_parse_line(struct upstream_list *ups,
							const char *str, uint16_t def_port, void *data)
{
	return rspamd_upstreams_parse_line_len(ups, str, strlen(str),
										   def_port, data);
}

gboolean
rspamd_upstreams_from_ucl(struct upstream_list *ups,
						  const ucl_object_t *in, uint16_t def_port, void *data)
{
	gboolean ret = FALSE;
	const ucl_object_t *cur;
	ucl_object_iter_t it = NULL;

	it = ucl_object_iterate_new(in);

	while ((cur = ucl_object_iterate_safe(it, true)) != NULL) {
		if (ucl_object_type(cur) == UCL_STRING) {
			ret = rspamd_upstreams_parse_line(ups, ucl_object_tostring(cur),
											  def_port, data);
		}
	}

	ucl_object_iterate_free(it);

	return ret;
}

void rspamd_upstreams_destroy(struct upstream_list *ups)
{
	unsigned int i;
	struct upstream *up;
	struct upstream_list_watcher *w, *tmp;

	if (ups != NULL) {
		g_ptr_array_free(ups->alive, TRUE);

		for (i = 0; i < ups->ups->len; i++) {
			up = g_ptr_array_index(ups->ups, i);
			up->ls = NULL;
			REF_RELEASE(up);
		}

		DL_FOREACH_SAFE(ups->watchers, w, tmp)
		{
			if (w->dtor) {
				w->dtor(w->ud);
			}
			g_free(w);
		}

		g_free(ups->ups_line);
		g_ptr_array_free(ups->ups, TRUE);
#ifdef UPSTREAMS_THREAD_SAFE
		rspamd_mutex_free(ups->lock);
#endif
		g_free(ups);
	}
}

static void
rspamd_upstream_restore_cb(gpointer elt, gpointer ls)
{
	struct upstream *up = (struct upstream *) elt;
	struct upstream_list *ups = (struct upstream_list *) ls;
	struct upstream_list_watcher *w;

	/* Here the upstreams list is already locked */
	RSPAMD_UPSTREAM_LOCK(up);

	if (ev_can_stop(&up->ev)) {
		ev_timer_stop(up->ctx->event_loop, &up->ev);
	}

	g_ptr_array_add(ups->alive, up);
	up->active_idx = ups->alive->len - 1;
	RSPAMD_UPSTREAM_UNLOCK(up);

	DL_FOREACH(up->ls->watchers, w)
	{
		if (w->events_mask & RSPAMD_UPSTREAM_WATCH_ONLINE) {
			w->func(up, RSPAMD_UPSTREAM_WATCH_ONLINE, up->errors, w->ud);
		}
	}

	/* For revive event */
	g_assert(up->ref.refcount > 1);
	REF_RELEASE(up);
}

static struct upstream *
rspamd_upstream_get_random(struct upstream_list *ups,
						   struct upstream *except)
{
	for (;;) {
		unsigned int idx = ottery_rand_range(ups->alive->len - 1);
		struct upstream *up;

		up = g_ptr_array_index(ups->alive, idx);

		if (except && up == except) {
			continue;
		}

		return up;
	}
}

static struct upstream *
rspamd_upstream_get_round_robin(struct upstream_list *ups,
								struct upstream *except,
								gboolean use_cur)
{
	unsigned int max_weight = 0, min_checked = G_MAXUINT;
	struct upstream *up = NULL, *selected = NULL, *min_checked_sel = NULL;
	unsigned int i;

	/* Select upstream with the maximum cur_weight */
	RSPAMD_UPSTREAM_LOCK(ups);

	for (i = 0; i < ups->alive->len; i++) {
		up = g_ptr_array_index(ups->alive, i);

		if (except != NULL && up == except) {
			continue;
		}

		if (use_cur) {
			if (up->cur_weight > max_weight) {
				selected = up;
				max_weight = up->cur_weight;
			}
		}
		else {
			if (up->weight > max_weight) {
				selected = up;
				max_weight = up->weight;
			}
		}

