http-client-connection.c

/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "net.h"
#include "str.h"
#include "hash.h"
#include "llist.h"
#include "array.h"
#include "ioloop.h"
#include "istream.h"
#include "istream-timeout.h"
#include "ostream.h"
#include "time-util.h"
#include "file-lock.h"
#include "iostream-rawlog.h"
#include "iostream-ssl.h"
#include "http-response-parser.h"

#include "http-client-private.h"

/*
 * Connection
 */

static void http_client_connection_ready(struct http_client_connection *conn);
static void http_client_connection_input(struct connection *_conn);

static inline void
http_client_connection_ref_request(struct http_client_connection *conn,
	struct http_client_request *req)
{
	i_assert(req->conn == NULL);
	req->conn = conn;
	http_client_request_ref(req);
}

static inline bool
http_client_connection_unref_request(struct http_client_connection *conn,
	struct http_client_request **_req)
{
	struct http_client_request *req = *_req;

	i_assert(req->conn == conn);
	req->conn = NULL;
	return http_client_request_unref(_req);
}

static inline void
http_client_connection_failure(struct http_client_connection *conn,
					 const char *reason)
{
	struct http_client_peer *peer = conn->peer;

	conn->connect_failed = TRUE;
	http_client_peer_connection_failure(peer, reason);
}

unsigned int
http_client_connection_count_pending(struct http_client_connection *conn)
{
	unsigned int pending_count = array_count(&conn->request_wait_list);

	if (conn->in_req_callback || conn->pending_request != NULL)
		pending_count++;
	return pending_count;
}

bool http_client_connection_is_idle(struct http_client_connection *conn)
{
	return (conn->to_idle != NULL);
}

bool http_client_connection_is_active(struct http_client_connection *conn)
{
	if (!conn->connected)
		return FALSE;

	if (conn->in_req_callback || conn->pending_request != NULL)
		return TRUE;

	return (array_is_created(&conn->request_wait_list) &&
		array_count(&conn->request_wait_list) > 0);
}

static void
http_client_connection_retry_requests(struct http_client_connection *conn,
	unsigned int status, const char *error)
{
	const struct http_client_settings *set = &conn->peer->client->set;
	struct http_client_request *req, **req_idx;

	if (!array_is_created(&conn->request_wait_list))
		return;

	if (set->no_auto_retry) {
		e_debug(conn->event, "Aborting pending requests with error");
	} else {
		e_debug(conn->event, "Retrying pending requests");
	}

	array_foreach_modifiable(&conn->request_wait_list, req_idx) {
		req = *req_idx;
		/* drop reference from connection */
		if (!http_client_connection_unref_request(conn, req_idx))
			continue;
		/* retry the request, which may drop it */
		if (req->state < HTTP_REQUEST_STATE_FINISHED) {
			if (set->no_auto_retry)
				http_client_request_error(&req, status, error);
			else
				http_client_request_retry(req, status, error);
		}
	}	
	array_clear(&conn->request_wait_list);
}

static void
http_client_connection_server_close(struct http_client_connection **_conn)
{
	struct http_client_connection *conn = *_conn;
	struct http_client_peer *peer = conn->peer;
	struct http_client *client = peer->client;
	struct http_client_request *req, **req_idx;

	e_debug(conn->event, "Server explicitly closed connection");

	array_foreach_modifiable(&conn->request_wait_list, req_idx) {
		req = *req_idx;
		/* drop reference from connection */
		if (!http_client_connection_unref_request(conn, req_idx))
			continue;
		/* resubmit the request, which may drop it */
		if (req->state < HTTP_REQUEST_STATE_FINISHED)
			http_client_request_resubmit(req);
	}	
	array_clear(&conn->request_wait_list);

	if (client != NULL && client->waiting)
		io_loop_stop(client->ioloop);

	http_client_connection_close(_conn);
}

static void
http_client_connection_abort_error(struct http_client_connection **_conn,
	unsigned int status, const char *error)
{
	struct http_client_connection *conn = *_conn;
	struct http_client_request *req, **req_idx;

	e_debug(conn->event, "Aborting connection: %s", error);

	array_foreach_modifiable(&conn->request_wait_list, req_idx) {
		req = *req_idx;
		i_assert(req->submitted);
		/* drop reference from connection */
		if (!http_client_connection_unref_request(conn, req_idx))
			continue;
		/* drop request if not already aborted */
		http_client_request_error(&req, status, error);
	}
	array_clear(&conn->request_wait_list);
	http_client_connection_close(_conn);
}

static void
http_client_connection_abort_any_requests(struct http_client_connection *conn)
{
	struct http_client_request *req, **req_idx;

	if (array_is_created(&conn->request_wait_list)) {
		array_foreach_modifiable(&conn->request_wait_list, req_idx) {
			req = *req_idx;
			i_assert(req->submitted);
			/* drop reference from connection */
			if (!http_client_connection_unref_request(conn, req_idx))
				continue;
			/* drop request if not already aborted */
			http_client_request_error(&req,
				HTTP_CLIENT_REQUEST_ERROR_ABORTED,
				"Aborting");
		}
		array_clear(&conn->request_wait_list);
	}
	if (conn->pending_request != NULL) {
		req = conn->pending_request;
		/* drop reference from connection */
		if (http_client_connection_unref_request(conn, &conn->pending_request)) {
			/* drop request if not already aborted */
			http_client_request_error(&req,
				HTTP_CLIENT_REQUEST_ERROR_ABORTED,
				"Aborting");
		}
	}
}

static const char *
http_client_connection_get_timing_info(struct http_client_connection *conn)
{
	struct http_client_request *const *requestp;
	unsigned int connected_msecs;
	string_t *str = t_str_new(64);

	if (array_count(&conn->request_wait_list) > 0) {
		requestp = array_idx(&conn->request_wait_list, 0);

		str_append(str, "Request ");
		http_client_request_append_stats_text(*requestp, str);
	} else {
		str_append(str, "No requests");
		if (conn->conn.last_input != 0) {
			str_printfa(str, ", last input %d secs ago",
				    (int)(ioloop_time - conn->conn.last_input));
		}
	}
	connected_msecs = timeval_diff_msecs(&ioloop_timeval, &conn->connected_timestamp);
	str_printfa(str, ", connected %u.%03u secs ago",
		    connected_msecs/1000, connected_msecs%1000);
	return str_c(str);
}

static void
http_client_connection_abort_temp_error(struct http_client_connection **_conn,
	unsigned int status, const char *error)
{
	struct http_client_connection *conn = *_conn;

	error = t_strdup_printf("%s (%s)", error,
				http_client_connection_get_timing_info(conn));

	e_debug(conn->event,
		"Aborting connection with temporary error: %s", error);

	http_client_connection_retry_requests(conn, status, error);
	http_client_connection_close(_conn);
}

static void
http_client_connection_lost(struct http_client_connection **_conn,
	const char *error) ATTR_NULL(2)
{
	struct http_client_connection *conn = *_conn;
	const char *sslerr;

	if (error == NULL)
		error = "Connection lost";
	else
		error = t_strdup_printf("Connection lost: %s", error);

