doc: Add `show ipv6 rpf X:X::X:X` command to docs

[mirror_frr.git] / zebra / dplane_fpm_nl.c

/*
 * Zebra dataplane plugin for Forwarding Plane Manager (FPM) using netlink.
 *
 * Copyright (C) 2019 Network Device Education Foundation, Inc. ("NetDEF")
 *                    Rafael Zalamena
 *
 * 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; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifdef HAVE_CONFIG_H
#include "config.h" /* Include this explicitly */
#endif

#include <arpa/inet.h>

#include <sys/types.h>
#include <sys/socket.h>

#include <errno.h>
#include <string.h>

#include "lib/zebra.h"
#include "lib/json.h"
#include "lib/libfrr.h"
#include "lib/frratomic.h"
#include "lib/command.h"
#include "lib/memory.h"
#include "lib/network.h"
#include "lib/ns.h"
#include "lib/frr_pthread.h"
#include "zebra/debug.h"
#include "zebra/interface.h"
#include "zebra/zebra_dplane.h"
#include "zebra/zebra_mpls.h"
#include "zebra/zebra_router.h"
#include "zebra/interface.h"
#include "zebra/zebra_vxlan_private.h"
#include "zebra/zebra_evpn.h"
#include "zebra/zebra_evpn_mac.h"
#include "zebra/kernel_netlink.h"
#include "zebra/rt_netlink.h"
#include "zebra/debug.h"
#include "fpm/fpm.h"

#define SOUTHBOUND_DEFAULT_ADDR INADDR_LOOPBACK
#define SOUTHBOUND_DEFAULT_PORT 2620

/**
 * FPM header:
 * {
 *   version: 1 byte (always 1),
 *   type: 1 byte (1 for netlink, 2 protobuf),
 *   len: 2 bytes (network order),
 * }
 *
 * This header is used with any format to tell the users how many bytes to
 * expect.
 */
#define FPM_HEADER_SIZE 4

static const char *prov_name = "dplane_fpm_nl";

struct fpm_nl_ctx {
        /* data plane connection. */
        int socket;
        bool disabled;
        bool connecting;
        bool use_nhg;
        struct sockaddr_storage addr;

        /* data plane buffers. */
        struct stream *ibuf;
        struct stream *obuf;
        pthread_mutex_t obuf_mutex;

        /*
         * data plane context queue:
         * When a FPM server connection becomes a bottleneck, we must keep the
         * data plane contexts until we get a chance to process them.
         */
        struct dplane_ctx_list_head ctxqueue;
        pthread_mutex_t ctxqueue_mutex;

        /* data plane events. */
        struct zebra_dplane_provider *prov;
        struct frr_pthread *fthread;
        struct thread *t_connect;
        struct thread *t_read;
        struct thread *t_write;
        struct thread *t_event;
        struct thread *t_nhg;
        struct thread *t_dequeue;

        /* zebra events. */
        struct thread *t_lspreset;
        struct thread *t_lspwalk;
        struct thread *t_nhgreset;
        struct thread *t_nhgwalk;
        struct thread *t_ribreset;
        struct thread *t_ribwalk;
        struct thread *t_rmacreset;
        struct thread *t_rmacwalk;

        /* Statistic counters. */
        struct {
                /* Amount of bytes read into ibuf. */
                _Atomic uint32_t bytes_read;
                /* Amount of bytes written from obuf. */
                _Atomic uint32_t bytes_sent;
                /* Output buffer current usage. */
                _Atomic uint32_t obuf_bytes;
                /* Output buffer peak usage. */
                _Atomic uint32_t obuf_peak;

                /* Amount of connection closes. */
                _Atomic uint32_t connection_closes;
                /* Amount of connection errors. */
                _Atomic uint32_t connection_errors;

                /* Amount of user configurations: FNE_RECONNECT. */
                _Atomic uint32_t user_configures;
                /* Amount of user disable requests: FNE_DISABLE. */
                _Atomic uint32_t user_disables;

                /* Amount of data plane context processed. */
                _Atomic uint32_t dplane_contexts;
                /* Amount of data plane contexts enqueued. */
                _Atomic uint32_t ctxqueue_len;
                /* Peak amount of data plane contexts enqueued. */
                _Atomic uint32_t ctxqueue_len_peak;

                /* Amount of buffer full events. */
                _Atomic uint32_t buffer_full;
        } counters;
} *gfnc;

enum fpm_nl_events {
        /* Ask for FPM to reconnect the external server. */
        FNE_RECONNECT,
        /* Disable FPM. */
        FNE_DISABLE,
        /* Reset counters. */
        FNE_RESET_COUNTERS,
        /* Toggle next hop group feature. */
        FNE_TOGGLE_NHG,
        /* Reconnect request by our own code to avoid races. */
        FNE_INTERNAL_RECONNECT,

        /* LSP walk finished. */
        FNE_LSP_FINISHED,
        /* Next hop groups walk finished. */
        FNE_NHG_FINISHED,
        /* RIB walk finished. */
        FNE_RIB_FINISHED,
        /* RMAC walk finished. */
        FNE_RMAC_FINISHED,
};

#define FPM_RECONNECT(fnc)                                                     \
        thread_add_event((fnc)->fthread->master, fpm_process_event, (fnc),     \
                         FNE_INTERNAL_RECONNECT, &(fnc)->t_event)

#define WALK_FINISH(fnc, ev)                                                   \
        thread_add_event((fnc)->fthread->master, fpm_process_event, (fnc),     \
                         (ev), NULL)

/*
 * Prototypes.
 */
static void fpm_process_event(struct thread *t);
static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx);
static void fpm_lsp_send(struct thread *t);
static void fpm_lsp_reset(struct thread *t);
static void fpm_nhg_send(struct thread *t);
static void fpm_nhg_reset(struct thread *t);
static void fpm_rib_send(struct thread *t);
static void fpm_rib_reset(struct thread *t);
static void fpm_rmac_send(struct thread *t);
static void fpm_rmac_reset(struct thread *t);

/*
 * CLI.
 */
#define FPM_STR "Forwarding Plane Manager configuration\n"

DEFUN(fpm_set_address, fpm_set_address_cmd,
      "fpm address <A.B.C.D|X:X::X:X> [port (1-65535)]",
      FPM_STR
      "FPM remote listening server address\n"
      "Remote IPv4 FPM server\n"
      "Remote IPv6 FPM server\n"
      "FPM remote listening server port\n"
      "Remote FPM server port\n")
{
        struct sockaddr_in *sin;
        struct sockaddr_in6 *sin6;
        uint16_t port = 0;
        uint8_t naddr[INET6_BUFSIZ];

        if (argc == 5)
                port = strtol(argv[4]->arg, NULL, 10);

