ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done)
{
	int32		len;
	char	   *buf;
	ProtocolVersion proto;
	MemoryContext oldcontext;

	pq_startmsgread();

	/*
	 * Grab the first byte of the length word separately, so that we can tell
	 * whether we have no data at all or an incomplete packet.  (This might
	 * sound inefficient, but it's not really, because of buffering in
	 * pqcomm.c.)
	 */
	if (pq_getbytes((char *) &len, 1) == EOF)
	{
		/*
		 * If we get no data at all, don't clutter the log with a complaint;
		 * such cases often occur for legitimate reasons.  An example is that
		 * we might be here after responding to NEGOTIATE_SSL_CODE, and if the
		 * client didn't like our response, it'll probably just drop the
		 * connection.  Service-monitoring software also often just opens and
		 * closes a connection without sending anything.  (So do port
		 * scanners, which may be less benign, but it's not really our job to
		 * notice those.)
		 */
		return STATUS_ERROR;
	}

	if (pq_getbytes(((char *) &len) + 1, 3) == EOF)
	{
		/* Got a partial length word, so bleat about that */
		if (!ssl_done && !gss_done)
			ereport(COMMERROR,
					(errcode(ERRCODE_PROTOCOL_VIOLATION),
					 errmsg("incomplete startup packet")));
		return STATUS_ERROR;
	}

	len = pg_ntoh32(len);
	len -= 4;

	if (len < (int32) sizeof(ProtocolVersion) ||
		len > MAX_STARTUP_PACKET_LENGTH)
	{
		ereport(COMMERROR,
				(errcode(ERRCODE_PROTOCOL_VIOLATION),
				 errmsg("invalid length of startup packet")));
		return STATUS_ERROR;
	}

	/*
	 * Allocate space to hold the startup packet, plus one extra byte that's
	 * initialized to be zero.  This ensures we will have null termination of
	 * all strings inside the packet.
	 */
	buf = palloc(len + 1);
	buf[len] = '\0';

	if (pq_getbytes(buf, len) == EOF)
	{
		ereport(COMMERROR,
				(errcode(ERRCODE_PROTOCOL_VIOLATION),
				 errmsg("incomplete startup packet")));
		return STATUS_ERROR;
	}
	pq_endmsgread();

	/*
	 * The first field is either a protocol version number or a special
	 * request code.
	 */
	port->proto = proto = pg_ntoh32(*((ProtocolVersion *) buf));

	if (proto == CANCEL_REQUEST_CODE)
	{
		processCancelRequest(port, buf);
		/* Not really an error, but we don't want to proceed further */
		return STATUS_ERROR;
	}

	if (proto == NEGOTIATE_SSL_CODE && !ssl_done)
	{
		char		SSLok;

#ifdef USE_SSL
		/* No SSL when disabled or on Unix sockets */
		if (!LoadedSSL || IS_AF_UNIX(port->laddr.addr.ss_family))
			SSLok = 'N';
		else
			SSLok = 'S';		/* Support for SSL */
#else
		SSLok = 'N';			/* No support for SSL */
#endif

retry1:
		if (send(port->sock, &SSLok, 1, 0) != 1)
		{
			if (errno == EINTR)
				goto retry1;	/* if interrupted, just retry */
			ereport(COMMERROR,
					(errcode_for_socket_access(),
					 errmsg("failed to send SSL negotiation response: %m")));
			return STATUS_ERROR;	/* close the connection */
		}

#ifdef USE_SSL
		if (SSLok == 'S' && secure_open_server(port) == -1)
			return STATUS_ERROR;
#endif

		/*
		 * regular startup packet, cancel, etc packet should follow, but not
		 * another SSL negotiation request, and a GSS request should only
		 * follow if SSL was rejected (client may negotiate in either order)
		 */
		return ProcessStartupPacket(port, true, SSLok == 'S');
	}
	else if (proto == NEGOTIATE_GSS_CODE && !gss_done)
	{
		char		GSSok = 'N';

#ifdef ENABLE_GSS
		/* No GSSAPI encryption when on Unix socket */
		if (!IS_AF_UNIX(port->laddr.addr.ss_family))
			GSSok = 'G';
#endif

		while (send(port->sock, &GSSok, 1, 0) != 1)
		{
			if (errno == EINTR)
				continue;
			ereport(COMMERROR,
					(errcode_for_socket_access(),
					 errmsg("failed to send GSSAPI negotiation response: %m")));
			return STATUS_ERROR;	/* close the connection */
		}

