smtp-server-connection.c

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

#include "lib.h"
#include "llist.h"
#include "array.h"
#include "str.h"
#include "ioloop.h"
#include "istream.h"
#include "ostream.h"
#include "iostream.h"
#include "connection.h"
#include "iostream-rawlog.h"
#include "iostream-ssl.h"
#include "master-service.h"
#include "master-service-ssl.h"

#include "smtp-command-parser.h"
#include "smtp-server-private.h"

const char *const smtp_server_state_names[] = {
	"GREETING",
	"XCLIENT",
	"HELO",
	"STARTTLS",
	"AUTH",
	"READY",
	"MAIL FROM",
	"RCPT TO",
	"DATA"
};

/*
 * Logging
 */

void smtp_server_connection_debug(struct smtp_server_connection *conn,
				  const char *format, ...)
{
	va_list args;

	if (conn->set.debug) {
		va_start(args, format);
		i_debug("%s-server: conn %s: %s",
			smtp_protocol_name(conn->set.protocol),
			smtp_server_connection_label(conn),
			t_strdup_vprintf(format, args));
		va_end(args);
	}
}

void smtp_server_connection_error(struct smtp_server_connection *conn,
				  const char *format, ...)
{
	va_list args;

	va_start(args, format);
	i_error("%s-server: conn %s: %s",
		smtp_protocol_name(conn->set.protocol),
		smtp_server_connection_label(conn),
		t_strdup_vprintf(format, args));
	va_end(args);
}

/*
 * Connection
 */

static void
smtp_server_connection_input(struct connection *_conn);
static int
smtp_server_connection_output(struct smtp_server_connection *conn);
static void
smtp_server_connection_disconnect(struct smtp_server_connection *conn,
				  const char *reason) ATTR_NULL(2);

static void
smtp_server_connection_update_stats(struct smtp_server_connection *conn)
{
	if (conn->conn.input != NULL)
		conn->stats.input = conn->conn.input->v_offset;
	if (conn->conn.output != NULL)
		conn->stats.output = conn->conn.output->offset;
}

const struct smtp_server_stats *
smtp_server_connection_get_stats(struct smtp_server_connection *conn)
{
	smtp_server_connection_update_stats(conn);
	return &conn->stats;
}

void smtp_server_connection_input_halt(struct smtp_server_connection *conn)
{
	if (conn->conn.io != NULL)
		io_remove(&conn->conn.io);
}

void smtp_server_connection_input_resume(struct smtp_server_connection *conn)
{
	struct smtp_server_command *cmd;
	bool cmd_locked = FALSE;

	if (conn->conn.io == NULL) {
		/* only resume when we actually can */
		if (conn->input_locked || conn->input_broken ||
			conn->disconnected)
			return;
		if (conn->command_queue_count >
			conn->server->set.max_pipelined_commands)
			return;

		/* is queued command still blocking input? */
		cmd = conn->command_queue_head;
		while (cmd != NULL) {
			if (cmd->input_locked) {
				cmd_locked = TRUE;
				break;
			}
			cmd = cmd->next;
		}
		if (cmd_locked)
			return;

		/* restore input handler */
		conn->conn.io = io_add_istream(conn->conn.input,
		    smtp_server_connection_input, &conn->conn);
	}

	if (conn->conn.io != NULL &&
		i_stream_have_bytes_left(conn->conn.input)) {
		io_set_pending(conn->conn.io);
	}
}

void smtp_server_connection_input_lock(struct smtp_server_connection *conn)
{
	conn->input_locked = TRUE;
	smtp_server_connection_input_halt(conn);
}

void smtp_server_connection_input_unlock(struct smtp_server_connection *conn)
{
	conn->input_locked = FALSE;
	smtp_server_connection_input_resume(conn);
}

#undef smtp_server_connection_input_capture
void smtp_server_connection_input_capture(struct smtp_server_connection *conn,
	smtp_server_input_callback_t *callback, void *context)
{
	i_assert(!conn->input_broken && !conn->disconnected);
	if (conn->conn.io != NULL)
		io_remove(&conn->conn.io);
	conn->conn.io = io_add_istream(conn->conn.input, *callback, context);
}

static void
smtp_server_connection_update_rawlog(struct smtp_server_connection *conn)
{
	struct stat st;

	if (conn->set.rawlog_dir == NULL)
		return;

	if (!conn->rawlog_checked) {
		conn->rawlog_checked = TRUE;
		if (stat(conn->set.rawlog_dir, &st) == 0)
			conn->rawlog_enabled = TRUE;
	}
	if (conn->rawlog_enabled) {
		iostream_rawlog_create(conn->set.rawlog_dir,
				       &conn->conn.input, &conn->conn.output);
	}
}

static void
smtp_server_connection_streams_changed(struct smtp_server_connection *conn)
{
	smtp_server_connection_update_rawlog(conn);
	smtp_command_parser_set_stream(conn->smtp_parser, conn->conn.input);

	o_stream_set_flush_callback(conn->conn.output,
		smtp_server_connection_output, conn);
	o_stream_set_flush_pending(conn->conn.output, TRUE);
}

void smtp_server_connection_set_streams(struct smtp_server_connection *conn,
	struct istream *input, struct ostream *output)
{
	struct istream *old_input = conn->conn.input;
	struct ostream *old_output = conn->conn.output;

	i_assert(conn->created_from_streams);

	conn->conn.input = input;
	i_stream_ref(conn->conn.input);

