/*
 * Ouroboros - Copyright (C) 2016 - 2018
 *
 * Data Transfer Component
 *
 *    Dimitri Staessens <dimitri.staessens@ugent.be>
 *    Sander Vrijders   <sander.vrijders@ugent.be>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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., http://www.fsf.org/about/contact/.
 */

#define _POSIX_C_SOURCE 200112L

#include "config.h"

#define DT               "dt"
#define OUROBOROS_PREFIX DT

/* FIXME: fix #defines and remove endian.h include. */
#include <ouroboros/endian.h>
#include <ouroboros/bitmap.h>
#include <ouroboros/errno.h>
#include <ouroboros/logs.h>
#include <ouroboros/dev.h>
#include <ouroboros/notifier.h>
#include <ouroboros/rib.h>
#ifdef IPCP_FLOW_STATS
#include <ouroboros/fccntl.h>
#endif

#include "connmgr.h"
#include "ipcp.h"
#include "dt.h"
#include "dt_pci.h"
#include "pff.h"
#include "routing.h"
#include "sdu_sched.h"
#include "comp.h"
#include "fa.h"

#include <stdlib.h>
#include <stdbool.h>
#include <pthread.h>
#include <string.h>
#include <inttypes.h>
#include <assert.h>

#define QOS_BLOCK_LEN 672
#define STAT_FILE_LEN (189 + QOS_BLOCK_LEN * QOS_CUBE_MAX)

#ifndef CLOCK_REALTIME_COARSE
#define CLOCK_REALTIME_COARSE CLOCK_REALTIME
#endif

struct comp_info {
        void   (* post_sdu)(void * comp, struct shm_du_buff * sdb);
        void * comp;
        char * name;
};

struct {
        struct sdu_sched * sdu_sched;

        struct pff *       pff[QOS_CUBE_MAX];
        struct routing_i * routing[QOS_CUBE_MAX];
#ifdef IPCP_FLOW_STATS
        struct {
                time_t          stamp;
                uint64_t        addr;
                size_t          snd_pkt[QOS_CUBE_MAX];
                size_t          rcv_pkt[QOS_CUBE_MAX];
                size_t          snd_bytes[QOS_CUBE_MAX];
                size_t          rcv_bytes[QOS_CUBE_MAX];
                size_t          lcl_r_pkt[QOS_CUBE_MAX];
                size_t          lcl_r_bytes[QOS_CUBE_MAX];
                size_t          lcl_w_pkt[QOS_CUBE_MAX];
                size_t          lcl_w_bytes[QOS_CUBE_MAX];
                size_t          r_drp_pkt[QOS_CUBE_MAX];
                size_t          r_drp_bytes[QOS_CUBE_MAX];
                size_t          w_drp_pkt[QOS_CUBE_MAX];
                size_t          w_drp_bytes[QOS_CUBE_MAX];
                size_t          f_nhp_pkt[QOS_CUBE_MAX];
                size_t          f_nhp_bytes[QOS_CUBE_MAX];
                pthread_mutex_t lock;
        } stat[PROG_MAX_FLOWS];

        size_t             n_flows;
#endif
        struct bmp *       res_fds;
        struct comp_info   comps[PROG_RES_FDS];
        pthread_rwlock_t   lock;

        pthread_t          listener;
} dt;

static int dt_stat_read(const char * path,
                        char *       buf,
                        size_t       len)
{
#ifdef IPCP_FLOW_STATS
        int         fd;
        int         i;
        char        str[QOS_BLOCK_LEN + 1];
        char        addrstr[20];
        char        tmstr[20];
        size_t      rxqlen = 0;
        size_t      txqlen = 0;
        struct tm * tm;

