/* GSMTAP support code in libmsomcore */
/*
 * (C) 2010-2011 by Harald Welte <laforge@gnumonks.org>
 *
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

#include "../config.h"

#include <osmocom/core/gsmtap_util.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/gsmtap.h>
#include <osmocom/core/msgb.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/select.h>
#include <osmocom/core/socket.h>
#include <osmocom/core/byteswap.h>
#include <osmocom/gsm/protocol/gsm_04_08.h>
#include <osmocom/gsm/rsl.h>

#include <sys/types.h>

#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>

/*! \addtogroup gsmtap
 *  @{
 *  \brief GSMTAP utility routines. Encapsulates GSM messages over UDP
 */
/*! \file gsmtap_util.c */


/*! \brief convert RSL channel number to GSMTAP channel type
 *  \param[in] rsl_chantype RSL channel type
 *  \param[in] link_id RSL link identifier
 *  \returns GSMTAP channel type
 */
uint8_t chantype_rsl2gsmtap(uint8_t rsl_chantype, uint8_t link_id)
{
	uint8_t ret = GSMTAP_CHANNEL_UNKNOWN;

	switch (rsl_chantype) {
	case RSL_CHAN_Bm_ACCHs:
		ret = GSMTAP_CHANNEL_TCH_F;
		break;
	case RSL_CHAN_Lm_ACCHs:
		ret = GSMTAP_CHANNEL_TCH_H;
		break;
	case RSL_CHAN_SDCCH4_ACCH:
		ret = GSMTAP_CHANNEL_SDCCH4;
		break;
	case RSL_CHAN_SDCCH8_ACCH:
		ret = GSMTAP_CHANNEL_SDCCH8;
		break;
	case RSL_CHAN_BCCH:
		ret = GSMTAP_CHANNEL_BCCH;
		break;
	case RSL_CHAN_RACH:
		ret = GSMTAP_CHANNEL_RACH;
		break;
	case RSL_CHAN_PCH_AGCH:
		/* it could also be AGCH... */
		ret = GSMTAP_CHANNEL_PCH;
		break;
	}

	if (link_id & 0x40)
		ret |= GSMTAP_CHANNEL_ACCH;

	return ret;
}

/*! \brief create an arbitrary type GSMTAP message
 *  \param[in] type The GSMTAP_TYPE_xxx constant of the message to create
 *  \param[in] arfcn GSM ARFCN (Channel Number)
 *  \param[in] ts GSM time slot
 *  \param[in] chan_type Channel Type
 *  \param[in] ss Sub-slot
 *  \param[in] fn GSM Frame Number
 *  \param[in] signal_dbm Signal Strength (dBm)
 *  \param[in] snr Signal/Noise Ratio (SNR)
 *  \param[in] data Pointer to data buffer
 *  \param[in] len Length of \ref data
 *  \return dynamically allocated message buffer containing data
 *
 * This function will allocate a new msgb and fill it with a GSMTAP
 * header containing the information
 */
struct msgb *gsmtap_makemsg_ex(uint8_t type, uint16_t arfcn, uint8_t ts, uint8_t chan_type,
			    uint8_t ss, uint32_t fn, int8_t signal_dbm,
			    uint8_t snr, const uint8_t *data, unsigned int len)
{
	struct msgb *msg;
	struct gsmtap_hdr *gh;
	uint8_t *dst;

	msg = msgb_alloc(sizeof(*gh) + len, "gsmtap_tx");
	if (!msg)
		return NULL;

	gh = (struct gsmtap_hdr *) msgb_put(msg, sizeof(*gh));

	gh->version = GSMTAP_VERSION;
	gh->hdr_len = sizeof(*gh)/4;
	gh->type = type;
	gh->timeslot = ts;
	gh->sub_slot = ss;
	gh->arfcn = osmo_htons(arfcn);
	gh->snr_db = snr;
	gh->signal_dbm = signal_dbm;
	gh->frame_number = osmo_htonl(fn);
	gh->sub_type = chan_type;
	gh->antenna_nr = 0;

	dst = msgb_put(msg, len);
	memcpy(dst, data, len);

