flap_connection.c

Linux下的多协议即时通讯程序源代码

 * of your modules has just given you a SNAC of the group 0x0004 to send
 * you.  Maybe an IM destined for some twit in Greenland.  So you start
 * at the top of your connection list, looking for a connection that
 * claims to support group 0x0004.  You find one.  Why, that neat BOS
 * connection of yours can do that.  So you send it on its way.
 *
 * Now, say, that fellow from Greenland has friends and they all want to
 * meet up with you in a lame chat room.  This has landed you a SNAC
 * in the family 0x000e and you have to admit you're a bit lost.  You've
 * searched your connection list for someone who wants to make your life
 * easy and deliver this SNAC for you, but there isn't one there.
 *
 * Here comes the good bit.  Without even letting anyone know, particularly
 * the module that decided to send this SNAC, and definitely not that twit
 * in Greenland, you send out a service request.  In this request, you have
 * marked the need for a connection supporting group 0x000e.  A few seconds
 * later, you receive a service redirect with an IP address and a cookie in
 * it.  Great, you say.  Now I have something to do.  Off you go, making
 * that connection.  One of the first things you get from this new server
 * is a message saying that indeed it does support the group you were looking
 * for.  So you continue and send rate confirmation and all that.
 *
 * Then you remember you had that SNAC to send, and now you have a means to
 * do it, and you do, and everyone is happy.  Except the Greenlander, who is
 * still stuck in the bitter cold.
 *
 * Oh, and this is useful for building the Migration SNACs, too.  In the
 * future, this may help convince me to implement rate limit mitigation
 * for real.  We'll see.
 *
 * Just to make me look better, I'll say that I've known about this great
 * scheme for quite some time now.  But I still haven't convinced myself
 * to make libfaim work that way.  It would take a fair amount of effort,
 * and probably some client API changes as well.  (Whenever I don't want
 * to do something, I just say it would change the client API.  Then I
 * instantly have a couple of supporters of not doing it.)
 *
 * Generally, addgroup is only called by the internal handling of the
 * server ready SNAC.  So if you want to do something before that, you'll
 * have to be more creative.  That is done rather early, though, so I don't
 * think you have to worry about it.  Unless you're me.  I care deeply
 * about such inane things.
 *
 */

/**
 * Find a FlapConnection that supports the given oscar
 * family.
 */
FlapConnection *
flap_connection_findbygroup(OscarData *od, guint16 group)
{
	GSList *cur;

	for (cur = od->oscar_connections; cur != NULL; cur = cur->next)
	{
		FlapConnection *conn;
		GSList *l;

		conn = cur->data;

		for (l = conn->groups; l != NULL; l = l->next)
		{
			if (GPOINTER_TO_UINT(l->data) == group)
				return conn;
		}
	}

	return NULL;
}

/**
 * Locates a connection of the specified type in the
 * specified session.
 *
 * TODO: Use flap_connection_findbygroup everywhere and get rid of this.
 *
 * @param od The session to search.
 * @param type The type of connection to look for.
 *
 * @return Returns the first connection found of the given target type,
 *         or NULL if none could be found.
 */
FlapConnection *
flap_connection_getbytype(OscarData *od, int type)
{
	GSList *cur;

	for (cur = od->oscar_connections; cur != NULL; cur = cur->next)
	{
		FlapConnection *conn;
		conn = cur->data;
		if ((conn->type == type) && (conn->connected))
			return conn;
	}

	return NULL;
}

FlapConnection *
flap_connection_getbytype_all(OscarData *od, int type)
{
	GSList *cur;

	for (cur = od->oscar_connections; cur; cur = cur->next)
	{
		FlapConnection *conn;
		conn = cur->data;
		if (conn->type == type)
			return conn;
	}

	return NULL;
}

/**
 * Allocate a new FLAP frame.
 *
 * @param channel The FLAP channel.  This is almost always 2.
 */
FlapFrame *
flap_frame_new(OscarData *od, guint16 channel, int datalen)
{
	FlapFrame *frame;

