/* Core SS7 xUA Server */

/* (C) 2015-2017 by Harald Welte <laforge@gnumonks.org>
 * (C) 2023 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
 * All Rights Reserved
 *
 * SPDX-License-Identifier: GPL-2.0+
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 */

#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <inttypes.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/sctp.h>

#include <osmocom/sigtran/osmo_ss7.h>
#include <osmocom/sigtran/mtp_sap.h>
#include <osmocom/sigtran/protocol/mtp.h>
#include <osmocom/sigtran/protocol/sua.h>
#include <osmocom/sigtran/protocol/m3ua.h>

#include <osmocom/core/linuxlist.h>
#include <osmocom/core/select.h>
#include <osmocom/core/utils.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/msgb.h>
#include <osmocom/core/socket.h>
#include <osmocom/core/sockaddr_str.h>
#include <osmocom/core/osmo_io.h>

#include <osmocom/netif/stream.h>
#include <osmocom/netif/ipa.h>
#include <osmocom/netif/sctp.h>

#include "sccp_internal.h"
#include "xua_internal.h"
#include "ss7_asp.h"
#include "ss7_internal.h"
#include "xua_asp_fsm.h"
#include "xua_as_fsm.h"
#include "ss7_xua_srv.h"

/***********************************************************************
 * SS7 xUA Server
 ***********************************************************************/

/* Server has accept()ed a new SCTP association / TCP connection, let's find the ASP for
 * it (if any) */
static int xua_accept_cb(struct osmo_stream_srv_link *link, int fd)
{
	struct osmo_xua_server *oxs = osmo_stream_srv_link_get_data(link);
	struct osmo_stream_srv *srv;
	struct osmo_ss7_asp *asp;
	char *sock_name = osmo_sock_get_name(link, fd);
	const char *proto_name = get_value_string(osmo_ss7_asp_protocol_vals, oxs->cfg.proto);
	int rc = 0;

	LOGP(DLSS7, LOGL_INFO, "%s: New %s connection accepted\n", sock_name, proto_name);

	asp = ss7_asp_find_by_socket_addr(fd, oxs->cfg.trans_proto);
	if (asp) {
		LOGP(DLSS7, LOGL_INFO, "%s: matched connection to ASP %s\n", sock_name, asp->cfg.name);
		if (!asp->cfg.is_server) {
			LOGPASP(asp, DLSS7, LOGL_NOTICE,
				"Reject incoming new connection from %s for ASP configured as 'transport-role client'\n",
				sock_name);
			close(fd);
			talloc_free(sock_name);
			return 0;
		}
		if (asp->cfg.adm_state == OSMO_SS7_ASP_ADM_S_SHUTDOWN) {
			LOGPASP(asp, DLSS7, LOGL_NOTICE,
				"Reject incoming new connection from %s for ASP in adm state %s\n",
				sock_name, get_value_string(osmo_ss7_asp_admin_state_names, asp->cfg.adm_state));
			close(fd);
			talloc_free(sock_name);
			return 0;
		}
		/* we need to check if we already have a socket associated, and close it.  Otherwise it might
		 * happen that both the listen-fd for this accept() and the old socket are marked 'readable'
		 * during the same scheduling interval, and we're processing them in the "wrong" order, i.e.
		 * we first see the accept of the new fd before we see the close on the old fd */
		if (asp->server) {
			LOGPASP(asp, DLSS7, LOGL_FATAL, "accept of new connection from %s before old was closed "
				"-> close old one\n", sock_name);
			ss7_asp_disconnect_stream(asp);
			/* Dynamic ASPs (transport-role=server) may be destroyed as a consequence, re-fetch the ASP: */
			asp = ss7_asp_find_by_socket_addr(fd, oxs->cfg.trans_proto);
		}
	}

	if (!asp && !oxs->cfg.accept_dyn_reg) {
		LOGP(DLSS7, LOGL_NOTICE, "%s: %s connection without matching "
			"ASP definition and no dynamic registration enabled, terminating\n",
			sock_name, proto_name);
		close(fd);
		talloc_free(sock_name);
		return -1;
	}