	if (conn->ssl_iostream != NULL) {
		sslerr = ssl_iostream_get_last_error(conn->ssl_iostream);
		if (sslerr != NULL) {
			error = t_strdup_printf("%s (last SSL error: %s)",
						error, sslerr);
		}
		if (ssl_iostream_has_handshake_failed(conn->ssl_iostream)) {
			/* this isn't really a "connection lost", but that we
			   don't trust the remote's SSL certificate. don't
			   retry. */
			http_client_connection_abort_error(_conn,
				HTTP_CLIENT_REQUEST_ERROR_BAD_RESPONSE, error);
			return;
		}
	}

	conn->lost_prematurely = (conn->conn.input != NULL &&
		conn->conn.input->v_offset == 0 &&
		i_stream_get_data_size(conn->conn.input) == 0);
	http_client_connection_abort_temp_error(_conn,
		HTTP_CLIENT_REQUEST_ERROR_CONNECTION_LOST, error);
}

int http_client_connection_check_ready(struct http_client_connection *conn)
{
	const struct http_client_settings *set = &conn->peer->client->set;
	int ret;

	if (conn->in_req_callback) {
		/* this can happen when a nested ioloop is created inside request
		   callback. we currently don't reuse connections that are occupied
		   this way, but theoretically we could, although that would add
		   quite a bit of complexity.
		 */
		return 0;
	}

	if (!conn->connected || conn->output_locked || conn->output_broken ||
		conn->close_indicated || conn->tunneling ||
		http_client_connection_count_pending(conn) >=
			set->max_pipelined_requests)
		return 0;

	if (conn->last_ioloop != NULL && conn->last_ioloop != current_ioloop) {
		conn->last_ioloop = current_ioloop;
		/* Active ioloop is different from what we saw earlier;
		   we may have missed a disconnection event on this connection.
		   Verify status by reading from connection. */
		if ((ret=i_stream_read(conn->conn.input)) == -1) {
			int stream_errno = conn->conn.input->stream_errno;

			i_assert(conn->conn.input->stream_errno != 0 || conn->conn.input->eof);
			http_client_connection_lost(&conn,
				t_strdup_printf("read(%s) failed: %s",
						i_stream_get_name(conn->conn.input),
						stream_errno != 0 ?
						i_stream_get_error(conn->conn.input) :
						"EOF"));
			return -1;
		}

		/* we may have read some data */
		if (i_stream_get_data_size(conn->conn.input) > 0)
			i_stream_set_input_pending(conn->conn.input, TRUE);
	}
	return 1;
}

static void
http_client_connection_detach_peer(struct http_client_connection *conn)
{
	struct http_client_peer *peer = conn->peer;
	struct http_client_connection *const *conn_idx;
	ARRAY_TYPE(http_client_connection) *conn_arr;
	bool found = FALSE;

	if (peer == NULL)
		return;

	http_client_peer_ref(peer);
	conn_arr = &peer->conns;
	array_foreach(conn_arr, conn_idx) {
		if (*conn_idx == conn) {
			array_delete(conn_arr, array_foreach_idx(conn_arr, conn_idx), 1);
			found = TRUE;
			break;
		}
	}

	i_assert(found);

	conn->peer = NULL;
	e_debug(conn->event, "Detached peer");

	if (conn->connect_succeeded)
		http_client_peer_connection_lost(peer, conn->lost_prematurely);
	http_client_peer_unref(&peer);
}

static void
http_client_connection_idle_timeout(struct http_client_connection *conn)
{
	e_debug(conn->event, "Idle connection timed out");

	/* cannot get here unless connection was established at some point */
	i_assert(conn->connect_succeeded);

	http_client_connection_close(&conn);
}

void http_client_connection_lost_peer(struct http_client_connection *conn)
{
	struct http_client_peer *peer = conn->peer;
	struct http_client *client = peer->client;
	const struct http_client_settings *set = &client->set;
	struct http_client_peer_pool *ppool = conn->ppool;
	struct http_client_peer_shared *pshared = ppool->peer;
	struct http_client_context *cctx = pshared->cctx;
	unsigned int timeout, count;

	if (!conn->connected) {
		http_client_connection_unref(&conn);
		return;
	}

	i_assert(!conn->in_req_callback);

	if (conn->to_idle == NULL) {
		count = array_count(&ppool->conns);
		i_assert(count > 0);

		/* set timeout for this connection */
		if (count > http_client_peer_shared_max_connections(pshared)) {
			/* instant death for (urgent) connections above limit */
			timeout = 0;
		} else {
			unsigned int idle_count = array_count(&ppool->idle_conns);

			/* kill duplicate connections quicker;
				 linearly based on the number of connections */
			i_assert(count >= idle_count + 1);
			timeout = (set->max_parallel_connections - idle_count) *
				(set->max_idle_time_msecs / set->max_parallel_connections);
		}

		e_debug(conn->event,
			"Lost peer; going idle (timeout = %u msecs)",
			timeout);

		conn->to_idle = timeout_add_to(cctx->ioloop, timeout,
			http_client_connection_idle_timeout, conn);
		array_append(&ppool->idle_conns, &conn, 1);
	} else {
		e_debug(conn->event, "Lost peer; already idle");
	}

	http_client_connection_detach_peer(conn);
}

void http_client_connection_check_idle(struct http_client_connection *conn)
{
	struct http_client_peer *peer;
	struct http_client_peer_pool *ppool = conn->ppool;
	struct http_client_context *cctx = ppool->peer->cctx;
	struct http_client *client;
	const struct http_client_settings *set;
	unsigned int timeout, count;

	peer = conn->peer;
	if (peer == NULL) {
		i_assert(conn->to_idle != NULL);
		return;
	}

	if (conn->to_idle != NULL) {
		/* timeout already set */
		return;
	}

	client = peer->client;
	set = &client->set;

	if (conn->connected &&
		array_is_created(&conn->request_wait_list) &&
		array_count(&conn->request_wait_list) == 0 &&
		!conn->in_req_callback &&
		conn->incoming_payload == NULL &&
		set->max_idle_time_msecs > 0) {

		i_assert(peer != NULL);
		client = peer->client;

		if (client->waiting)
			io_loop_stop(client->ioloop);

		count = array_count(&peer->conns);
		i_assert(count > 0);

		/* set timeout for this connection */
		if (count > set->max_parallel_connections) {
			/* instant death for (urgent) connections above limit */
			timeout = 0;
		} else {
			unsigned int idle_count = array_count(&ppool->idle_conns);