	frame = g_new0(FlapFrame, 1);
	frame->channel = channel;

	if (datalen > 0)
		byte_stream_new(&frame->data, datalen);

	return frame;
}

static void
parse_snac(OscarData *od, FlapConnection *conn, FlapFrame *frame)
{
	aim_module_t *cur;
	aim_modsnac_t snac;

	if (byte_stream_empty(&frame->data) < 10)
		return;

	snac.family = byte_stream_get16(&frame->data);
	snac.subtype = byte_stream_get16(&frame->data);
	snac.flags = byte_stream_get16(&frame->data);
	snac.id = byte_stream_get32(&frame->data);

	/* SNAC flags are apparently uniform across all SNACs, so we handle them here */
	if (snac.flags & 0x0001) {
		/*
		 * This means the SNAC will be followed by another SNAC with
		 * related information.  We don't need to do anything about
		 * this here.
		 */
	}
	if (snac.flags & 0x8000) {
		/*
		 * This packet contains the version of the family that this SNAC is
		 * in.  You get this when your SSI module is version 2 or higher.
		 * For now we have no need for this, but you could always save
		 * it as a part of aim_modnsac_t, or something.  The format is...
		 * 2 byte length of total mini-header (which is 6 bytes), then TLV
		 * of  type 0x0001, length 0x0002, value is the 2 byte version
		 * number
		 */
		byte_stream_advance(&frame->data, byte_stream_get16(&frame->data));
	}

	for (cur = (aim_module_t *)od->modlistv; cur; cur = cur->next) {

		if (!(cur->flags & AIM_MODFLAG_MULTIFAMILY) &&
				(cur->family != snac.family))
			continue;

		if (cur->snachandler(od, conn, cur, frame, &snac, &frame->data))
			return;
	}
}

static void
parse_fakesnac(OscarData *od, FlapConnection *conn, FlapFrame *frame, guint16 family, guint16 subtype)
{
	aim_module_t *cur;
	aim_modsnac_t snac;

	snac.family = family;
	snac.subtype = subtype;
	snac.flags = snac.id = 0;

	for (cur = (aim_module_t *)od->modlistv; cur; cur = cur->next) {

		if (!(cur->flags & AIM_MODFLAG_MULTIFAMILY) &&
				(cur->family != snac.family))
			continue;

		if (cur->snachandler(od, conn, cur, frame, &snac, &frame->data))
			return;
	}
}

static void
parse_flap_ch4(OscarData *od, FlapConnection *conn, FlapFrame *frame)
{
	GSList *tlvlist;
	char *msg = NULL;
	guint16 code = 0;
	aim_rxcallback_t userfunc;

	if (byte_stream_empty(&frame->data) == 0) {
		/* XXX should do something with this */
		return;
	}

	/* An ICQ account is logging in */
	if (conn->type == SNAC_FAMILY_AUTH)
	{
		parse_fakesnac(od, conn, frame, 0x0017, 0x0003);
		return;
	}

	tlvlist = aim_tlvlist_read(&frame->data);

	if (aim_tlv_gettlv(tlvlist, 0x0009, 1))
		code = aim_tlv_get16(tlvlist, 0x0009, 1);

	if (aim_tlv_gettlv(tlvlist, 0x000b, 1))
		msg = aim_tlv_getstr(tlvlist, 0x000b, 1);

	if ((userfunc = aim_callhandler(od, AIM_CB_FAM_SPECIAL, AIM_CB_SPECIAL_CONNERR)))
		userfunc(od, conn, frame, code, msg);

	aim_tlvlist_free(tlvlist);

	g_free(msg);
}

/**
 * Takes a new incoming FLAP frame and sends it to the appropriate
 * handler function to be parsed.
 */
static void
parse_flap(OscarData *od, FlapConnection *conn, FlapFrame *frame)
{
	if (frame->channel == 0x01) {
		guint32 flap_version = byte_stream_get32(&frame->data);
		if (flap_version != 0x00000001)
		{
				/* Error! */
				purple_debug_warning("oscar", "Expecting FLAP version "
					"0x00000001 but received FLAP version %08lx.  Closing connection.\n",
					flap_version);
				flap_connection_schedule_destroy(conn,
						OSCAR_DISCONNECT_INVALID_DATA, NULL);
		}
		else
			conn->connected = TRUE;

