Merge pull request #11997 from sri-mohan1/sri-zebra-dbg1

[mirror_frr.git] / zebra / kernel_netlink.c

/* Kernel communication using netlink interface.
 * Copyright (C) 1999 Kunihiro Ishiguro
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra 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, or (at your option) any
 * later version.
 *
 * GNU Zebra 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
 */

#include <zebra.h>

#ifdef HAVE_NETLINK

#include "linklist.h"
#include "if.h"
#include "log.h"
#include "prefix.h"
#include "connected.h"
#include "table.h"
#include "memory.h"
#include "rib.h"
#include "thread.h"
#include "privs.h"
#include "nexthop.h"
#include "vrf.h"
#include "mpls.h"
#include "lib_errors.h"
#include "hash.h"

#include "zebra/zebra_router.h"
#include "zebra/zebra_ns.h"
#include "zebra/zebra_vrf.h"
#include "zebra/rt.h"
#include "zebra/debug.h"
#include "zebra/kernel_netlink.h"
#include "zebra/rt_netlink.h"
#include "zebra/if_netlink.h"
#include "zebra/rule_netlink.h"
#include "zebra/tc_netlink.h"
#include "zebra/netconf_netlink.h"
#include "zebra/zebra_errors.h"

#ifndef SO_RCVBUFFORCE
#define SO_RCVBUFFORCE  (33)
#endif

/* Hack for GNU libc version 2. */
#ifndef MSG_TRUNC
#define MSG_TRUNC      0x20
#endif /* MSG_TRUNC */

#ifndef NLMSG_TAIL
#define NLMSG_TAIL(nmsg)                                                       \
        ((struct rtattr *)(((uint8_t *)(nmsg))                                 \
                           + NLMSG_ALIGN((nmsg)->nlmsg_len)))
#endif

#ifndef RTA_TAIL
#define RTA_TAIL(rta)                                                          \
        ((struct rtattr *)(((uint8_t *)(rta)) + RTA_ALIGN((rta)->rta_len)))
#endif

#ifndef RTNL_FAMILY_IP6MR
#define RTNL_FAMILY_IP6MR 129
#endif

#ifndef RTPROT_MROUTED
#define RTPROT_MROUTED 17
#endif

#define NL_DEFAULT_BATCH_BUFSIZE (16 * NL_PKT_BUF_SIZE)

/*
 * We limit the batch's size to a number smaller than the length of the
 * underlying buffer since the last message that wouldn't fit the batch would go
 * over the upper boundary and then it would have to be encoded again into a new
 * buffer. If the difference between the limit and the length of the buffer is
 * big enough (bigger than the biggest Netlink message) then this situation
 * won't occur.
 */
#define NL_DEFAULT_BATCH_SEND_THRESHOLD (15 * NL_PKT_BUF_SIZE)

static const struct message nlmsg_str[] = {{RTM_NEWROUTE, "RTM_NEWROUTE"},
                                           {RTM_DELROUTE, "RTM_DELROUTE"},
                                           {RTM_GETROUTE, "RTM_GETROUTE"},
                                           {RTM_NEWLINK, "RTM_NEWLINK"},
                                           {RTM_SETLINK, "RTM_SETLINK"},
                                           {RTM_DELLINK, "RTM_DELLINK"},
                                           {RTM_GETLINK, "RTM_GETLINK"},
                                           {RTM_NEWADDR, "RTM_NEWADDR"},
                                           {RTM_DELADDR, "RTM_DELADDR"},
                                           {RTM_GETADDR, "RTM_GETADDR"},
                                           {RTM_NEWNEIGH, "RTM_NEWNEIGH"},
                                           {RTM_DELNEIGH, "RTM_DELNEIGH"},
                                           {RTM_GETNEIGH, "RTM_GETNEIGH"},
                                           {RTM_NEWRULE, "RTM_NEWRULE"},
                                           {RTM_DELRULE, "RTM_DELRULE"},
                                           {RTM_GETRULE, "RTM_GETRULE"},
                                           {RTM_NEWNEXTHOP, "RTM_NEWNEXTHOP"},
                                           {RTM_DELNEXTHOP, "RTM_DELNEXTHOP"},
                                           {RTM_GETNEXTHOP, "RTM_GETNEXTHOP"},
                                           {RTM_NEWNETCONF, "RTM_NEWNETCONF"},
                                           {RTM_DELNETCONF, "RTM_DELNETCONF"},
                                           {RTM_NEWTUNNEL, "RTM_NEWTUNNEL"},
                                           {RTM_DELTUNNEL, "RTM_DELTUNNEL"},
                                           {RTM_GETTUNNEL, "RTM_GETTUNNEL"},
                                           {RTM_NEWQDISC, "RTM_NEWQDISC"},
                                           {RTM_DELQDISC, "RTM_DELQDISC"},
                                           {RTM_GETQDISC, "RTM_GETQDISC"},
                                           {RTM_NEWTCLASS, "RTM_NEWTCLASS"},
                                           {RTM_DELTCLASS, "RTM_DELTCLASS"},
                                           {RTM_GETTCLASS, "RTM_GETTCLASS"},
                                           {RTM_NEWTFILTER, "RTM_NEWTFILTER"},
                                           {RTM_DELTFILTER, "RTM_DELTFILTER"},
                                           {RTM_GETTFILTER, "RTM_GETTFILTER"},
                                           {0}};

static const struct message rtproto_str[] = {
        {RTPROT_REDIRECT, "redirect"},
        {RTPROT_KERNEL, "kernel"},
        {RTPROT_BOOT, "boot"},
        {RTPROT_STATIC, "static"},
        {RTPROT_GATED, "GateD"},
        {RTPROT_RA, "router advertisement"},
        {RTPROT_MRT, "MRT"},
        {RTPROT_ZEBRA, "Zebra"},
#ifdef RTPROT_BIRD
        {RTPROT_BIRD, "BIRD"},
#endif /* RTPROT_BIRD */
        {RTPROT_MROUTED, "mroute"},
        {RTPROT_BGP, "BGP"},
        {RTPROT_OSPF, "OSPF"},
        {RTPROT_ISIS, "IS-IS"},
        {RTPROT_RIP, "RIP"},
        {RTPROT_RIPNG, "RIPNG"},
        {RTPROT_ZSTATIC, "static"},
        {0}};

static const struct message family_str[] = {{AF_INET, "ipv4"},
                                            {AF_INET6, "ipv6"},
                                            {AF_BRIDGE, "bridge"},
                                            {RTNL_FAMILY_IPMR, "ipv4MR"},
                                            {RTNL_FAMILY_IP6MR, "ipv6MR"},
                                            {0}};

static const struct message rttype_str[] = {{RTN_UNSPEC, "none"},
                                            {RTN_UNICAST, "unicast"},
                                            {RTN_LOCAL, "local"},
                                            {RTN_BROADCAST, "broadcast"},
                                            {RTN_ANYCAST, "anycast"},
                                            {RTN_MULTICAST, "multicast"},
                                            {RTN_BLACKHOLE, "blackhole"},
                                            {RTN_UNREACHABLE, "unreachable"},
                                            {RTN_PROHIBIT, "prohibited"},
                                            {RTN_THROW, "throw"},
                                            {RTN_NAT, "nat"},
                                            {RTN_XRESOLVE, "resolver"},
                                            {0}};

extern struct thread_master *master;

extern struct zebra_privs_t zserv_privs;

DEFINE_MTYPE_STATIC(ZEBRA, NL_BUF, "Zebra Netlink buffers");

/* Hashtable and mutex to allow lookup of nlsock structs by socket/fd value.
 * We have both the main and dplane pthreads using these structs, so we have
 * to protect the hash with a lock.
 */
static struct hash *nlsock_hash;
pthread_mutex_t nlsock_mutex;

/* Lock and unlock wrappers for nlsock hash */
#define NLSOCK_LOCK() pthread_mutex_lock(&nlsock_mutex)
#define NLSOCK_UNLOCK() pthread_mutex_unlock(&nlsock_mutex)

size_t nl_batch_tx_bufsize;
char *nl_batch_tx_buf;

_Atomic uint32_t nl_batch_bufsize = NL_DEFAULT_BATCH_BUFSIZE;
_Atomic uint32_t nl_batch_send_threshold = NL_DEFAULT_BATCH_SEND_THRESHOLD;

struct nl_batch {
        void *buf;
        size_t bufsiz;
        size_t limit;

        void *buf_head;
        size_t curlen;
        size_t msgcnt;

        const struct zebra_dplane_info *zns;

        struct dplane_ctx_q ctx_list;