	conn->conn.output = output;
	o_stream_ref(conn->conn.output);
	o_stream_set_no_error_handling(conn->conn.output, TRUE);

	i_stream_unref(&old_input);
	o_stream_unref(&old_output);

	smtp_server_connection_streams_changed(conn);
}

void smtp_server_connection_set_ssl_streams(struct smtp_server_connection *conn,
	struct istream *input, struct ostream *output)
{
	conn->ssl_secured = TRUE;
	conn->set.capabilities &= ~SMTP_CAPABILITY_STARTTLS;

	smtp_server_connection_set_streams(conn, input, output);
}

static void
smtp_server_connection_idle_timeout(struct smtp_server_connection *conn)
{
	smtp_server_connection_terminate(&conn,
		"4.4.2", "Disconnected for inactivity");
}

void smtp_server_connection_timeout_stop(struct smtp_server_connection *conn)
{
	if (conn->to_idle != NULL) {
		smtp_server_connection_debug(conn, "Timeout stop");

		timeout_remove(&conn->to_idle);
	}
}

void smtp_server_connection_timeout_start(struct smtp_server_connection *conn)
{
	if (conn->disconnected)
		return;

	if (conn->to_idle == NULL &&
		conn->set.max_client_idle_time_msecs > 0) {
		smtp_server_connection_debug(conn, "Timeout start");

		conn->to_idle = timeout_add(
			conn->set.max_client_idle_time_msecs,
			smtp_server_connection_idle_timeout, conn);
	}
}

void smtp_server_connection_timeout_reset(struct smtp_server_connection *conn)
{
	if (conn->to_idle != NULL)
		timeout_reset(conn->to_idle);
}

static void
smtp_server_connection_timeout_update(struct smtp_server_connection *conn)
{
	struct smtp_server_command *cmd = conn->command_queue_head;

	if (cmd == NULL) {
		smtp_server_connection_timeout_start(conn);
		return;
	}

	switch (cmd->state) {
	case SMTP_SERVER_COMMAND_STATE_NEW:
		smtp_server_connection_timeout_start(conn);
		break;
	case SMTP_SERVER_COMMAND_STATE_PROCESSING:
		if (cmd->input_captured) {
			/* command updates timeout internally */
			return;
		}
		smtp_server_connection_timeout_stop(conn);
		break;
	case SMTP_SERVER_COMMAND_STATE_SUBMITTED_REPLY:
	case SMTP_SERVER_COMMAND_STATE_READY_TO_REPLY:
		smtp_server_connection_timeout_stop(conn);
		break;
	case SMTP_SERVER_COMMAND_STATE_FINISHED:
	case SMTP_SERVER_COMMAND_STATE_ABORTED:
		i_unreached();
	}
}

static void
smtp_server_connection_ready(struct smtp_server_connection *conn)
{
	conn->raw_input = conn->conn.input;
	conn->raw_output = conn->conn.output;

	smtp_server_connection_update_rawlog(conn);

	conn->smtp_parser = smtp_command_parser_init(conn->conn.input,
		&conn->server->set.command_limits);
	o_stream_set_flush_callback(conn->conn.output,
		smtp_server_connection_output, conn);

	o_stream_cork(conn->conn.output);
	if (conn->authenticated) {
		/* RFC 4954, Section 4:
		   Should the client successfully complete the exchange, the
		   SMTP server issues a 235 reply. */
		smtp_server_connection_send_line(conn,
			"235 2.7.0 Logged in.");
	} else {
		smtp_server_connection_send_line(conn,
			"220 %s %s", conn->set.hostname,
			conn->set.login_greeting);
	}
	if (!conn->corked)
		o_stream_uncork(conn->conn.output);
}

static void smtp_server_connection_destroy(struct connection *_conn)
{
	struct smtp_server_connection *conn =
		(struct smtp_server_connection *)_conn;

	smtp_server_connection_disconnect(conn, NULL);
	smtp_server_connection_unref(&conn);
}

static bool
smtp_server_connection_handle_command(struct smtp_server_connection *conn,
	const char *cmd_name, const char *cmd_params)
{
	struct smtp_server_connection *tmp_conn = conn;
	struct smtp_server_command *cmd;

	smtp_server_connection_ref(tmp_conn);
	cmd = smtp_server_command_new(tmp_conn, cmd_name, cmd_params);
	if (!smtp_server_connection_unref(&tmp_conn)) {
		/* the command start callback managed to get this connection
		   destroyed */
		return FALSE;
	}

	if (cmd != NULL && conn->command_queue_head == cmd)
		smtp_server_command_next_to_reply(cmd);

	smtp_server_connection_timeout_update(conn);
	return (cmd == NULL || !cmd->input_locked);
}

int smtp_server_connection_ssl_init(struct smtp_server_connection *conn)
{
	const char *error;

	smtp_server_connection_debug(conn, "Starting SSL handshake");

	if (conn->raw_input != conn->conn.input) {
		/* recreate rawlog after STARTTLS */
		i_stream_ref(conn->raw_input);
		o_stream_ref(conn->raw_output);
		i_stream_destroy(&conn->conn.input);
		o_stream_destroy(&conn->conn.output);
		conn->conn.input = conn->raw_input;
		conn->conn.output = conn->raw_output;
	}

	if (master_service_ssl_init(master_service,
				&conn->conn.input, &conn->conn.output,
				&conn->ssl_iostream, &error) < 0) {
		smtp_server_connection_error(conn,
			"Couldn't initialize SSL server for %s: %s",
			conn->conn.name, error);
		return -1;
	}