	srv = osmo_stream_srv_create2(oxs, link, fd, NULL);
	if (!srv) {
		LOGP(DLSS7, LOGL_ERROR, "%s: Unable to create stream server "
		     "for connection\n", sock_name);
		close(fd);
		talloc_free(sock_name);
		return -1;
	}

	osmo_iofd_set_alloc_info(osmo_stream_srv_get_iofd(srv), M3UA_MSG_SIZE, M3UA_MSG_HEADROOM);

	switch (oxs->cfg.proto) {
	case OSMO_SS7_ASP_PROT_IPA:
		osmo_stream_srv_set_read_cb(srv, ss7_asp_ipa_srv_conn_rx_cb);
		osmo_stream_srv_set_segmentation_cb(srv, osmo_ipa_segmentation_cb);
		break;
	case OSMO_SS7_ASP_PROT_M3UA:
		if (oxs->cfg.trans_proto == IPPROTO_SCTP)
			osmo_stream_srv_set_read_cb(srv, &ss7_asp_xua_srv_conn_rx_cb);
		else if (oxs->cfg.trans_proto == IPPROTO_TCP) {
			osmo_stream_srv_set_read_cb(srv, &ss7_asp_m3ua_tcp_srv_conn_rx_cb);
			osmo_stream_srv_set_segmentation_cb(srv, xua_tcp_segmentation_cb);
		} else
			OSMO_ASSERT(0);
		break;
	default:
		OSMO_ASSERT(oxs->cfg.trans_proto == IPPROTO_SCTP);
		osmo_stream_srv_set_read_cb(srv, &ss7_asp_xua_srv_conn_rx_cb);
		osmo_stream_srv_set_segmentation_cb(srv, NULL);
		break;
	}
	osmo_stream_srv_set_closed_cb(srv, ss7_asp_xua_srv_conn_closed_cb);

	if (!asp) {
		/* Dynamic registration: */
		char namebuf[32];
		char hostbuf[INET6_ADDRSTRLEN];
		const char *hostbuf_ptr = &hostbuf[0];
		char portbuf[16];
		static uint32_t dyn_asp_num = 0;
		snprintf(namebuf, sizeof(namebuf), "asp-dyn-%u", dyn_asp_num++);
		asp = osmo_ss7_asp_find_or_create2(oxs->inst, namebuf, 0, 0,
						   oxs->cfg.trans_proto,
						   oxs->cfg.proto);
		if (!asp) {
			osmo_stream_srv_destroy(srv);
			talloc_free(sock_name);
			return -1;
		}

		osmo_sock_get_ip_and_port(fd, hostbuf, sizeof(hostbuf), portbuf, sizeof(portbuf), false);
		LOGP(DLSS7, LOGL_INFO, "%s: created dynamic ASP %s\n", sock_name, asp->cfg.name);
		asp->cfg.is_server = true;
		asp->cfg.role = OSMO_SS7_ASP_ROLE_SG;
		asp->cfg.local.port = oxs->cfg.local.port;
		asp->cfg.remote.port = atoi(portbuf);
		asp->dyn_allocated = true;
		asp->server = srv;
		ss7_asp_peer_set_hosts(&asp->cfg.local, asp,
						(const char * const*)oxs->cfg.local.host,
						oxs->cfg.local.host_cnt);
		ss7_asp_peer_set_hosts(&asp->cfg.remote, asp,
						&hostbuf_ptr, 1);
		if ((rc = xua_asp_fsm_start(asp, LOGL_DEBUG)) < 0) {
			talloc_free(sock_name);
			osmo_ss7_asp_destroy(asp);
			return rc;
		}
		OSMO_ASSERT(asp->fi);
	}
	OSMO_ASSERT(asp);