        /*
         * Pointer to the queue of completed contexts outbound back
         * towards the dataplane module.
         */
        struct dplane_ctx_q *ctx_out_q;
};

int netlink_config_write_helper(struct vty *vty)
{
        uint32_t size =
                atomic_load_explicit(&nl_batch_bufsize, memory_order_relaxed);
        uint32_t threshold = atomic_load_explicit(&nl_batch_send_threshold,
                                                  memory_order_relaxed);

        if (size != NL_DEFAULT_BATCH_BUFSIZE
            || threshold != NL_DEFAULT_BATCH_SEND_THRESHOLD)
                vty_out(vty, "zebra kernel netlink batch-tx-buf %u %u\n", size,
                        threshold);

        if (if_netlink_frr_protodown_r_bit_is_set())
                vty_out(vty, "zebra protodown reason-bit %u\n",
                        if_netlink_get_frr_protodown_r_bit());

        return 0;
}

void netlink_set_batch_buffer_size(uint32_t size, uint32_t threshold, bool set)
{
        if (!set) {
                size = NL_DEFAULT_BATCH_BUFSIZE;
                threshold = NL_DEFAULT_BATCH_SEND_THRESHOLD;
        }

        atomic_store_explicit(&nl_batch_bufsize, size, memory_order_relaxed);
        atomic_store_explicit(&nl_batch_send_threshold, threshold,
                              memory_order_relaxed);
}

int netlink_talk_filter(struct nlmsghdr *h, ns_id_t ns_id, int startup)
{
        /*
         * This is an error condition that must be handled during
         * development.
         *
         * The netlink_talk_filter function is used for communication
         * down the netlink_cmd pipe and we are expecting
         * an ack being received.  So if we get here
         * then we did not receive the ack and instead
         * received some other message in an unexpected
         * way.
         */
        zlog_debug("%s: ignoring message type 0x%04x(%s) NS %u", __func__,
                   h->nlmsg_type, nl_msg_type_to_str(h->nlmsg_type), ns_id);
        return 0;
}

static int netlink_recvbuf(struct nlsock *nl, uint32_t newsize)
{
        uint32_t oldsize;
        socklen_t newlen = sizeof(newsize);
        socklen_t oldlen = sizeof(oldsize);
        int ret;

        ret = getsockopt(nl->sock, SOL_SOCKET, SO_RCVBUF, &oldsize, &oldlen);
        if (ret < 0) {
                flog_err_sys(EC_LIB_SOCKET,
                             "Can't get %s receive buffer size: %s", nl->name,
                             safe_strerror(errno));
                return -1;
        }

        /* Try force option (linux >= 2.6.14) and fall back to normal set */
        frr_with_privs(&zserv_privs) {
                ret = setsockopt(nl->sock, SOL_SOCKET, SO_RCVBUFFORCE,
                                 &rcvbufsize, sizeof(rcvbufsize));
        }
        if (ret < 0)
                ret = setsockopt(nl->sock, SOL_SOCKET, SO_RCVBUF, &rcvbufsize,
                                 sizeof(rcvbufsize));
        if (ret < 0) {
                flog_err_sys(EC_LIB_SOCKET,
                             "Can't set %s receive buffer size: %s", nl->name,
                             safe_strerror(errno));
                return -1;
        }

        ret = getsockopt(nl->sock, SOL_SOCKET, SO_RCVBUF, &newsize, &newlen);
        if (ret < 0) {
                flog_err_sys(EC_LIB_SOCKET,
                             "Can't get %s receive buffer size: %s", nl->name,
                             safe_strerror(errno));
                return -1;
        }
        return 0;
}

static const char *group2str(uint32_t group)
{
        switch (group) {
        case RTNLGRP_TUNNEL:
                return "RTNLGRP_TUNNEL";
        default:
                return "UNKNOWN";
        }
}

/* Make socket for Linux netlink interface. */
static int netlink_socket(struct nlsock *nl, unsigned long groups,
                          uint32_t ext_groups[], uint8_t ext_group_size,
                          ns_id_t ns_id)
{
        int ret;
        struct sockaddr_nl snl;
        int sock;
        int namelen;

        frr_with_privs(&zserv_privs) {
                sock = ns_socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE, ns_id);
                if (sock < 0) {
                        zlog_err("Can't open %s socket: %s", nl->name,
                                 safe_strerror(errno));
                        return -1;
                }

                memset(&snl, 0, sizeof(snl));
                snl.nl_family = AF_NETLINK;
                snl.nl_groups = groups;

                if (ext_group_size) {
                        uint8_t i;

                        for (i = 0; i < ext_group_size; i++) {
#if defined SOL_NETLINK
                                ret = setsockopt(sock, SOL_NETLINK,
                                                 NETLINK_ADD_MEMBERSHIP,
                                                 &ext_groups[i],
                                                 sizeof(ext_groups[i]));
                                if (ret < 0) {
                                        zlog_notice(
                                                "can't setsockopt NETLINK_ADD_MEMBERSHIP for group %s(%u), this linux kernel does not support it: %s(%d)",
                                                group2str(ext_groups[i]),
                                                ext_groups[i],
                                                safe_strerror(errno), errno);
                                }
#else
                                zlog_notice(
                                        "Unable to use NETLINK_ADD_MEMBERSHIP via SOL_NETLINK for %s(%u) since the linux kernel does not support the socket option",
                                        group2str(ext_groups[i]),
                                        ext_groups[i]);
#endif
                        }
                }

                /* Bind the socket to the netlink structure for anything. */
                ret = bind(sock, (struct sockaddr *)&snl, sizeof(snl));
        }

        if (ret < 0) {
                zlog_err("Can't bind %s socket to group 0x%x: %s", nl->name,
                         snl.nl_groups, safe_strerror(errno));
                close(sock);
                return -1;
        }

        /* multiple netlink sockets will have different nl_pid */
        namelen = sizeof(snl);
        ret = getsockname(sock, (struct sockaddr *)&snl, (socklen_t *)&namelen);
        if (ret < 0 || namelen != sizeof(snl)) {
                flog_err_sys(EC_LIB_SOCKET, "Can't get %s socket name: %s",
                             nl->name, safe_strerror(errno));
                close(sock);
                return -1;
        }

        nl->snl = snl;
        nl->sock = sock;
        nl->buflen = NL_RCV_PKT_BUF_SIZE;
        nl->buf = XMALLOC(MTYPE_NL_BUF, nl->buflen);

        return ret;
}

/*
 * Dispatch an incoming netlink message; used by the zebra main pthread's
 * netlink event reader.
 */
static int netlink_information_fetch(struct nlmsghdr *h, ns_id_t ns_id,
                                     int startup)
{
        /*
         * When we handle new message types here
         * because we are starting to install them
         * then lets check the netlink_install_filter
         * and see if we should add the corresponding
         * allow through entry there.
         * Probably not needed to do but please
         * think about it.
         */
        switch (h->nlmsg_type) {
        case RTM_NEWROUTE:
                return netlink_route_change(h, ns_id, startup);
        case RTM_DELROUTE:
                return netlink_route_change(h, ns_id, startup);
        case RTM_NEWLINK:
                return netlink_link_change(h, ns_id, startup);
        case RTM_DELLINK:
                return netlink_link_change(h, ns_id, startup);
        case RTM_NEWNEIGH:
        case RTM_DELNEIGH:
        case RTM_GETNEIGH:
                return netlink_neigh_change(h, ns_id);
        case RTM_NEWRULE:
                return netlink_rule_change(h, ns_id, startup);
        case RTM_DELRULE:
                return netlink_rule_change(h, ns_id, startup);
        case RTM_NEWNEXTHOP:
                return netlink_nexthop_change(h, ns_id, startup);
        case RTM_DELNEXTHOP:
                return netlink_nexthop_change(h, ns_id, startup);

        /* Messages handled in the dplane thread */
        case RTM_NEWADDR:
        case RTM_DELADDR:
        case RTM_NEWNETCONF:
        case RTM_DELNETCONF:
        case RTM_NEWTUNNEL:
        case RTM_DELTUNNEL:
        case RTM_GETTUNNEL:
                return 0;
        default:
                /*
                 * If we have received this message then
                 * we have made a mistake during development
                 * and we need to write some code to handle
                 * this message type or not ask for
                 * it to be sent up to us
                 */
                flog_err(EC_ZEBRA_UNKNOWN_NLMSG,
                         "Unknown netlink nlmsg_type %s(%d) vrf %u",
                         nl_msg_type_to_str(h->nlmsg_type), h->nlmsg_type,
                         ns_id);
                break;
        }
        return 0;
}