	if (ssl_iostream_handshake(conn->ssl_iostream) < 0) {
		smtp_server_connection_error(conn,
			"SSL handshake failed: %s",
			ssl_iostream_get_last_error(conn->ssl_iostream));
		return -1;
	}

	conn->ssl_secured = TRUE;
	conn->set.capabilities &= ~SMTP_CAPABILITY_STARTTLS;

	if (conn->ssl_start)
		smtp_server_connection_ready(conn);
	else
		smtp_server_connection_streams_changed(conn);
	return 0;
}

static void
smtp_server_connection_handle_input(struct smtp_server_connection *conn)
{
	struct smtp_server_command *pending_command;
	enum smtp_command_parse_error error_code;
	const char *cmd_name, *cmd_params, *error;
	int ret;

	/* check whether we are continuing a command */
	pending_command = NULL;
	if (conn->command_queue_tail != NULL) {
		pending_command = (conn->command_queue_tail->state ==
			SMTP_SERVER_COMMAND_STATE_SUBMITTED_REPLY ?
				conn->command_queue_tail : NULL);
	}

	smtp_server_connection_timeout_reset(conn);

	/* parse commands */
	ret = 1;
	while (!conn->closing && ret != 0) {
		while ((ret = smtp_command_parse_next(conn->smtp_parser,
			&cmd_name, &cmd_params, &error_code, &error)) > 0) {

			if (pending_command != NULL) {
				/* previous command is now fully read and ready
				   to reply */
				smtp_server_command_ready_to_reply(pending_command);
				pending_command = NULL;
			}

			smtp_server_connection_debug(conn,
				"Received new command: %s %s",
				cmd_name, cmd_params);

			conn->stats.command_count++;

			/* handle command
			   cmd may be destroyed after this */
			if (!smtp_server_connection_handle_command(conn,
				cmd_name, cmd_params))
				return;

			if (conn->disconnected)
				return;
			/* client indicated it will close after this command;
			   stop trying to read more. */
			if (conn->closing)
				break;

			if (conn->command_queue_count >=
				conn->server->set.max_pipelined_commands) {
				smtp_server_connection_input_halt(conn);
				return;
			}

			if (conn->command_queue_tail != NULL) {
				pending_command = (conn->command_queue_tail->state ==
					SMTP_SERVER_COMMAND_STATE_SUBMITTED_REPLY ?
						conn->command_queue_tail : NULL);
			}
		}

		if (ret < 0 && conn->conn.input->eof) {
			int stream_errno = conn->conn.input->stream_errno;
			if (stream_errno != 0 && stream_errno != EPIPE &&
				stream_errno != ECONNRESET) {
				smtp_server_connection_error(conn,
					"Connection lost: read(%s) failed: %s",
					i_stream_get_name(conn->conn.input),
					i_stream_get_error(conn->conn.input));
				smtp_server_connection_close(&conn,
					"Read failure");
			} else {
				smtp_server_connection_debug(conn,
					"Connection lost: Remote disconnected");

				if (conn->command_queue_head == NULL) {
					/* no pending commands; close */
					smtp_server_connection_close(&conn,
						"Remote closed connection");
				} else if (conn->command_queue_head->state <
					SMTP_SERVER_COMMAND_STATE_SUBMITTED_REPLY) {
					/* unfinished command; close */
					smtp_server_connection_close(&conn,
						"Remote closed connection unexpectedly");
				} else {
					/* a command is still processing;
					   only drop input io for now */
					conn->input_broken = TRUE;
					smtp_server_connection_input_halt(conn);
				}
			}
			return;
		}

		if (ret < 0) {
			struct smtp_server_command *cmd;

			smtp_server_connection_debug(conn,
				"Client sent invalid command: %s", error);

			switch (error_code) {
			case SMTP_COMMAND_PARSE_ERROR_BROKEN_COMMAND:
				conn->input_broken = TRUE;
				/* fall through */
			case SMTP_COMMAND_PARSE_ERROR_BAD_COMMAND:
				cmd = smtp_server_command_alloc(conn);
				smtp_server_command_fail(cmd,
					500, "5.5.2", "Invalid command syntax");
				break;
			case SMTP_COMMAND_PARSE_ERROR_LINE_TOO_LONG:
				cmd = smtp_server_command_alloc(conn);
				smtp_server_command_fail(cmd,
					500, "5.5.2", "Line too long");
				break;
			case SMTP_COMMAND_PARSE_ERROR_DATA_TOO_LARGE:
				/* Command data size exceeds the absolute limit;
				   i.e. beyond which we don't even want to skip
				   data anymore. The command error is usually
				   already submitted by the application and sent
				   to the client. */
				smtp_server_connection_close(&conn,
					"Command data size exceeds absolute limit");
				return;
			case SMTP_COMMAND_PARSE_ERROR_BROKEN_STREAM:
				smtp_server_connection_close(&conn,
					"Command data ended prematurely");
				return;
			default:
				i_unreached();
			}
		}

		if (conn->disconnected)
			return;
		if (conn->input_broken || conn->closing) {
			smtp_server_connection_input_halt(conn);
			return;
		}

		if (ret == 0 && pending_command != NULL &&
			!smtp_command_parser_pending_data(conn->smtp_parser)) {
			/* previous command is now fully read and ready to
			   reply */
			smtp_server_command_ready_to_reply(pending_command);
		}
	}
}