	/* update the ASP reference back to the server over which the
	 * connection came in */
	asp->server = srv;
	asp->xua_server = oxs;
	llist_add_tail(&asp->siblings, &oxs->asp_list);

	/* update the ASP socket name */
	talloc_free(asp->sock_name);
	asp->sock_name = talloc_reparent(link, asp, sock_name);
	osmo_stream_srv_set_name(asp->server, asp->cfg.name);
	/* make sure the conn_cb() is called with the asp as private
	 * data */
	osmo_stream_srv_set_data(srv, asp);

	switch (asp->cfg.trans_proto) {
	case IPPROTO_TCP:
		rc = ss7_asp_apply_tcp_pars(asp);
		break;
	case IPPROTO_SCTP:
		rc = ss7_asp_apply_peer_primary_address(asp);
		rc = ss7_asp_apply_primary_address(asp);
		break;
	}

	/* send M-SCTP_ESTABLISH.ind to Layer Manager */
	osmo_fsm_inst_dispatch(asp->fi, XUA_ASP_E_SCTP_EST_IND, 0);
	xua_asp_send_xlm_prim_simple(asp, OSMO_XLM_PRIM_M_SCTP_ESTABLISH, PRIM_OP_INDICATION);

	return rc;
}

/*! \brief create a new xUA server configured with given ip/port
 *  \param[in] inst SS7 Instance on which we operate
 *  \param[in] trans_proto transport protocol to use (one of IPPROTO_*)
 *  \param[in] proto protocol (xUA variant) to use
 *  \param[in] local_port local SCTP port to bind/listen to
 *  \param[in] local_host local IP address to bind/listen to (optional)
 *  \returns callee-allocated \ref osmo_xua_server in case of success
 */
struct osmo_xua_server *
ss7_xua_server_create2(struct osmo_ss7_instance *inst,
			    int trans_proto, enum osmo_ss7_asp_protocol proto,
			    uint16_t local_port, const char *local_host)
{
	struct osmo_xua_server *oxs;

	if (!ss7_asp_protocol_check_trans_proto(proto, trans_proto)) {
		LOGP(DLSCCP, LOGL_ERROR,
		     "ASP protocol '%s' with transport protocol %d is not supported",
		     osmo_ss7_asp_protocol_name(proto), trans_proto);
		return NULL;
	}

	OSMO_ASSERT(ss7_initialized);
	oxs = talloc_zero(inst, struct osmo_xua_server);
	if (!oxs)
		return NULL;

	LOGP(DLSS7, LOGL_INFO, "Creating %s Server %s:%u\n",
		get_value_string(osmo_ss7_asp_protocol_vals, proto), local_host, local_port);

	INIT_LLIST_HEAD(&oxs->asp_list);

	oxs->cfg.trans_proto = trans_proto;
	oxs->cfg.proto = proto;
	oxs->cfg.local.port = local_port;

	oxs->server = osmo_stream_srv_link_create(oxs);
	osmo_stream_srv_link_set_name(oxs->server, osmo_ss7_asp_protocol_name(proto));
	osmo_stream_srv_link_set_data(oxs->server, oxs);
	osmo_stream_srv_link_set_accept_cb(oxs->server, xua_accept_cb);

	osmo_stream_srv_link_set_nodelay(oxs->server, true);
	osmo_stream_srv_link_set_port(oxs->server, oxs->cfg.local.port);
	osmo_stream_srv_link_set_proto(oxs->server, trans_proto);

	ss7_xua_server_set_local_host(oxs, local_host);

	LOGP(DLSS7, LOGL_INFO, "Created %s server on %s:%" PRIu16 "\n",
		get_value_string(osmo_ss7_asp_protocol_vals, proto), local_host, local_port);

	oxs->inst = inst;
	llist_add_tail(&oxs->list, &inst->xua_servers);