/*
 * Dispatch an incoming netlink message; used by the dataplane pthread's
 * netlink event reader code.
 */
static int dplane_netlink_information_fetch(struct nlmsghdr *h, ns_id_t ns_id,
                                            int startup)
{
        /*
         * Dispatch the incoming messages that the dplane pthread handles
         */
        switch (h->nlmsg_type) {
        case RTM_NEWADDR:
        case RTM_DELADDR:
                return netlink_interface_addr_dplane(h, ns_id, startup);

        case RTM_NEWNETCONF:
        case RTM_DELNETCONF:
                return netlink_netconf_change(h, ns_id, startup);

        /* TODO -- other messages for the dplane socket and pthread */

        case RTM_NEWLINK:
        case RTM_DELLINK:

        default:
                break;
        }

        return 0;
}

static void kernel_read(struct thread *thread)
{
        struct zebra_ns *zns = (struct zebra_ns *)THREAD_ARG(thread);
        struct zebra_dplane_info dp_info;

        /* Capture key info from ns struct */
        zebra_dplane_info_from_zns(&dp_info, zns, false);

        netlink_parse_info(netlink_information_fetch, &zns->netlink, &dp_info,
                           5, false);

        thread_add_read(zrouter.master, kernel_read, zns, zns->netlink.sock,
                        &zns->t_netlink);
}

/*
 * Called by the dplane pthread to read incoming OS messages and dispatch them.
 */
int kernel_dplane_read(struct zebra_dplane_info *info)
{
        struct nlsock *nl = kernel_netlink_nlsock_lookup(info->sock);

        netlink_parse_info(dplane_netlink_information_fetch, nl, info, 5,
                           false);

        return 0;
}

/*
 * Filter out messages from self that occur on listener socket,
 * caused by our actions on the command socket(s)
 *
 * When we add new Netlink message types we probably
 * do not need to add them here as that we are filtering
 * on the routes we actually care to receive( which is rarer
 * then the normal course of operations).  We are intentionally
 * allowing some messages from ourselves through
 * ( I'm looking at you Interface based netlink messages )
 * so that we only have to write one way to handle incoming
 * address add/delete and xxxNETCONF changes.
 */
static void netlink_install_filter(int sock, uint32_t pid, uint32_t dplane_pid)
{
        /*
         * BPF_JUMP instructions and where you jump to are based upon
         * 0 as being the next statement.  So count from 0.  Writing
         * this down because every time I look at this I have to
         * re-remember it.
         */
        struct sock_filter filter[] = {
                /*
                 * Logic:
                 *   if (nlmsg_pid == pid ||
                 *       nlmsg_pid == dplane_pid) {
                 *       if (the incoming nlmsg_type ==
                 *           RTM_NEWADDR || RTM_DELADDR || RTM_NEWNETCONF ||
                 *           RTM_DELNETCONF)
                 *           keep this message
                 *       else
                 *           skip this message
                 *   } else
                 *       keep this netlink message
                 */
                /*
                 * 0: Load the nlmsg_pid into the BPF register
                 */
                BPF_STMT(BPF_LD | BPF_ABS | BPF_W,
                         offsetof(struct nlmsghdr, nlmsg_pid)),
                /*
                 * 1: Compare to pid
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(pid), 1, 0),
                /*
                 * 2: Compare to dplane pid
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(dplane_pid), 0, 6),
                /*
                 * 3: Load the nlmsg_type into BPF register
                 */
                BPF_STMT(BPF_LD | BPF_ABS | BPF_H,
                         offsetof(struct nlmsghdr, nlmsg_type)),
                /*
                 * 4: Compare to RTM_NEWADDR
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(RTM_NEWADDR), 4, 0),
                /*
                 * 5: Compare to RTM_DELADDR
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(RTM_DELADDR), 3, 0),
                /*
                 * 6: Compare to RTM_NEWNETCONF
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(RTM_NEWNETCONF), 2,
                         0),
                /*
                 * 7: Compare to RTM_DELNETCONF
                 */
                BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(RTM_DELNETCONF), 1,
                         0),
                /*
                 * 8: This is the end state of we want to skip the
                 *    message
                 */
                BPF_STMT(BPF_RET | BPF_K, 0),
                /* 9: This is the end state of we want to keep
                 *     the message
                 */
                BPF_STMT(BPF_RET | BPF_K, 0xffff),
        };

        struct sock_fprog prog = {
                .len = array_size(filter), .filter = filter,
        };

        if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &prog, sizeof(prog))
            < 0)
                flog_err_sys(EC_LIB_SOCKET, "Can't install socket filter: %s",
                             safe_strerror(errno));
}

void netlink_parse_rtattr_flags(struct rtattr **tb, int max, struct rtattr *rta,
                                int len, unsigned short flags)
{
        unsigned short type;

        memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
        while (RTA_OK(rta, len)) {
                type = rta->rta_type & ~flags;
                if ((type <= max) && (!tb[type]))
                        tb[type] = rta;
                rta = RTA_NEXT(rta, len);
        }
}

void netlink_parse_rtattr(struct rtattr **tb, int max, struct rtattr *rta,
                          int len)
{
        memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
        while (RTA_OK(rta, len)) {
                if (rta->rta_type <= max)
                        tb[rta->rta_type] = rta;
                rta = RTA_NEXT(rta, len);
        }
}

/**
 * netlink_parse_rtattr_nested() - Parses a nested route attribute
 * @tb:         Pointer to array for storing rtattr in.
 * @max:        Max number to store.
 * @rta:        Pointer to rtattr to look for nested items in.
 */
void netlink_parse_rtattr_nested(struct rtattr **tb, int max,
                                 struct rtattr *rta)
{
        netlink_parse_rtattr(tb, max, RTA_DATA(rta), RTA_PAYLOAD(rta));
}

bool nl_addraw_l(struct nlmsghdr *n, unsigned int maxlen, const void *data,
                 unsigned int len)
{
        if (NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len) > maxlen) {
                zlog_err("ERROR message exceeded bound of %d", maxlen);
                return false;
        }

        memcpy(NLMSG_TAIL(n), data, len);
        memset((uint8_t *)NLMSG_TAIL(n) + len, 0, NLMSG_ALIGN(len) - len);
        n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len);

        return true;
}

bool nl_attr_put(struct nlmsghdr *n, unsigned int maxlen, int type,
                 const void *data, unsigned int alen)
{
        int len;
        struct rtattr *rta;

        len = RTA_LENGTH(alen);

        if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen)
                return false;

        rta = (struct rtattr *)(((char *)n) + NLMSG_ALIGN(n->nlmsg_len));
        rta->rta_type = type;
        rta->rta_len = len;

        if (data)
                memcpy(RTA_DATA(rta), data, alen);
        else
                assert(alen == 0);

        n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);

        return true;
}

bool nl_attr_put8(struct nlmsghdr *n, unsigned int maxlen, int type,
                  uint8_t data)
{
        return nl_attr_put(n, maxlen, type, &data, sizeof(uint8_t));
}

bool nl_attr_put16(struct nlmsghdr *n, unsigned int maxlen, int type,
                   uint16_t data)
{
        return nl_attr_put(n, maxlen, type, &data, sizeof(uint16_t));
}

bool nl_attr_put32(struct nlmsghdr *n, unsigned int maxlen, int type,
                   uint32_t data)
{
        return nl_attr_put(n, maxlen, type, &data, sizeof(uint32_t));
}

struct rtattr *nl_attr_nest(struct nlmsghdr *n, unsigned int maxlen, int type)
{
        struct rtattr *nest = NLMSG_TAIL(n);

        if (!nl_attr_put(n, maxlen, type, NULL, 0))
                return NULL;

        nest->rta_type |= NLA_F_NESTED;
        return nest;
}

int nl_attr_nest_end(struct nlmsghdr *n, struct rtattr *nest)
{
        nest->rta_len = (uint8_t *)NLMSG_TAIL(n) - (uint8_t *)nest;
        return n->nlmsg_len;
}

struct rtnexthop *nl_attr_rtnh(struct nlmsghdr *n, unsigned int maxlen)
{
        struct rtnexthop *rtnh = (struct rtnexthop *)NLMSG_TAIL(n);

        if (NLMSG_ALIGN(n->nlmsg_len) + RTNH_ALIGN(sizeof(struct rtnexthop))
            > maxlen)
                return NULL;

