/*
 * Copyright (C) 2019 by Sukchan Lee <acetcom@gmail.com>
 *
 * This file is part of Open5GS.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 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 <https://www.gnu.org/licenses/>.
 */

#include "ogs-gtp.h"

#include "mme-event.h"
#include "mme-gtp-path.h"
#include "mme-path.h"
#include "s1ap-path.h"
#include "mme-s11-build.h"
#include "mme-sm.h"

static void _gtpv2_c_recv_cb(short when, ogs_socket_t fd, void *data)
{
    int rv;
    char buf[OGS_ADDRSTRLEN];

    ssize_t size;
    mme_event_t *e = NULL;
    ogs_pkbuf_t *pkbuf = NULL;
    ogs_sockaddr_t from;
    mme_sgw_t *sgw = NULL;

    ogs_assert(fd != INVALID_SOCKET);

    pkbuf = ogs_pkbuf_alloc(NULL, OGS_MAX_SDU_LEN);
    ogs_assert(pkbuf);
    ogs_pkbuf_put(pkbuf, OGS_MAX_SDU_LEN);

    size = ogs_recvfrom(fd, pkbuf->data, pkbuf->len, 0, &from);
    if (size <= 0) {
        ogs_log_message(OGS_LOG_ERROR, ogs_socket_errno,
                "ogs_recvfrom() failed");
        ogs_pkbuf_free(pkbuf);
        return;
    }

    ogs_pkbuf_trim(pkbuf, size);

    sgw = mme_sgw_find_by_addr(&from);
    if (!sgw) {
        ogs_error("Unknown SGW : %s", OGS_ADDR(&from, buf));
        ogs_pkbuf_free(pkbuf);
        return;
    }
    ogs_assert(sgw);

    e = mme_event_new(MME_EVT_S11_MESSAGE);
    ogs_assert(e);
    e->gnode = (ogs_gtp_node_t *)sgw;
    e->pkbuf = pkbuf;

    rv = ogs_queue_push(ogs_app()->queue, e);
    if (rv != OGS_OK) {
        ogs_error("ogs_queue_push() failed:%d", (int)rv);
        ogs_pkbuf_free(e->pkbuf);
        mme_event_free(e);
    }
}

static void timeout(ogs_gtp_xact_t *xact, void *data)
{
    mme_ue_t *mme_ue = NULL;
    enb_ue_t *enb_ue = NULL;
    mme_sess_t *sess = NULL;
    mme_bearer_t *bearer = NULL;
    uint8_t type = 0;

    ogs_assert(xact);
    type = xact->seq[0].type;

    switch (type) {
    case OGS_GTP2_RELEASE_ACCESS_BEARERS_REQUEST_TYPE:
    case OGS_GTP2_CREATE_INDIRECT_DATA_FORWARDING_TUNNEL_REQUEST_TYPE:
    case OGS_GTP2_DELETE_INDIRECT_DATA_FORWARDING_TUNNEL_REQUEST_TYPE:
        mme_ue = data;
        ogs_assert(mme_ue);
        break;
    case OGS_GTP2_CREATE_SESSION_REQUEST_TYPE:
    case OGS_GTP2_DELETE_SESSION_REQUEST_TYPE:
        sess = data;
        ogs_assert(sess);
        mme_ue = sess->mme_ue;
        ogs_assert(mme_ue);
        break;
    case OGS_GTP2_MODIFY_BEARER_REQUEST_TYPE:
    case OGS_GTP2_BEARER_RESOURCE_COMMAND_TYPE:
        bearer = data;
        ogs_assert(bearer);
        sess = bearer->sess;
        ogs_assert(sess);
        mme_ue = sess->mme_ue;
        ogs_assert(mme_ue);
        break;
    default:
        ogs_fatal("Invalid type [%d]", type);
        ogs_assert_if_reached();
        break;
    }

    ogs_assert(mme_ue);

    switch (type) {
    case OGS_GTP2_DELETE_SESSION_REQUEST_TYPE:
        /*
         * If SESSION_CONTEXT_WILL_DELETED(MME_UE) is not cleared,
         * The MME cannot send Delete-Session-Request to the SGW-C.
         * As such, it could be the infinite loop occurred in EMM state machine.
         *
         * To prevent this situation,
         * force clearing SESSION_CONTEXT_WILL_DELETED variable
         * when MME does not receive Delete-Session-Response message from SGW-C.
         */
        CLEAR_SESSION_CONTEXT(mme_ue);