	return msg;
}

/*! \brief create L1/L2 data and put it into GSMTAP
 *  \param[in] arfcn GSM ARFCN (Channel Number)
 *  \param[in] ts GSM time slot
 *  \param[in] chan_type Channel Type
 *  \param[in] ss Sub-slot
 *  \param[in] fn GSM Frame Number
 *  \param[in] signal_dbm Signal Strength (dBm)
 *  \param[in] snr Signal/Noise Ratio (SNR)
 *  \param[in] data Pointer to data buffer
 *  \param[in] len Length of \ref data
 *  \return message buffer or NULL in case of error
 *
 * This function will allocate a new msgb and fill it with a GSMTAP
 * header containing the information
 */
struct msgb *gsmtap_makemsg(uint16_t arfcn, uint8_t ts, uint8_t chan_type,
			    uint8_t ss, uint32_t fn, int8_t signal_dbm,
			    uint8_t snr, const uint8_t *data, unsigned int len)
{
	return gsmtap_makemsg_ex(GSMTAP_TYPE_UM, arfcn, ts, chan_type,
		ss, fn, signal_dbm, snr, data, len);
}

#ifdef HAVE_SYS_SOCKET_H

#include <sys/socket.h>
#include <netinet/in.h>

/*! \brief Create a new (sending) GSMTAP source socket 
 *  \param[in] host host name or IP address in string format
 *  \param[in] port UDP port number in host byte order
 *  \return file descriptor of the new socket
 *
 * Opens a GSMTAP source (sending) socket, conncet it to host/port and
 * return resulting fd.  If \a host is NULL, the destination address
 * will be localhost.  If \a port is 0, the default \ref
 * GSMTAP_UDP_PORT will be used.
 * */
int gsmtap_source_init_fd(const char *host, uint16_t port)
{
	if (port == 0)
		port = GSMTAP_UDP_PORT;
	if (host == NULL)
		host = "localhost";

	return osmo_sock_init(AF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, host, port,
				OSMO_SOCK_F_CONNECT);
}

/*! \brief Add a local sink to an existing GSMTAP source and return fd
 *  \param[in] gsmtap_fd file descriptor of the gsmtap socket
 *  \returns file descriptor of locally bound receive socket
 *
 *  In case the GSMTAP socket is connected to a local destination
 *  IP/port, this function creates a corresponding receiving socket
 *  bound to that destination IP + port.
 *
 *  In case the gsmtap socket is not connected to a local IP/port, or
 *  creation of the receiving socket fails, a negative error code is
 *  returned.
 */
int gsmtap_source_add_sink_fd(int gsmtap_fd)
{
	struct sockaddr_storage ss;
	socklen_t ss_len = sizeof(ss);
	int rc;

	rc = getpeername(gsmtap_fd, (struct sockaddr *)&ss, &ss_len);
	if (rc < 0)
		return rc;

	if (osmo_sockaddr_is_local((struct sockaddr *)&ss, ss_len) == 1) {
		rc = osmo_sock_init_sa((struct sockaddr *)&ss, SOCK_DGRAM,
					IPPROTO_UDP, OSMO_SOCK_F_BIND);
		if (rc >= 0)
			return rc;
	}

	return -ENODEV;
}

/*! \brief Send a \ref msgb through a GSMTAP source
 *  \param[in] gti GSMTAP instance
 *  \param[in] msg message buffer
 *  \return 0 in case of success; negative in case of error
 */
int gsmtap_sendmsg(struct gsmtap_inst *gti, struct msgb *msg)
{
	if (!gti)
		return -ENODEV;

	if (gti->ofd_wq_mode)
		return osmo_wqueue_enqueue(&gti->wq, msg);
	else {
		/* try immediate send and return error if any */
		int rc;

		rc = write(gsmtap_inst_fd(gti), msg->data, msg->len);
		if (rc <= 0) {
			return rc;
		} else if (rc >= msg->len) {
			msgb_free(msg);
			return 0;
		} else {
			/* short write */
			return -EIO;
		}
	}
}