	} else if (frame->channel == 0x02) {
		parse_snac(od, conn, frame);

	} else if (frame->channel == 0x04) {
		parse_flap_ch4(od, conn, frame);

	} else if (frame->channel == 0x05) {
		/* TODO: Reset our keepalive watchdog? */

	}
}

/**
 * Read in all available data on the socket for a given connection.
 * All complete FLAPs handled immedate after they're received.
 * Incomplete FLAP data is stored locally and appended to the next
 * time this callback is triggered.
 */
void
flap_connection_recv_cb(gpointer data, gint source, PurpleInputCondition cond)
{
	FlapConnection *conn;
	ssize_t read;

	conn = data;

	/* Read data until we run out of data and break out of the loop */
	while (TRUE)
	{
		/* Start reading a new FLAP */
		if (conn->buffer_incoming.data.data == NULL)
		{
			/* Read the first 6 bytes (the FLAP header) */
			read = recv(conn->fd, conn->header + conn->header_received,
					6 - conn->header_received, 0);

			/* Check if the FLAP server closed the connection */
			if (read == 0)
			{
				flap_connection_schedule_destroy(conn,
						OSCAR_DISCONNECT_REMOTE_CLOSED, NULL);
				break;
			}

			/* If there was an error then close the connection */
			if (read < 0)
			{
				if ((errno == EAGAIN) || (errno == EWOULDBLOCK))
					/* No worries */
					break;

				/* Error! */
				flap_connection_schedule_destroy(conn,
						OSCAR_DISCONNECT_LOST_CONNECTION, strerror(errno));
				break;
			}

			/* If we don't even have a complete FLAP header then do nothing */
			conn->header_received += read;
			if (conn->header_received < 6)
				break;

			/* All FLAP frames must start with the byte 0x2a */
			if (aimutil_get8(&conn->header[0]) != 0x2a)
			{
				flap_connection_schedule_destroy(conn,
						OSCAR_DISCONNECT_INVALID_DATA, NULL);
				break;
			}

			/* Verify the sequence number sent by the server. */
#if 0
			/* TODO: Need to initialize conn->seqnum_in somewhere before we can use this. */
			if (aimutil_get16(&conn->header[1]) != conn->seqnum_in++)
			{
				/* Received an out-of-order FLAP! */
				flap_connection_schedule_destroy(conn,
						OSCAR_DISCONNECT_INVALID_DATA, NULL);
				break;
			}
#endif

			/* Initialize a new temporary FlapFrame for incoming data */
			conn->buffer_incoming.channel = aimutil_get8(&conn->header[1]);
			conn->buffer_incoming.seqnum = aimutil_get16(&conn->header[2]);
			conn->buffer_incoming.data.len = aimutil_get16(&conn->header[4]);
			conn->buffer_incoming.data.data = g_new(guint8, conn->buffer_incoming.data.len);
			conn->buffer_incoming.data.offset = 0;
		}

		if (conn->buffer_incoming.data.len - conn->buffer_incoming.data.offset)
		{
			/* Read data into the temporary FlapFrame until it is complete */
			read = recv(conn->fd,
						&conn->buffer_incoming.data.data[conn->buffer_incoming.data.offset],
						conn->buffer_incoming.data.len - conn->buffer_incoming.data.offset,
						0);