        enb_ue = enb_ue_cycle(mme_ue->enb_ue);
        if (enb_ue) {
            ogs_assert(OGS_OK ==
                s1ap_send_ue_context_release_command(enb_ue,
                    S1AP_Cause_PR_nas, S1AP_CauseNas_normal_release,
                    S1AP_UE_CTX_REL_UE_CONTEXT_REMOVE, 0));
        } else {
            ogs_warn("No S1 Context");
        }
        break;
    case OGS_GTP2_BEARER_RESOURCE_COMMAND_TYPE:
        /* Nothing to do */
        break;
    default:
        mme_send_delete_session_or_mme_ue_context_release(mme_ue);
        break;
    }

    ogs_error("GTP Timeout : IMSI[%s] Message-Type[%d]",
            mme_ue->imsi_bcd, type);
}

int mme_gtp_open(void)
{
    int rv;
    ogs_socknode_t *node = NULL;
    ogs_sock_t *sock = NULL;
    mme_sgw_t *sgw = NULL;

    ogs_list_for_each(&ogs_gtp_self()->gtpc_list, node) {
        sock = ogs_gtp_server(node);
        if (!sock) return OGS_ERROR;

        node->poll = ogs_pollset_add(ogs_app()->pollset,
                OGS_POLLIN, sock->fd, _gtpv2_c_recv_cb, sock);
        ogs_assert(node->poll);
    }
    ogs_list_for_each(&ogs_gtp_self()->gtpc_list6, node) {
        sock = ogs_gtp_server(node);
        if (!sock) return OGS_ERROR;

        node->poll = ogs_pollset_add(ogs_app()->pollset,
                OGS_POLLIN, sock->fd, _gtpv2_c_recv_cb, sock);
        ogs_assert(node->poll);
    }

    OGS_SETUP_GTPC_SERVER;

    mme_self()->pgw_addr = mme_pgw_addr_find_by_apn(
            &mme_self()->pgw_list, AF_INET, NULL);
    mme_self()->pgw_addr6 = mme_pgw_addr_find_by_apn(
            &mme_self()->pgw_list, AF_INET6, NULL);
    ogs_assert(mme_self()->pgw_addr || mme_self()->pgw_addr6);

    ogs_list_for_each(&mme_self()->sgw_list, sgw) {
        rv = ogs_gtp_connect(
                ogs_gtp_self()->gtpc_sock, ogs_gtp_self()->gtpc_sock6,
                (ogs_gtp_node_t *)sgw);
        ogs_assert(rv == OGS_OK);
    }

    return OGS_OK;
}

void mme_gtp_close(void)
{
    ogs_socknode_remove_all(&ogs_gtp_self()->gtpc_list);
    ogs_socknode_remove_all(&ogs_gtp_self()->gtpc_list6);
}

int mme_gtp_send_create_session_request(mme_sess_t *sess, int create_action)
{
    int rv;
    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;
    ogs_gtp_xact_t *xact = NULL;
    mme_ue_t *mme_ue = NULL;

    mme_ue = sess->mme_ue;
    ogs_assert(mme_ue);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_CREATE_SESSION_REQUEST_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_create_session_request(h.type, sess);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    xact = ogs_gtp_xact_local_create(mme_ue->gnode, &h, pkbuf, timeout, sess);
    ogs_expect_or_return_val(xact, OGS_ERROR);
    xact->create_action = create_action;

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_modify_bearer_request(mme_bearer_t *bearer, int uli_presence)
{
    int rv;

    ogs_gtp_xact_t *xact = NULL;
    mme_ue_t *mme_ue = NULL;

    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;

    ogs_assert(bearer);
    mme_ue = bearer->mme_ue;
    ogs_assert(mme_ue);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_MODIFY_BEARER_REQUEST_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_modify_bearer_request(h.type, bearer, uli_presence);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    xact = ogs_gtp_xact_local_create(mme_ue->gnode, &h, pkbuf, timeout, bearer);
    ogs_expect_or_return_val(xact, OGS_ERROR);

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_delete_session_request(mme_sess_t *sess, int action)
{
    int rv;
    ogs_pkbuf_t *s11buf = NULL;
    ogs_gtp2_header_t h;
    ogs_gtp_xact_t *xact = NULL;
    mme_ue_t *mme_ue = NULL;

    ogs_assert(action);
    ogs_assert(sess);
    mme_ue = sess->mme_ue;
    ogs_assert(mme_ue);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_DELETE_SESSION_REQUEST_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    s11buf = mme_s11_build_delete_session_request(h.type, sess);
    ogs_expect_or_return_val(s11buf, OGS_ERROR);

    xact = ogs_gtp_xact_local_create(mme_ue->gnode, &h, s11buf, timeout, sess);
    ogs_expect_or_return_val(xact, OGS_ERROR);
    xact->delete_action = action;