        memset(rtnh, 0, sizeof(struct rtnexthop));
        n->nlmsg_len =
                NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(sizeof(struct rtnexthop));

        return rtnh;
}

void nl_attr_rtnh_end(struct nlmsghdr *n, struct rtnexthop *rtnh)
{
        rtnh->rtnh_len = (uint8_t *)NLMSG_TAIL(n) - (uint8_t *)rtnh;
}

bool nl_rta_put(struct rtattr *rta, unsigned int maxlen, int type,
                const void *data, int alen)
{
        struct rtattr *subrta;
        int len = RTA_LENGTH(alen);

        if (RTA_ALIGN(rta->rta_len) + RTA_ALIGN(len) > maxlen) {
                zlog_err("ERROR max allowed bound %d exceeded for rtattr",
                         maxlen);
                return false;
        }
        subrta = (struct rtattr *)(((char *)rta) + RTA_ALIGN(rta->rta_len));
        subrta->rta_type = type;
        subrta->rta_len = len;
        if (alen)
                memcpy(RTA_DATA(subrta), data, alen);
        rta->rta_len = NLMSG_ALIGN(rta->rta_len) + RTA_ALIGN(len);

        return true;
}

bool nl_rta_put16(struct rtattr *rta, unsigned int maxlen, int type,
                  uint16_t data)
{
        return nl_rta_put(rta, maxlen, type, &data, sizeof(uint16_t));
}

bool nl_rta_put64(struct rtattr *rta, unsigned int maxlen, int type,
                  uint64_t data)
{
        return nl_rta_put(rta, maxlen, type, &data, sizeof(uint64_t));
}

struct rtattr *nl_rta_nest(struct rtattr *rta, unsigned int maxlen, int type)
{
        struct rtattr *nest = RTA_TAIL(rta);

        if (nl_rta_put(rta, maxlen, type, NULL, 0))
                return NULL;

        nest->rta_type |= NLA_F_NESTED;

        return nest;
}

int nl_rta_nest_end(struct rtattr *rta, struct rtattr *nest)
{
        nest->rta_len = (uint8_t *)RTA_TAIL(rta) - (uint8_t *)nest;

        return rta->rta_len;
}

const char *nl_msg_type_to_str(uint16_t msg_type)
{
        return lookup_msg(nlmsg_str, msg_type, "");
}

const char *nl_rtproto_to_str(uint8_t rtproto)
{
        return lookup_msg(rtproto_str, rtproto, "");
}

const char *nl_family_to_str(uint8_t family)
{
        return lookup_msg(family_str, family, "");
}

const char *nl_rttype_to_str(uint8_t rttype)
{
        return lookup_msg(rttype_str, rttype, "");
}

#define NLA_OK(nla, len)                                                       \
        ((len) >= (int)sizeof(struct nlattr)                                   \
         && (nla)->nla_len >= sizeof(struct nlattr)                            \
         && (nla)->nla_len <= (len))
#define NLA_NEXT(nla, attrlen)                                                 \
        ((attrlen) -= NLA_ALIGN((nla)->nla_len),                               \
         (struct nlattr *)(((char *)(nla)) + NLA_ALIGN((nla)->nla_len)))
#define NLA_LENGTH(len) (NLA_ALIGN(sizeof(struct nlattr)) + (len))
#define NLA_DATA(nla) ((struct nlattr *)(((char *)(nla)) + NLA_LENGTH(0)))

#define ERR_NLA(err, inner_len)                                                \
        ((struct nlattr *)(((char *)(err))                                     \
                           + NLMSG_ALIGN(sizeof(struct nlmsgerr))              \
                           + NLMSG_ALIGN((inner_len))))

static void netlink_parse_nlattr(struct nlattr **tb, int max,
                                 struct nlattr *nla, int len)
{
        while (NLA_OK(nla, len)) {
                if (nla->nla_type <= max)
                        tb[nla->nla_type] = nla;
                nla = NLA_NEXT(nla, len);
        }
}

static void netlink_parse_extended_ack(struct nlmsghdr *h)
{
        struct nlattr *tb[NLMSGERR_ATTR_MAX + 1] = {};
        const struct nlmsgerr *err = (const struct nlmsgerr *)NLMSG_DATA(h);
        const struct nlmsghdr *err_nlh = NULL;
        /* Length not including nlmsghdr */
        uint32_t len = 0;
        /* Inner error netlink message length */
        uint32_t inner_len = 0;
        const char *msg = NULL;
        uint32_t off = 0;

        if (!(h->nlmsg_flags & NLM_F_CAPPED))
                inner_len = (uint32_t)NLMSG_PAYLOAD(&err->msg, 0);

        len = (uint32_t)(NLMSG_PAYLOAD(h, sizeof(struct nlmsgerr)) - inner_len);

        netlink_parse_nlattr(tb, NLMSGERR_ATTR_MAX, ERR_NLA(err, inner_len),
                             len);

        if (tb[NLMSGERR_ATTR_MSG])
                msg = (const char *)NLA_DATA(tb[NLMSGERR_ATTR_MSG]);

        if (tb[NLMSGERR_ATTR_OFFS]) {
                off = *(uint32_t *)NLA_DATA(tb[NLMSGERR_ATTR_OFFS]);

                if (off > h->nlmsg_len) {
                        zlog_err("Invalid offset for NLMSGERR_ATTR_OFFS");
                } else if (!(h->nlmsg_flags & NLM_F_CAPPED)) {
                        /*
                         * Header of failed message
                         * we are not doing anything currently with it
                         * but noticing it for later.
                         */
                        err_nlh = &err->msg;
                        zlog_debug("%s: Received %s extended Ack", __func__,
                                   nl_msg_type_to_str(err_nlh->nlmsg_type));
                }
        }

        if (msg && *msg != '\0') {
                bool is_err = !!err->error;

                if (is_err)
                        zlog_err("Extended Error: %s", msg);
                else
                        flog_warn(EC_ZEBRA_NETLINK_EXTENDED_WARNING,
                                  "Extended Warning: %s", msg);
        }
}

/*
 * netlink_send_msg - send a netlink message of a certain size.
 *
 * Returns -1 on error. Otherwise, it returns the number of bytes sent.
 */
static ssize_t netlink_send_msg(const struct nlsock *nl, void *buf,
                                size_t buflen)
{
        struct sockaddr_nl snl = {};
        struct iovec iov = {};
        struct msghdr msg = {};
        ssize_t status;
        int save_errno = 0;

        iov.iov_base = buf;
        iov.iov_len = buflen;
        msg.msg_name = &snl;
        msg.msg_namelen = sizeof(snl);
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;

        snl.nl_family = AF_NETLINK;

        /* Send message to netlink interface. */
        frr_with_privs(&zserv_privs) {
                status = sendmsg(nl->sock, &msg, 0);
                save_errno = errno;
        }

        if (IS_ZEBRA_DEBUG_KERNEL_MSGDUMP_SEND) {
                zlog_debug("%s: >> netlink message dump [sent]", __func__);
#ifdef NETLINK_DEBUG
                nl_dump(buf, buflen);
#else
                zlog_hexdump(buf, buflen);
#endif /* NETLINK_DEBUG */
        }

        if (status == -1) {
                flog_err_sys(EC_LIB_SOCKET, "%s error: %s", __func__,
                             safe_strerror(save_errno));
                return -1;
        }

        return status;
}

/*
 * netlink_recv_msg - receive a netlink message.
 *
 * Returns -1 on error, 0 if read would block or the number of bytes received.
 */
static int netlink_recv_msg(struct nlsock *nl, struct msghdr *msg)
{
        struct iovec iov;
        int status;

        iov.iov_base = nl->buf;
        iov.iov_len = nl->buflen;
        msg->msg_iov = &iov;
        msg->msg_iovlen = 1;

        do {
                int bytes;

                bytes = recv(nl->sock, NULL, 0, MSG_PEEK | MSG_TRUNC);

                if (bytes >= 0 && (size_t)bytes > nl->buflen) {
                        nl->buf = XREALLOC(MTYPE_NL_BUF, nl->buf, bytes);
                        nl->buflen = bytes;
                        iov.iov_base = nl->buf;
                        iov.iov_len = nl->buflen;
                }

                status = recvmsg(nl->sock, msg, 0);
        } while (status == -1 && errno == EINTR);

        if (status == -1) {
                if (errno == EWOULDBLOCK || errno == EAGAIN)
                        return 0;
                flog_err(EC_ZEBRA_RECVMSG_OVERRUN, "%s recvmsg overrun: %s",
                         nl->name, safe_strerror(errno));
                /*
                 * In this case we are screwed. There is no good way to recover
                 * zebra at this point.
                 */
                exit(-1);
        }