        /* Handle IPv4 addresses. */
        if (inet_pton(AF_INET, argv[2]->arg, naddr) == 1) {
                sin = (struct sockaddr_in *)&gfnc->addr;

                memset(sin, 0, sizeof(*sin));
                sin->sin_family = AF_INET;
                sin->sin_port =
                        port ? htons(port) : htons(SOUTHBOUND_DEFAULT_PORT);
#ifdef HAVE_STRUCT_SOCKADDR_SA_LEN
                sin->sin_len = sizeof(*sin);
#endif /* HAVE_STRUCT_SOCKADDR_SA_LEN */
                memcpy(&sin->sin_addr, naddr, sizeof(sin->sin_addr));

                goto ask_reconnect;
        }

        /* Handle IPv6 addresses. */
        if (inet_pton(AF_INET6, argv[2]->arg, naddr) != 1) {
                vty_out(vty, "%% Invalid address: %s\n", argv[2]->arg);
                return CMD_WARNING;
        }

        sin6 = (struct sockaddr_in6 *)&gfnc->addr;
        memset(sin6, 0, sizeof(*sin6));
        sin6->sin6_family = AF_INET6;
        sin6->sin6_port = port ? htons(port) : htons(SOUTHBOUND_DEFAULT_PORT);
#ifdef HAVE_STRUCT_SOCKADDR_SA_LEN
        sin6->sin6_len = sizeof(*sin6);
#endif /* HAVE_STRUCT_SOCKADDR_SA_LEN */
        memcpy(&sin6->sin6_addr, naddr, sizeof(sin6->sin6_addr));

ask_reconnect:
        thread_add_event(gfnc->fthread->master, fpm_process_event, gfnc,
                         FNE_RECONNECT, &gfnc->t_event);
        return CMD_SUCCESS;
}

DEFUN(no_fpm_set_address, no_fpm_set_address_cmd,
      "no fpm address [<A.B.C.D|X:X::X:X> [port <1-65535>]]",
      NO_STR
      FPM_STR
      "FPM remote listening server address\n"
      "Remote IPv4 FPM server\n"
      "Remote IPv6 FPM server\n"
      "FPM remote listening server port\n"
      "Remote FPM server port\n")
{
        thread_add_event(gfnc->fthread->master, fpm_process_event, gfnc,
                         FNE_DISABLE, &gfnc->t_event);
        return CMD_SUCCESS;
}

DEFUN(fpm_use_nhg, fpm_use_nhg_cmd,
      "fpm use-next-hop-groups",
      FPM_STR
      "Use netlink next hop groups feature.\n")
{
        /* Already enabled. */
        if (gfnc->use_nhg)
                return CMD_SUCCESS;

        thread_add_event(gfnc->fthread->master, fpm_process_event, gfnc,
                         FNE_TOGGLE_NHG, &gfnc->t_nhg);

        return CMD_SUCCESS;
}

DEFUN(no_fpm_use_nhg, no_fpm_use_nhg_cmd,
      "no fpm use-next-hop-groups",
      NO_STR
      FPM_STR
      "Use netlink next hop groups feature.\n")
{
        /* Already disabled. */
        if (!gfnc->use_nhg)
                return CMD_SUCCESS;

        thread_add_event(gfnc->fthread->master, fpm_process_event, gfnc,
                         FNE_TOGGLE_NHG, &gfnc->t_nhg);

        return CMD_SUCCESS;
}

DEFUN(fpm_reset_counters, fpm_reset_counters_cmd,
      "clear fpm counters",
      CLEAR_STR
      FPM_STR
      "FPM statistic counters\n")
{
        thread_add_event(gfnc->fthread->master, fpm_process_event, gfnc,
                         FNE_RESET_COUNTERS, &gfnc->t_event);
        return CMD_SUCCESS;
}

DEFUN(fpm_show_counters, fpm_show_counters_cmd,
      "show fpm counters",
      SHOW_STR
      FPM_STR
      "FPM statistic counters\n")
{
        vty_out(vty, "%30s\n%30s\n", "FPM counters", "============");

#define SHOW_COUNTER(label, counter) \
        vty_out(vty, "%28s: %u\n", (label), (counter))

        SHOW_COUNTER("Input bytes", gfnc->counters.bytes_read);
        SHOW_COUNTER("Output bytes", gfnc->counters.bytes_sent);
        SHOW_COUNTER("Output buffer current size", gfnc->counters.obuf_bytes);
        SHOW_COUNTER("Output buffer peak size", gfnc->counters.obuf_peak);
        SHOW_COUNTER("Connection closes", gfnc->counters.connection_closes);
        SHOW_COUNTER("Connection errors", gfnc->counters.connection_errors);
        SHOW_COUNTER("Data plane items processed",
                     gfnc->counters.dplane_contexts);
        SHOW_COUNTER("Data plane items enqueued",
                     gfnc->counters.ctxqueue_len);
        SHOW_COUNTER("Data plane items queue peak",
                     gfnc->counters.ctxqueue_len_peak);
        SHOW_COUNTER("Buffer full hits", gfnc->counters.buffer_full);
        SHOW_COUNTER("User FPM configurations", gfnc->counters.user_configures);
        SHOW_COUNTER("User FPM disable requests", gfnc->counters.user_disables);

#undef SHOW_COUNTER

        return CMD_SUCCESS;
}

DEFUN(fpm_show_counters_json, fpm_show_counters_json_cmd,
      "show fpm counters json",
      SHOW_STR
      FPM_STR
      "FPM statistic counters\n"
      JSON_STR)
{
        struct json_object *jo;

        jo = json_object_new_object();
        json_object_int_add(jo, "bytes-read", gfnc->counters.bytes_read);
        json_object_int_add(jo, "bytes-sent", gfnc->counters.bytes_sent);
        json_object_int_add(jo, "obuf-bytes", gfnc->counters.obuf_bytes);
        json_object_int_add(jo, "obuf-bytes-peak", gfnc->counters.obuf_peak);
        json_object_int_add(jo, "connection-closes",
                            gfnc->counters.connection_closes);
        json_object_int_add(jo, "connection-errors",
                            gfnc->counters.connection_errors);
        json_object_int_add(jo, "data-plane-contexts",
                            gfnc->counters.dplane_contexts);
        json_object_int_add(jo, "data-plane-contexts-queue",
                            gfnc->counters.ctxqueue_len);
        json_object_int_add(jo, "data-plane-contexts-queue-peak",
                            gfnc->counters.ctxqueue_len_peak);
        json_object_int_add(jo, "buffer-full-hits", gfnc->counters.buffer_full);
        json_object_int_add(jo, "user-configures",
                            gfnc->counters.user_configures);
        json_object_int_add(jo, "user-disables", gfnc->counters.user_disables);
        vty_json(vty, jo);

        return CMD_SUCCESS;
}

static int fpm_write_config(struct vty *vty)
{
        struct sockaddr_in *sin;
        struct sockaddr_in6 *sin6;
        int written = 0;

        if (gfnc->disabled)
                return written;

        switch (gfnc->addr.ss_family) {
        case AF_INET:
                written = 1;
                sin = (struct sockaddr_in *)&gfnc->addr;
                vty_out(vty, "fpm address %pI4", &sin->sin_addr);
                if (sin->sin_port != htons(SOUTHBOUND_DEFAULT_PORT))
                        vty_out(vty, " port %d", ntohs(sin->sin_port));

                vty_out(vty, "\n");
                break;
        case AF_INET6:
                written = 1;
                sin6 = (struct sockaddr_in6 *)&gfnc->addr;
                vty_out(vty, "fpm address %pI6", &sin6->sin6_addr);
                if (sin6->sin6_port != htons(SOUTHBOUND_DEFAULT_PORT))
                        vty_out(vty, " port %d", ntohs(sin6->sin6_port));

                vty_out(vty, "\n");
                break;

        default:
                break;
        }

        if (!gfnc->use_nhg) {
                vty_out(vty, "no fpm use-next-hop-groups\n");
                written = 1;
        }

        return written;
}

static struct cmd_node fpm_node = {
        .name = "fpm",
        .node = FPM_NODE,
        .prompt = "",
        .config_write = fpm_write_config,
};