			/* kill duplicate connections quicker;
				 linearly based on the number of connections */
			i_assert(array_count(&ppool->conns) >= idle_count + 1);
			timeout = (set->max_parallel_connections - idle_count) *
				(set->max_idle_time_msecs / set->max_parallel_connections);
		}

		e_debug(conn->event, 
			"No more requests queued; going idle (timeout = %u msecs)",
			timeout);

		conn->to_idle = timeout_add_to(cctx->ioloop, timeout,
			http_client_connection_idle_timeout, conn);

		array_append(&ppool->idle_conns, &conn, 1);
	}
}

static void
http_client_connection_stop_idle(struct http_client_connection *conn)
{
	struct http_client_connection *const *conn_idx;
	ARRAY_TYPE(http_client_connection) *conn_arr;

	if (conn->to_idle != NULL)
		timeout_remove(&conn->to_idle);

	conn_arr = &conn->ppool->idle_conns;
	array_foreach(conn_arr, conn_idx) {
		if (*conn_idx == conn) {
			array_delete(conn_arr, array_foreach_idx(conn_arr, conn_idx), 1);
			break;
		}
	}
}

void http_client_connection_claim_idle(struct http_client_connection *conn,
	struct http_client_peer *peer)
{
	e_debug(conn->event, "Claimed as idle");

	i_assert(peer->ppool == conn->ppool);
	http_client_connection_stop_idle(conn);

	if (conn->peer == NULL || conn->peer != peer) {
		http_client_connection_detach_peer(conn);

		conn->peer = peer;
		conn->debug = peer->client->set.debug;
		array_append(&peer->conns, &conn, 1);
	}
}

static void
http_client_connection_request_timeout(struct http_client_connection *conn)
{
	conn->conn.input->stream_errno = ETIMEDOUT;
	http_client_connection_abort_temp_error(&conn,
		HTTP_CLIENT_REQUEST_ERROR_TIMED_OUT, "Request timed out");
}

void http_client_connection_start_request_timeout(
	struct http_client_connection *conn)
{
	struct http_client_context *cctx = conn->ppool->peer->cctx;
	struct http_client_peer *peer = conn->peer;
	struct http_client *client = peer->client;
	const struct http_client_settings *set = &client->set;
	unsigned int timeout_msecs =
		set->request_timeout_msecs;

	if (conn->pending_request != NULL)
		return;

	i_assert(array_is_created(&conn->request_wait_list));
	if (array_count(&conn->request_wait_list) > 0) {
		struct http_client_request *const *requestp;
		requestp = array_idx(&conn->request_wait_list, 0);
		timeout_msecs = (*requestp)->attempt_timeout_msecs;
	}

	if (timeout_msecs == 0)
		;
	else if (conn->to_requests != NULL)
		timeout_reset(conn->to_requests);
	else {
		conn->to_requests = timeout_add_to(
			cctx->ioloop, timeout_msecs,
			http_client_connection_request_timeout, conn);
	}
}

void http_client_connection_reset_request_timeout(
	struct http_client_connection *conn)
{
	if (conn->to_requests != NULL)
		timeout_reset(conn->to_requests);
}

void http_client_connection_stop_request_timeout(
	struct http_client_connection *conn)
{
	timeout_remove(&conn->to_requests);
}

static void
http_client_connection_continue_timeout(struct http_client_connection *conn)
{
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	struct http_client_request *const *wait_reqs;
	struct http_client_request *req;
	unsigned int wait_count;
	const char *error;

	i_assert(conn->pending_request == NULL);

	timeout_remove(&conn->to_response);
	pshared->no_payload_sync = TRUE;

	e_debug(conn->event, 
		"Expected 100-continue response timed out; sending payload anyway");

	wait_reqs = array_get(&conn->request_wait_list, &wait_count);
	i_assert(wait_count == 1);
	req = wait_reqs[wait_count-1];

	req->payload_sync_continue = TRUE;
	if (http_client_request_send_more(req, FALSE, &error) < 0) {
		http_client_connection_lost(&conn,
			t_strdup_printf("Failed to send request: %s", error));
	}
}

int http_client_connection_next_request(struct http_client_connection *conn)
{
	struct http_client_peer *peer = conn->peer;
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	struct http_client_context *cctx = pshared->cctx;
	struct http_client_request *req = NULL;
	const char *error;
	bool pipelined;
	int ret;

	if ((ret=http_client_connection_check_ready(conn)) <= 0) {
		if (ret == 0) {
			e_debug(conn->event, "Not ready for next request");
		}
		return ret;
	}

	/* claim request, but no urgent request can be second in line */
	pipelined = array_count(&conn->request_wait_list) > 0 ||
		conn->pending_request != NULL;
	req = http_client_peer_claim_request(peer, pipelined);
	if (req == NULL)
		return 0;	

	i_assert(req->state == HTTP_REQUEST_STATE_QUEUED);

	http_client_connection_stop_idle(conn);

	req->payload_sync_continue = FALSE;
	if (pshared->no_payload_sync)
		req->payload_sync = FALSE;

	/* add request to wait list and add a reference */
	array_append(&conn->request_wait_list, &req, 1);
	http_client_connection_ref_request(conn, req);

	e_debug(conn->event, "Claimed request %s",
		http_client_request_label(req));

	if (http_client_request_send(req, pipelined, &error) < 0) {
		http_client_connection_lost(&conn,
			t_strdup_printf("Failed to send request: %s", error));
		return -1;
	}

	if (req->connect_tunnel)
		conn->tunneling = TRUE;

	/* RFC 7231, Section 5.1.1: Expect

		 o  A client that sends a 100-continue expectation is not required to
		    wait for any specific length of time; such a client MAY proceed to
		    send the message body even if it has not yet received a response.
		    Furthermore, since 100 (Continue) responses cannot be sent through
		    an HTTP/1.0 intermediary, such a client SHOULD NOT wait for an
		    indefinite period before sending the message body.
	 */
	if (req->payload_sync && !pshared->seen_100_response) {
		i_assert(!pipelined);
		i_assert(req->payload_chunked || req->payload_size > 0);
		i_assert(conn->to_response == NULL);
		conn->to_response = timeout_add_to(cctx->ioloop,
			HTTP_CLIENT_CONTINUE_TIMEOUT_MSECS,
			http_client_connection_continue_timeout, conn);
	}

	return 1;
}

static void http_client_connection_destroy(struct connection *_conn)
{
	struct http_client_connection *conn =
		(struct http_client_connection *)_conn;
	const char *error;
	unsigned int msecs;

	switch (_conn->disconnect_reason) {
	case CONNECTION_DISCONNECT_CONNECT_TIMEOUT:
		if (conn->connected_timestamp.tv_sec == 0) {
			msecs = timeval_diff_msecs(&ioloop_timeval,
						   &conn->connect_start_timestamp);
			error = t_strdup_printf(
				"connect(%s) failed: Connection timed out in %u.%03u secs",
				_conn->name, msecs/1000, msecs%1000);
		} else {
			msecs = timeval_diff_msecs(&ioloop_timeval,
						   &conn->connected_timestamp);
			error = t_strdup_printf(
				"SSL handshaking with %s failed: Connection timed out in %u.%03u secs",
				_conn->name, msecs/1000, msecs%1000);
		}
		e_debug(conn->event, "%s", error);
		http_client_connection_failure(conn, error);
		break;
	case CONNECTION_DISCONNECT_CONN_CLOSED:
		if (conn->connect_failed) {
			i_assert(!array_is_created(&conn->request_wait_list) ||
				array_count(&conn->request_wait_list) == 0);
			break;
		}
		http_client_connection_lost(&conn,
			(_conn->input == NULL ? NULL :
				i_stream_get_error(_conn->input)));
		return;
	default:
		break;
	}

	http_client_connection_close(&conn);
}

static void http_client_payload_finished(struct http_client_connection *conn)
{
	struct http_client_context *cctx = conn->ppool->peer->cctx;

	timeout_remove(&conn->to_input);
	conn->conn.io = io_add_istream_to(cctx->ioloop, conn->conn.input,
					  http_client_connection_input,
					  &conn->conn);
	if (array_count(&conn->request_wait_list) > 0)
		http_client_connection_start_request_timeout(conn);
}

static void
http_client_payload_destroyed_timeout(struct http_client_connection *conn)
{
	if (conn->close_indicated) {
		http_client_connection_server_close(&conn);
		return;
	}
	http_client_connection_input(&conn->conn);
}

static void http_client_payload_destroyed(struct http_client_request *req)
{
	struct http_client_connection *conn = req->conn;
	struct http_client_context *cctx = conn->ppool->peer->cctx;

	i_assert(conn != NULL);
	i_assert(conn->pending_request == req);
	i_assert(conn->incoming_payload != NULL);
	i_assert(conn->conn.io == NULL);

	e_debug(conn->event,
		"Response payload stream destroyed (%u ms after initial response)",
		timeval_diff_msecs(&ioloop_timeval, &req->response_time));