#ifdef ENABLE_GSS
		if (GSSok == 'G' && secure_open_gssapi(port) == -1)
			return STATUS_ERROR;
#endif

		/*
		 * regular startup packet, cancel, etc packet should follow, but not
		 * another GSS negotiation request, and an SSL request should only
		 * follow if GSS was rejected (client may negotiate in either order)
		 */
		return ProcessStartupPacket(port, GSSok == 'G', true);
	}

	/* Could add additional special packet types here */

	/*
	 * Set FrontendProtocol now so that ereport() knows what format to send if
	 * we fail during startup.
	 */
	FrontendProtocol = proto;

	/* Check that the major protocol version is in range. */
	if (PG_PROTOCOL_MAJOR(proto) < PG_PROTOCOL_MAJOR(PG_PROTOCOL_EARLIEST) ||
		PG_PROTOCOL_MAJOR(proto) > PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST))
		ereport(FATAL,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("unsupported frontend protocol %u.%u: server supports %u.0 to %u.%u",
						PG_PROTOCOL_MAJOR(proto), PG_PROTOCOL_MINOR(proto),
						PG_PROTOCOL_MAJOR(PG_PROTOCOL_EARLIEST),
						PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST),
						PG_PROTOCOL_MINOR(PG_PROTOCOL_LATEST))));

	/*
	 * Now fetch parameters out of startup packet and save them into the Port
	 * structure.  All data structures attached to the Port struct must be
	 * allocated in TopMemoryContext so that they will remain available in a
	 * running backend (even after PostmasterContext is destroyed).  We need
	 * not worry about leaking this storage on failure, since we aren't in the
	 * postmaster process anymore.
	 */
	oldcontext = MemoryContextSwitchTo(TopMemoryContext);

	/* Handle protocol version 3 startup packet */
	{
		int32		offset = sizeof(ProtocolVersion);
		List	   *unrecognized_protocol_options = NIL;

		/*
		 * Scan packet body for name/option pairs.  We can assume any string
		 * beginning within the packet body is null-terminated, thanks to
		 * zeroing extra byte above.
		 */
		port->guc_options = NIL;

		while (offset < len)
		{
			char	   *nameptr = buf + offset;
			int32		valoffset;
			char	   *valptr;

			if (*nameptr == '\0')
				break;			/* found packet terminator */
			valoffset = offset + strlen(nameptr) + 1;
			if (valoffset >= len)
				break;			/* missing value, will complain below */
			valptr = buf + valoffset;

			if (strcmp(nameptr, "database") == 0)
				port->database_name = pstrdup(valptr);
			else if (strcmp(nameptr, "user") == 0)
				port->user_name = pstrdup(valptr);
			else if (strcmp(nameptr, "options") == 0)
				port->cmdline_options = pstrdup(valptr);
			else if (strcmp(nameptr, "replication") == 0)
			{
				/*
				 * Due to backward compatibility concerns the replication
				 * parameter is a hybrid beast which allows the value to be
				 * either boolean or the string 'database'. The latter
				 * connects to a specific database which is e.g. required for
				 * logical decoding while.
				 */
				if (strcmp(valptr, "database") == 0)
				{
					am_walsender = true;
					am_db_walsender = true;
				}
				else if (!parse_bool(valptr, &am_walsender))
					ereport(FATAL,
							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
							 errmsg("invalid value for parameter \"%s\": \"%s\"",
									"replication",
									valptr),
							 errhint("Valid values are: \"false\", 0, \"true\", 1, \"database\".")));
			}
			else if (strncmp(nameptr, "_pq_.", 5) == 0)
			{
				/*
				 * Any option beginning with _pq_. is reserved for use as a
				 * protocol-level option, but at present no such options are
				 * defined.
				 */
				unrecognized_protocol_options =
					lappend(unrecognized_protocol_options, pstrdup(nameptr));
			}
			else
			{
				/* Assume it's a generic GUC option */
				port->guc_options = lappend(port->guc_options,
											pstrdup(nameptr));
				port->guc_options = lappend(port->guc_options,
											pstrdup(valptr));