/*
 * FPM functions.
 */
static void fpm_connect(struct thread *t);

static void fpm_reconnect(struct fpm_nl_ctx *fnc)
{
        /* Cancel all zebra threads first. */
        thread_cancel_async(zrouter.master, &fnc->t_lspreset, NULL);
        thread_cancel_async(zrouter.master, &fnc->t_lspwalk, NULL);
        thread_cancel_async(zrouter.master, &fnc->t_nhgreset, NULL);
        thread_cancel_async(zrouter.master, &fnc->t_nhgwalk, NULL);
        thread_cancel_async(zrouter.master, &fnc->t_ribreset, NULL);
        thread_cancel_async(zrouter.master, &fnc->t_ribwalk, NULL);
        thread_cancel_async(zrouter.master, &fnc->t_rmacreset, NULL);
        thread_cancel_async(zrouter.master, &fnc->t_rmacwalk, NULL);

        /*
         * Grab the lock to empty the streams (data plane might try to
         * enqueue updates while we are closing).
         */
        frr_mutex_lock_autounlock(&fnc->obuf_mutex);

        /* Avoid calling close on `-1`. */
        if (fnc->socket != -1) {
                close(fnc->socket);
                fnc->socket = -1;
        }

        stream_reset(fnc->ibuf);
        stream_reset(fnc->obuf);
        THREAD_OFF(fnc->t_read);
        THREAD_OFF(fnc->t_write);

        /* FPM is disabled, don't attempt to connect. */
        if (fnc->disabled)
                return;

        thread_add_timer(fnc->fthread->master, fpm_connect, fnc, 3,
                         &fnc->t_connect);
}

static void fpm_read(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        fpm_msg_hdr_t fpm;
        ssize_t rv;
        char buf[65535];
        struct nlmsghdr *hdr;
        struct zebra_dplane_ctx *ctx;
        size_t available_bytes;
        size_t hdr_available_bytes;

        /* Let's ignore the input at the moment. */
        rv = stream_read_try(fnc->ibuf, fnc->socket,
                             STREAM_WRITEABLE(fnc->ibuf));
        if (rv == 0) {
                atomic_fetch_add_explicit(&fnc->counters.connection_closes, 1,
                                          memory_order_relaxed);

                if (IS_ZEBRA_DEBUG_FPM)
                        zlog_debug("%s: connection closed", __func__);

                FPM_RECONNECT(fnc);
                return;
        }
        if (rv == -1) {
                atomic_fetch_add_explicit(&fnc->counters.connection_errors, 1,
                                          memory_order_relaxed);
                zlog_warn("%s: connection failure: %s", __func__,
                          strerror(errno));
                FPM_RECONNECT(fnc);
                return;
        }

        /* Schedule the next read */
        thread_add_read(fnc->fthread->master, fpm_read, fnc, fnc->socket,
                        &fnc->t_read);

        /* We've got an interruption. */
        if (rv == -2)
                return;


        /* Account all bytes read. */
        atomic_fetch_add_explicit(&fnc->counters.bytes_read, rv,
                                  memory_order_relaxed);

        available_bytes = STREAM_READABLE(fnc->ibuf);
        while (available_bytes) {
                if (available_bytes < (ssize_t)FPM_MSG_HDR_LEN) {
                        stream_pulldown(fnc->ibuf);
                        return;
                }

                fpm.version = stream_getc(fnc->ibuf);
                fpm.msg_type = stream_getc(fnc->ibuf);
                fpm.msg_len = stream_getw(fnc->ibuf);

                if (fpm.version != FPM_PROTO_VERSION &&
                    fpm.msg_type != FPM_MSG_TYPE_NETLINK) {
                        stream_reset(fnc->ibuf);
                        zlog_warn(
                                "%s: Received version/msg_type %u/%u, expected 1/1",
                                __func__, fpm.version, fpm.msg_type);

                        FPM_RECONNECT(fnc);
                        return;
                }

                /*
                 * If the passed in length doesn't even fill in the header
                 * something is wrong and reset.
                 */
                if (fpm.msg_len < FPM_MSG_HDR_LEN) {
                        zlog_warn(
                                "%s: Received message length: %u that does not even fill the FPM header",
                                __func__, fpm.msg_len);
                        FPM_RECONNECT(fnc);
                        return;
                }

                /*
                 * If we have not received the whole payload, reset the stream
                 * back to the beginning of the header and move it to the
                 * top.
                 */
                if (fpm.msg_len > available_bytes) {
                        stream_rewind_getp(fnc->ibuf, FPM_MSG_HDR_LEN);
                        stream_pulldown(fnc->ibuf);
                        return;
                }

                available_bytes -= FPM_MSG_HDR_LEN;

                /*
                 * Place the data from the stream into a buffer
                 */
                hdr = (struct nlmsghdr *)buf;
                stream_get(buf, fnc->ibuf, fpm.msg_len - FPM_MSG_HDR_LEN);
                hdr_available_bytes = fpm.msg_len - FPM_MSG_HDR_LEN;
                available_bytes -= hdr_available_bytes;

                /* Sanity check: must be at least header size. */
                if (hdr->nlmsg_len < sizeof(*hdr)) {
                        zlog_warn(
                                "%s: [seq=%u] invalid message length %u (< %zu)",
                                __func__, hdr->nlmsg_seq, hdr->nlmsg_len,
                                sizeof(*hdr));
                        continue;
                }
                if (hdr->nlmsg_len > fpm.msg_len) {
                        zlog_warn(
                                "%s: Received a inner header length of %u that is greater than the fpm total length of %u",
                                __func__, hdr->nlmsg_len, fpm.msg_len);
                        FPM_RECONNECT(fnc);
                }
                /* Not enough bytes available. */
                if (hdr->nlmsg_len > hdr_available_bytes) {
                        zlog_warn(
                                "%s: [seq=%u] invalid message length %u (> %zu)",
                                __func__, hdr->nlmsg_seq, hdr->nlmsg_len,
                                available_bytes);
                        continue;
                }

                if (!(hdr->nlmsg_flags & NLM_F_REQUEST)) {
                        if (IS_ZEBRA_DEBUG_FPM)
                                zlog_debug(
                                        "%s: [seq=%u] not a request, skipping",
                                        __func__, hdr->nlmsg_seq);

                        /*
                         * This request is a bust, go to the next one
                         */
                        continue;
                }

                switch (hdr->nlmsg_type) {
                case RTM_NEWROUTE:
                        ctx = dplane_ctx_alloc();
                        dplane_ctx_set_op(ctx, DPLANE_OP_ROUTE_NOTIFY);
                        if (netlink_route_change_read_unicast_internal(
                                    hdr, 0, false, ctx) != 1) {
                                dplane_ctx_fini(&ctx);
                                stream_pulldown(fnc->ibuf);
                                /*
                                 * Let's continue to read other messages
                                 * Even if we ignore this one.
                                 */
                        }
                        break;
                default:
                        if (IS_ZEBRA_DEBUG_FPM)
                                zlog_debug(
                                        "%s: Received message type %u which is not currently handled",
                                        __func__, hdr->nlmsg_type);
                        break;
                }
        }

        stream_reset(fnc->ibuf);
}

static void fpm_write(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        socklen_t statuslen;
        ssize_t bwritten;
        int rv, status;
        size_t btotal;

        if (fnc->connecting == true) {
                status = 0;
                statuslen = sizeof(status);

                rv = getsockopt(fnc->socket, SOL_SOCKET, SO_ERROR, &status,
                                &statuslen);
                if (rv == -1 || status != 0) {
                        if (rv != -1)
                                zlog_warn("%s: connection failed: %s", __func__,
                                          strerror(status));
                        else
                                zlog_warn("%s: SO_ERROR failed: %s", __func__,
                                          strerror(status));