	/* caller is allowed to change the socket fd to blocking while reading
	   the payload. make sure here that it's switched back. */
	net_set_nonblock(conn->conn.fd_in, TRUE);

	/* drop reference from connection */
	if (http_client_connection_unref_request(conn, &conn->pending_request)) {
		/* finish request if not already aborted */
		http_client_request_finish(req);
	}

	conn->incoming_payload = NULL;

	/* input stream may have pending input. make sure input handler
	   gets called (but don't do it directly, since we get get here
	   somewhere from the API user's code, which we can't really know what
	   state it is in). this call also triggers sending a new request if
	   necessary. */
	if (!conn->disconnected) {
		conn->to_input = timeout_add_short_to(
			cctx->ioloop, 0,
			http_client_payload_destroyed_timeout, conn);
	}

	/* room for new requests */
	if (http_client_connection_check_ready(conn) > 0)
		http_client_peer_trigger_request_handler(conn->peer);
}

void http_client_connection_request_destroyed(
	struct http_client_connection *conn, struct http_client_request *req)
{
	struct istream *payload;

	i_assert(req->conn == conn);
	if (conn->pending_request != req)
		return;

	e_debug(conn->event, "Pending request destroyed prematurely");

	payload = conn->incoming_payload;
	if (payload == NULL) {
		/* payload already gone */
		return;
	}

	/* destroy the payload, so that the timeout istream is closed */
	i_stream_ref(payload);
	i_stream_destroy(&payload);

	payload = conn->incoming_payload;
	if (payload == NULL) {
		/* not going to happen, but check for it anyway */
		return;
	}

	/* the application still holds a reference to the payload stream, but it
	   is closed and we don't care about it anymore, so act as though it is
	   destroyed. */
	i_stream_remove_destroy_callback(payload,
					 http_client_payload_destroyed);
	http_client_payload_destroyed(req);
}

static bool
http_client_connection_return_response(
	struct http_client_connection *conn,
	struct http_client_request *req,
	struct http_response *response)
{
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	struct http_client_context *cctx = pshared->cctx;
	struct istream *payload;
	bool retrying;

	i_assert(!conn->in_req_callback);
	i_assert(conn->incoming_payload == NULL);
	i_assert(conn->pending_request == NULL);

	http_client_connection_ref(conn);
	http_client_connection_ref_request(conn, req);
	req->state = HTTP_REQUEST_STATE_GOT_RESPONSE;

	if (response->payload != NULL) {
		/* wrap the stream to capture the destroy event without
		   destroying the actual payload stream. we are already expected
		   to be on the correct ioloop, so there should be no need to
		   switch the stream's ioloop here. */
		conn->incoming_payload = response->payload =
			i_stream_create_timeout(response->payload,
				req->attempt_timeout_msecs);
		i_stream_add_destroy_callback(response->payload,
					      http_client_payload_destroyed,
					      req);
		/* the callback may add its own I/O, so we need to remove
		   our one before calling it */
		io_remove(&conn->conn.io);
		/* we've received the request itself, and we can't reset the
		   timeout during the payload reading. */
		http_client_connection_stop_request_timeout(conn);
	}
	
	conn->in_req_callback = TRUE;
	retrying = !http_client_request_callback(req, response);
	if (conn->disconnected) {
		/* the callback managed to get this connection disconnected */
		if (!retrying)
			http_client_request_finish(req);
		http_client_connection_unref_request(conn, &req);
		http_client_connection_unref(&conn);
		return FALSE;
	}
	conn->in_req_callback = FALSE;

	if (retrying) {
		/* retrying, don't destroy the request */
		if (response->payload != NULL) {
			i_stream_remove_destroy_callback(conn->incoming_payload,
							 http_client_payload_destroyed);
			i_stream_unref(&conn->incoming_payload);
			conn->conn.io = io_add_istream_to(cctx->ioloop,
							  conn->conn.input,
							  http_client_connection_input,
							  &conn->conn);
		}
		http_client_connection_unref_request(conn, &req);
		return http_client_connection_unref(&conn);
	}

	if (response->payload != NULL) {
		req->state = HTTP_REQUEST_STATE_PAYLOAD_IN;
		payload = response->payload;
		response->payload = NULL;

		/* maintain request reference while payload is pending */
		conn->pending_request = req;

		/* request is dereferenced in payload destroy callback */
		i_stream_unref(&payload);

		if (conn->to_input != NULL && conn->conn.input != NULL) {
			/* already finished reading the payload */
			http_client_payload_finished(conn);
		}
	} else {
		http_client_request_finish(req);
		http_client_connection_unref_request(conn, &req);
	}

	if (conn->incoming_payload == NULL && conn->conn.input != NULL) {
		i_assert(conn->conn.io != NULL ||
			pshared->addr.type == HTTP_CLIENT_PEER_ADDR_RAW);
		return http_client_connection_unref(&conn);
	}
	http_client_connection_unref(&conn);
	return FALSE;
}

static void http_client_connection_input(struct connection *_conn)
{
	struct http_client_connection *conn =
		(struct http_client_connection *)_conn;
	struct http_client_peer *peer = conn->peer;
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	struct http_response response;
	struct http_client_request *const *reqs;
	struct http_client_request *req = NULL, *req_ref;
	enum http_response_payload_type payload_type;
	unsigned int count;
	int finished = 0, ret;
	const char *error;

	i_assert(conn->incoming_payload == NULL);

	_conn->last_input = ioloop_time;

	if (conn->ssl_iostream != NULL &&
		!ssl_iostream_is_handshaked(conn->ssl_iostream)) {
		/* finish SSL negotiation by reading from input stream */
		while ((ret=i_stream_read(conn->conn.input)) > 0 || ret == -2) {
			if (ssl_iostream_is_handshaked(conn->ssl_iostream))
				break;
		}
		if (ret < 0) {
			int stream_errno = conn->conn.input->stream_errno;

			/* failed somehow */
			i_assert(ret != -2);
			error = t_strdup_printf(
				"SSL handshaking with %s failed: "
				"read(%s) failed: %s",
				_conn->name,
				i_stream_get_name(conn->conn.input),
				stream_errno != 0 ?
					i_stream_get_error(conn->conn.input) : "EOF");
			http_client_connection_failure(conn, error);
			e_debug(conn->event, "%s", error);
			http_client_connection_close(&conn);
			return;
		}

		if (!ssl_iostream_is_handshaked(conn->ssl_iostream)) {
			/* not finished */
			i_assert(ret == 0);
			return;
		}