        /* NOTE: we may need stronger checks. */
        fd = atoi(path);

        if (len < STAT_FILE_LEN)
                return 0;

        buf[0] = '\0';

        pthread_mutex_lock(&dt.stat[fd].lock);

        if (dt.stat[fd].stamp == 0) {
                pthread_mutex_unlock(&dt.stat[fd].lock);
                return 0;
        }

        if (dt.stat[fd].addr == ipcpi.dt_addr)
                sprintf(addrstr, "%s", dt.comps[fd].name);
        else
                sprintf(addrstr, "%" PRIu64, dt.stat[fd].addr);

        tm = localtime(&dt.stat[fd].stamp);
        strftime(tmstr, sizeof(tmstr), "%F %T", tm);

        if (fd >= PROG_RES_FDS) {
                fccntl(fd, FLOWGRXQLEN, &rxqlen);
                fccntl(fd, FLOWGTXQLEN, &txqlen);
        }

        sprintf(buf,
                "Flow established at:      %20s\n"
                "Endpoint address:         %20s\n"
                "Queued packets (rx):      %20zu\n"
                "Queued packets (tx):      %20zu\n\n",
                tmstr, addrstr, rxqlen, txqlen);

        for (i = 0; i < QOS_CUBE_MAX; ++i) {
                sprintf(str,
                        "Qos cube %3d:\n"
                        " sent (packets):          %20zu\n"
                        " sent (bytes):            %20zu\n"
                        " rcvd (packets):          %20zu\n"
                        " rcvd (bytes):            %20zu\n"
                        " local sent (packets):    %20zu\n"
                        " local sent (bytes):      %20zu\n"
                        " local rcvd (packets):    %20zu\n"
                        " local rcvd (bytes):      %20zu\n"
                        " dropped ttl (packets):   %20zu\n"
                        " dropped ttl (bytes):     %20zu\n"
                        " failed writes (packets): %20zu\n"
                        " failed writes (bytes):   %20zu\n"
                        " failed nhop (packets):   %20zu\n"
                        " failed nhop (bytes):     %20zu\n",
                        i,
                        dt.stat[fd].snd_pkt[i],
                        dt.stat[fd].snd_bytes[i],
                        dt.stat[fd].rcv_pkt[i],
                        dt.stat[fd].rcv_bytes[i],
                        dt.stat[fd].lcl_w_pkt[i],
                        dt.stat[fd].lcl_w_bytes[i],
                        dt.stat[fd].lcl_r_pkt[i],
                        dt.stat[fd].lcl_r_bytes[i],
                        dt.stat[fd].r_drp_pkt[i],
                        dt.stat[fd].r_drp_bytes[i],
                        dt.stat[fd].w_drp_pkt[i],
                        dt.stat[fd].w_drp_bytes[i],
                        dt.stat[fd].f_nhp_pkt[i],
                        dt.stat[fd].f_nhp_bytes[i]
                        );
                strcat(buf, str);
        }

        pthread_mutex_unlock(&dt.stat[fd].lock);

        return STAT_FILE_LEN;
#else
        (void) path;
        (void) buf;
        (void) len;
        return 0;
#endif
}

static int dt_stat_readdir(char *** buf)
{
#ifdef IPCP_FLOW_STATS
        char   entry[RIB_PATH_LEN + 1];
        size_t i;
        int    idx = 0;

        pthread_rwlock_rdlock(&dt.lock);

        if (dt.n_flows < 1) {
                pthread_rwlock_unlock(&dt.lock);
                return 0;
        }

        *buf = malloc(sizeof(**buf) * dt.n_flows);
        if (*buf == NULL) {
                pthread_rwlock_unlock(&dt.lock);
                return -ENOMEM;
        }

        for (i = 0; i < PROG_MAX_FLOWS; ++i) {
                pthread_mutex_lock(&dt.stat[i].lock);

                if (dt.stat[i].stamp == 0) {
                        pthread_mutex_unlock(&dt.stat[i].lock);
                        /* Optimization: skip unused res_fds. */
                        if (i < PROG_RES_FDS)
                                i = PROG_RES_FDS;
                        continue;
                }

                sprintf(entry, "%zu", i);