                        atomic_fetch_add_explicit(
                                &fnc->counters.connection_errors, 1,
                                memory_order_relaxed);

                        FPM_RECONNECT(fnc);
                        return;
                }

                fnc->connecting = false;

                /*
                 * Starting with LSPs walk all FPM objects, marking them
                 * as unsent and then replaying them.
                 */
                thread_add_timer(zrouter.master, fpm_lsp_reset, fnc, 0,
                                 &fnc->t_lspreset);

                /* Permit receiving messages now. */
                thread_add_read(fnc->fthread->master, fpm_read, fnc,
                                fnc->socket, &fnc->t_read);
        }

        frr_mutex_lock_autounlock(&fnc->obuf_mutex);

        while (true) {
                /* Stream is empty: reset pointers and return. */
                if (STREAM_READABLE(fnc->obuf) == 0) {
                        stream_reset(fnc->obuf);
                        break;
                }

                /* Try to write all at once. */
                btotal = stream_get_endp(fnc->obuf) -
                        stream_get_getp(fnc->obuf);
                bwritten = write(fnc->socket, stream_pnt(fnc->obuf), btotal);
                if (bwritten == 0) {
                        atomic_fetch_add_explicit(
                                &fnc->counters.connection_closes, 1,
                                memory_order_relaxed);

                        if (IS_ZEBRA_DEBUG_FPM)
                                zlog_debug("%s: connection closed", __func__);
                        break;
                }
                if (bwritten == -1) {
                        /* Attempt to continue if blocked by a signal. */
                        if (errno == EINTR)
                                continue;
                        /* Receiver is probably slow, lets give it some time. */
                        if (errno == EAGAIN || errno == EWOULDBLOCK)
                                break;

                        atomic_fetch_add_explicit(
                                &fnc->counters.connection_errors, 1,
                                memory_order_relaxed);
                        zlog_warn("%s: connection failure: %s", __func__,
                                  strerror(errno));

                        FPM_RECONNECT(fnc);
                        return;
                }

                /* Account all bytes sent. */
                atomic_fetch_add_explicit(&fnc->counters.bytes_sent, bwritten,
                                          memory_order_relaxed);

                /* Account number of bytes free. */
                atomic_fetch_sub_explicit(&fnc->counters.obuf_bytes, bwritten,
                                          memory_order_relaxed);

                stream_forward_getp(fnc->obuf, (size_t)bwritten);
        }

        /* Stream is not empty yet, we must schedule more writes. */
        if (STREAM_READABLE(fnc->obuf)) {
                stream_pulldown(fnc->obuf);
                thread_add_write(fnc->fthread->master, fpm_write, fnc,
                                 fnc->socket, &fnc->t_write);
                return;
        }
}

static void fpm_connect(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        struct sockaddr_in *sin = (struct sockaddr_in *)&fnc->addr;
        struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&fnc->addr;
        socklen_t slen;
        int rv, sock;
        char addrstr[INET6_ADDRSTRLEN];

        sock = socket(fnc->addr.ss_family, SOCK_STREAM, 0);
        if (sock == -1) {
                zlog_err("%s: fpm socket failed: %s", __func__,
                         strerror(errno));
                thread_add_timer(fnc->fthread->master, fpm_connect, fnc, 3,
                                 &fnc->t_connect);
                return;
        }

        set_nonblocking(sock);

        if (fnc->addr.ss_family == AF_INET) {
                inet_ntop(AF_INET, &sin->sin_addr, addrstr, sizeof(addrstr));
                slen = sizeof(*sin);
        } else {
                inet_ntop(AF_INET6, &sin6->sin6_addr, addrstr, sizeof(addrstr));
                slen = sizeof(*sin6);
        }

        if (IS_ZEBRA_DEBUG_FPM)
                zlog_debug("%s: attempting to connect to %s:%d", __func__,
                           addrstr, ntohs(sin->sin_port));

        rv = connect(sock, (struct sockaddr *)&fnc->addr, slen);
        if (rv == -1 && errno != EINPROGRESS) {
                atomic_fetch_add_explicit(&fnc->counters.connection_errors, 1,
                                          memory_order_relaxed);
                close(sock);
                zlog_warn("%s: fpm connection failed: %s", __func__,
                          strerror(errno));
                thread_add_timer(fnc->fthread->master, fpm_connect, fnc, 3,
                                 &fnc->t_connect);
                return;
        }

        fnc->connecting = (errno == EINPROGRESS);
        fnc->socket = sock;
        if (!fnc->connecting)
                thread_add_read(fnc->fthread->master, fpm_read, fnc, sock,
                                &fnc->t_read);
        thread_add_write(fnc->fthread->master, fpm_write, fnc, sock,
                         &fnc->t_write);

        /*
         * Starting with LSPs walk all FPM objects, marking them
         * as unsent and then replaying them.
         *
         * If we are not connected, then delay the objects reset/send.
         */
        if (!fnc->connecting)
                thread_add_timer(zrouter.master, fpm_lsp_reset, fnc, 0,
                                 &fnc->t_lspreset);
}

/**
 * Encode data plane operation context into netlink and enqueue it in the FPM
 * output buffer.
 *
 * @param fnc the netlink FPM context.
 * @param ctx the data plane operation context data.
 * @return 0 on success or -1 on not enough space.
 */
static int fpm_nl_enqueue(struct fpm_nl_ctx *fnc, struct zebra_dplane_ctx *ctx)
{
        uint8_t nl_buf[NL_PKT_BUF_SIZE];
        size_t nl_buf_len;
        ssize_t rv;
        uint64_t obytes, obytes_peak;
        enum dplane_op_e op = dplane_ctx_get_op(ctx);

        /*
         * If we were configured to not use next hop groups, then quit as soon
         * as possible.
         */
        if ((!fnc->use_nhg)
            && (op == DPLANE_OP_NH_DELETE || op == DPLANE_OP_NH_INSTALL
                || op == DPLANE_OP_NH_UPDATE))
                return 0;

        nl_buf_len = 0;

        frr_mutex_lock_autounlock(&fnc->obuf_mutex);

        switch (op) {
        case DPLANE_OP_ROUTE_UPDATE:
        case DPLANE_OP_ROUTE_DELETE:
                rv = netlink_route_multipath_msg_encode(RTM_DELROUTE, ctx,
                                                        nl_buf, sizeof(nl_buf),
                                                        true, fnc->use_nhg);
                if (rv <= 0) {
                        zlog_err(
                                "%s: netlink_route_multipath_msg_encode failed",
                                __func__);
                        return 0;
                }

                nl_buf_len = (size_t)rv;

                /* UPDATE operations need a INSTALL, otherwise just quit. */
                if (op == DPLANE_OP_ROUTE_DELETE)
                        break;