static void smtp_server_connection_input(struct connection *_conn)
{
	struct smtp_server_connection *conn =
		(struct smtp_server_connection *)_conn;

	i_assert(!conn->input_broken);

	if (conn->handling_input)
		return;

	smtp_server_connection_timeout_reset(conn);

	if (conn->ssl_start && conn->ssl_iostream == NULL) {
		if (smtp_server_connection_ssl_init(conn) < 0) {
			smtp_server_connection_close(&conn,
				"SSL Initialization failed");
			return;
		}
		if (conn->halted) {
			smtp_server_connection_input_lock(conn);
			return;
		}
	}
	i_assert(!conn->halted);


	if (conn->command_queue_count >
		conn->server->set.max_pipelined_commands) {
		smtp_server_connection_input_halt(conn);
		return;
	}

	smtp_server_connection_ref(conn);
	conn->handling_input = TRUE;
	if (conn->callbacks != NULL &&
		conn->callbacks->conn_cmd_input_pre != NULL) {
		conn->callbacks->conn_cmd_input_pre(conn->context);
	}
	smtp_server_connection_handle_input(conn);
	if (conn->callbacks != NULL &&
		conn->callbacks->conn_cmd_input_post != NULL) {
		conn->callbacks->conn_cmd_input_post(conn->context);
	}
	conn->handling_input = FALSE;
	smtp_server_connection_unref(&conn);
}

bool smtp_server_connection_pending_command_data(
	struct smtp_server_connection *conn)
{
	if (conn->smtp_parser == NULL)
		return FALSE;
	return smtp_command_parser_pending_data(conn->smtp_parser);
}

/*
 * Command reply handling
 */

static bool
smtp_server_connection_next_reply(struct smtp_server_connection *conn)
{
	struct smtp_server_command *cmd;
	const char *error = NULL;
	unsigned int i;

	cmd = conn->command_queue_head;
	if (cmd == NULL) {
		/* no commands pending */
		smtp_server_connection_debug(conn,
			"No more commands pending");
		return FALSE;
	}

	if (cmd->state < SMTP_SERVER_COMMAND_STATE_READY_TO_REPLY) {
		smtp_server_command_next_to_reply(cmd);
		return FALSE;
	}

	i_assert(cmd->state == SMTP_SERVER_COMMAND_STATE_READY_TO_REPLY &&
		 array_is_created(&cmd->replies));

	smtp_server_command_completed(cmd);

	/* send command replies */
	// FIXME: handle LMTP DATA command with enormous number of recipients;
	// i.e. don't keep filling output stream with replies indefinitely.
	for (i = 0; i < cmd->replies_expected; i++) {
		struct smtp_server_reply *reply;

		reply = array_idx_modifiable(&cmd->replies, i);

		if (!reply->submitted) {
			i_assert(!reply->sent);
			cmd->state = SMTP_SERVER_COMMAND_STATE_PROCESSING;
			break;
		}
		if (smtp_server_reply_send(reply, &error) < 0) {
			if (error != NULL) {
				smtp_server_connection_error(conn,
					"Failed to send reply: %s", error);
				smtp_server_connection_close(&conn,
					"Write failure");
			} else {
				smtp_server_connection_debug(conn,
					"Failed to send reply: "
					"Remote disconnected");
				smtp_server_connection_close(&conn,
					"Remote closed connection");
			}
			return FALSE;
		}
	}
	if (cmd->state == SMTP_SERVER_COMMAND_STATE_PROCESSING)
		return FALSE;

	smtp_server_command_finished(cmd);
	return TRUE;
}

void smtp_server_connection_cork(struct smtp_server_connection *conn)
{
	conn->corked = TRUE;
	if (conn->conn.output != NULL)
		o_stream_cork(conn->conn.output);
}

void smtp_server_connection_uncork(struct smtp_server_connection *conn)
{
	if (conn->conn.output != NULL) {
		o_stream_uncork(conn->conn.output);
		smtp_server_connection_trigger_output(conn);
	}
	conn->corked = FALSE;
}

static void
smtp_server_connection_send_replies(struct smtp_server_connection *conn)
{
	/* send more replies until no more replies remain, the output
	   blocks again, or the connection is closed */
	while (!conn->disconnected && smtp_server_connection_next_reply(conn));

	smtp_server_connection_timeout_update(conn);

	/* accept more commands if possible */
	smtp_server_connection_input_resume(conn);
}

int smtp_server_connection_flush(struct smtp_server_connection *conn)
{
	struct ostream *output = conn->conn.output;
	int ret;

	if ((ret = o_stream_flush(output)) <= 0) {
		if (ret < 0) {
			if (errno != EPIPE && errno != ECONNRESET) {
				smtp_server_connection_error(conn,
					"Connection lost: write(%s) failed: %s",
					o_stream_get_name(output),
					o_stream_get_error(output));
				smtp_server_connection_close(&conn,
					"Write failure");
			} else {
				smtp_server_connection_debug(conn,
					"Connection lost: Remote disconnected");
				smtp_server_connection_close(&conn,
					"Remote closed connection unexpectedly");
			}
		}
		return ret;
	}
	return 1;
}

static int
smtp_server_connection_output(struct smtp_server_connection *conn)
{
	int ret;

	smtp_server_connection_debug(conn,
		"Sending replies");

	smtp_server_connection_ref(conn);
	o_stream_cork(conn->conn.output);
	if ((ret=smtp_server_connection_flush(conn)) > 0) {
		smtp_server_connection_timeout_reset(conn);
		smtp_server_connection_send_replies(conn);
	}
	if (!conn->corked && conn->conn.output != NULL)
		o_stream_uncork(conn->conn.output);
	smtp_server_connection_unref(&conn);
	return ret;
}

void smtp_server_connection_trigger_output(
	struct smtp_server_connection *conn)
{
	if (conn->conn.output != NULL) {
		smtp_server_connection_debug(conn,
			"Trigger output");
		o_stream_set_flush_pending(conn->conn.output, TRUE);
	}
}