                (*buf)[idx] = malloc(strlen(entry) + 1);
                if ((*buf)[idx] == NULL) {
                        while (idx-- > 0)
                                free((*buf)[idx]);
                        free(buf);
                        pthread_mutex_unlock(&dt.stat[i].lock);
                        pthread_rwlock_unlock(&dt.lock);
                        return -ENOMEM;
                }

                strcpy((*buf)[idx++], entry);

                pthread_mutex_unlock(&dt.stat[i].lock);
        }

        pthread_rwlock_unlock(&dt.lock);

        assert((size_t) idx == dt.n_flows);

        return idx;
#else
        (void) buf;
        return 0;
#endif
}

static int dt_stat_getattr(const char *  path,
                           struct stat * st)
{
#ifdef IPCP_FLOW_STATS
        int fd;

        fd = atoi(path);

        st->st_mode  = S_IFREG | 0755;
        st->st_nlink = 1;
        st->st_uid   = getuid();
        st->st_gid   = getgid();

        pthread_mutex_lock(&dt.stat[fd].lock);

        if (dt.stat[fd].stamp != -1) {
                st->st_size  = STAT_FILE_LEN;
                st->st_mtime = dt.stat[fd].stamp;
        } else {
                st->st_size  = 0;
                st->st_mtime = 0;
        }

        pthread_mutex_unlock(&dt.stat[fd].lock);
#else
        (void) path;
        (void) st;
#endif
        return 0;
}

static struct rib_ops r_ops = {
        .read    = dt_stat_read,
        .readdir = dt_stat_readdir,
        .getattr = dt_stat_getattr
};

#ifdef IPCP_FLOW_STATS

static void stat_used(int      fd,
                      uint64_t addr)
{
        struct timespec now;

        clock_gettime(CLOCK_REALTIME_COARSE, &now);

        pthread_mutex_lock(&dt.stat[fd].lock);

        memset(&dt.stat[fd], 0, sizeof(dt.stat[fd]));

        dt.stat[fd].stamp = (addr != INVALID_ADDR) ? now.tv_sec : 0;
        dt.stat[fd].addr = addr;

        pthread_mutex_unlock(&dt.stat[fd].lock);

        pthread_rwlock_wrlock(&dt.lock);

        (addr != INVALID_ADDR) ? ++dt.n_flows : --dt.n_flows;

        pthread_rwlock_unlock(&dt.lock);
}
#endif

static void handle_event(void *       self,
                         int          event,
                         const void * o)
{
        struct conn * c;

        (void) self;

        c = (struct conn *) o;

        switch (event) {
        case NOTIFY_DT_CONN_ADD:
#ifdef IPCP_FLOW_STATS
                stat_used(c->flow_info.fd, c->conn_info.addr);
#endif
                sdu_sched_add(dt.sdu_sched, c->flow_info.fd);
                log_dbg("Added fd %d to SDU scheduler.", c->flow_info.fd);
                break;
        case NOTIFY_DT_CONN_DEL:
#ifdef IPCP_FLOW_STATS
                stat_used(c->flow_info.fd, INVALID_ADDR);
#endif
                sdu_sched_del(dt.sdu_sched, c->flow_info.fd);
                log_dbg("Removed fd %d from SDU scheduler.", c->flow_info.fd);
                break;
        default:
                break;
        }
}

static void sdu_handler(int                  fd,
                        qoscube_t            qc,
                        struct shm_du_buff * sdb)
{
        struct dt_pci dt_pci;
        int           ret;
        int           ofd;
#ifdef IPCP_FLOW_STATS
        size_t        len;
#else
        (void)        fd;
#endif

#ifdef IPCP_FLOW_STATS
        len = shm_du_buff_tail(sdb) - shm_du_buff_head(sdb);
#endif
        memset(&dt_pci, 0, sizeof(dt_pci));
        dt_pci_des(sdb, &dt_pci);
        if (dt_pci.dst_addr != ipcpi.dt_addr) {
                if (dt_pci.ttl == 0) {
                        log_dbg("TTL was zero.");
                        ipcp_sdb_release(sdb);
#ifdef IPCP_FLOW_STATS
                        pthread_mutex_lock(&dt.stat[fd].lock);