                /* FALL THROUGH */
        case DPLANE_OP_ROUTE_INSTALL:
                rv = netlink_route_multipath_msg_encode(
                        RTM_NEWROUTE, ctx, &nl_buf[nl_buf_len],
                        sizeof(nl_buf) - nl_buf_len, true, fnc->use_nhg);
                if (rv <= 0) {
                        zlog_err(
                                "%s: netlink_route_multipath_msg_encode failed",
                                __func__);
                        return 0;
                }

                nl_buf_len += (size_t)rv;
                break;

        case DPLANE_OP_MAC_INSTALL:
        case DPLANE_OP_MAC_DELETE:
                rv = netlink_macfdb_update_ctx(ctx, nl_buf, sizeof(nl_buf));
                if (rv <= 0) {
                        zlog_err("%s: netlink_macfdb_update_ctx failed",
                                 __func__);
                        return 0;
                }

                nl_buf_len = (size_t)rv;
                break;

        case DPLANE_OP_NH_DELETE:
                rv = netlink_nexthop_msg_encode(RTM_DELNEXTHOP, ctx, nl_buf,
                                                sizeof(nl_buf), true);
                if (rv <= 0) {
                        zlog_err("%s: netlink_nexthop_msg_encode failed",
                                 __func__);
                        return 0;
                }

                nl_buf_len = (size_t)rv;
                break;
        case DPLANE_OP_NH_INSTALL:
        case DPLANE_OP_NH_UPDATE:
                rv = netlink_nexthop_msg_encode(RTM_NEWNEXTHOP, ctx, nl_buf,
                                                sizeof(nl_buf), true);
                if (rv <= 0) {
                        zlog_err("%s: netlink_nexthop_msg_encode failed",
                                 __func__);
                        return 0;
                }

                nl_buf_len = (size_t)rv;
                break;

        case DPLANE_OP_LSP_INSTALL:
        case DPLANE_OP_LSP_UPDATE:
        case DPLANE_OP_LSP_DELETE:
                rv = netlink_lsp_msg_encoder(ctx, nl_buf, sizeof(nl_buf));
                if (rv <= 0) {
                        zlog_err("%s: netlink_lsp_msg_encoder failed",
                                 __func__);
                        return 0;
                }

                nl_buf_len += (size_t)rv;
                break;

        /* Un-handled by FPM at this time. */
        case DPLANE_OP_PW_INSTALL:
        case DPLANE_OP_PW_UNINSTALL:
        case DPLANE_OP_ADDR_INSTALL:
        case DPLANE_OP_ADDR_UNINSTALL:
        case DPLANE_OP_NEIGH_INSTALL:
        case DPLANE_OP_NEIGH_UPDATE:
        case DPLANE_OP_NEIGH_DELETE:
        case DPLANE_OP_VTEP_ADD:
        case DPLANE_OP_VTEP_DELETE:
        case DPLANE_OP_SYS_ROUTE_ADD:
        case DPLANE_OP_SYS_ROUTE_DELETE:
        case DPLANE_OP_ROUTE_NOTIFY:
        case DPLANE_OP_LSP_NOTIFY:
        case DPLANE_OP_RULE_ADD:
        case DPLANE_OP_RULE_DELETE:
        case DPLANE_OP_RULE_UPDATE:
        case DPLANE_OP_NEIGH_DISCOVER:
        case DPLANE_OP_BR_PORT_UPDATE:
        case DPLANE_OP_IPTABLE_ADD:
        case DPLANE_OP_IPTABLE_DELETE:
        case DPLANE_OP_IPSET_ADD:
        case DPLANE_OP_IPSET_DELETE:
        case DPLANE_OP_IPSET_ENTRY_ADD:
        case DPLANE_OP_IPSET_ENTRY_DELETE:
        case DPLANE_OP_NEIGH_IP_INSTALL:
        case DPLANE_OP_NEIGH_IP_DELETE:
        case DPLANE_OP_NEIGH_TABLE_UPDATE:
        case DPLANE_OP_GRE_SET:
        case DPLANE_OP_INTF_ADDR_ADD:
        case DPLANE_OP_INTF_ADDR_DEL:
        case DPLANE_OP_INTF_NETCONFIG:
        case DPLANE_OP_INTF_INSTALL:
        case DPLANE_OP_INTF_UPDATE:
        case DPLANE_OP_INTF_DELETE:
        case DPLANE_OP_TC_QDISC_INSTALL:
        case DPLANE_OP_TC_QDISC_UNINSTALL:
        case DPLANE_OP_TC_CLASS_ADD:
        case DPLANE_OP_TC_CLASS_DELETE:
        case DPLANE_OP_TC_CLASS_UPDATE:
        case DPLANE_OP_TC_FILTER_ADD:
        case DPLANE_OP_TC_FILTER_DELETE:
        case DPLANE_OP_TC_FILTER_UPDATE:
        case DPLANE_OP_NONE:
                break;

        }

        /* Skip empty enqueues. */
        if (nl_buf_len == 0)
                return 0;

        /* We must know if someday a message goes beyond 65KiB. */
        assert((nl_buf_len + FPM_HEADER_SIZE) <= UINT16_MAX);

        /* Check if we have enough buffer space. */
        if (STREAM_WRITEABLE(fnc->obuf) < (nl_buf_len + FPM_HEADER_SIZE)) {
                atomic_fetch_add_explicit(&fnc->counters.buffer_full, 1,
                                          memory_order_relaxed);

                if (IS_ZEBRA_DEBUG_FPM)
                        zlog_debug(
                                "%s: buffer full: wants to write %zu but has %zu",
                                __func__, nl_buf_len + FPM_HEADER_SIZE,
                                STREAM_WRITEABLE(fnc->obuf));

                return -1;
        }

        /*
         * Fill in the FPM header information.
         *
         * See FPM_HEADER_SIZE definition for more information.
         */
        stream_putc(fnc->obuf, 1);
        stream_putc(fnc->obuf, 1);
        stream_putw(fnc->obuf, nl_buf_len + FPM_HEADER_SIZE);

        /* Write current data. */
        stream_write(fnc->obuf, nl_buf, (size_t)nl_buf_len);

        /* Account number of bytes waiting to be written. */
        atomic_fetch_add_explicit(&fnc->counters.obuf_bytes,
                                  nl_buf_len + FPM_HEADER_SIZE,
                                  memory_order_relaxed);
        obytes = atomic_load_explicit(&fnc->counters.obuf_bytes,
                                      memory_order_relaxed);
        obytes_peak = atomic_load_explicit(&fnc->counters.obuf_peak,
                                           memory_order_relaxed);
        if (obytes_peak < obytes)
                atomic_store_explicit(&fnc->counters.obuf_peak, obytes,
                                      memory_order_relaxed);

        /* Tell the thread to start writing. */
        thread_add_write(fnc->fthread->master, fpm_write, fnc, fnc->socket,
                         &fnc->t_write);

        return 0;
}

/*
 * LSP walk/send functions
 */
struct fpm_lsp_arg {
        struct zebra_dplane_ctx *ctx;
        struct fpm_nl_ctx *fnc;
        bool complete;
};

static int fpm_lsp_send_cb(struct hash_bucket *bucket, void *arg)
{
        struct zebra_lsp *lsp = bucket->data;
        struct fpm_lsp_arg *fla = arg;