/*
 *
 */

static struct connection_settings smtp_server_connection_set = {
	.input_max_size = (size_t)-1,
	.output_max_size = (size_t)-1,
	.client = FALSE
};

static const struct connection_vfuncs smtp_server_connection_vfuncs = {
	.destroy = smtp_server_connection_destroy,
	.input = smtp_server_connection_input
};

struct connection_list *
smtp_server_connection_list_init(void)
{
	return connection_list_init(&smtp_server_connection_set,
		&smtp_server_connection_vfuncs);
}

static struct smtp_server_connection * ATTR_NULL(5, 6)
smtp_server_connection_alloc(struct smtp_server *server,
	const struct smtp_server_settings *set, int fd_in, int fd_out,
	const struct ip_addr *remote_ip, in_port_t remote_port,
	const struct smtp_server_callbacks *callbacks, void *context)
{
	static unsigned int id = 0;
	struct smtp_server_connection *conn;
	pool_t pool;

	pool = pool_alloconly_create("smtp server", 512);
	conn = p_new(pool, struct smtp_server_connection, 1);
	conn->pool = pool;
	conn->refcount = 1;
	conn->id = id++;
	conn->server = server;
	conn->callbacks = callbacks;
	conn->context = context;

	/* merge settings with global server settings */
	conn->set = server->set;
	if (set != NULL) {
		conn->set.protocol = server->set.protocol;
		if (set->rawlog_dir != NULL && *set->rawlog_dir != '\0')
			conn->set.rawlog_dir = p_strdup(pool, set->rawlog_dir);
		if (set->hostname != NULL && *set->hostname != '\0')
			conn->set.hostname = p_strdup(pool, set->hostname);
		if (set->login_greeting != NULL &&
			*set->login_greeting != '\0') {
			conn->set.login_greeting =
				p_strdup(pool, set->login_greeting);
		}
		if (set->capabilities != 0)
			conn->set.capabilities = set->capabilities;
		if (set->max_client_idle_time_msecs > 0) {
			conn->set.max_client_idle_time_msecs =
				set->max_client_idle_time_msecs;
		}
		if (set->max_pipelined_commands > 0) {
			conn->set.max_pipelined_commands =
				set->max_pipelined_commands;
		}
		if (set->max_bad_commands > 0) {
			conn->set.max_bad_commands = set->max_bad_commands;
		}
		if (set->max_recipients > 0)
			conn->set.max_recipients = set->max_recipients;
		smtp_command_limits_merge(&conn->set.command_limits,
					  &set->command_limits);

		if (set->xclient_extensions != NULL) {
			server->set.xclient_extensions =
				p_strarray_dup(pool, set->xclient_extensions);
		}

		if (set->socket_send_buffer_size > 0) {
			conn->set.socket_send_buffer_size =
				set->socket_send_buffer_size;
		}
		if (set->socket_recv_buffer_size > 0) {
			conn->set.socket_recv_buffer_size =
				set->socket_recv_buffer_size;
		}

		conn->set.tls_required =
			conn->set.tls_required || set->tls_required;
		conn->set.auth_optional =
			conn->set.auth_optional || set->auth_optional;
		conn->set.rcpt_domain_optional =
			conn->set.rcpt_domain_optional ||
				set->rcpt_domain_optional;
		conn->set.param_extensions =
			conn->set.param_extensions || set->param_extensions;
		conn->set.debug = conn->set.debug || set->debug;
	}

	conn->remote_pid = (pid_t)-1;
	conn->remote_uid = (uid_t)-1;
	if (remote_ip != NULL && remote_ip->family != 0) {
		conn->remote_ip = *remote_ip;
		conn->remote_port = remote_port;
		conn->socket_family = conn->remote_ip.family;
	} else if (fd_in != fd_out || net_getpeername(fd_in,
		&conn->remote_ip, &conn->remote_port) < 0) {
		/* tty connection probably */
	} else {
		if (conn->remote_ip.family == 0) {
			struct net_unix_cred cred;

			/* unix */
			conn->socket_family = AF_UNIX;
			if (net_getunixcred(fd_in, &cred) >= 0) {
				conn->remote_pid = cred.pid;
				conn->remote_uid = cred.uid;
			}
		} else {
			/* ip / ip6 */
			conn->socket_family = conn->remote_ip.family;
		}
	}

	net_set_nonblock(fd_in, TRUE);
	if (fd_in != fd_out)
		net_set_nonblock(fd_out, TRUE);
	(void)net_set_tcp_nodelay(fd_out, TRUE);

	set = &conn->set;
	if (set->socket_send_buffer_size > 0) {
		if (net_set_send_buffer_size(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(fd_in,
			set->socket_recv_buffer_size) < 0)
			i_error("net_set_recv_buffer_size(%"PRIuSIZE_T") failed: %m",
				set->socket_recv_buffer_size);
	}

	return conn;
}

static const char *
smtp_server_connection_get_name(struct smtp_server_connection *conn)
{
	const char *name;