                        ++dt.stat[fd].rcv_pkt[qc];
                        dt.stat[fd].rcv_bytes[qc] += len;
                        ++dt.stat[fd].r_drp_pkt[qc];
                        dt.stat[fd].r_drp_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[fd].lock);
#endif
                        return;
                }

                /* FIXME: Use qoscube from PCI instead of incoming flow. */
                ofd = pff_nhop(dt.pff[qc], dt_pci.dst_addr);
                if (ofd < 0) {
                        log_dbg("No next hop for %" PRIu64, dt_pci.dst_addr);
                        ipcp_sdb_release(sdb);
#ifdef IPCP_FLOW_STATS
                        pthread_mutex_lock(&dt.stat[fd].lock);

                        ++dt.stat[fd].rcv_pkt[qc];
                        dt.stat[fd].rcv_bytes[qc] += len;
                        ++dt.stat[fd].f_nhp_pkt[qc];
                        dt.stat[fd].f_nhp_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[fd].lock);
#endif
                        return;
                }

                ret = ipcp_flow_write(ofd, sdb);
                if (ret < 0) {
                        log_dbg("Failed to write SDU to fd %d.", ofd);
                        if (ret == -EFLOWDOWN)
                                notifier_event(NOTIFY_DT_FLOW_DOWN, &ofd);
                        ipcp_sdb_release(sdb);
#ifdef IPCP_FLOW_STATS
                        pthread_mutex_lock(&dt.stat[fd].lock);

                        ++dt.stat[fd].rcv_pkt[qc];
                        dt.stat[fd].rcv_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[fd].lock);
                        pthread_mutex_lock(&dt.stat[ofd].lock);

                        ++dt.stat[ofd].w_drp_pkt[qc];
                        dt.stat[ofd].w_drp_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[ofd].lock);
#endif
                        return;
                }
#ifdef IPCP_FLOW_STATS
                pthread_mutex_lock(&dt.stat[fd].lock);

                ++dt.stat[fd].rcv_pkt[qc];
                dt.stat[fd].rcv_bytes[qc] += len;

                pthread_mutex_unlock(&dt.stat[fd].lock);
                pthread_mutex_lock(&dt.stat[ofd].lock);

                ++dt.stat[ofd].snd_pkt[qc];
                dt.stat[ofd].snd_bytes[qc] += len;

                pthread_mutex_unlock(&dt.stat[ofd].lock);
#endif
        } else {
                dt_pci_shrink(sdb);
                if (dt_pci.eid >= PROG_RES_FDS) {
                        if (ipcp_flow_write(dt_pci.eid, sdb)) {
                                ipcp_sdb_release(sdb);
#ifdef IPCP_FLOW_STATS
                                pthread_mutex_lock(&dt.stat[dt_pci.eid].lock);
                                ++dt.stat[fd].rcv_pkt[qc];
                                dt.stat[fd].rcv_bytes[qc] += len;
                                ++dt.stat[dt_pci.eid].w_drp_pkt[qc];
                                dt.stat[dt_pci.eid].w_drp_bytes[qc] += len;

                                pthread_mutex_unlock(&dt.stat[dt_pci.eid].lock);
#endif

                        }
#ifdef IPCP_FLOW_STATS
                        pthread_mutex_lock(&dt.stat[fd].lock);

                        ++dt.stat[fd].rcv_pkt[qc];
                        dt.stat[fd].rcv_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[fd].lock);
                        pthread_mutex_lock(&dt.stat[dt_pci.eid].lock);

                        ++dt.stat[dt_pci.eid].rcv_pkt[qc];
                        dt.stat[dt_pci.eid].rcv_bytes[qc] += len;
                        ++dt.stat[dt_pci.eid].lcl_r_pkt[qc];
                        dt.stat[dt_pci.eid].lcl_r_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[dt_pci.eid].lock);
#endif
                        return;
                }

                if (dt.comps[dt_pci.eid].post_sdu == NULL) {
                        log_err("No registered component on eid %d.",
                                dt_pci.eid);
                        ipcp_sdb_release(sdb);
#ifdef IPCP_FLOW_STATS
                        pthread_mutex_lock(&dt.stat[fd].lock);