        /* Skip entries which have already been sent */
        if (CHECK_FLAG(lsp->flags, LSP_FLAG_FPM))
                return HASHWALK_CONTINUE;

        dplane_ctx_reset(fla->ctx);
        dplane_ctx_lsp_init(fla->ctx, DPLANE_OP_LSP_INSTALL, lsp);

        if (fpm_nl_enqueue(fla->fnc, fla->ctx) == -1) {
                fla->complete = false;
                return HASHWALK_ABORT;
        }

        /* Mark entry as sent */
        SET_FLAG(lsp->flags, LSP_FLAG_FPM);
        return HASHWALK_CONTINUE;
}

static void fpm_lsp_send(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        struct zebra_vrf *zvrf = vrf_info_lookup(VRF_DEFAULT);
        struct fpm_lsp_arg fla;

        fla.fnc = fnc;
        fla.ctx = dplane_ctx_alloc();
        fla.complete = true;

        hash_walk(zvrf->lsp_table, fpm_lsp_send_cb, &fla);

        dplane_ctx_fini(&fla.ctx);

        if (fla.complete) {
                WALK_FINISH(fnc, FNE_LSP_FINISHED);

                /* Now move onto routes */
                thread_add_timer(zrouter.master, fpm_nhg_reset, fnc, 0,
                                 &fnc->t_nhgreset);
        } else {
                /* Didn't finish - reschedule LSP walk */
                thread_add_timer(zrouter.master, fpm_lsp_send, fnc, 0,
                                 &fnc->t_lspwalk);
        }
}

/*
 * Next hop walk/send functions.
 */
struct fpm_nhg_arg {
        struct zebra_dplane_ctx *ctx;
        struct fpm_nl_ctx *fnc;
        bool complete;
};

static int fpm_nhg_send_cb(struct hash_bucket *bucket, void *arg)
{
        struct nhg_hash_entry *nhe = bucket->data;
        struct fpm_nhg_arg *fna = arg;

        /* This entry was already sent, skip it. */
        if (CHECK_FLAG(nhe->flags, NEXTHOP_GROUP_FPM))
                return HASHWALK_CONTINUE;

        /* Reset ctx to reuse allocated memory, take a snapshot and send it. */
        dplane_ctx_reset(fna->ctx);
        dplane_ctx_nexthop_init(fna->ctx, DPLANE_OP_NH_INSTALL, nhe);
        if (fpm_nl_enqueue(fna->fnc, fna->ctx) == -1) {
                /* Our buffers are full, lets give it some cycles. */
                fna->complete = false;
                return HASHWALK_ABORT;
        }

        /* Mark group as sent, so it doesn't get sent again. */
        SET_FLAG(nhe->flags, NEXTHOP_GROUP_FPM);

        return HASHWALK_CONTINUE;
}

static void fpm_nhg_send(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        struct fpm_nhg_arg fna;

        fna.fnc = fnc;
        fna.ctx = dplane_ctx_alloc();
        fna.complete = true;

        /* Send next hops. */
        if (fnc->use_nhg)
                hash_walk(zrouter.nhgs_id, fpm_nhg_send_cb, &fna);

        /* `free()` allocated memory. */
        dplane_ctx_fini(&fna.ctx);

        /* We are done sending next hops, lets install the routes now. */
        if (fna.complete) {
                WALK_FINISH(fnc, FNE_NHG_FINISHED);
                thread_add_timer(zrouter.master, fpm_rib_reset, fnc, 0,
                                 &fnc->t_ribreset);
        } else /* Otherwise reschedule next hop group again. */
                thread_add_timer(zrouter.master, fpm_nhg_send, fnc, 0,
                                 &fnc->t_nhgwalk);
}

/**
 * Send all RIB installed routes to the connected data plane.
 */
static void fpm_rib_send(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        rib_dest_t *dest;
        struct route_node *rn;
        struct route_table *rt;
        struct zebra_dplane_ctx *ctx;
        rib_tables_iter_t rt_iter;

        /* Allocate temporary context for all transactions. */
        ctx = dplane_ctx_alloc();

        rt_iter.state = RIB_TABLES_ITER_S_INIT;
        while ((rt = rib_tables_iter_next(&rt_iter))) {
                for (rn = route_top(rt); rn; rn = srcdest_route_next(rn)) {
                        dest = rib_dest_from_rnode(rn);
                        /* Skip bad route entries. */
                        if (dest == NULL || dest->selected_fib == NULL)
                                continue;

                        /* Check for already sent routes. */
                        if (CHECK_FLAG(dest->flags, RIB_DEST_UPDATE_FPM))
                                continue;

                        /* Enqueue route install. */
                        dplane_ctx_reset(ctx);
                        dplane_ctx_route_init(ctx, DPLANE_OP_ROUTE_INSTALL, rn,
                                              dest->selected_fib);
                        if (fpm_nl_enqueue(fnc, ctx) == -1) {
                                /* Free the temporary allocated context. */
                                dplane_ctx_fini(&ctx);

                                thread_add_timer(zrouter.master, fpm_rib_send,
                                                 fnc, 1, &fnc->t_ribwalk);
                                return;
                        }

                        /* Mark as sent. */
                        SET_FLAG(dest->flags, RIB_DEST_UPDATE_FPM);
                }
        }

        /* Free the temporary allocated context. */
        dplane_ctx_fini(&ctx);

        /* All RIB routes sent! */
        WALK_FINISH(fnc, FNE_RIB_FINISHED);

        /* Schedule next event: RMAC reset. */
        thread_add_event(zrouter.master, fpm_rmac_reset, fnc, 0,
                         &fnc->t_rmacreset);
}

/*
 * The next three functions will handle RMAC enqueue.
 */
struct fpm_rmac_arg {
        struct zebra_dplane_ctx *ctx;
        struct fpm_nl_ctx *fnc;
        struct zebra_l3vni *zl3vni;
        bool complete;
};

static void fpm_enqueue_rmac_table(struct hash_bucket *bucket, void *arg)
{
        struct fpm_rmac_arg *fra = arg;
        struct zebra_mac *zrmac = bucket->data;
        struct zebra_if *zif = fra->zl3vni->vxlan_if->info;
        struct zebra_vxlan_vni *vni;
        struct zebra_if *br_zif;
        vlanid_t vid;
        bool sticky;

        /* Entry already sent. */
        if (CHECK_FLAG(zrmac->flags, ZEBRA_MAC_FPM_SENT) || !fra->complete)
                return;

        sticky = !!CHECK_FLAG(zrmac->flags,
                              (ZEBRA_MAC_STICKY | ZEBRA_MAC_REMOTE_DEF_GW));
        br_zif = (struct zebra_if *)(zif->brslave_info.br_if->info);
        vni = zebra_vxlan_if_vni_find(zif, fra->zl3vni->vni);
        vid = IS_ZEBRA_IF_BRIDGE_VLAN_AWARE(br_zif) ? vni->access_vlan : 0;

        dplane_ctx_reset(fra->ctx);
        dplane_ctx_set_op(fra->ctx, DPLANE_OP_MAC_INSTALL);
        dplane_mac_init(fra->ctx, fra->zl3vni->vxlan_if,
                        zif->brslave_info.br_if, vid, &zrmac->macaddr, vni->vni,
                        zrmac->fwd_info.r_vtep_ip, sticky, 0 /*nhg*/,
                        0 /*update_flags*/);
        if (fpm_nl_enqueue(fra->fnc, fra->ctx) == -1) {
                thread_add_timer(zrouter.master, fpm_rmac_send,
                                 fra->fnc, 1, &fra->fnc->t_rmacwalk);
                fra->complete = false;
        }
}

static void fpm_enqueue_l3vni_table(struct hash_bucket *bucket, void *arg)
{
        struct fpm_rmac_arg *fra = arg;
        struct zebra_l3vni *zl3vni = bucket->data;

        fra->zl3vni = zl3vni;
        hash_iterate(zl3vni->rmac_table, fpm_enqueue_rmac_table, zl3vni);
}

static void fpm_rmac_send(struct thread *t)
{
        struct fpm_rmac_arg fra;

        fra.fnc = THREAD_ARG(t);
        fra.ctx = dplane_ctx_alloc();
        fra.complete = true;
        hash_iterate(zrouter.l3vni_table, fpm_enqueue_l3vni_table, &fra);
        dplane_ctx_fini(&fra.ctx);