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

void mme_gtp_send_delete_all_sessions(mme_ue_t *mme_ue, int action)
{
    mme_sess_t *sess = NULL, *next_sess = NULL;

    ogs_assert(mme_ue);
    ogs_assert(action);

    if (SESSION_CONTEXT_WILL_DELETED(mme_ue)) {
        ogs_warn("[%s] Delete-Session-Request has already sent",
                mme_ue->imsi_bcd);
        return;
    }

    mme_ue->session_context_will_deleted = 1;

    sess = mme_sess_first(mme_ue);
    while (sess != NULL) {
        next_sess = mme_sess_next(sess);

        if (MME_HAVE_SGW_S1U_PATH(sess)) {
            mme_bearer_t *bearer = mme_default_bearer_in_sess(sess);
            ogs_assert(bearer);

            if (bearer &&
                OGS_FSM_CHECK(&bearer->sm, esm_state_pdn_will_disconnect)) {
                ogs_warn("PDN will disconnect[EBI:%d]", bearer->ebi);
            } else {
                mme_gtp_send_delete_session_request(sess, action);
            }
        } else {
            mme_sess_remove(sess);
        }

        sess = next_sess;
    }
}

int mme_gtp_send_create_bearer_response(
        mme_bearer_t *bearer, uint8_t cause_value)
{
    int rv;

    ogs_gtp_xact_t *xact = NULL;
    mme_ue_t *mme_ue = NULL;

    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;

    ogs_assert(bearer);
    mme_ue = bearer->mme_ue;
    ogs_assert(mme_ue);
    xact = ogs_gtp_xact_cycle(bearer->create.xact);
    ogs_assert(xact);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_CREATE_BEARER_RESPONSE_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_create_bearer_response(h.type, bearer, cause_value);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    rv = ogs_gtp_xact_update_tx(xact, &h, pkbuf);
    ogs_expect_or_return_val(rv == OGS_OK, OGS_ERROR);

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_update_bearer_response(
        mme_bearer_t *bearer, uint8_t cause_value)
{
    int rv;

    ogs_gtp_xact_t *xact = NULL;
    mme_ue_t *mme_ue = NULL;

    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;

    ogs_assert(bearer);
    mme_ue = bearer->mme_ue;
    ogs_assert(mme_ue);
    xact = ogs_gtp_xact_cycle(bearer->update.xact);
    ogs_assert(xact);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_UPDATE_BEARER_RESPONSE_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_update_bearer_response(h.type, bearer, cause_value);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    rv = ogs_gtp_xact_update_tx(xact, &h, pkbuf);
    ogs_expect_or_return_val(rv == OGS_OK, OGS_ERROR);

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_delete_bearer_response(
        mme_bearer_t *bearer, uint8_t cause_value)
{
    int rv;

    ogs_gtp_xact_t *xact = NULL;
    mme_ue_t *mme_ue = NULL;

    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;

    ogs_assert(bearer);
    mme_ue = bearer->mme_ue;
    ogs_assert(mme_ue);
    xact = ogs_gtp_xact_cycle(bearer->delete.xact);
    ogs_assert(xact);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_DELETE_BEARER_RESPONSE_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_delete_bearer_response(h.type, bearer, cause_value);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    rv = ogs_gtp_xact_update_tx(xact, &h, pkbuf);
    ogs_expect_or_return_val(rv == OGS_OK, OGS_ERROR);

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_release_access_bearers_request(mme_ue_t *mme_ue, int action)
{
    int rv;
    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;
    ogs_gtp_xact_t *xact = NULL;

    ogs_assert(action);
    ogs_assert(mme_ue);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_RELEASE_ACCESS_BEARERS_REQUEST_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_release_access_bearers_request(h.type);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    xact = ogs_gtp_xact_local_create(mme_ue->gnode, &h, pkbuf, timeout, mme_ue);
    ogs_expect_or_return_val(xact, OGS_ERROR);
    xact->release_action = action;

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

void mme_gtp_send_release_all_ue_in_enb(mme_enb_t *enb, int action)
{
    mme_ue_t *mme_ue = NULL;
    enb_ue_t *enb_ue = NULL;

    ogs_list_for_each(&enb->enb_ue_list, enb_ue) {
        mme_ue = enb_ue->mme_ue;

        if (mme_ue) {
            ogs_assert(OGS_OK ==
                mme_gtp_send_release_access_bearers_request(mme_ue, action));