                        ++dt.stat[fd].rcv_pkt[qc];
                        dt.stat[fd].rcv_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[fd].lock);
                        pthread_mutex_lock(&dt.stat[dt_pci.eid].lock);

                        ++dt.stat[dt_pci.eid].w_drp_pkt[qc];
                        dt.stat[dt_pci.eid].w_drp_bytes[qc] += len;

                        pthread_mutex_unlock(&dt.stat[dt_pci.eid].lock);
#endif
                        return;
                }
#ifdef IPCP_FLOW_STATS
                pthread_mutex_lock(&dt.stat[fd].lock);

                ++dt.stat[fd].rcv_pkt[qc];
                dt.stat[fd].rcv_bytes[qc] += len;
                ++dt.stat[fd].lcl_r_pkt[qc];
                dt.stat[fd].lcl_r_bytes[qc] += len;

                pthread_mutex_unlock(&dt.stat[fd].lock);
                pthread_mutex_lock(&dt.stat[dt_pci.eid].lock);

                ++dt.stat[dt_pci.eid].snd_pkt[qc];
                dt.stat[dt_pci.eid].snd_bytes[qc] += len;

                pthread_mutex_unlock(&dt.stat[dt_pci.eid].lock);
#endif
                dt.comps[dt_pci.eid].post_sdu(dt.comps[dt_pci.eid].comp, sdb);
        }
}

static void * dt_conn_handle(void * o)
{
        struct conn conn;

        (void) o;

        while (true) {
                if (connmgr_wait(COMPID_DT, &conn)) {
                        log_err("Failed to get next DT connection.");
                        continue;
                }

                /* NOTE: connection acceptance policy could be here. */

                notifier_event(NOTIFY_DT_CONN_ADD, &conn);
        }

        return 0;
}

int dt_init(enum pol_routing pr,
            enum pol_pff     pp,
            uint8_t          addr_size,
            uint8_t          eid_size,
            uint8_t          max_ttl)
{
        int              i;
        int              j;
        char             dtstr[256];
        struct conn_info info;

        memset(&info, 0, sizeof(info));

        strcpy(info.comp_name, DT_COMP);
        strcpy(info.protocol, DT_PROTO);
        info.pref_version = 1;
        info.pref_syntax  = PROTO_FIXED;
        info.addr         = ipcpi.dt_addr;

        if (dt_pci_init(addr_size, eid_size, max_ttl)) {
                log_err("Failed to init shm dt_pci.");
                goto fail_pci_init;
        }

        if (notifier_reg(handle_event, NULL)) {
                log_err("Failed to register with notifier.");
                goto fail_notifier_reg;
        }

        if (connmgr_comp_init(COMPID_DT, &info)) {
                log_err("Failed to register with connmgr.");
                goto fail_connmgr_comp_init;
        }

        if (routing_init(pr)) {
                log_err("Failed to init routing.");
                goto fail_routing;
        }

        for (i = 0; i < QOS_CUBE_MAX; ++i) {
                dt.pff[i] = pff_create(pp);
                if (dt.pff[i] == NULL) {
                        log_err("Failed to create a PFF.");
                        for (j = 0; j < i; ++j)
                                pff_destroy(dt.pff[j]);
                        goto fail_pff;
                }
        }

        for (i = 0; i < QOS_CUBE_MAX; ++i) {
                dt.routing[i] = routing_i_create(dt.pff[i]);
                if (dt.routing[i] == NULL) {
                        for (j = 0; j < i; ++j)
                                routing_i_destroy(dt.routing[j]);
                        goto fail_routing_i;
                }
        }

        if (pthread_rwlock_init(&dt.lock, NULL)) {
                log_err("Failed to init rwlock.");
                goto fail_rwlock_init;
        }