        /* RMAC walk completed. */
        if (fra.complete)
                WALK_FINISH(fra.fnc, FNE_RMAC_FINISHED);
}

/*
 * Resets the next hop FPM flags so we send all next hops again.
 */
static void fpm_nhg_reset_cb(struct hash_bucket *bucket, void *arg)
{
        struct nhg_hash_entry *nhe = bucket->data;

        /* Unset FPM installation flag so it gets installed again. */
        UNSET_FLAG(nhe->flags, NEXTHOP_GROUP_FPM);
}

static void fpm_nhg_reset(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);

        hash_iterate(zrouter.nhgs_id, fpm_nhg_reset_cb, NULL);

        /* Schedule next step: send next hop groups. */
        thread_add_event(zrouter.master, fpm_nhg_send, fnc, 0, &fnc->t_nhgwalk);
}

/*
 * Resets the LSP FPM flag so we send all LSPs again.
 */
static void fpm_lsp_reset_cb(struct hash_bucket *bucket, void *arg)
{
        struct zebra_lsp *lsp = bucket->data;

        UNSET_FLAG(lsp->flags, LSP_FLAG_FPM);
}

static void fpm_lsp_reset(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        struct zebra_vrf *zvrf = vrf_info_lookup(VRF_DEFAULT);

        hash_iterate(zvrf->lsp_table, fpm_lsp_reset_cb, NULL);

        /* Schedule next step: send LSPs */
        thread_add_event(zrouter.master, fpm_lsp_send, fnc, 0, &fnc->t_lspwalk);
}

/**
 * Resets the RIB FPM flags so we send all routes again.
 */
static void fpm_rib_reset(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        rib_dest_t *dest;
        struct route_node *rn;
        struct route_table *rt;
        rib_tables_iter_t rt_iter;

        rt_iter.state = RIB_TABLES_ITER_S_INIT;
        while ((rt = rib_tables_iter_next(&rt_iter))) {
                for (rn = route_top(rt); rn; rn = srcdest_route_next(rn)) {
                        dest = rib_dest_from_rnode(rn);
                        /* Skip bad route entries. */
                        if (dest == NULL)
                                continue;

                        UNSET_FLAG(dest->flags, RIB_DEST_UPDATE_FPM);
                }
        }

        /* Schedule next step: send RIB routes. */
        thread_add_event(zrouter.master, fpm_rib_send, fnc, 0, &fnc->t_ribwalk);
}

/*
 * The next three function will handle RMAC table reset.
 */
static void fpm_unset_rmac_table(struct hash_bucket *bucket, void *arg)
{
        struct zebra_mac *zrmac = bucket->data;

        UNSET_FLAG(zrmac->flags, ZEBRA_MAC_FPM_SENT);
}

static void fpm_unset_l3vni_table(struct hash_bucket *bucket, void *arg)
{
        struct zebra_l3vni *zl3vni = bucket->data;

        hash_iterate(zl3vni->rmac_table, fpm_unset_rmac_table, zl3vni);
}

static void fpm_rmac_reset(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);

        hash_iterate(zrouter.l3vni_table, fpm_unset_l3vni_table, NULL);

        /* Schedule next event: send RMAC entries. */
        thread_add_event(zrouter.master, fpm_rmac_send, fnc, 0,
                         &fnc->t_rmacwalk);
}

static void fpm_process_queue(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        struct zebra_dplane_ctx *ctx;
        bool no_bufs = false;
        uint64_t processed_contexts = 0;

        while (true) {
                /* No space available yet. */
                if (STREAM_WRITEABLE(fnc->obuf) < NL_PKT_BUF_SIZE) {
                        no_bufs = true;
                        break;
                }

                /* Dequeue next item or quit processing. */
                frr_with_mutex (&fnc->ctxqueue_mutex) {
                        ctx = dplane_ctx_dequeue(&fnc->ctxqueue);
                }
                if (ctx == NULL)
                        break;

                /*
                 * Intentionally ignoring the return value
                 * as that we are ensuring that we can write to
                 * the output data in the STREAM_WRITEABLE
                 * check above, so we can ignore the return
                 */
                if (fnc->socket != -1)
                        (void)fpm_nl_enqueue(fnc, ctx);

                /* Account the processed entries. */
                processed_contexts++;
                atomic_fetch_sub_explicit(&fnc->counters.ctxqueue_len, 1,
                                          memory_order_relaxed);

                dplane_ctx_set_status(ctx, ZEBRA_DPLANE_REQUEST_SUCCESS);
                dplane_provider_enqueue_out_ctx(fnc->prov, ctx);
        }

        /* Update count of processed contexts */
        atomic_fetch_add_explicit(&fnc->counters.dplane_contexts,
                                  processed_contexts, memory_order_relaxed);

        /* Re-schedule if we ran out of buffer space */
        if (no_bufs)
                thread_add_timer(fnc->fthread->master, fpm_process_queue,
                                 fnc, 0, &fnc->t_dequeue);

        /*
         * Let the dataplane thread know if there are items in the
         * output queue to be processed. Otherwise they may sit
         * until the dataplane thread gets scheduled for new,
         * unrelated work.
         */
        if (dplane_provider_out_ctx_queue_len(fnc->prov) > 0)
                dplane_provider_work_ready();
}

/**
 * Handles external (e.g. CLI, data plane or others) events.
 */
static void fpm_process_event(struct thread *t)
{
        struct fpm_nl_ctx *fnc = THREAD_ARG(t);
        enum fpm_nl_events event = THREAD_VAL(t);

        switch (event) {
        case FNE_DISABLE:
                zlog_info("%s: manual FPM disable event", __func__);
                fnc->disabled = true;
                atomic_fetch_add_explicit(&fnc->counters.user_disables, 1,
                                          memory_order_relaxed);

                /* Call reconnect to disable timers and clean up context. */
                fpm_reconnect(fnc);
                break;

        case FNE_RECONNECT:
                zlog_info("%s: manual FPM reconnect event", __func__);
                fnc->disabled = false;
                atomic_fetch_add_explicit(&fnc->counters.user_configures, 1,
                                          memory_order_relaxed);
                fpm_reconnect(fnc);
                break;

        case FNE_RESET_COUNTERS:
                zlog_info("%s: manual FPM counters reset event", __func__);
                memset(&fnc->counters, 0, sizeof(fnc->counters));
                break;

        case FNE_TOGGLE_NHG:
                zlog_info("%s: toggle next hop groups support", __func__);
                fnc->use_nhg = !fnc->use_nhg;
                fpm_reconnect(fnc);
                break;

        case FNE_INTERNAL_RECONNECT:
                fpm_reconnect(fnc);
                break;

        case FNE_NHG_FINISHED:
                if (IS_ZEBRA_DEBUG_FPM)
                        zlog_debug("%s: next hop groups walk finished",
                                   __func__);
                break;
        case FNE_RIB_FINISHED:
                if (IS_ZEBRA_DEBUG_FPM)
                        zlog_debug("%s: RIB walk finished", __func__);
                break;
        case FNE_RMAC_FINISHED:
                if (IS_ZEBRA_DEBUG_FPM)
                        zlog_debug("%s: RMAC walk finished", __func__);
                break;
        case FNE_LSP_FINISHED:
                if (IS_ZEBRA_DEBUG_FPM)
                        zlog_debug("%s: LSP walk finished", __func__);
                break;
        }
}