        } else {
            ogs_warn("mme_gtp_send_release_all_ue_in_enb()");
            ogs_warn("    ENB_UE_S1AP_ID[%d] MME_UE_S1AP_ID[%d] Action[%d]",
                enb_ue->enb_ue_s1ap_id, enb_ue->mme_ue_s1ap_id, action);

            if (action == OGS_GTP_RELEASE_S1_CONTEXT_REMOVE_BY_LO_CONNREFUSED ||
                action == OGS_GTP_RELEASE_S1_CONTEXT_REMOVE_BY_RESET_ALL) {
                enb_ue_remove(enb_ue);
            } else {
                /* At this point, it does not support other action */
                ogs_assert_if_reached();
            }
        }
    }
}

int mme_gtp_send_downlink_data_notification_ack(
        mme_bearer_t *bearer, uint8_t cause_value)
{
    int rv;
    mme_ue_t *mme_ue = NULL;
    ogs_gtp_xact_t *xact = NULL;

    ogs_gtp2_header_t h;
    ogs_pkbuf_t *s11buf = NULL;

    ogs_assert(bearer);
    xact = ogs_gtp_xact_cycle(bearer->notify.xact);
    ogs_assert(xact);
    mme_ue = bearer->mme_ue;
    ogs_assert(mme_ue);

    /* Build Downlink data notification ack */
    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_DOWNLINK_DATA_NOTIFICATION_ACKNOWLEDGE_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    s11buf = mme_s11_build_downlink_data_notification_ack(h.type, cause_value);
    ogs_expect_or_return_val(s11buf, OGS_ERROR);

    rv = ogs_gtp_xact_update_tx(xact, &h, s11buf);
    ogs_expect_or_return_val(rv == OGS_OK, OGS_ERROR);

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_create_indirect_data_forwarding_tunnel_request(
        mme_ue_t *mme_ue)
{
    int rv;
    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;
    ogs_gtp_xact_t *xact = NULL;

    ogs_assert(mme_ue);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_CREATE_INDIRECT_DATA_FORWARDING_TUNNEL_REQUEST_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_create_indirect_data_forwarding_tunnel_request(
            h.type, mme_ue);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    xact = ogs_gtp_xact_local_create(mme_ue->gnode, &h, pkbuf, timeout, mme_ue);
    ogs_expect_or_return_val(xact, OGS_ERROR);

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_delete_indirect_data_forwarding_tunnel_request(
        mme_ue_t *mme_ue, int action)
{
    int rv;
    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;
    ogs_gtp_xact_t *xact = NULL;

    ogs_assert(action);
    ogs_assert(mme_ue);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_DELETE_INDIRECT_DATA_FORWARDING_TUNNEL_REQUEST_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = ogs_pkbuf_alloc(NULL, OGS_TLV_MAX_HEADROOM);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);
    ogs_pkbuf_reserve(pkbuf, OGS_TLV_MAX_HEADROOM);

    xact = ogs_gtp_xact_local_create(mme_ue->gnode, &h, pkbuf, timeout, mme_ue);
    ogs_expect_or_return_val(xact, OGS_ERROR);
    xact->delete_indirect_action = action;

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}

int mme_gtp_send_bearer_resource_command(
        mme_bearer_t *bearer, ogs_nas_eps_message_t *nas_message)
{
    int rv;
    ogs_gtp2_header_t h;
    ogs_pkbuf_t *pkbuf = NULL;
    ogs_gtp_xact_t *xact = NULL;

    mme_ue_t *mme_ue = NULL;

    ogs_assert(bearer);
    mme_ue = bearer->mme_ue;
    ogs_assert(mme_ue);

    memset(&h, 0, sizeof(ogs_gtp2_header_t));
    h.type = OGS_GTP2_BEARER_RESOURCE_COMMAND_TYPE;
    h.teid = mme_ue->sgw_s11_teid;

    pkbuf = mme_s11_build_bearer_resource_command(h.type, bearer, nas_message);
    ogs_expect_or_return_val(pkbuf, OGS_ERROR);

    xact = ogs_gtp_xact_local_create(mme_ue->gnode, &h, pkbuf, timeout, bearer);
    ogs_expect_or_return_val(xact, OGS_ERROR);
    xact->xid |= OGS_GTP_CMD_XACT_ID;

    rv = ogs_gtp_xact_commit(xact);
    ogs_expect(rv == OGS_OK);

    return rv;
}