		/*
		 * This code is used when all upstreams have zero weight
		 * The logic is to select least currently used upstream and penalise
		 * upstream with errors. The error penalty should no be too high
		 * to avoid sudden traffic drop in this case.
		 */
		if (up->checked + up->errors * 2 < min_checked) {
			min_checked_sel = up;
			min_checked = up->checked;
		}
	}

	if (max_weight == 0) {
		/* All upstreams have zero weight */
		if (min_checked > G_MAXUINT / 2) {
			/* Reset all checked counters to avoid overflow */
			for (i = 0; i < ups->alive->len; i++) {
				up = g_ptr_array_index(ups->alive, i);
				up->checked = 0;
			}
		}

		selected = min_checked_sel;
	}

	if (use_cur && selected) {
		if (selected->cur_weight > 0) {
			selected->cur_weight--;
		}
		else {
			selected->cur_weight = selected->weight;
		}
	}

	RSPAMD_UPSTREAM_UNLOCK(ups);

	return selected;
}

/*
 * The key idea of this function is obtained from the following paper:
 * A Fast, Minimal Memory, Consistent Hash Algorithm
 * John Lamping, Eric Veach
 *
 * http://arxiv.org/abs/1406.2294
 */
static uint32_t
rspamd_consistent_hash(uint64_t key, uint32_t nbuckets)
{
	int64_t b = -1, j = 0;

	while (j < nbuckets) {
		b = j;
		key *= 2862933555777941757ULL + 1;
		j = (b + 1) * (double) (1ULL << 31) / (double) ((key >> 33) + 1ULL);
	}

	return b;
}

static struct upstream *
rspamd_upstream_get_hashed(struct upstream_list *ups,
						   struct upstream *except,
						   const uint8_t *key, unsigned int keylen)
{
	uint64_t k;
	uint32_t idx;
	static const unsigned int max_tries = 20;
	struct upstream *up = NULL;

	/* Generate 64 bits input key */
	k = rspamd_cryptobox_fast_hash_specific(RSPAMD_CRYPTOBOX_XXHASH64,
											key, keylen, ups->hash_seed);

	RSPAMD_UPSTREAM_LOCK(ups);
	/*
	 * Select new upstream from all upstreams
	 */
	for (unsigned int i = 0; i < max_tries; i++) {
		idx = rspamd_consistent_hash(k, ups->ups->len);
		up = g_ptr_array_index(ups->ups, idx);

		if (up->active_idx < 0 || (except != NULL && up == except)) {
			/* Found inactive or excluded upstream */
			k = mum_hash_step(k, ups->hash_seed);
		}
		else {
			break;
		}
	}
	RSPAMD_UPSTREAM_UNLOCK(ups);

	if (up->active_idx >= 0) {
		return up;
	}

	/* We failed to find any active upstream */
	up = rspamd_upstream_get_random(ups, except);
	msg_info("failed to find hashed upstream for %s, fallback to random: %s",
			 ups->ups_line, up->name);

	return up;
}

static struct upstream *
rspamd_upstream_get_common(struct upstream_list *ups,
						   struct upstream *except,
						   enum rspamd_upstream_rotation default_type,
						   const unsigned char *key, gsize keylen,
						   gboolean forced)
{
	enum rspamd_upstream_rotation type;
	struct upstream *up = NULL;

	RSPAMD_UPSTREAM_LOCK(ups);
	if (ups->alive->len == 0) {
		/* We have no upstreams alive */
		msg_warn("there are no alive upstreams left for %s, revive all of them",
				 ups->ups_line);
		g_ptr_array_foreach(ups->ups, rspamd_upstream_restore_cb, ups);
	}
	RSPAMD_UPSTREAM_UNLOCK(ups);

	if (ups->alive->len == 1 && default_type != RSPAMD_UPSTREAM_SEQUENTIAL) {
		/* Fast path */
		up = g_ptr_array_index(ups->alive, 0);
		goto end;
	}

	if (!forced) {
		type = ups->rot_alg != RSPAMD_UPSTREAM_UNDEF ? ups->rot_alg : default_type;
	}
	else {
		type = default_type != RSPAMD_UPSTREAM_UNDEF ? default_type : ups->rot_alg;
	}

	if (type == RSPAMD_UPSTREAM_HASHED && (keylen == 0 || key == NULL)) {
		/* Cannot use hashed rotation when no key is specified, switch to random */
		type = RSPAMD_UPSTREAM_RANDOM;
	}