/*
 * Data plane functions.
 */
static int fpm_nl_start(struct zebra_dplane_provider *prov)
{
        struct fpm_nl_ctx *fnc;

        fnc = dplane_provider_get_data(prov);
        fnc->fthread = frr_pthread_new(NULL, prov_name, prov_name);
        assert(frr_pthread_run(fnc->fthread, NULL) == 0);
        fnc->ibuf = stream_new(NL_PKT_BUF_SIZE);
        fnc->obuf = stream_new(NL_PKT_BUF_SIZE * 128);
        pthread_mutex_init(&fnc->obuf_mutex, NULL);
        fnc->socket = -1;
        fnc->disabled = true;
        fnc->prov = prov;
        dplane_ctx_q_init(&fnc->ctxqueue);
        pthread_mutex_init(&fnc->ctxqueue_mutex, NULL);

        /* Set default values. */
        fnc->use_nhg = true;

        return 0;
}

static int fpm_nl_finish_early(struct fpm_nl_ctx *fnc)
{
        /* Disable all events and close socket. */
        THREAD_OFF(fnc->t_lspreset);
        THREAD_OFF(fnc->t_lspwalk);
        THREAD_OFF(fnc->t_nhgreset);
        THREAD_OFF(fnc->t_nhgwalk);
        THREAD_OFF(fnc->t_ribreset);
        THREAD_OFF(fnc->t_ribwalk);
        THREAD_OFF(fnc->t_rmacreset);
        THREAD_OFF(fnc->t_rmacwalk);
        THREAD_OFF(fnc->t_event);
        THREAD_OFF(fnc->t_nhg);
        thread_cancel_async(fnc->fthread->master, &fnc->t_read, NULL);
        thread_cancel_async(fnc->fthread->master, &fnc->t_write, NULL);
        thread_cancel_async(fnc->fthread->master, &fnc->t_connect, NULL);

        if (fnc->socket != -1) {
                close(fnc->socket);
                fnc->socket = -1;
        }

        return 0;
}

static int fpm_nl_finish_late(struct fpm_nl_ctx *fnc)
{
        /* Stop the running thread. */
        frr_pthread_stop(fnc->fthread, NULL);

        /* Free all allocated resources. */
        pthread_mutex_destroy(&fnc->obuf_mutex);
        pthread_mutex_destroy(&fnc->ctxqueue_mutex);
        stream_free(fnc->ibuf);
        stream_free(fnc->obuf);
        free(gfnc);
        gfnc = NULL;

        return 0;
}

static int fpm_nl_finish(struct zebra_dplane_provider *prov, bool early)
{
        struct fpm_nl_ctx *fnc;

        fnc = dplane_provider_get_data(prov);
        if (early)
                return fpm_nl_finish_early(fnc);

        return fpm_nl_finish_late(fnc);
}

static int fpm_nl_process(struct zebra_dplane_provider *prov)
{
        struct zebra_dplane_ctx *ctx;
        struct fpm_nl_ctx *fnc;
        int counter, limit;
        uint64_t cur_queue, peak_queue = 0, stored_peak_queue;

        fnc = dplane_provider_get_data(prov);
        limit = dplane_provider_get_work_limit(prov);
        for (counter = 0; counter < limit; counter++) {
                ctx = dplane_provider_dequeue_in_ctx(prov);
                if (ctx == NULL)
                        break;

                /*
                 * Skip all notifications if not connected, we'll walk the RIB
                 * anyway.
                 */
                if (fnc->socket != -1 && fnc->connecting == false) {
                        /*
                         * Update the number of queued contexts *before*
                         * enqueueing, to ensure counter consistency.
                         */
                        atomic_fetch_add_explicit(&fnc->counters.ctxqueue_len,
                                                  1, memory_order_relaxed);

                        frr_with_mutex (&fnc->ctxqueue_mutex) {
                                dplane_ctx_enqueue_tail(&fnc->ctxqueue, ctx);
                        }

                        cur_queue = atomic_load_explicit(
                                &fnc->counters.ctxqueue_len,
                                memory_order_relaxed);
                        if (peak_queue < cur_queue)
                                peak_queue = cur_queue;
                        continue;
                }

                dplane_ctx_set_status(ctx, ZEBRA_DPLANE_REQUEST_SUCCESS);
                dplane_provider_enqueue_out_ctx(prov, ctx);
        }

        /* Update peak queue length, if we just observed a new peak */
        stored_peak_queue = atomic_load_explicit(
                &fnc->counters.ctxqueue_len_peak, memory_order_relaxed);
        if (stored_peak_queue < peak_queue)
                atomic_store_explicit(&fnc->counters.ctxqueue_len_peak,
                                      peak_queue, memory_order_relaxed);

        if (atomic_load_explicit(&fnc->counters.ctxqueue_len,
                                 memory_order_relaxed)
            > 0)
                thread_add_timer(fnc->fthread->master, fpm_process_queue,
                                 fnc, 0, &fnc->t_dequeue);

        /* Ensure dataplane thread is rescheduled if we hit the work limit */
        if (counter >= limit)
                dplane_provider_work_ready();

        return 0;
}

static int fpm_nl_new(struct thread_master *tm)
{
        struct zebra_dplane_provider *prov = NULL;
        int rv;

        gfnc = calloc(1, sizeof(*gfnc));
        rv = dplane_provider_register(prov_name, DPLANE_PRIO_POSTPROCESS,
                                      DPLANE_PROV_FLAG_THREADED, fpm_nl_start,
                                      fpm_nl_process, fpm_nl_finish, gfnc,
                                      &prov);

        if (IS_ZEBRA_DEBUG_DPLANE)
                zlog_debug("%s register status: %d", prov_name, rv);

        install_node(&fpm_node);
        install_element(ENABLE_NODE, &fpm_show_counters_cmd);
        install_element(ENABLE_NODE, &fpm_show_counters_json_cmd);
        install_element(ENABLE_NODE, &fpm_reset_counters_cmd);
        install_element(CONFIG_NODE, &fpm_set_address_cmd);
        install_element(CONFIG_NODE, &no_fpm_set_address_cmd);
        install_element(CONFIG_NODE, &fpm_use_nhg_cmd);
        install_element(CONFIG_NODE, &no_fpm_use_nhg_cmd);

        return 0;
}

static int fpm_nl_init(void)
{
        hook_register(frr_late_init, fpm_nl_new);
        return 0;
}

FRR_MODULE_SETUP(
        .name = "dplane_fpm_nl",
        .version = "0.0.1",
        .description = "Data plane plugin for FPM using netlink.",
        .init = fpm_nl_init,
);