        dt.res_fds = bmp_create(PROG_RES_FDS, 0);
        if (dt.res_fds == NULL)
                goto fail_res_fds;
#ifdef IPCP_FLOW_STATS
        memset(dt.stat, 0, sizeof(dt.stat));

        for (i = 0; i < PROG_MAX_FLOWS; ++i)
                if (pthread_mutex_init(&dt.stat[i].lock, NULL)) {
                        for (j = 0; j < i; ++j)
                                pthread_mutex_destroy(&dt.stat[j].lock);
                        goto fail_stat_lock;
                }

        dt.n_flows = 0;
#endif
        sprintf(dtstr, "%s.%" PRIu64, DT, ipcpi.dt_addr);
        if (rib_reg(dtstr, &r_ops))
                goto fail_rib_reg;

        return 0;

 fail_rib_reg:
#ifdef IPCP_FLOW_STATS
        for (i = 0; i < PROG_MAX_FLOWS; ++i)
                pthread_mutex_destroy(&dt.stat[i].lock);
 fail_stat_lock:
#endif
        bmp_destroy(dt.res_fds);
 fail_res_fds:
        pthread_rwlock_destroy(&dt.lock);
 fail_rwlock_init:
        for (j = 0; j < QOS_CUBE_MAX; ++j)
                routing_i_destroy(dt.routing[j]);
 fail_routing_i:
        for (i = 0; i < QOS_CUBE_MAX; ++i)
                pff_destroy(dt.pff[i]);
 fail_pff:
        routing_fini();
 fail_routing:
        connmgr_comp_fini(COMPID_DT);
 fail_connmgr_comp_init:
        notifier_unreg(&handle_event);
 fail_notifier_reg:
        dt_pci_fini();
 fail_pci_init:
        return -1;
}

void dt_fini(void)
{
        int i;

        rib_unreg(DT);
#ifdef IPCP_FLOW_STATS
        for (i = 0; i < PROG_MAX_FLOWS; ++i)
                pthread_mutex_destroy(&dt.stat[i].lock);
#endif
        bmp_destroy(dt.res_fds);

        pthread_rwlock_destroy(&dt.lock);

        for (i = 0; i < QOS_CUBE_MAX; ++i)
                routing_i_destroy(dt.routing[i]);

        for (i = 0; i < QOS_CUBE_MAX; ++i)
                pff_destroy(dt.pff[i]);

        routing_fini();

        connmgr_comp_fini(COMPID_DT);

        notifier_unreg(&handle_event);

        dt_pci_fini();
}

int dt_start(void)
{
        dt.sdu_sched = sdu_sched_create(sdu_handler);
        if (dt.sdu_sched == NULL) {
                log_err("Failed to create N-1 SDU scheduler.");
                return -1;
        }

        if (pthread_create(&dt.listener, NULL, dt_conn_handle, NULL)) {
                log_err("Failed to create listener thread.");
                sdu_sched_destroy(dt.sdu_sched);
                return -1;
        }

        return 0;
}

void dt_stop(void)
{
        pthread_cancel(dt.listener);
        pthread_join(dt.listener, NULL);
        sdu_sched_destroy(dt.sdu_sched);
}

int dt_reg_comp(void * comp,
                void (* func)(void * func, struct shm_du_buff *),
                char * name)
{
        int res_fd;

        assert(func);

        pthread_rwlock_wrlock(&dt.lock);

        res_fd = bmp_allocate(dt.res_fds);
        if (!bmp_is_id_valid(dt.res_fds, res_fd)) {
                log_warn("Reserved fds depleted.");
                pthread_rwlock_unlock(&dt.lock);
                return -EBADF;
        }

        assert(dt.comps[res_fd].post_sdu == NULL);
        assert(dt.comps[res_fd].comp == NULL);
        assert(dt.comps[res_fd].name == NULL);

        dt.comps[res_fd].post_sdu = func;
        dt.comps[res_fd].comp     = comp;
        dt.comps[res_fd].name     = name;