	/* get a name for this connection */
	switch (conn->socket_family) {
	case 0:
		name = t_strdup_printf("[%u]", conn->id);
		break;
	case AF_UNIX:
		if (conn->remote_uid == (uid_t)-1) {
			name = t_strdup_printf("unix [%u]", conn->id);
		} else if (conn->remote_pid == (pid_t)-1) {
			name = t_strdup_printf("unix:uid=%u [%u]",
				conn->remote_uid, conn->id);
		} else {
			name = t_strdup_printf("unix:pid=%u,uid=%u [%u]",
				conn->remote_pid, conn->remote_uid, conn->id);
		}
		break;
	case AF_INET6:
		name = t_strdup_printf("[%s]:%u [%u]",
			net_ip2addr(&conn->remote_ip), conn->remote_port, conn->id);
		break;
	case AF_INET:
		name = t_strdup_printf("%s:%u [%u]",
			net_ip2addr(&conn->remote_ip), conn->remote_port, conn->id);
		break;
	default:
		i_unreached();
	}

	return name;
}

struct smtp_server_connection *
smtp_server_connection_create(struct smtp_server *server,
	int fd_in, int fd_out,
	const struct ip_addr *remote_ip, in_port_t remote_port,
	bool ssl_start, const struct smtp_server_settings *set,
	const struct smtp_server_callbacks *callbacks, void *context)
{
	struct smtp_server_connection *conn;
	const char *name;

	conn = smtp_server_connection_alloc(server,
		set, fd_in, fd_out, remote_ip, remote_port,
		callbacks, context);
	name = smtp_server_connection_get_name(conn);
	connection_init_server(server->conn_list,
		&conn->conn, name, fd_in, fd_out);

	conn->ssl_start = ssl_start;
	if (ssl_start)
		conn->set.capabilities &= ~SMTP_CAPABILITY_STARTTLS;

	/* halt input until started */
	smtp_server_connection_halt(conn);

	smtp_server_connection_debug(conn, "Connection created");

	return conn;
}

struct smtp_server_connection *
smtp_server_connection_create_from_streams(struct smtp_server *server,
	struct istream *input, struct ostream *output,
	const struct ip_addr *remote_ip, in_port_t remote_port,
	const struct smtp_server_settings *set,
	const struct smtp_server_callbacks *callbacks, void *context)
{
	struct smtp_server_connection *conn;
	const char *name;
	int fd_in, fd_out;

	fd_in = i_stream_get_fd(input);
	fd_out = o_stream_get_fd(output);
	i_assert(fd_in >= 0);
	i_assert(fd_out >= 0);

	conn = smtp_server_connection_alloc(server, set,
		fd_in, fd_out, remote_ip, remote_port,
		callbacks, context);
	name = smtp_server_connection_get_name(conn);
	connection_init_from_streams(server->conn_list,
		&conn->conn, name, input, output);
	conn->created_from_streams = TRUE;

	/* halt input until started */
	smtp_server_connection_halt(conn);

	smtp_server_connection_debug(conn, "Connection created");

	return conn;
}

void smtp_server_connection_ref(struct smtp_server_connection *conn)
{
	conn->refcount++;
}

static const char *
smtp_server_connection_get_disconnect_reason(
	struct smtp_server_connection *conn)
{
	const char *err;

	if (conn->ssl_iostream != NULL &&
	    !ssl_iostream_is_handshaked(conn->ssl_iostream)) {
		err = ssl_iostream_get_last_error(conn->ssl_iostream);
		if (err != NULL) {
			return t_strdup_printf(
				"TLS handshaking failed: %s", err);
		}
	}

	return io_stream_get_disconnect_reason(conn->conn.input,
					       conn->conn.output);
}

static void
smtp_server_connection_disconnect(struct smtp_server_connection *conn,
				  const char *reason)
{
	if (conn->disconnected)
		return;
	conn->disconnected = TRUE;

	if (reason == NULL)
		reason = smtp_server_connection_get_disconnect_reason(conn);
	smtp_server_connection_debug(conn, "Disconnected: %s", reason);
	conn->disconnect_reason = i_strdup(reason);

	/* preserve statistics */
	smtp_server_connection_update_stats(conn);

	smtp_server_connection_timeout_stop(conn);
	if (conn->conn.output != NULL)
		o_stream_uncork(conn->conn.output);
	if (conn->smtp_parser != NULL)
		smtp_command_parser_deinit(&conn->smtp_parser);
	ssl_iostream_destroy(&conn->ssl_iostream);

	if (conn->callbacks != NULL &&
		conn->callbacks->conn_disconnect != NULL) {
		/* the callback may close the fd, so remove IO before that */
		io_remove(&conn->conn.io);
		conn->callbacks->conn_disconnect(conn->context,
						 reason);
	}

	if (!conn->created_from_streams)
		connection_disconnect(&conn->conn);
	else {
		conn->conn.fd_in = conn->conn.fd_out = -1;
		io_remove(&conn->conn.io);
		i_stream_unref(&conn->conn.input);
		o_stream_unref(&conn->conn.output);
	}
}

bool smtp_server_connection_unref(struct smtp_server_connection **_conn)
{
	struct smtp_server_connection *conn = *_conn;
	struct smtp_server_command *cmd, *cmd_next;

	*_conn = NULL;