        if (status == 0) {
                flog_err_sys(EC_LIB_SOCKET, "%s EOF", nl->name);
                return -1;
        }

        if (msg->msg_namelen != sizeof(struct sockaddr_nl)) {
                flog_err(EC_ZEBRA_NETLINK_LENGTH_ERROR,
                         "%s sender address length error: length %d", nl->name,
                         msg->msg_namelen);
                return -1;
        }

        if (IS_ZEBRA_DEBUG_KERNEL_MSGDUMP_RECV) {
                zlog_debug("%s: << netlink message dump [recv]", __func__);
#ifdef NETLINK_DEBUG
                nl_dump(nl->buf, status);
#else
                zlog_hexdump(nl->buf, status);
#endif /* NETLINK_DEBUG */
        }

        return status;
}

/*
 * netlink_parse_error - parse a netlink error message
 *
 * Returns 1 if this message is acknowledgement, 0 if this error should be
 * ignored, -1 otherwise.
 */
static int netlink_parse_error(const struct nlsock *nl, struct nlmsghdr *h,
                               bool is_cmd, bool startup)
{
        struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h);
        int errnum = err->error;
        int msg_type = err->msg.nlmsg_type;

        if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr))) {
                flog_err(EC_ZEBRA_NETLINK_LENGTH_ERROR,
                         "%s error: message truncated", nl->name);
                return -1;
        }

        /*
         * Parse the extended information before we actually handle it. At this
         * point in time we do not do anything other than report the issue.
         */
        if (h->nlmsg_flags & NLM_F_ACK_TLVS)
                netlink_parse_extended_ack(h);

        /* If the error field is zero, then this is an ACK. */
        if (err->error == 0) {
                if (IS_ZEBRA_DEBUG_KERNEL) {
                        zlog_debug("%s: %s ACK: type=%s(%u), seq=%u, pid=%u",
                                   __func__, nl->name,
                                   nl_msg_type_to_str(err->msg.nlmsg_type),
                                   err->msg.nlmsg_type, err->msg.nlmsg_seq,
                                   err->msg.nlmsg_pid);
                }

                return 1;
        }

        /*
         * Deal with errors that occur because of races in link handling
         * or types are not supported in kernel.
         */
        if (is_cmd &&
            ((msg_type == RTM_DELROUTE &&
              (-errnum == ENODEV || -errnum == ESRCH)) ||
             (msg_type == RTM_NEWROUTE &&
              (-errnum == ENETDOWN || -errnum == EEXIST)) ||
             ((msg_type == RTM_NEWTUNNEL || msg_type == RTM_DELTUNNEL ||
               msg_type == RTM_GETTUNNEL) &&
              (-errnum == EOPNOTSUPP)))) {
                if (IS_ZEBRA_DEBUG_KERNEL)
                        zlog_debug("%s: error: %s type=%s(%u), seq=%u, pid=%u",
                                   nl->name, safe_strerror(-errnum),
                                   nl_msg_type_to_str(msg_type), msg_type,
                                   err->msg.nlmsg_seq, err->msg.nlmsg_pid);
                return 0;
        }

        /*
         * We see RTM_DELNEIGH when shutting down an interface with an IPv4
         * link-local.  The kernel should have already deleted the neighbor so
         * do not log these as an error.
         */
        if (msg_type == RTM_DELNEIGH
            || (is_cmd && msg_type == RTM_NEWROUTE
                && (-errnum == ESRCH || -errnum == ENETUNREACH))) {
                /*
                 * This is known to happen in some situations, don't log as
                 * error.
                 */
                if (IS_ZEBRA_DEBUG_KERNEL)
                        zlog_debug("%s error: %s, type=%s(%u), seq=%u, pid=%u",
                                   nl->name, safe_strerror(-errnum),
                                   nl_msg_type_to_str(msg_type), msg_type,
                                   err->msg.nlmsg_seq, err->msg.nlmsg_pid);
        } else {
                if ((msg_type != RTM_GETNEXTHOP) || !startup)
                        flog_err(EC_ZEBRA_UNEXPECTED_MESSAGE,
                                 "%s error: %s, type=%s(%u), seq=%u, pid=%u",
                                 nl->name, safe_strerror(-errnum),
                                 nl_msg_type_to_str(msg_type), msg_type,
                                 err->msg.nlmsg_seq, err->msg.nlmsg_pid);
        }

        return -1;
}

/*
 * netlink_parse_info
 *
 * Receive message from netlink interface and pass those information
 *  to the given function.
 *
 * filter  -> Function to call to read the results
 * nl      -> netlink socket information
 * zns     -> The zebra namespace data
 * count   -> How many we should read in, 0 means as much as possible
 * startup -> Are we reading in under startup conditions? passed to
 *            the filter.
 */
int netlink_parse_info(int (*filter)(struct nlmsghdr *, ns_id_t, int),
                       struct nlsock *nl, const struct zebra_dplane_info *zns,
                       int count, bool startup)
{
        int status;
        int ret = 0;
        int error;
        int read_in = 0;

        while (1) {
                struct sockaddr_nl snl;
                struct msghdr msg = {.msg_name = (void *)&snl,
                                     .msg_namelen = sizeof(snl)};
                struct nlmsghdr *h;

                if (count && read_in >= count)
                        return 0;

                status = netlink_recv_msg(nl, &msg);
                if (status == -1)
                        return -1;
                else if (status == 0)
                        break;

                read_in++;
                for (h = (struct nlmsghdr *)nl->buf;
                     (status >= 0 && NLMSG_OK(h, (unsigned int)status));
                     h = NLMSG_NEXT(h, status)) {
                        /* Finish of reading. */
                        if (h->nlmsg_type == NLMSG_DONE)
                                return ret;

                        /* Error handling. */
                        if (h->nlmsg_type == NLMSG_ERROR) {
                                int err = netlink_parse_error(
                                        nl, h, zns->is_cmd, startup);

                                if (err == 1) {
                                        if (!(h->nlmsg_flags & NLM_F_MULTI))
                                                return 0;
                                        continue;
                                } else
                                        return err;
                        }

                        /*
                         * What is the right thing to do?  The kernel
                         * is telling us that the dump request was interrupted
                         * and we more than likely are out of luck and have
                         * missed data from the kernel.  At this point in time
                         * lets just note that this is happening.
                         */
                        if (h->nlmsg_flags & NLM_F_DUMP_INTR)
                                flog_err(
                                        EC_ZEBRA_NETLINK_BAD_SEQUENCE,
                                        "netlink recvmsg: The Dump request was interrupted");

                        /* OK we got netlink message. */
                        if (IS_ZEBRA_DEBUG_KERNEL)
                                zlog_debug(
                                        "%s: %s type %s(%u), len=%d, seq=%u, pid=%u",
                                        __func__, nl->name,
                                        nl_msg_type_to_str(h->nlmsg_type),
                                        h->nlmsg_type, h->nlmsg_len,
                                        h->nlmsg_seq, h->nlmsg_pid);


                        /*
                         * Ignore messages that maybe sent from
                         * other actors besides the kernel
                         */
                        if (snl.nl_pid != 0) {
                                zlog_debug("Ignoring message from pid %u",
                                           snl.nl_pid);
                                continue;
                        }

                        error = (*filter)(h, zns->ns_id, startup);
                        if (error < 0) {
                                zlog_debug("%s filter function error",
                                           nl->name);
                                ret = error;
                        }
                }

                /* After error care. */
                if (msg.msg_flags & MSG_TRUNC) {
                        flog_err(EC_ZEBRA_NETLINK_LENGTH_ERROR,
                                 "%s error: message truncated", nl->name);
                        continue;
                }
                if (status) {
                        flog_err(EC_ZEBRA_NETLINK_LENGTH_ERROR,
                                 "%s error: data remnant size %d", nl->name,
                                 status);
                        return -1;
                }
        }
        return ret;
}