	/* The SUA code internally needs SCCP to work */
	if (proto == OSMO_SS7_ASP_PROT_SUA)
		osmo_ss7_ensure_sccp(inst);

	return oxs;
}

/*! \brief create a new xUA server configured with given ip/port
 *  \param[in] ctx talloc allocation context
 *  \param[in] proto protocol (xUA variant) to use
 *  \param[in] local_port local SCTP port to bind/listen to
 *  \param[in] local_host local IP address to bind/listen to (optional)
 *  \returns callee-allocated \ref osmo_xua_server in case of success
 */
struct osmo_xua_server *
ss7_xua_server_create(struct osmo_ss7_instance *inst,
			   enum osmo_ss7_asp_protocol proto,
			   uint16_t local_port, const char *local_host)
{
	const int trans_proto = ss7_default_trans_proto_for_asp_proto(proto);

	return ss7_xua_server_create2(inst, trans_proto, proto,
					   local_port, local_host);
}

static int ss7_xua_srv_apply_sctp_init_pars(struct osmo_xua_server *xs)
{
	uint8_t byte;
	OSMO_ASSERT(xs->server);

	byte = 1; /*AUTH is needed by ASCONF. enable, don't abort socket creation if AUTH can't be enabled */
	osmo_stream_srv_link_set_param(xs->server, OSMO_STREAM_SRV_LINK_PAR_SCTP_SOCKOPT_AUTH_SUPPORTED,
				       &byte, sizeof(byte));
	byte = 1; /* enable, don't abort socket creation if ASCONF can't be enabled */
	osmo_stream_srv_link_set_param(xs->server, OSMO_STREAM_SRV_LINK_PAR_SCTP_SOCKOPT_ASCONF_SUPPORTED,
				       &byte, sizeof(byte));
	if (xs->cfg.sctp_init.num_ostreams_present)
		osmo_stream_srv_link_set_param(xs->server, OSMO_STREAM_SRV_LINK_PAR_SCTP_INIT_NUM_OSTREAMS,
					&xs->cfg.sctp_init.num_ostreams_value,
					sizeof(xs->cfg.sctp_init.num_ostreams_value));
	if (xs->cfg.sctp_init.max_instreams_present)
		osmo_stream_srv_link_set_param(xs->server, OSMO_STREAM_SRV_LINK_PAR_SCTP_INIT_MAX_INSTREAMS,
					&xs->cfg.sctp_init.max_instreams_value,
					sizeof(xs->cfg.sctp_init.max_instreams_value));
	return 0;
}

/*! \brief Set the xUA server to bind/listen to the currently configured ip/port
 *  \param[in] xs xUA server to operate
 *  \returns 0 on success, negative value on error.
 */
int
ss7_xua_server_bind(struct osmo_xua_server *xs)
{
	char buf[512];
	int rc;
	const char *proto = get_value_string(osmo_ss7_asp_protocol_vals, xs->cfg.proto);

	rc = ss7_asp_peer_snprintf(buf, sizeof(buf), &xs->cfg.local);
	if (rc < 0) {
		LOGP(DLSS7, LOGL_INFO, "Failed parsing %s Server osmo_ss7_asp_peer\n", proto);
	} else {
		LOGP(DLSS7, LOGL_INFO, "(Re)binding %s Server to %s\n",
		     proto, buf);
	}

	/* Applying xUA Server config which may have changed through VTY on the srv_link before opening it: */
	if (xs->cfg.trans_proto == IPPROTO_SCTP) {
		if ((rc = ss7_xua_srv_apply_sctp_init_pars(xs)) < 0)
			LOGP(DLSS7, LOGL_NOTICE, "Failed applying %s Server SCTP INIT parameters\n", proto);
	}

	return osmo_stream_srv_link_open(xs->server);
}

int
ss7_xua_server_set_local_host(struct osmo_xua_server *xs, const char *local_host)
{
	return ss7_xua_server_set_local_hosts(xs, &local_host, 1);
}

int
ss7_xua_server_set_local_hosts(struct osmo_xua_server *xs, const char **local_hosts, size_t local_host_cnt)
{
	int rc;
	OSMO_ASSERT(ss7_initialized);