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

	smtp_server_connection_disconnect(conn, NULL);

	smtp_server_connection_debug(conn, "Connection destroy");

	/* drop transaction */
	smtp_server_connection_reset_state(conn);

	/* clear command queue */
	cmd = conn->command_queue_head;
	while (cmd != NULL) {
		cmd_next = cmd->next;
		smtp_server_command_abort(&cmd);
		cmd = cmd_next;
	}

	if (conn->callbacks != NULL &&
		conn->callbacks->conn_destroy != NULL)
		conn->callbacks->conn_destroy(conn->context);

	connection_deinit(&conn->conn);

	i_free(conn->helo_domain);
	i_free(conn->helo_login);
	i_free(conn->username);
	i_free(conn->disconnect_reason);
	pool_unref(&conn->pool);
	return FALSE;
}

void smtp_server_connection_send_line(struct smtp_server_connection *conn,
				      const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	T_BEGIN {
		string_t *str;

		str = t_str_new(256);
		str_vprintfa(str, fmt, args);
		str_append(str, "\r\n");
		o_stream_nsend(conn->conn.output, str_data(str), str_len(str));
	} T_END;
	va_end(args);
}

void smtp_server_connection_reply_immediate(
	struct smtp_server_connection *conn,
	unsigned int status, const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	T_BEGIN {
		string_t *str;

		str = t_str_new(256);
		str_printfa(str, "%03u ", status);
		str_vprintfa(str, fmt, args);
		str_append(str, "\r\n");
		o_stream_nsend(conn->conn.output, str_data(str), str_len(str));
	} T_END;
	va_end(args);

	/* send immediately */
	if (o_stream_is_corked(conn->conn.output)) {
		o_stream_uncork(conn->conn.output);
		o_stream_cork(conn->conn.output);
	}
}

void smtp_server_connection_login(struct smtp_server_connection *conn,
	const char *username, const char *helo,
	const unsigned char *pdata, unsigned int pdata_len,
	bool ssl_secured)
{
	i_assert(!conn->started);
	i_assert(conn->username == NULL);

	conn->set.capabilities &= ~SMTP_CAPABILITY_STARTTLS;
	conn->username = i_strdup(username);
	conn->helo_login = i_strdup(helo);
	conn->authenticated = TRUE;
	conn->ssl_secured = ssl_secured;

	if (pdata_len > 0) {
		if (!i_stream_add_data(conn->conn.input, pdata, pdata_len))
			i_panic("Couldn't add client input to stream");
	}
}

void smtp_server_connection_start_pending(struct smtp_server_connection *conn)
{
	i_assert(!conn->started);
	conn->started = TRUE;

	conn->raw_input = conn->conn.input;
	conn->raw_output = conn->conn.output;

	if (!conn->ssl_start)
		smtp_server_connection_ready(conn);
	else if (conn->ssl_iostream == NULL)
		smtp_server_connection_input_unlock(conn);
}

void smtp_server_connection_start(struct smtp_server_connection *conn)
{
	smtp_server_connection_start_pending(conn);
	smtp_server_connection_resume(conn);
}

void smtp_server_connection_halt(struct smtp_server_connection *conn)
{
	conn->halted = TRUE;
	smtp_server_connection_timeout_stop(conn);
	if (!conn->started || !conn->ssl_start || conn->ssl_iostream != NULL)
		smtp_server_connection_input_lock(conn);
}

void smtp_server_connection_resume(struct smtp_server_connection *conn)
{
	smtp_server_connection_input_unlock(conn);
	smtp_server_connection_timeout_update(conn);
	conn->halted = FALSE;
}

void smtp_server_connection_close(struct smtp_server_connection **_conn,
				  const char *reason)
{
	struct smtp_server_connection *conn = *_conn;

	*_conn = NULL;

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

	smtp_server_connection_disconnect(conn, reason);
	smtp_server_connection_unref(&conn);
}

void smtp_server_connection_terminate(struct smtp_server_connection **_conn,
				      const char *enh_code, const char *reason)
{
	struct smtp_server_connection *conn = *_conn;

	*_conn = NULL;

	if (conn->closed)
		return;

	i_assert(enh_code[0] == '4' && enh_code[1] == '.');

	smtp_server_connection_send_line(conn,
		"421 %s %s %s", enh_code, conn->set.hostname, reason);

	smtp_server_connection_close(&conn, reason);
}

struct smtp_server_helo_data *
smtp_server_connection_get_helo_data(struct smtp_server_connection *conn)
{
	return &conn->helo;
}

enum smtp_server_state
smtp_server_connection_get_state(struct smtp_server_connection *conn)
{
	return conn->state.state;
}

void smtp_server_connection_set_state(struct smtp_server_connection *conn,
				      enum smtp_server_state state)
{
	if (conn->state.state != state) {
		conn->state.state = state;

		if (conn->callbacks != NULL &&
			conn->callbacks->conn_state_changed != NULL) {
			conn->callbacks->conn_state_changed(conn->context, state);
		}
	}
}

const char *
smtp_server_connection_get_security_string(struct smtp_server_connection *conn)
{
	if (conn->ssl_iostream == NULL)
		return NULL;
	return ssl_iostream_get_security_string(conn->ssl_iostream);
}

void smtp_server_connection_reset_state(struct smtp_server_connection *conn)
{
	smtp_server_connection_debug(conn, "Connection state reset");

	if (conn->state.trans != NULL) {
		if (conn->callbacks != NULL &&
			conn->callbacks->conn_trans_free != NULL) {
			conn->callbacks->conn_trans_free(conn->context,
							 conn->state.trans);
		}
		smtp_server_transaction_free(&conn->state.trans);
	}