/*
 * netlink_talk_info
 *
 * sendmsg() to netlink socket then recvmsg().
 * Calls netlink_parse_info to parse returned data
 *
 * filter   -> The filter to read final results from kernel
 * nlmsghdr -> The data to send to the kernel
 * dp_info -> The dataplane and netlink socket information
 * startup  -> Are we reading in under startup conditions
 *             This is passed through eventually to filter.
 */
static int netlink_talk_info(int (*filter)(struct nlmsghdr *, ns_id_t,
                                           int startup),
                             struct nlmsghdr *n,
                             struct zebra_dplane_info *dp_info, bool startup)
{
        struct nlsock *nl;

        nl = kernel_netlink_nlsock_lookup(dp_info->sock);
        n->nlmsg_seq = dp_info->seq;
        n->nlmsg_pid = nl->snl.nl_pid;

        if (IS_ZEBRA_DEBUG_KERNEL)
                zlog_debug(
                        "netlink_talk: %s type %s(%u), len=%d seq=%u flags 0x%x",
                        nl->name, nl_msg_type_to_str(n->nlmsg_type),
                        n->nlmsg_type, n->nlmsg_len, n->nlmsg_seq,
                        n->nlmsg_flags);

        if (netlink_send_msg(nl, n, n->nlmsg_len) == -1)
                return -1;

        /*
         * Get reply from netlink socket.
         * The reply should either be an acknowlegement or an error.
         */
        return netlink_parse_info(filter, nl, dp_info, 0, startup);
}

/*
 * Synchronous version of netlink_talk_info. Converts args to suit the
 * common version, which is suitable for both sync and async use.
 */
int netlink_talk(int (*filter)(struct nlmsghdr *, ns_id_t, int startup),
                 struct nlmsghdr *n, struct nlsock *nl, struct zebra_ns *zns,
                 bool startup)
{
        struct zebra_dplane_info dp_info;

        /* Increment sequence number before capturing snapshot of ns socket
         * info.
         */
        nl->seq++;

        /* Capture info in intermediate info struct */
        zebra_dplane_info_from_zns(&dp_info, zns, (nl == &(zns->netlink_cmd)));

        return netlink_talk_info(filter, n, &dp_info, startup);
}

/* Issue request message to kernel via netlink socket. GET messages
 * are issued through this interface.
 */
int netlink_request(struct nlsock *nl, void *req)
{
        struct nlmsghdr *n = (struct nlmsghdr *)req;

        /* Check netlink socket. */
        if (nl->sock < 0) {
                flog_err_sys(EC_LIB_SOCKET, "%s socket isn't active.",
                             nl->name);
                return -1;
        }

        /* Fill common fields for all requests. */
        n->nlmsg_pid = nl->snl.nl_pid;
        n->nlmsg_seq = ++nl->seq;

        if (netlink_send_msg(nl, req, n->nlmsg_len) == -1)
                return -1;

        return 0;
}

static int nl_batch_read_resp(struct nl_batch *bth)
{
        struct nlmsghdr *h;
        struct sockaddr_nl snl;
        struct msghdr msg = {};
        int status, seq;
        struct nlsock *nl;
        struct zebra_dplane_ctx *ctx;
        bool ignore_msg;

        nl = kernel_netlink_nlsock_lookup(bth->zns->sock);

        msg.msg_name = (void *)&snl;
        msg.msg_namelen = sizeof(snl);

        /*
         * The responses are not batched, so we need to read and process one
         * message at a time.
         */
        while (true) {
                status = netlink_recv_msg(nl, &msg);
                /*
                 * status == -1 is a full on failure somewhere
                 * since we don't know where the problem happened
                 * we must mark all as failed
                 *
                 * Else we mark everything as worked
                 *
                 */
                if (status == -1 || status == 0) {
                        while ((ctx = dplane_ctx_dequeue(&(bth->ctx_list))) !=
                               NULL) {
                                if (status == -1)
                                        dplane_ctx_set_status(
                                                ctx,
                                                ZEBRA_DPLANE_REQUEST_FAILURE);
                                dplane_ctx_enqueue_tail(bth->ctx_out_q, ctx);
                        }
                        return status;
                }

                h = (struct nlmsghdr *)nl->buf;
                ignore_msg = false;
                seq = h->nlmsg_seq;
                /*
                 * Find the corresponding context object. Received responses are
                 * in the same order as requests we sent, so we can simply
                 * iterate over the context list and match responses with
                 * requests at same time.
                 */
                while (true) {
                        ctx = dplane_ctx_get_head(&(bth->ctx_list));
                        if (ctx == NULL) {
                                /*
                                 * This is a situation where we have gotten
                                 * into a bad spot.  We need to know that
                                 * this happens( does it? )
                                 */
                                zlog_err(
                                        "%s:WARNING Received netlink Response for an error and no Contexts to associate with it",
                                        __func__);
                                break;
                        }

                        /*
                         * 'update' context objects take two consecutive
                         * sequence numbers.
                         */
                        if (dplane_ctx_is_update(ctx) &&
                            dplane_ctx_get_ns(ctx)->seq + 1 == seq) {
                                /*
                                 * This is the situation where we get a response
                                 * to a message that should be ignored.
                                 */
                                ignore_msg = true;
                                break;
                        }

                        ctx = dplane_ctx_dequeue(&(bth->ctx_list));
                        dplane_ctx_enqueue_tail(bth->ctx_out_q, ctx);

                        /* We have found corresponding context object. */
                        if (dplane_ctx_get_ns(ctx)->seq == seq)
                                break;

                        if (dplane_ctx_get_ns(ctx)->seq > seq)
                                zlog_warn(
                                        "%s:WARNING Received %u is less than any context on the queue ctx->seq %u",
                                        __func__, seq,
                                        dplane_ctx_get_ns(ctx)->seq);
                }

                if (ignore_msg) {
                        /*
                         * If we ignore the message due to an update
                         * above we should still fricking decode the
                         * message for our operator to understand
                         * what is going on
                         */
                        int err = netlink_parse_error(nl, h, bth->zns->is_cmd,
                                                      false);

                        zlog_debug("%s: netlink error message seq=%d %d",
                                   __func__, h->nlmsg_seq, err);
                        continue;
                }

                /*
                 * We received a message with the sequence number that isn't
                 * associated with any dplane context object.
                 */
                if (ctx == NULL) {
                        if (IS_ZEBRA_DEBUG_KERNEL)
                                zlog_debug(
                                        "%s: skipping unassociated response, seq number %d NS %u",
                                        __func__, h->nlmsg_seq,
                                        bth->zns->ns_id);
                        continue;
                }

                if (h->nlmsg_type == NLMSG_ERROR) {
                        int err = netlink_parse_error(nl, h, bth->zns->is_cmd,
                                                      false);

                        if (err == -1)
                                dplane_ctx_set_status(
                                        ctx, ZEBRA_DPLANE_REQUEST_FAILURE);

                        if (IS_ZEBRA_DEBUG_KERNEL)
                                zlog_debug("%s: netlink error message seq=%d ",
                                           __func__, h->nlmsg_seq);
                        continue;
                }

                /*
                 * If we get here then we did not receive neither the ack nor
                 * the error and instead received some other message in an
                 * unexpected way.
                 */
                if (IS_ZEBRA_DEBUG_KERNEL)
                        zlog_debug("%s: ignoring message type 0x%04x(%s) NS %u",
                                   __func__, h->nlmsg_type,
                                   nl_msg_type_to_str(h->nlmsg_type),
                                   bth->zns->ns_id);
        }

        return 0;
}

static void nl_batch_reset(struct nl_batch *bth)
{
        bth->buf_head = bth->buf;
        bth->curlen = 0;
        bth->msgcnt = 0;
        bth->zns = NULL;

        TAILQ_INIT(&(bth->ctx_list));
}

static void nl_batch_init(struct nl_batch *bth, struct dplane_ctx_q *ctx_out_q)
{
        /*
         * If the size of the buffer has changed, free and then allocate a new
         * one.
         */
        size_t bufsize =
                atomic_load_explicit(&nl_batch_bufsize, memory_order_relaxed);
        if (bufsize != nl_batch_tx_bufsize) {
                if (nl_batch_tx_buf)
                        XFREE(MTYPE_NL_BUF, nl_batch_tx_buf);

                nl_batch_tx_buf = XCALLOC(MTYPE_NL_BUF, bufsize);
                nl_batch_tx_bufsize = bufsize;
        }

        bth->buf = nl_batch_tx_buf;
        bth->bufsiz = bufsize;
        bth->limit = atomic_load_explicit(&nl_batch_send_threshold,
                                          memory_order_relaxed);

        bth->ctx_out_q = ctx_out_q;

        nl_batch_reset(bth);
}

static void nl_batch_send(struct nl_batch *bth)
{
        struct zebra_dplane_ctx *ctx;
        bool err = false;

        if (bth->curlen != 0 && bth->zns != NULL) {
                struct nlsock *nl =
                        kernel_netlink_nlsock_lookup(bth->zns->sock);

                if (IS_ZEBRA_DEBUG_KERNEL)
                        zlog_debug("%s: %s, batch size=%zu, msg cnt=%zu",
                                   __func__, nl->name, bth->curlen,
                                   bth->msgcnt);

                if (netlink_send_msg(nl, bth->buf, bth->curlen) == -1)
                        err = true;

                if (!err) {
                        if (nl_batch_read_resp(bth) == -1)
                                err = true;
                }
        }