			/* Check if the FLAP server closed the connection */
			if (read == 0)
			{
				flap_connection_schedule_destroy(conn,
						OSCAR_DISCONNECT_REMOTE_CLOSED, NULL);
				break;
			}

			if (read < 0)
			{
				if ((errno == EAGAIN) || (errno == EWOULDBLOCK))
					/* No worries */
					break;

				/* Error! */
				flap_connection_schedule_destroy(conn,
						OSCAR_DISCONNECT_LOST_CONNECTION, strerror(errno));
				break;
			}

			conn->buffer_incoming.data.offset += read;
			if (conn->buffer_incoming.data.offset < conn->buffer_incoming.data.len)
				/* Waiting for more data to arrive */
				break;
		}

		/* We have a complete FLAP!  Handle it and continue reading */
		byte_stream_rewind(&conn->buffer_incoming.data);
		parse_flap(conn->od, conn, &conn->buffer_incoming);
		conn->lastactivity = time(NULL);

		g_free(conn->buffer_incoming.data.data);
		conn->buffer_incoming.data.data = NULL;

		conn->header_received = 0;
	}
}

static void
send_cb(gpointer data, gint source, PurpleInputCondition cond)
{
	FlapConnection *conn;
	int writelen, ret;

	conn = data;
	writelen = purple_circ_buffer_get_max_read(conn->buffer_outgoing);

	if (writelen == 0)
	{
		purple_input_remove(conn->watcher_outgoing);
		conn->watcher_outgoing = 0;
		return;
	}

	ret = send(conn->fd, conn->buffer_outgoing->outptr, writelen, 0);
	if (ret <= 0)
	{
		if (ret < 0 && ((errno == EAGAIN) || (errno == EWOULDBLOCK)))
			/* No worries */
			return;

		/* Error! */
		purple_input_remove(conn->watcher_outgoing);
		conn->watcher_outgoing = 0;
		close(conn->fd);
		conn->fd = -1;
		flap_connection_schedule_destroy(conn,
				OSCAR_DISCONNECT_LOST_CONNECTION, strerror(errno));
		return;
	}

	purple_circ_buffer_mark_read(conn->buffer_outgoing, ret);
}

static void
flap_connection_send_byte_stream(ByteStream *bs, FlapConnection *conn, size_t count)
{
	if (conn == NULL)
		return;

	/* Make sure we don't send past the end of the bs */
	if (count > byte_stream_empty(bs))
		count = byte_stream_empty(bs); /* truncate to remaining space */

	if (count == 0)
		return;

	/* Add everything to our outgoing buffer */
	purple_circ_buffer_append(conn->buffer_outgoing, bs->data, count);

	/* If we haven't already started writing stuff, then start the cycle */
	if ((conn->watcher_outgoing == 0) && (conn->fd >= 0))
	{
		conn->watcher_outgoing = purple_input_add(conn->fd,
				PURPLE_INPUT_WRITE, send_cb, conn);
		send_cb(conn, conn->fd, 0);
	}
}

static void
sendframe_flap(FlapConnection *conn, FlapFrame *frame)
{
	ByteStream bs;
	int payloadlen, bslen;

	payloadlen = byte_stream_curpos(&frame->data);

	byte_stream_new(&bs, 6 + payloadlen);

	/* FLAP header */
	byte_stream_put8(&bs, 0x2a);
	byte_stream_put8(&bs, frame->channel);
	byte_stream_put16(&bs, frame->seqnum);
	byte_stream_put16(&bs, payloadlen);

	/* Payload */
	byte_stream_rewind(&frame->data);
	byte_stream_putbs(&bs, &frame->data, payloadlen);

	bslen = byte_stream_curpos(&bs);
	byte_stream_rewind(&bs);
	flap_connection_send_byte_stream(&bs, conn, bslen);

	g_free(bs.data); /* XXX byte_stream_free */
}

void
flap_connection_send(FlapConnection *conn, FlapFrame *frame)
{
	frame->seqnum = ++(conn->seqnum_out);
	sendframe_flap(conn, frame);
	flap_frame_destroy(frame);
}