	/* RFC 3030, Section 2:
	   The RSET command, when issued after the first BDAT and before the
	   BDAT LAST, clears all segments sent during that transaction and resets
	   the session.
	 */
	if (conn->state.data_input != NULL)
		i_stream_destroy(&conn->state.data_input);
	conn->state.data_chain = NULL;

	/* reset state */
	i_zero(&conn->state);
	smtp_server_connection_set_state(conn, SMTP_SERVER_STATE_READY);
}

void smtp_server_connection_clear(struct smtp_server_connection *conn)
{
	smtp_server_connection_debug(conn, "Connection clear");

	i_free(conn->helo_domain);
	i_free(conn->helo_login);
	i_zero(&conn->helo);
	smtp_server_connection_reset_state(conn);
}

void smtp_server_connection_set_capabilities(
	struct smtp_server_connection *conn, enum smtp_capability capabilities)
{
	conn->set.capabilities = capabilities;
}

void *smtp_server_connection_get_context(struct smtp_server_connection *conn)
{
	return conn->context;
}

bool smtp_server_connection_is_ssl_secured(struct smtp_server_connection *conn)
{
	return conn->ssl_secured;
}

bool smtp_server_connection_is_trusted(struct smtp_server_connection *conn)
{
	if (conn->callbacks == NULL || conn->callbacks->conn_is_trusted == NULL)
		return FALSE;
	return conn->callbacks->conn_is_trusted(conn->context);
}

enum smtp_protocol
smtp_server_connection_get_protocol(struct smtp_server_connection *conn)
{
	return conn->set.protocol;
}

const char *
smtp_server_connection_get_protocol_name(struct smtp_server_connection *conn)
{
	string_t *pname = t_str_new(16);

	switch (conn->set.protocol) {
	case SMTP_PROTOCOL_SMTP:
		if (conn->helo.old_smtp)
			str_append(pname, "SMTP");
		else
			str_append(pname, "ESMTP");
		break;
	case SMTP_PROTOCOL_LMTP:
		str_append(pname, "LMTP");
		break;
	default:
		i_unreached();
	}
	if (conn->ssl_secured)
		str_append_c(pname, 'S');
	if (conn->authenticated)
		str_append_c(pname, 'A');
	return str_c(pname);
}

struct smtp_server_transaction *
smtp_server_connection_get_transaction(struct smtp_server_connection *conn)
{
	return conn->state.trans;
}

const char *
smtp_server_connection_get_transaction_id(struct smtp_server_connection *conn)
{
	if (conn->state.trans == NULL)
		return NULL;
	return conn->state.trans->id;
}

void smtp_server_connection_get_proxy_data(struct smtp_server_connection *conn,
					   struct smtp_proxy_data *proxy_data)
{
	i_zero(proxy_data);
	proxy_data->source_ip = conn->remote_ip;
	proxy_data->source_port = conn->remote_port;
	if (conn->helo.domain_valid)
		proxy_data->helo = conn->helo.domain;
	proxy_data->login = conn->username;

	if (conn->proxy_proto != SMTP_PROXY_PROTOCOL_UNKNOWN)
		proxy_data->proto = conn->proxy_proto;
	else if (conn->set.protocol == SMTP_PROTOCOL_LMTP)
		proxy_data->proto = SMTP_PROXY_PROTOCOL_LMTP;
	else if (conn->helo.old_smtp)
		proxy_data->proto = SMTP_PROXY_PROTOCOL_SMTP;
	else
		proxy_data->proto = SMTP_PROXY_PROTOCOL_ESMTP;

	proxy_data->ttl_plus_1 = conn->proxy_ttl_plus_1;
	proxy_data->timeout_secs = conn->proxy_timeout_secs;
}

void smtp_server_connection_set_proxy_data(struct smtp_server_connection *conn,
	const struct smtp_proxy_data *proxy_data)
{
	if (proxy_data->source_ip.family != 0)
		conn->remote_ip = proxy_data->source_ip;
	if (proxy_data->source_port != 0)
		conn->remote_port = proxy_data->source_port;
	if (proxy_data->helo != NULL) {
		i_free(conn->helo_domain);
		conn->helo_domain = i_strdup(proxy_data->helo);
		conn->helo.domain = conn->helo_domain;
		conn->helo.domain_valid = TRUE;
	}
	if (proxy_data->login != NULL) {
		i_free(conn->username);
		conn->username = i_strdup(proxy_data->login);
	}
	if (proxy_data->proto != SMTP_PROXY_PROTOCOL_UNKNOWN)
		conn->proxy_proto = proxy_data->proto;

	if (proxy_data->ttl_plus_1 > 0)
		conn->proxy_ttl_plus_1 = proxy_data->ttl_plus_1;
	if (conn->proxy_timeout_secs > 0)
		conn->proxy_timeout_secs = proxy_data->timeout_secs;

	if (conn->callbacks != NULL &&
		conn->callbacks->conn_proxy_data_updated != NULL)
		conn->callbacks->conn_proxy_data_updated(conn, proxy_data);
}

void smtp_server_connection_switch_ioloop(struct smtp_server_connection *conn)
{
	if (conn->to_idle != NULL)
		conn->to_idle = io_loop_move_timeout(&conn->to_idle);
	connection_switch_ioloop(&conn->conn);
}