				/*
				 * Copy application_name to port if we come across it.  This
				 * is done so we can log the application_name in the
				 * connection authorization message.  Note that the GUC would
				 * be used but we haven't gone through GUC setup yet.
				 */
				if (strcmp(nameptr, "application_name") == 0)
				{
					char	   *tmp_app_name = pstrdup(valptr);

					pg_clean_ascii(tmp_app_name);

					port->application_name = tmp_app_name;
				}
			}
			offset = valoffset + strlen(valptr) + 1;
		}

		/*
		 * If we didn't find a packet terminator exactly at the end of the
		 * given packet length, complain.
		 */
		if (offset != len - 1)
			ereport(FATAL,
					(errcode(ERRCODE_PROTOCOL_VIOLATION),
					 errmsg("invalid startup packet layout: expected terminator as last byte")));

		/*
		 * If the client requested a newer protocol version or if the client
		 * requested any protocol options we didn't recognize, let them know
		 * the newest minor protocol version we do support and the names of
		 * any unrecognized options.
		 */
		if (PG_PROTOCOL_MINOR(proto) > PG_PROTOCOL_MINOR(PG_PROTOCOL_LATEST) ||
			unrecognized_protocol_options != NIL)
			SendNegotiateProtocolVersion(unrecognized_protocol_options);
	}

	/* Check a user name was given. */
	if (port->user_name == NULL || port->user_name[0] == '\0')
		ereport(FATAL,
				(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
				 errmsg("no PostgreSQL user name specified in startup packet")));

	/* The database defaults to the user name. */
	if (port->database_name == NULL || port->database_name[0] == '\0')
		port->database_name = pstrdup(port->user_name);

	if (Db_user_namespace)
	{
		/*
		 * If user@, it is a global user, remove '@'. We only want to do this
		 * if there is an '@' at the end and no earlier in the user string or
		 * they may fake as a local user of another database attaching to this
		 * database.
		 */
		if (strchr(port->user_name, '@') ==
			port->user_name + strlen(port->user_name) - 1)
			*strchr(port->user_name, '@') = '\0';
		else
		{
			/* Append '@' and dbname */
			port->user_name = psprintf("%s@%s", port->user_name, port->database_name);
		}
	}

	/*
	 * Truncate given database and user names to length of a Postgres name.
	 * This avoids lookup failures when overlength names are given.
	 */
	if (strlen(port->database_name) >= NAMEDATALEN)
		port->database_name[NAMEDATALEN - 1] = '\0';
	if (strlen(port->user_name) >= NAMEDATALEN)
		port->user_name[NAMEDATALEN - 1] = '\0';

	if (am_walsender)
		MyBackendType = B_WAL_SENDER;
	else
		MyBackendType = B_BACKEND;

	/*
	 * Normal walsender backends, e.g. for streaming replication, are not
	 * connected to a particular database. But walsenders used for logical
	 * replication need to connect to a specific database. We allow streaming
	 * replication commands to be issued even if connected to a database as it
	 * can make sense to first make a basebackup and then stream changes
	 * starting from that.
	 */
	if (am_walsender && !am_db_walsender)
		port->database_name[0] = '\0';

	/*
	 * Done putting stuff in TopMemoryContext.
	 */
	MemoryContextSwitchTo(oldcontext);

	/*
	 * If we're going to reject the connection due to database state, say so
	 * now instead of wasting cycles on an authentication exchange. (This also
	 * allows a pg_ping utility to be written.)
	 */
	switch (port->canAcceptConnections)
	{
		case CAC_STARTUP:
			ereport(FATAL,
					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
					 errmsg("the database system is starting up")));
			break;
		case CAC_NOTCONSISTENT:
			if (EnableHotStandby)
				ereport(FATAL,
						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
						 errmsg("the database system is not yet accepting connections"),
						 errdetail("Consistent recovery state has not been yet reached.")));
			else
				ereport(FATAL,
						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
						 errmsg("the database system is not accepting connections"),
						 errdetail("Hot standby mode is disabled.")));
			break;
		case CAC_SHUTDOWN:
			ereport(FATAL,
					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
					 errmsg("the database system is shutting down")));
			break;
		case CAC_RECOVERY:
			ereport(FATAL,
					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
					 errmsg("the database system is in recovery mode")));
			break;
		case CAC_TOOMANY:
			ereport(FATAL,
					(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
					 errmsg("sorry, too many clients already")));
			break;
		case CAC_SUPERUSER:
			/* OK for now, will check in InitPostgres */
			break;
		case CAC_OK:
			break;
	}

	return STATUS_OK;
}
Unknown