		/* ready for first request */
		http_client_connection_ready(conn);
	}

	if (conn->to_input != NULL) {
		/* We came here from a timeout added by
		   http_client_payload_destroyed(). The IO couldn't be added
		   back immediately in there, because the HTTP API user may
		   still have had its own IO pointed to the same fd. It should
		   be removed by now, so we can add it back. */
		http_client_payload_finished(conn);
		finished++;
	}

	/* we've seen activity from the server; reset request timeout */
	http_client_connection_reset_request_timeout(conn);

	/* get first waiting request */
	reqs = array_get(&conn->request_wait_list, &count);
	if (count > 0) {
		req = reqs[0];

		/* determine whether to expect a response payload */
		payload_type = http_client_request_get_payload_type(req);
	} else {
		req = NULL;
		payload_type = HTTP_RESPONSE_PAYLOAD_TYPE_ALLOWED;
	}

	/* drop connection with broken output if last possible input was
	   received */
	if (conn->output_broken && (count == 0 ||
		(count == 1 && req->state == HTTP_REQUEST_STATE_ABORTED))) {
		http_client_connection_server_close(&conn);
		return;
	}

	while ((ret=http_response_parse_next
		(conn->http_parser, payload_type, &response, &error)) > 0) {
		bool aborted, early = FALSE;

		if (req == NULL) {
			/* server sent response without any requests in the wait list */
			if (response.status == 408) {
				e_debug(conn->event,
					"Server explicitly closed connection: 408 %s",
					response.reason);
			} else {
				e_debug(conn->event,
					"Got unexpected input from server: %u %s",
					response.status, response.reason);
			}
			http_client_connection_close(&conn);
			return;
		}
		req->response_time = ioloop_timeval;

		/* Got some response; cancel response timeout */
		timeout_remove(&conn->to_response);

		/* RFC 7231, Section 6.2:

		   A client MUST be able to parse one or more 1xx responses received
		   prior to a final response, even if the client does not expect one.  A
		   user agent MAY ignore unexpected 1xx responses.
		 */
		if (req->payload_sync && response.status == 100) {
			if (req->payload_sync_continue) {
				e_debug(conn->event,
					"Got 100-continue response after timeout");
				continue;
			}

			pshared->no_payload_sync = FALSE;
			pshared->seen_100_response = TRUE;
			req->payload_sync_continue = TRUE;

			e_debug(conn->event,
				"Got expected 100-continue response");

			if (req->state == HTTP_REQUEST_STATE_ABORTED) {
				e_debug(conn->event,
					"Request aborted before sending payload was complete.");
				http_client_connection_close(&conn);
				return;
			}

			if (http_client_request_send_more(req, FALSE, &error) < 0) {
				http_client_connection_lost(&conn,
					t_strdup_printf("Failed to send request: %s", error));
			}
			return;
		} else if (response.status / 100 == 1) {
			/* ignore other 1xx for now */
			e_debug(conn->event,
				"Got unexpected %u response; ignoring", response.status);
			continue;
		} else 	if (!req->payload_sync &&
			req->state == HTTP_REQUEST_STATE_PAYLOAD_OUT) {
			/* got early response from server while we're still sending request
			   payload. we cannot recover from this reliably, so we stop sending
			   payload and close the connection once the response is processed */
			e_debug(conn->event,
				"Got early input from server; "
				"request payload not completely sent (will close connection)");
			o_stream_unset_flush_callback(conn->conn.output);
			conn->output_broken = early = TRUE;
		}

		e_debug(conn->event,
			"Got %u response for request %s (took %u ms + %u ms in queue)",
			response.status, http_client_request_label(req),
			timeval_diff_msecs(&req->response_time, &req->sent_time),
			timeval_diff_msecs(&req->sent_time, &req->submit_time));

		/* make sure connection output is unlocked if 100-continue failed */
		if (req->payload_sync && !req->payload_sync_continue) {
			e_debug(conn->event, "Unlocked output");
			conn->output_locked = FALSE;
		}

		/* remove request from queue */
		array_delete(&conn->request_wait_list, 0, 1);
		aborted = (req->state == HTTP_REQUEST_STATE_ABORTED);
		req_ref = req;
		if (!http_client_connection_unref_request(conn, &req_ref)) {
			i_assert(aborted);
			req = NULL;
		}

		conn->close_indicated = response.connection_close;

		if (!aborted) {
			bool handled = FALSE;

			/* response cannot be 2xx if request payload was not completely sent
			 */
			if (early && response.status / 100 == 2) {
				http_client_request_error(&req,
					HTTP_CLIENT_REQUEST_ERROR_BAD_RESPONSE,
					"Server responded with success response "
					"before all payload was sent");
				http_client_connection_close(&conn);
				return;
			} 

			/* don't redirect/retry if we're sending data in small
			   blocks via http_client_request_send_payload()
			   and we're not waiting for 100 continue */
			if (!req->payload_wait ||
				(req->payload_sync && !req->payload_sync_continue)) {
				/* failed Expect: */
				if (response.status == 417 && req->payload_sync) {
					/* drop Expect: continue */
					req->payload_sync = FALSE;
					conn->output_locked = FALSE;
					pshared->no_payload_sync = TRUE;
					if (http_client_request_try_retry(req))
						handled = TRUE;
				/* redirection */
				} else if (!req->client->set.no_auto_redirect &&
					response.status / 100 == 3 && response.status != 304 &&
					response.location != NULL) {
					/* redirect (possibly after delay) */
					if (http_client_request_delay_from_response(req, &response) >= 0) {
						http_client_request_redirect
							(req, response.status, response.location);
						handled = TRUE;
					}
				/* service unavailable */
				} else if (response.status == 503) {
					/* automatically retry after delay if indicated */
					if ( response.retry_after != (time_t)-1 &&
						http_client_request_delay_from_response(req, &response) > 0 &&
						http_client_request_try_retry(req))
						handled = TRUE;
				/* request timeout (by server) */
				} else if (response.status == 408) {
					/* automatically retry */
					if (http_client_request_try_retry(req))
						handled = TRUE;
					/* connection close is implicit, although server should indicate
					   that explicitly */
					conn->close_indicated = TRUE;
				}
			}

			if (!handled) {
				/* response for application */
				if (!http_client_connection_return_response
					(conn, req, &response))
					return;
			}
		}

		finished++;

		/* server closing connection? */
		if (conn->close_indicated) {
			http_client_connection_server_close(&conn);
			return;
		}

		/* get next waiting request */
		reqs = array_get(&conn->request_wait_list, &count);
		if (count > 0) {
			req = reqs[0];

			/* determine whether to expect a response payload */
			payload_type = http_client_request_get_payload_type(req);
		} else {
			/* no more requests waiting for the connection */
			req = NULL;
			payload_type = HTTP_RESPONSE_PAYLOAD_TYPE_ALLOWED;
		}

		/* drop connection with broken output if last possible input was
		   received */
		if (conn->output_broken && (count == 0 ||
			(count == 1 && req->state == HTTP_REQUEST_STATE_ABORTED))) {
			http_client_connection_server_close(&conn);
			return;
		}
	}

	if (ret <= 0 &&
	    (conn->conn.input->eof || conn->conn.input->stream_errno != 0)) {
		int stream_errno = conn->conn.input->stream_errno;
		http_client_connection_lost(&conn,
			t_strdup_printf("read(%s) failed: %s",
					i_stream_get_name(conn->conn.input),
					stream_errno != 0 ?
					i_stream_get_error(conn->conn.input) :
					"EOF"));
		return;
	}

	if (ret < 0) {
		http_client_connection_abort_error(&conn,
			HTTP_CLIENT_REQUEST_ERROR_BAD_RESPONSE, error);
		return;
	}

	if (finished > 0) {
		/* connection still alive after (at least one) request;
		   we can pipeline -> mark for subsequent connections */
		pshared->allows_pipelining = TRUE;