        /* Move remaining contexts to the outbound queue. */
        while (true) {
                ctx = dplane_ctx_dequeue(&(bth->ctx_list));
                if (ctx == NULL)
                        break;

                if (err)
                        dplane_ctx_set_status(ctx,
                                              ZEBRA_DPLANE_REQUEST_FAILURE);

                dplane_ctx_enqueue_tail(bth->ctx_out_q, ctx);
        }

        nl_batch_reset(bth);
}

enum netlink_msg_status netlink_batch_add_msg(
        struct nl_batch *bth, struct zebra_dplane_ctx *ctx,
        ssize_t (*msg_encoder)(struct zebra_dplane_ctx *, void *, size_t),
        bool ignore_res)
{
        int seq;
        ssize_t size;
        struct nlmsghdr *msgh;
        struct nlsock *nl;

        size = (*msg_encoder)(ctx, bth->buf_head, bth->bufsiz - bth->curlen);

        /*
         * If there was an error while encoding the message (other than buffer
         * overflow) then return an error.
         */
        if (size < 0)
                return FRR_NETLINK_ERROR;

        /*
         * If the message doesn't fit entirely in the buffer then send the batch
         * and retry.
         */
        if (size == 0) {
                nl_batch_send(bth);
                size = (*msg_encoder)(ctx, bth->buf_head,
                                      bth->bufsiz - bth->curlen);
                /*
                 * If the message doesn't fit in the empty buffer then just
                 * return an error.
                 */
                if (size <= 0)
                        return FRR_NETLINK_ERROR;
        }

        seq = dplane_ctx_get_ns(ctx)->seq;
        nl = kernel_netlink_nlsock_lookup(dplane_ctx_get_ns_sock(ctx));

        if (ignore_res)
                seq++;

        msgh = (struct nlmsghdr *)bth->buf_head;
        msgh->nlmsg_seq = seq;
        msgh->nlmsg_pid = nl->snl.nl_pid;

        bth->zns = dplane_ctx_get_ns(ctx);
        bth->buf_head = ((char *)bth->buf_head) + size;
        bth->curlen += size;
        bth->msgcnt++;

        return FRR_NETLINK_QUEUED;
}

static enum netlink_msg_status nl_put_msg(struct nl_batch *bth,
                                          struct zebra_dplane_ctx *ctx)
{
        if (dplane_ctx_is_skip_kernel(ctx))
                return FRR_NETLINK_SUCCESS;

        switch (dplane_ctx_get_op(ctx)) {

        case DPLANE_OP_ROUTE_INSTALL:
        case DPLANE_OP_ROUTE_UPDATE:
        case DPLANE_OP_ROUTE_DELETE:
                return netlink_put_route_update_msg(bth, ctx);

        case DPLANE_OP_NH_INSTALL:
        case DPLANE_OP_NH_UPDATE:
        case DPLANE_OP_NH_DELETE:
                return netlink_put_nexthop_update_msg(bth, ctx);

        case DPLANE_OP_LSP_INSTALL:
        case DPLANE_OP_LSP_UPDATE:
        case DPLANE_OP_LSP_DELETE:
                return netlink_put_lsp_update_msg(bth, ctx);

        case DPLANE_OP_PW_INSTALL:
        case DPLANE_OP_PW_UNINSTALL:
                return netlink_put_pw_update_msg(bth, ctx);

        case DPLANE_OP_ADDR_INSTALL:
        case DPLANE_OP_ADDR_UNINSTALL:
                return netlink_put_address_update_msg(bth, ctx);

        case DPLANE_OP_MAC_INSTALL:
        case DPLANE_OP_MAC_DELETE:
                return netlink_put_mac_update_msg(bth, ctx);

        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_NEIGH_DISCOVER:
        case DPLANE_OP_NEIGH_IP_INSTALL:
        case DPLANE_OP_NEIGH_IP_DELETE:
        case DPLANE_OP_NEIGH_TABLE_UPDATE:
                return netlink_put_neigh_update_msg(bth, ctx);

        case DPLANE_OP_RULE_ADD:
        case DPLANE_OP_RULE_DELETE:
        case DPLANE_OP_RULE_UPDATE:
                return netlink_put_rule_update_msg(bth, ctx);

        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_BR_PORT_UPDATE:
                return FRR_NETLINK_SUCCESS;

        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:
                return FRR_NETLINK_ERROR;

        case DPLANE_OP_GRE_SET:
                return netlink_put_gre_set_msg(bth, ctx);

        case DPLANE_OP_INTF_ADDR_ADD:
        case DPLANE_OP_INTF_ADDR_DEL:
        case DPLANE_OP_NONE:
                return FRR_NETLINK_ERROR;

        case DPLANE_OP_INTF_NETCONFIG:
                return netlink_put_intf_netconfig(bth, ctx);

        case DPLANE_OP_INTF_INSTALL:
        case DPLANE_OP_INTF_UPDATE:
        case DPLANE_OP_INTF_DELETE:
                return netlink_put_intf_update_msg(bth, ctx);

        case DPLANE_OP_TC_INSTALL:
        case DPLANE_OP_TC_UPDATE:
        case DPLANE_OP_TC_DELETE:
                return netlink_put_tc_update_msg(bth, ctx);
        }

        return FRR_NETLINK_ERROR;
}

void kernel_update_multi(struct dplane_ctx_q *ctx_list)
{
        struct nl_batch batch;
        struct zebra_dplane_ctx *ctx;
        struct dplane_ctx_q handled_list;
        enum netlink_msg_status res;

        TAILQ_INIT(&handled_list);
        nl_batch_init(&batch, &handled_list);

        while (true) {
                ctx = dplane_ctx_dequeue(ctx_list);
                if (ctx == NULL)
                        break;

                if (batch.zns != NULL
                    && batch.zns->ns_id != dplane_ctx_get_ns(ctx)->ns_id)
                        nl_batch_send(&batch);

                /*
                 * Assume all messages will succeed and then mark only the ones
                 * that failed.
                 */
                dplane_ctx_set_status(ctx, ZEBRA_DPLANE_REQUEST_SUCCESS);

                res = nl_put_msg(&batch, ctx);

                dplane_ctx_enqueue_tail(&(batch.ctx_list), ctx);
                if (res == FRR_NETLINK_ERROR)
                        dplane_ctx_set_status(ctx,
                                              ZEBRA_DPLANE_REQUEST_FAILURE);

                if (batch.curlen > batch.limit)
                        nl_batch_send(&batch);
        }

        nl_batch_send(&batch);

        TAILQ_INIT(ctx_list);
        dplane_ctx_list_append(ctx_list, &handled_list);
}

struct nlsock *kernel_netlink_nlsock_lookup(int sock)
{
        struct nlsock lookup, *retval;

        lookup.sock = sock;

        NLSOCK_LOCK();
        retval = hash_lookup(nlsock_hash, &lookup);
        NLSOCK_UNLOCK();

        return retval;
}

/* Insert nlsock entry into hash */
static void kernel_netlink_nlsock_insert(struct nlsock *nls)
{
        NLSOCK_LOCK();
        (void)hash_get(nlsock_hash, nls, hash_alloc_intern);
        NLSOCK_UNLOCK();
}

/* Remove nlsock entry from hash */
static void kernel_netlink_nlsock_remove(struct nlsock *nls)
{
        NLSOCK_LOCK();
        (void)hash_release(nlsock_hash, nls);
        NLSOCK_UNLOCK();
}

static uint32_t kernel_netlink_nlsock_key(const void *arg)
{
        const struct nlsock *nl = arg;

        return nl->sock;
}

static bool kernel_netlink_nlsock_hash_equal(const void *arg1, const void *arg2)
{
        const struct nlsock *nl1 = arg1;
        const struct nlsock *nl2 = arg2;

        if (nl1->sock == nl2->sock)
                return true;

        return false;
}

/* Exported interface function.  This function simply calls
   netlink_socket (). */
void kernel_init(struct zebra_ns *zns)
{
        uint32_t groups, dplane_groups, ext_groups;
#if defined SOL_NETLINK
        int one, ret;
#endif