        pthread_rwlock_unlock(&dt.lock);
#ifdef IPCP_FLOW_STATS
        stat_used(res_fd, ipcpi.dt_addr);
#endif
        return res_fd;
}

int dt_write_sdu(uint64_t             dst_addr,
                 qoscube_t            qc,
                 int                  np1_fd,
                 struct shm_du_buff * sdb)
{
        int           fd;
        struct dt_pci dt_pci;
        int           ret;
#ifdef IPCP_FLOW_STATS
        size_t        len;
#endif
        assert(sdb);
        assert(dst_addr != ipcpi.dt_addr);

        fd = pff_nhop(dt.pff[qc], dst_addr);
        if (fd < 0) {
                log_dbg("Could not get nhop for addr %" PRIu64 ".", dst_addr);
#ifdef IPCP_FLOW_STATS
                len = shm_du_buff_tail(sdb) - shm_du_buff_head(sdb);

                pthread_mutex_lock(&dt.stat[np1_fd].lock);

                ++dt.stat[np1_fd].lcl_r_pkt[qc];
                dt.stat[np1_fd].lcl_r_bytes[qc] += len;
                ++dt.stat[np1_fd].f_nhp_pkt[qc];
                dt.stat[np1_fd].f_nhp_bytes[qc] += len;

                pthread_mutex_unlock(&dt.stat[np1_fd].lock);
#endif
                return -1;
        }

        dt_pci.dst_addr = dst_addr;
        dt_pci.qc       = qc;
        dt_pci.eid      = np1_fd;

        if (dt_pci_ser(sdb, &dt_pci)) {
                log_dbg("Failed to serialize PDU.");
#ifdef IPCP_FLOW_STATS
                len = shm_du_buff_tail(sdb) - shm_du_buff_head(sdb);
#endif
                goto fail_write;
        }
#ifdef IPCP_FLOW_STATS
        len = shm_du_buff_tail(sdb) - shm_du_buff_head(sdb);
#endif
        ret = ipcp_flow_write(fd, sdb);
        if (ret < 0) {
                log_dbg("Failed to write SDU to fd %d.", fd);
                if (ret == -EFLOWDOWN)
                        notifier_event(NOTIFY_DT_FLOW_DOWN, &fd);
                goto fail_write;
        }
#ifdef IPCP_FLOW_STATS
        pthread_mutex_lock(&dt.stat[np1_fd].lock);

        ++dt.stat[np1_fd].lcl_r_pkt[qc];
        dt.stat[np1_fd].lcl_r_bytes[qc] += len;

        pthread_mutex_unlock(&dt.stat[np1_fd].lock);
        pthread_mutex_lock(&dt.stat[fd].lock);

        if (dt_pci.eid < PROG_RES_FDS) {
                ++dt.stat[fd].lcl_w_pkt[qc];
                dt.stat[fd].lcl_w_bytes[qc] += len;
        }
        ++dt.stat[fd].snd_pkt[qc];
        dt.stat[fd].snd_bytes[qc] += len;

        pthread_mutex_unlock(&dt.stat[fd].lock);
#endif
        return 0;

 fail_write:
#ifdef IPCP_FLOW_STATS
        pthread_mutex_lock(&dt.stat[np1_fd].lock);

        ++dt.stat[np1_fd].lcl_w_pkt[qc];
        dt.stat[np1_fd].lcl_w_bytes[qc] += len;

        pthread_mutex_unlock(&dt.stat[np1_fd].lock);
        pthread_mutex_lock(&dt.stat[fd].lock);

        if (dt_pci.eid < PROG_RES_FDS) {
                ++dt.stat[fd].lcl_w_pkt[qc];
                dt.stat[fd].lcl_w_bytes[qc] += len;
        }
        ++dt.stat[fd].w_drp_pkt[qc];
        dt.stat[fd].w_drp_bytes[qc] += len;

        pthread_mutex_unlock(&dt.stat[fd].lock);
#endif
        return -1;
}