		/* room for new requests */
		if (peer != NULL &&
			http_client_connection_check_ready(conn) > 0)
			http_client_peer_trigger_request_handler(peer);
	}
}

int http_client_connection_output(struct http_client_connection *conn)
{
	struct http_client_request *const *reqs;
	struct ostream *output = conn->conn.output;
	unsigned int count;
	const char *error;
	int ret;

	/* we've seen activity from the server; reset request timeout */
	http_client_connection_reset_request_timeout(conn);

	if ((ret = o_stream_flush(output)) <= 0) {
		if (ret < 0) {
			http_client_connection_lost(&conn,
				t_strdup_printf("write(%s) failed: %s",
						o_stream_get_name(output),
						o_stream_get_error(output)));
		}
		return ret;
	}

	i_assert(!conn->output_broken);

	if (conn->ssl_iostream != NULL &&
		!ssl_iostream_is_handshaked(conn->ssl_iostream))
		return 1;

	reqs = array_get(&conn->request_wait_list, &count);
	if (count > 0 && conn->output_locked) {
		struct http_client_request *req = reqs[count-1];
		bool pipelined = (count > 1 || conn->pending_request != NULL);

		if (req->state == HTTP_REQUEST_STATE_ABORTED) {
			e_debug(conn->event,
				"Request aborted before sending payload was complete.");
			if (count == 1) {
				http_client_connection_close(&conn);
			} else {
				o_stream_unset_flush_callback(output);
				conn->output_broken = TRUE;
			}
			return 1;
		}

		if (!req->payload_sync || req->payload_sync_continue) {
			if (http_client_request_send_more(req, pipelined, &error) < 0) {
				http_client_connection_lost(&conn, error);
				return -1;
			}
			if (!conn->output_locked) {
				/* room for new requests */
				if (http_client_connection_check_ready(conn) > 0)
					http_client_peer_trigger_request_handler(conn->peer);
			}
		}
	}
	return 1;
}

void
http_client_connection_start_tunnel(struct http_client_connection **_conn,
	struct http_client_tunnel *tunnel)
{
	struct http_client_connection *conn = *_conn;

	i_assert(conn->tunneling);

	/* claim connection streams */
	i_zero(tunnel);
	tunnel->input = conn->conn.input;
	tunnel->output = conn->conn.output;
	tunnel->fd_in = conn->conn.fd_in;
	tunnel->fd_out = conn->conn.fd_out;

	/* detach from connection */
	conn->conn.input = NULL;
	conn->conn.output = NULL;
	conn->conn.fd_in = -1;
	conn->conn.fd_out = -1;
	conn->closing = TRUE;
	conn->connected = FALSE;
	connection_disconnect(&conn->conn);

	http_client_connection_unref(_conn);
}

static void 
http_client_connection_ready(struct http_client_connection *conn)
{
	struct http_client_peer *peer = conn->peer;
	struct http_client_peer_pool *ppool = conn->ppool;
	struct http_client_peer_shared *pshared = ppool->peer;
	ARRAY_TYPE(http_client_connection) *conn_arr;
	struct http_client_connection *const *conn_idx;
	const struct http_client_settings *set = &peer->client->set;

	e_debug(conn->event, "Ready for requests");

	/* connected */
	conn->connected = TRUE;
	conn->last_ioloop = current_ioloop;
	timeout_remove(&conn->to_connect);

	/* remove from pending list */
	conn_arr = &ppool->pending_conns;
	array_foreach(conn_arr, conn_idx) {
		if (*conn_idx == conn) {
			array_delete(conn_arr, array_foreach_idx(conn_arr, conn_idx), 1);
			break;
		}
	}

	/* indicate connection success */
	conn->connect_succeeded = TRUE;
	http_client_peer_connection_success(peer);

	/* start raw log */
	if (ppool->rawlog_dir != NULL) {
		iostream_rawlog_create(ppool->rawlog_dir,
				       &conn->conn.input, &conn->conn.output);
	}

	/* direct tunneling connections handle connect requests just by providing a
	   raw connection */
	if (pshared->addr.type == HTTP_CLIENT_PEER_ADDR_RAW) {
		struct http_client_request *req;

		
		req = http_client_peer_claim_request(conn->peer, FALSE);
		if (req != NULL) {
			struct http_response response;

			conn->tunneling = TRUE;

			i_zero(&response);
			response.status = 200;
			response.reason = "OK";

			(void)http_client_connection_return_response(conn, req, &response);
			return;
		} 
		
		e_debug(conn->event,
			"No raw connect requests pending; closing useless connection");
		http_client_connection_close(&conn);
		return;
	}

	/* start protocol I/O */
	conn->http_parser = http_response_parser_init
		(conn->conn.input, &set->response_hdr_limits, 0);
	o_stream_set_flush_callback(conn->conn.output,
    http_client_connection_output, conn);
}

static int
http_client_connection_ssl_handshaked(const char **error_r, void *context)
{
	struct http_client_connection *conn = context;
	struct http_client_peer *peer = conn->peer;
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	const struct http_client_settings *set = &peer->client->set;
	const char *error, *host = pshared->addr.a.tcp.https_name;

	if (ssl_iostream_check_cert_validity(conn->ssl_iostream, host, &error) == 0)
		e_debug(conn->event, "SSL handshake successful");
	else if (set->ssl->allow_invalid_cert) {
		e_debug(conn->event, "SSL handshake successful, "
			"ignoring invalid certificate: %s", error);
	} else {
		*error_r = error;
		return -1;
	}
	return 0;
}

static int 
http_client_connection_ssl_init(struct http_client_connection *conn,
				const char **error_r)
{
	struct http_client_peer *peer = conn->peer;
	struct http_client_peer_pool *ppool = conn->ppool;
	struct http_client_peer_shared *pshared = ppool->peer;
	const struct http_client_settings *set = &peer->client->set;
	struct ssl_iostream_settings ssl_set;
	struct ssl_iostream_context *ssl_ctx = ppool->ssl_ctx;
	const char *error;

	i_assert(ssl_ctx != NULL);

	ssl_set = *set->ssl;
	if (!set->ssl->allow_invalid_cert) {
		ssl_set.verbose_invalid_cert = TRUE;
	}

	e_debug(conn->event, "Starting SSL handshake");

	if (io_stream_create_ssl_client(ssl_ctx,
					pshared->addr.a.tcp.https_name, &ssl_set,
					&conn->conn.input, &conn->conn.output,
					&conn->ssl_iostream, &error) < 0) {
		*error_r = t_strdup_printf(
			"Couldn't initialize SSL client for %s: %s",
			conn->conn.name, error);
		return -1;
	}
	ssl_iostream_set_handshake_callback(conn->ssl_iostream,
					    http_client_connection_ssl_handshaked, conn);
	if (ssl_iostream_handshake(conn->ssl_iostream) < 0) {
		*error_r = t_strdup_printf("SSL handshake to %s failed: %s",
			conn->conn.name, ssl_iostream_get_last_error(conn->ssl_iostream));
		return -1;
	}

	if (ssl_iostream_is_handshaked(conn->ssl_iostream)) {
		http_client_connection_ready(conn);
	} else {
		/* wait for handshake to complete; connection input handler does the rest
		   by reading from the input stream */
		o_stream_set_flush_callback(conn->conn.output,
			http_client_connection_output, conn);
	}
	return 0;
}

static void 
http_client_connection_connected(struct connection *_conn, bool success)
{
	struct http_client_connection *conn =
		(struct http_client_connection *)_conn;
	struct http_client_peer *peer = conn->peer;
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	const struct http_client_settings *set = &peer->client->set;
	const char *error;

	if (!success) {
		http_client_connection_failure(conn, t_strdup_printf(
			"connect(%s) failed: %m", _conn->name));
	} else {
		conn->connected_timestamp = ioloop_timeval;
		e_debug(conn->event, "Connected");