/*! \brief send an arbitrary type through GSMTAP.
 *  See \ref gsmtap_makemsg_ex for arguments
 */
int gsmtap_send_ex(struct gsmtap_inst *gti, uint8_t type, uint16_t arfcn, uint8_t ts,
		uint8_t chan_type, uint8_t ss, uint32_t fn,
		int8_t signal_dbm, uint8_t snr, const uint8_t *data,
		unsigned int len)
{
	struct msgb *msg;

	if (!gti)
		return -ENODEV;

	msg = gsmtap_makemsg_ex(type, arfcn, ts, chan_type, ss, fn, signal_dbm,
			     snr, data, len);
	if (!msg)
		return -ENOMEM;

	return gsmtap_sendmsg(gti, msg);
}

/*! \brief send a message from L1/L2 through GSMTAP.
 *  See \ref gsmtap_makemsg for arguments
 */
int gsmtap_send(struct gsmtap_inst *gti, uint16_t arfcn, uint8_t ts,
		uint8_t chan_type, uint8_t ss, uint32_t fn,
		int8_t signal_dbm, uint8_t snr, const uint8_t *data,
		unsigned int len)
{
	return gsmtap_send_ex(gti, GSMTAP_TYPE_UM, arfcn, ts, chan_type, ss, fn,
		signal_dbm, snr, data, len);
}

/* Callback from select layer if we can write to the socket */
static int gsmtap_wq_w_cb(struct osmo_fd *ofd, struct msgb *msg)
{
	int rc;

	rc = write(ofd->fd, msg->data, msg->len);
	if (rc < 0) {
		return rc;
	}
	if (rc != msg->len) {
		return -EIO;
	}

	return 0;
}

/* Callback from select layer if we can read from the sink socket */
static int gsmtap_sink_fd_cb(struct osmo_fd *fd, unsigned int flags)
{
	int rc;
	uint8_t buf[4096];

	if (!(flags & BSC_FD_READ))
		return 0;

	rc = read(fd->fd, buf, sizeof(buf));
	if (rc < 0) {
		return rc;
	}
	/* simply discard any data arriving on the socket */

	return 0;
}

/*! \brief Add a local sink to an existing GSMTAP source and return fd
 *  \param[in] gsmtap_fd file descriptor of the gsmtap socket
 *  \returns file descriptor of locally bound receive socket
 *
 *  In case the GSMTAP socket is connected to a local destination
 *  IP/port, this function creates a corresponding receiving socket
 *  bound to that destination IP + port.
 *
 *  In case the gsmtap socket is not connected to a local IP/port, or
 *  creation of the receiving socket fails, a negative error code is
 *  returned.
 *
 *  The file descriptor of the receiving socket is automatically added
 *  to the libosmocore select() handling.
 */
int gsmtap_source_add_sink(struct gsmtap_inst *gti)
{
	int fd, rc;

	fd = gsmtap_source_add_sink_fd(gsmtap_inst_fd(gti));
	if (fd < 0)
		return fd;

	if (gti->ofd_wq_mode) {
		struct osmo_fd *sink_ofd;

		sink_ofd = &gti->sink_ofd;
		sink_ofd->fd = fd;
		sink_ofd->when = BSC_FD_READ;
		sink_ofd->cb = gsmtap_sink_fd_cb;

		rc = osmo_fd_register(sink_ofd);
		if (rc < 0) {
			close(fd);
			return rc;
		}
	}

	return fd;
}


/*! \brief Open GSMTAP source socket, connect and register osmo_fd
 *  \param[in] host host name or IP address in string format
 *  \param[in] port UDP port number in host byte order
 *  \param[in] ofd_wq_mode Register \ref osmo_wqueue (1) or not (0)
 *  \return callee-allocated \ref gsmtap_inst
 *
 * Open GSMTAP source (sending) socket, connect it to host/port,
 * allocate 'struct gsmtap_inst' and optionally osmo_fd/osmo_wqueue
 * registration.  This means it is like \ref gsmtap_init2 but integrated
 * with libosmocore \ref select */
struct gsmtap_inst *gsmtap_source_init(const char *host, uint16_t port,
					int ofd_wq_mode)
{
	struct gsmtap_inst *gti;
	int fd, rc;

	fd = gsmtap_source_init_fd(host, port);
	if (fd < 0)
		return NULL;

	gti = talloc_zero(NULL, struct gsmtap_inst);
	gti->ofd_wq_mode = ofd_wq_mode;
	gti->wq.bfd.fd = fd;
	gti->sink_ofd.fd = -1;

	if (ofd_wq_mode) {
		osmo_wqueue_init(&gti->wq, 64);
		gti->wq.write_cb = &gsmtap_wq_w_cb;

		rc = osmo_fd_register(&gti->wq.bfd);
		if (rc < 0) {
			close(fd);
			return NULL;
		}
	}

	return gti;
}

#endif /* HAVE_SYS_SOCKET_H */

/*! @} */