        /*
         * Initialize netlink sockets
         *
         * If RTMGRP_XXX exists use that, but at some point
         * I think the kernel developers realized that
         * keeping track of all the different values would
         * lead to confusion, so we need to convert the
         * RTNLGRP_XXX to a bit position for ourself
         */
        groups = RTMGRP_LINK                   |
                RTMGRP_IPV4_ROUTE              |
                RTMGRP_IPV4_IFADDR             |
                RTMGRP_IPV6_ROUTE              |
                RTMGRP_IPV6_IFADDR             |
                RTMGRP_IPV4_MROUTE             |
                RTMGRP_NEIGH                   |
                ((uint32_t) 1 << (RTNLGRP_IPV4_RULE - 1)) |
                ((uint32_t) 1 << (RTNLGRP_IPV6_RULE - 1)) |
                ((uint32_t) 1 << (RTNLGRP_NEXTHOP - 1));

        dplane_groups = (RTMGRP_LINK            |
                         RTMGRP_IPV4_IFADDR     |
                         RTMGRP_IPV6_IFADDR     |
                         ((uint32_t) 1 << (RTNLGRP_IPV4_NETCONF - 1)) |
                         ((uint32_t) 1 << (RTNLGRP_IPV6_NETCONF - 1)) |
                         ((uint32_t) 1 << (RTNLGRP_MPLS_NETCONF - 1)));

        /* Use setsockopt for > 31 group */
        ext_groups = RTNLGRP_TUNNEL;

        snprintf(zns->netlink.name, sizeof(zns->netlink.name),
                 "netlink-listen (NS %u)", zns->ns_id);
        zns->netlink.sock = -1;
        if (netlink_socket(&zns->netlink, groups, &ext_groups, 1, zns->ns_id) <
            0) {
                zlog_err("Failure to create %s socket",
                         zns->netlink.name);
                exit(-1);
        }

        kernel_netlink_nlsock_insert(&zns->netlink);

        snprintf(zns->netlink_cmd.name, sizeof(zns->netlink_cmd.name),
                 "netlink-cmd (NS %u)", zns->ns_id);
        zns->netlink_cmd.sock = -1;
        if (netlink_socket(&zns->netlink_cmd, 0, 0, 0, zns->ns_id) < 0) {
                zlog_err("Failure to create %s socket",
                         zns->netlink_cmd.name);
                exit(-1);
        }

        kernel_netlink_nlsock_insert(&zns->netlink_cmd);

        /* Outbound socket for dplane programming of the host OS. */
        snprintf(zns->netlink_dplane_out.name,
                 sizeof(zns->netlink_dplane_out.name), "netlink-dp (NS %u)",
                 zns->ns_id);
        zns->netlink_dplane_out.sock = -1;
        if (netlink_socket(&zns->netlink_dplane_out, 0, 0, 0, zns->ns_id) < 0) {
                zlog_err("Failure to create %s socket",
                         zns->netlink_dplane_out.name);
                exit(-1);
        }

        kernel_netlink_nlsock_insert(&zns->netlink_dplane_out);

        /* Inbound socket for OS events coming to the dplane. */
        snprintf(zns->netlink_dplane_in.name,
                 sizeof(zns->netlink_dplane_in.name), "netlink-dp-in (NS %u)",
                 zns->ns_id);
        zns->netlink_dplane_in.sock = -1;
        if (netlink_socket(&zns->netlink_dplane_in, dplane_groups, 0, 0,
                           zns->ns_id) < 0) {
                zlog_err("Failure to create %s socket",
                         zns->netlink_dplane_in.name);
                exit(-1);
        }

        kernel_netlink_nlsock_insert(&zns->netlink_dplane_in);

        /*
         * SOL_NETLINK is not available on all platforms yet
         * apparently.  It's in bits/socket.h which I am not
         * sure that we want to pull into our build system.
         */
#if defined SOL_NETLINK
        /*
         * Let's tell the kernel that we want to receive extended
         * ACKS over our command socket(s)
         */
        one = 1;
        ret = setsockopt(zns->netlink_cmd.sock, SOL_NETLINK, NETLINK_EXT_ACK,
                         &one, sizeof(one));

        if (ret < 0)
                zlog_notice("Registration for extended cmd ACK failed : %d %s",
                            errno, safe_strerror(errno));

        one = 1;
        ret = setsockopt(zns->netlink_dplane_out.sock, SOL_NETLINK,
                         NETLINK_EXT_ACK, &one, sizeof(one));

        if (ret < 0)
                zlog_notice("Registration for extended dp ACK failed : %d %s",
                            errno, safe_strerror(errno));

        /*
         * Trim off the payload of the original netlink message in the
         * acknowledgment. This option is available since Linux 4.2, so if
         * setsockopt fails, ignore the error.
         */
        one = 1;
        ret = setsockopt(zns->netlink_dplane_out.sock, SOL_NETLINK,
                         NETLINK_CAP_ACK, &one, sizeof(one));
        if (ret < 0)
                zlog_notice(
                        "Registration for reduced ACK packet size failed, probably running an early kernel");
#endif

        /* Register kernel socket. */
        if (fcntl(zns->netlink.sock, F_SETFL, O_NONBLOCK) < 0)
                flog_err_sys(EC_LIB_SOCKET, "Can't set %s socket flags: %s",
                             zns->netlink.name, safe_strerror(errno));

        if (fcntl(zns->netlink_cmd.sock, F_SETFL, O_NONBLOCK) < 0)
                zlog_err("Can't set %s socket error: %s(%d)",
                         zns->netlink_cmd.name, safe_strerror(errno), errno);

        if (fcntl(zns->netlink_dplane_out.sock, F_SETFL, O_NONBLOCK) < 0)
                zlog_err("Can't set %s socket error: %s(%d)",
                         zns->netlink_dplane_out.name, safe_strerror(errno),
                         errno);

        if (fcntl(zns->netlink_dplane_in.sock, F_SETFL, O_NONBLOCK) < 0)
                zlog_err("Can't set %s socket error: %s(%d)",
                         zns->netlink_dplane_in.name, safe_strerror(errno),
                         errno);

        /* Set receive buffer size if it's set from command line */
        if (rcvbufsize) {
                netlink_recvbuf(&zns->netlink, rcvbufsize);
                netlink_recvbuf(&zns->netlink_cmd, rcvbufsize);
                netlink_recvbuf(&zns->netlink_dplane_out, rcvbufsize);
                netlink_recvbuf(&zns->netlink_dplane_in, rcvbufsize);
        }

        /* Set filter for inbound sockets, to exclude events we've generated
         * ourselves.
         */
        netlink_install_filter(zns->netlink.sock, zns->netlink_cmd.snl.nl_pid,
                               zns->netlink_dplane_out.snl.nl_pid);

        netlink_install_filter(zns->netlink_dplane_in.sock,
                               zns->netlink_cmd.snl.nl_pid,
                               zns->netlink_dplane_out.snl.nl_pid);

        zns->t_netlink = NULL;

        thread_add_read(zrouter.master, kernel_read, zns,
                        zns->netlink.sock, &zns->t_netlink);

        rt_netlink_init();
}

/* Helper to clean up an nlsock */
static void kernel_nlsock_fini(struct nlsock *nls)
{
        if (nls && nls->sock >= 0) {
                kernel_netlink_nlsock_remove(nls);
                close(nls->sock);
                nls->sock = -1;
                XFREE(MTYPE_NL_BUF, nls->buf);
                nls->buflen = 0;
        }
}

void kernel_terminate(struct zebra_ns *zns, bool complete)
{
        THREAD_OFF(zns->t_netlink);

        kernel_nlsock_fini(&zns->netlink);

        kernel_nlsock_fini(&zns->netlink_cmd);

        kernel_nlsock_fini(&zns->netlink_dplane_in);

        /* During zebra shutdown, we need to leave the dataplane socket
         * around until all work is done.
         */
        if (complete)
                kernel_nlsock_fini(&zns->netlink_dplane_out);
}

/*
 * Global init for platform-/OS-specific things
 */
void kernel_router_init(void)
{
        /* Init nlsock hash and lock */
        pthread_mutex_init(&nlsock_mutex, NULL);
        nlsock_hash = hash_create_size(8, kernel_netlink_nlsock_key,
                                       kernel_netlink_nlsock_hash_equal,
                                       "Netlink Socket Hash");
}

/*
 * Global deinit for platform-/OS-specific things
 */
void kernel_router_terminate(void)
{
        pthread_mutex_destroy(&nlsock_mutex);

        hash_free(nlsock_hash);
        nlsock_hash = NULL;
}

#endif /* HAVE_NETLINK */