	switch (type) {
	default:
	case RSPAMD_UPSTREAM_RANDOM:
		up = rspamd_upstream_get_random(ups, except);
		break;
	case RSPAMD_UPSTREAM_HASHED:
		up = rspamd_upstream_get_hashed(ups, except, key, keylen);
		break;
	case RSPAMD_UPSTREAM_ROUND_ROBIN:
		up = rspamd_upstream_get_round_robin(ups, except, TRUE);
		break;
	case RSPAMD_UPSTREAM_MASTER_SLAVE:
		up = rspamd_upstream_get_round_robin(ups, except, FALSE);
		break;
	case RSPAMD_UPSTREAM_SEQUENTIAL:
		if (ups->cur_elt >= ups->alive->len) {
			ups->cur_elt = 0;
			return NULL;
		}

		up = g_ptr_array_index(ups->alive, ups->cur_elt++);
		break;
	}

end:
	if (up) {
		up->checked++;
	}

	return up;
}

struct upstream *
rspamd_upstream_get(struct upstream_list *ups,
					enum rspamd_upstream_rotation default_type,
					const unsigned char *key, gsize keylen)
{
	return rspamd_upstream_get_common(ups, NULL, default_type, key, keylen, FALSE);
}

struct upstream *
rspamd_upstream_get_forced(struct upstream_list *ups,
						   enum rspamd_upstream_rotation forced_type,
						   const unsigned char *key, gsize keylen)
{
	return rspamd_upstream_get_common(ups, NULL, forced_type, key, keylen, TRUE);
}

struct upstream *rspamd_upstream_get_except(struct upstream_list *ups,
											struct upstream *except,
											enum rspamd_upstream_rotation default_type,
											const unsigned char *key, gsize keylen)
{
	return rspamd_upstream_get_common(ups, except, default_type, key, keylen, FALSE);
}

void rspamd_upstream_reresolve(struct upstream_ctx *ctx)
{
	GList *cur;
	struct upstream *up;

	cur = ctx->upstreams->head;

	while (cur) {
		up = cur->data;
		g_assert(up != NULL);
		REF_RETAIN(up);
		rspamd_upstream_resolve_addrs(up->ls, up);
		REF_RELEASE(up);
		cur = g_list_next(cur);
	}
}

gpointer
rspamd_upstream_set_data(struct upstream *up, gpointer data)
{
	gpointer prev_data = up->data;
	up->data = data;

	return prev_data;
}

gpointer
rspamd_upstream_get_data(struct upstream *up)
{
	return up->data;
}


void rspamd_upstreams_foreach(struct upstream_list *ups,
							  rspamd_upstream_traverse_func cb, void *ud)
{
	struct upstream *up;
	unsigned int i;

	for (i = 0; i < ups->ups->len; i++) {
		up = g_ptr_array_index(ups->ups, i);

		cb(up, i, ud);
	}
}

void rspamd_upstreams_set_limits(struct upstream_list *ups,
								 double revive_time,
								 double revive_jitter,
								 double error_time,
								 double dns_timeout,
								 unsigned int max_errors,
								 unsigned int dns_retransmits)
{
	struct upstream_limits *nlimits;
	g_assert(ups != NULL);

	nlimits = rspamd_mempool_alloc(ups->ctx->pool, sizeof(*nlimits));
	memcpy(nlimits, ups->limits, sizeof(*nlimits));

	if (!isnan(revive_time)) {
		nlimits->revive_time = revive_time;
	}

	if (!isnan(revive_jitter)) {
		nlimits->revive_jitter = revive_jitter;
	}

	if (!isnan(error_time)) {
		nlimits->error_time = error_time;
	}

	if (!isnan(dns_timeout)) {
		nlimits->dns_timeout = dns_timeout;
	}

	if (max_errors > 0) {
		nlimits->max_errors = max_errors;
	}

	if (dns_retransmits > 0) {
		nlimits->dns_retransmits = dns_retransmits;
	}

	ups->limits = nlimits;
}

void rspamd_upstreams_add_watch_callback(struct upstream_list *ups,
										 enum rspamd_upstreams_watch_event events,
										 rspamd_upstream_watch_func func,
										 GFreeFunc dtor,
										 gpointer ud)
{
	struct upstream_list_watcher *nw;

	g_assert((events & RSPAMD_UPSTREAM_WATCH_ALL) != 0);

	nw = g_malloc(sizeof(*nw));
	nw->func = func;
	nw->events_mask = events;
	nw->ud = ud;
	nw->dtor = dtor;

	DL_APPEND(ups->watchers, nw);
}

struct upstream *
rspamd_upstream_ref(struct upstream *up)
{
	REF_RETAIN(up);
	return up;
}

void rspamd_upstream_unref(struct upstream *up)
{
	REF_RELEASE(up);
}