		(void)net_set_tcp_nodelay(_conn->fd_out, TRUE);
		if (set->socket_send_buffer_size > 0) {
			if (net_set_send_buffer_size(_conn->fd_out,
				set->socket_send_buffer_size) < 0)
				i_error("net_set_send_buffer_size(%"PRIuSIZE_T") failed: %m",
					set->socket_send_buffer_size);
		}
		if (set->socket_recv_buffer_size > 0) {
			if (net_set_recv_buffer_size(_conn->fd_in,
				set->socket_recv_buffer_size) < 0)
				i_error("net_set_recv_buffer_size(%"PRIuSIZE_T") failed: %m",
					set->socket_recv_buffer_size);
		}

		if (http_client_peer_addr_is_https(&pshared->addr)) {
			if (http_client_connection_ssl_init(conn, &error) < 0) {
				e_debug(conn->event, "%s", error);
				http_client_connection_failure(conn, error);
				http_client_connection_close(&conn);
			}
			return;
		}
		http_client_connection_ready(conn);
	}
}

static const struct connection_settings http_client_connection_set = {
	.input_max_size = (size_t)-1,
	.output_max_size = (size_t)-1,
	.client = TRUE,
	.delayed_unix_client_connected_callback = TRUE
};

static const struct connection_vfuncs http_client_connection_vfuncs = {
	.destroy = http_client_connection_destroy,
	.input = http_client_connection_input,
	.client_connected = http_client_connection_connected
};

struct connection_list *
http_client_connection_list_init(void)
{
	return connection_list_init
		(&http_client_connection_set, &http_client_connection_vfuncs);
}

static void
http_client_connection_delayed_connect_error(struct http_client_connection *conn)
{
	timeout_remove(&conn->to_input);
	errno = conn->connect_errno;
	http_client_connection_connected(&conn->conn, FALSE);
	http_client_connection_close(&conn);
}

static void http_client_connect_timeout(struct http_client_connection *conn)
{
	conn->conn.disconnect_reason = CONNECTION_DISCONNECT_CONNECT_TIMEOUT;
	http_client_connection_destroy(&conn->conn);
}

static void
http_client_connection_connect(struct http_client_connection *conn,
	unsigned int timeout_msecs)
{
	struct http_client_context *cctx = conn->ppool->peer->cctx;

	conn->connect_start_timestamp = ioloop_timeval;
	if (connection_client_connect(&conn->conn) < 0) {
		conn->connect_errno = errno;
		e_debug(conn->event, "Connect failed: %m");
		conn->to_input = timeout_add_short_to(cctx->ioloop, 0,
			http_client_connection_delayed_connect_error, conn);
		return;
	}
	connection_switch_ioloop_to(&conn->conn, cctx->ioloop);

	/* don't use connection.h timeout because we want this timeout
	   to include also the SSL handshake */
	if (timeout_msecs > 0) {
		conn->to_connect = timeout_add_to(
			cctx->ioloop, timeout_msecs,
			http_client_connect_timeout, conn);
	}
}

static void
http_client_connect_tunnel_timeout(struct http_client_connection *conn)
{
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	const char *error, *name = http_client_peer_addr2str(&pshared->addr);
	unsigned int msecs;

	msecs = timeval_diff_msecs(&ioloop_timeval,
				   &conn->connect_start_timestamp);
	error = t_strdup_printf(
		"Tunnel connect(%s) failed: "
		"Connection timed out in %u.%03u secs",
		name, msecs/1000, msecs%1000);

	e_debug(conn->event, "%s", error);
	http_client_connection_failure(conn, error);
	http_client_connection_close(&conn);
}

static void
http_client_connection_tunnel_response(const struct http_response *response,
			       struct http_client_connection *conn)
{
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	struct http_client_context *cctx = pshared->cctx;
	struct http_client_tunnel tunnel;
	const char *name = http_client_peer_addr2str(&pshared->addr);
	struct http_client_request *req = conn->connect_request;

	conn->connect_request = NULL;

	if (response->status != 200) {
		http_client_connection_failure(conn, t_strdup_printf(
			"Tunnel connect(%s) failed: %s", name,
				http_response_get_message(response)));
		return;
	}

	http_client_request_start_tunnel(req, &tunnel);

	connection_init_from_streams(cctx->conn_list, &conn->conn,
				     name, tunnel.input, tunnel.output);
	connection_switch_ioloop_to(&conn->conn, cctx->ioloop);
	i_stream_unref(&tunnel.input);
	o_stream_unref(&tunnel.output);
	conn->connect_initialized = TRUE;
}

static void
http_client_connection_connect_tunnel(struct http_client_connection *conn,
	const struct ip_addr *ip, in_port_t port,
	unsigned int timeout_msecs)
{
	struct http_client_context *cctx = conn->ppool->peer->cctx;
	struct http_client *client = conn->peer->client;

	conn->connect_start_timestamp = ioloop_timeval;

	conn->connect_request = http_client_request_connect_ip
		(client, ip, port, http_client_connection_tunnel_response, conn);
	http_client_request_set_urgent(conn->connect_request);
	http_client_request_submit(conn->connect_request);

	/* don't use connection.h timeout because we want this timeout
	   to include also the SSL handshake */
	if (timeout_msecs > 0) {
		conn->to_connect = timeout_add_to(
			cctx->ioloop, timeout_msecs,
			http_client_connect_tunnel_timeout, conn);
	}
}

struct http_client_connection *
http_client_connection_create(struct http_client_peer *peer)
{
	struct http_client_peer_shared *pshared = peer->shared;
	struct http_client_peer_pool *ppool = peer->ppool;
	struct http_client_context *cctx = pshared->cctx;
	struct http_client *client = peer->client;
	const struct http_client_settings *set = &client->set;
	struct http_client_connection *conn;
	static unsigned int id = 0;
	const struct http_client_peer_addr *addr = &pshared->addr;
	const char *conn_type = "UNKNOWN";
	unsigned int timeout_msecs;