	rc = ss7_asp_peer_set_hosts(&xs->cfg.local, xs, local_hosts, local_host_cnt);
	if (rc < 0)
		return rc;
	return osmo_stream_srv_link_set_addrs(xs->server, (const char **)xs->cfg.local.host, xs->cfg.local.host_cnt);
}

int
ss7_xua_server_add_local_host(struct osmo_xua_server *xs, const char *local_host)
{
	int rc;

	rc = ss7_asp_peer_add_host(&xs->cfg.local, xs, local_host);
	if (rc < 0)
		return rc;
	return osmo_stream_srv_link_set_addrs(xs->server, (const char **)xs->cfg.local.host, xs->cfg.local.host_cnt);
}

int
ss7_xua_server_del_local_host(struct osmo_xua_server *xs, const char *local_host)
{
	int rc;

	rc = ss7_asp_peer_del_host(&xs->cfg.local, local_host);
	if (rc < 0)
		return rc;
	return osmo_stream_srv_link_set_addrs(xs->server, (const char **)xs->cfg.local.host, xs->cfg.local.host_cnt);
}

bool ss7_xua_server_set_default_local_hosts(struct osmo_xua_server *oxs)
{
	/* If no local addr was set, or erased after _create(): */
	if (!oxs->cfg.local.host_cnt) {
		/* "::" Covers both IPv4 and IPv6 */
		if (ss7_ipv6_sctp_supported("::", true))
			ss7_xua_server_set_local_host(oxs, "::");
		else
			ss7_xua_server_set_local_host(oxs, "0.0.0.0");
		return true;
	}
	return false;
}

void ss7_xua_server_destroy(struct osmo_xua_server *xs)
{
	struct osmo_ss7_asp *asp, *asp2;

	if (xs->server) {
		osmo_stream_srv_link_close(xs->server);
		osmo_stream_srv_link_destroy(xs->server);
		xs->server = NULL;
	}

	/* iterate and close all connections established in relation with this server.
	 * Dynamic ASPs in SCTP=server are destroyed when connection is closed. */
	llist_for_each_entry_safe(asp, asp2, &xs->asp_list, siblings)
		ss7_asp_disconnect_stream(asp);

	llist_del(&xs->list);
	talloc_free(xs);
}

/*! \brief find an xUA server with the given parameters
 *  \param[in] inst SS7 Instance on which we operate
 *  \param[in] trans_proto transport protocol in use (one of IPPROTO_*)
 *  \param[in] proto protocol (xUA variant) in use
 *  \param[in] local_port local port of the server
 *  \returns \ref osmo_xua_server or NULL (not found)
 */
struct osmo_xua_server *
ss7_xua_server_find2(struct osmo_ss7_instance *inst,
			  int trans_proto,
			  enum osmo_ss7_asp_protocol proto,
			  uint16_t local_port)
{
	struct osmo_xua_server *xs;

	OSMO_ASSERT(ss7_initialized);
	llist_for_each_entry(xs, &inst->xua_servers, list) {
		if (trans_proto != xs->cfg.trans_proto)
			continue;
		if (proto != xs->cfg.proto)
			continue;
		if (local_port != xs->cfg.local.port)
			continue;
		return xs;
	}

	return NULL;
}

/*! \brief find an xUA server with the given parameters
 *  \param[in] inst SS7 Instance on which we operate
 *  \param[in] proto protocol (xUA variant) in use
 *  \param[in] local_port local port of the server
 *  \returns \ref osmo_xua_server or NULL (not found)
 */
struct osmo_xua_server *
ss7_xua_server_find(struct osmo_ss7_instance *inst,
			 enum osmo_ss7_asp_protocol proto,
			 uint16_t local_port)
{
	const int trans_proto = ss7_default_trans_proto_for_asp_proto(proto);

	return ss7_xua_server_find2(inst, trans_proto, proto, local_port);
}