	switch (pshared->addr.type) {
	case HTTP_CLIENT_PEER_ADDR_HTTP:
		conn_type = "HTTP";
		break;
	case HTTP_CLIENT_PEER_ADDR_HTTPS:
		conn_type = "HTTPS";
		break;
	case HTTP_CLIENT_PEER_ADDR_HTTPS_TUNNEL:
		conn_type = "Tunneled HTTPS";
		break;
	case HTTP_CLIENT_PEER_ADDR_RAW:
		conn_type = "Raw";
		break;
	case HTTP_CLIENT_PEER_ADDR_UNIX:
		conn_type = "Unix";
		break;
	}

	timeout_msecs = set->connect_timeout_msecs;
	if (timeout_msecs == 0)
		timeout_msecs = set->request_timeout_msecs;

	conn = i_new(struct http_client_connection, 1);
	conn->refcount = 1;
	conn->id = id++;
	conn->ppool = ppool;
	conn->peer = peer;
	conn->debug = client->set.debug;
	if (pshared->addr.type != HTTP_CLIENT_PEER_ADDR_RAW)
		i_array_init(&conn->request_wait_list, 16);
	conn->io_wait_timer = io_wait_timer_add_to(cctx->ioloop);

	conn->label = i_strdup_printf("%s [%d]",
		http_client_peer_shared_label(pshared), conn->id);
	conn->event = event_create(peer->client->event);
	event_set_append_log_prefix(conn->event,
		t_strdup_printf("conn %s: ", conn->label));

	switch (pshared->addr.type) {
	case HTTP_CLIENT_PEER_ADDR_HTTPS_TUNNEL:
		http_client_connection_connect_tunnel
			(conn, &addr->a.tcp.ip, addr->a.tcp.port, timeout_msecs);
		break;
	case HTTP_CLIENT_PEER_ADDR_UNIX:
		connection_init_client_unix(cctx->conn_list, &conn->conn,
			addr->a.un.path);
		conn->connect_initialized = TRUE;
		http_client_connection_connect(conn, timeout_msecs);
		break;
	default:
		connection_init_client_ip(cctx->conn_list, &conn->conn,
			&addr->a.tcp.ip, addr->a.tcp.port);
		conn->connect_initialized = TRUE;
		http_client_connection_connect(conn, timeout_msecs);
	}

	array_append(&ppool->pending_conns, &conn, 1);
	array_append(&ppool->conns, &conn, 1);
	array_append(&peer->conns, &conn, 1);

	http_client_peer_pool_ref(ppool);

	e_debug(conn->event,
		"%s connection created (%d parallel connections exist)%s",
		conn_type, array_count(&ppool->conns),
		(conn->to_input == NULL ? "" : " [broken]"));
	return conn;
}

void http_client_connection_ref(struct http_client_connection *conn)
{
	i_assert(conn->refcount > 0);
	conn->refcount++;
}

static void
http_client_connection_disconnect(struct http_client_connection *conn)
{
	struct http_client_peer_pool *ppool = conn->ppool;
	ARRAY_TYPE(http_client_connection) *conn_arr;
	struct http_client_connection *const *conn_idx;

	if (conn->disconnected)
		return;
	conn->disconnected = TRUE;

	e_debug(conn->event, "Connection disconnect");

	conn->closing = TRUE;
	conn->connected = FALSE;

	if (conn->connect_request != NULL)
		http_client_request_abort(&conn->connect_request);

	if (conn->incoming_payload != NULL) {
		/* the stream is still accessed by lib-http caller. */
		i_stream_remove_destroy_callback(conn->incoming_payload,
						 http_client_payload_destroyed);
		conn->incoming_payload = NULL;
	}

	http_client_connection_abort_any_requests(conn);

	if (conn->http_parser != NULL)
		http_response_parser_deinit(&conn->http_parser);

	if (conn->connect_initialized)
		connection_disconnect(&conn->conn);

	io_remove(&conn->io_req_payload);
	timeout_remove(&conn->to_requests);
	timeout_remove(&conn->to_connect);
	timeout_remove(&conn->to_input);
	timeout_remove(&conn->to_response);

	/* remove this connection from the lists */
	conn_arr = &ppool->conns;
	array_foreach(conn_arr, conn_idx) {
		if (*conn_idx == conn) {
			array_delete(conn_arr, array_foreach_idx(conn_arr, conn_idx), 1);
			break;
		}
	}
	conn_arr = &ppool->pending_conns;
	array_foreach(conn_arr, conn_idx) {
		if (*conn_idx == conn) {
			array_delete(conn_arr, array_foreach_idx(conn_arr, conn_idx), 1);
			break;
		}
	}

	http_client_connection_detach_peer(conn);

	http_client_connection_stop_idle(conn); // FIXME: needed?
}

bool http_client_connection_unref(struct http_client_connection **_conn)
{
	struct http_client_connection *conn = *_conn;
	struct http_client_peer_pool *ppool = conn->ppool;

	i_assert(conn->refcount > 0);

	*_conn = NULL;

	if (--conn->refcount > 0)
		return TRUE;

	e_debug(conn->event, "Connection destroy");

	http_client_connection_disconnect(conn);

	i_assert(conn->io_req_payload == NULL);
	i_assert(conn->to_requests == NULL);
	i_assert(conn->to_connect == NULL);
	i_assert(conn->to_input == NULL);
	i_assert(conn->to_idle == NULL);
	i_assert(conn->to_response == NULL);

	if (array_is_created(&conn->request_wait_list))
		array_free(&conn->request_wait_list);

	if (conn->ssl_iostream != NULL)
		ssl_iostream_unref(&conn->ssl_iostream);
	if (conn->connect_initialized)
		connection_deinit(&conn->conn);
	io_wait_timer_remove(&conn->io_wait_timer);
	
	event_unref(&conn->event);
	i_free(conn->label);
	i_free(conn);

	http_client_peer_pool_unref(&ppool);
	return FALSE;
}

void http_client_connection_close(struct http_client_connection **_conn)
{
	struct http_client_connection *conn = *_conn;

	e_debug(conn->event, "Connection close");

	http_client_connection_disconnect(conn);

	http_client_connection_unref(_conn);
}

void http_client_connection_switch_ioloop(struct http_client_connection *conn)
{
	struct http_client_peer_shared *pshared = conn->ppool->peer;
	struct http_client_context *cctx = pshared->cctx;
	struct ioloop *ioloop = cctx->ioloop;

	if (conn->io_req_payload != NULL) {
		conn->io_req_payload =
			io_loop_move_io_to(ioloop, &conn->io_req_payload);
	}
	if (conn->to_requests != NULL) {
		conn->to_requests =
			io_loop_move_timeout_to(ioloop, &conn->to_requests);
	}
	if (conn->to_connect != NULL) {
		conn->to_connect =
			io_loop_move_timeout_to(ioloop, &conn->to_connect);
	}
	if (conn->to_input != NULL) {
		conn->to_input =
			io_loop_move_timeout_to(ioloop, &conn->to_input);
	}
	if (conn->to_idle != NULL) {
		conn->to_idle =
			io_loop_move_timeout_to(ioloop, &conn->to_idle);
	}
	if (conn->to_response != NULL) {
		conn->to_response =
			io_loop_move_timeout_to(ioloop, &conn->to_response);
	}
	if (conn->incoming_payload != NULL)
		i_stream_switch_ioloop_to(conn->incoming_payload, ioloop);
	conn->io_wait_timer =
		io_wait_timer_move_to(&conn->io_wait_timer, ioloop);
	connection_switch_ioloop_to(&conn->conn, ioloop);
}